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Detoxification of Endocrine Disruptors in Water Using Visible-Light- Active Nanostructures: A Review
Abstract
The scarcity of pure water has become a global and major concern because of rapid industrialization in modern and exponentially populated civilization. No life can exist without water, and contamination-free water for the whole ecosystem is a primary demand. Therefore, the enhanced rate of water contamination and the infliction of living beings are considered to be challenging issues. It attracts great attention in the scientific community when water pollution by multifarious endocrine disruptors (EDs) such as plasticizers, herbicides, insecticides, pharmaceutical and personal care products, and food additives and sweeteners, which are discharged from industries, reach water resources, and finally appear in drinking water, is involved. The chemical contaminants of EDs disturb the functions of glands from where hormones or juices are secreted and mix with blood directly. Their persistence results in adverse toxic effects in all living beings, for example, declining reproduction, endometriosis, cancer, and many more diseases. These are not easily mineralized or removed from water compared to various organic dye molecules because of their typical characteristic light absorption in the UV region. Therefore, it is very urgent to mineralize wastewater from such types of contaminants. Among the existing technologies, visible-light-triggered photocatalytic degradation is accredited as cost-effective, renewable, and environmentally friendly. Besides, the utilization of cheap visible light as a driving force with strong mineralization efficiency under facile reaction conditions and no harmful end products enables it to have a more beneficial effect. This review describes different classes of EDs, their adverse toxic effects, and efficient degradation through remarkable active nanomaterials/nanocomposites reported from 2015 to 2020. The detailed mechanisms of pollutant adsorption on the nanostructure surface and their decomposition actions have been interpreted. Also, different pollutant degradation pathways have been attentively considered and well-explained. Besides, the future outlook has been elucidated at the end.
... EDCs, such as pesticides, and plastics compounds, can alter the function of the endocrine system, leading to the development of chronic diseases, such as cancer, reproduction disorders, neurological dysfunction, among others [1]. Bisphenol A (BPA) is one of the more studied endocrine compounds due to its wide use in the fabrication of epoxy resins, plastic bottles and food storage materials [2]. It has been reported that low-dose BPA (i.e., 1 nM) exposure in humans can cause carcinogenesis and epigenetic mutations [3]. ...
... This implies that the total cost of water treatment using photocatalytic BiOI films activated with LED lamps may be lower than with conventional lamps, which is attractive for its application at large scale. Therefore, the aims of this work are (1) to synthesize BiOI flower-like microspheres via a solvothermal method, (2) to prepare BiOI films on glass via a layer-by-layer deposition method and using the assynthetized BiOI flower-like microspheres, (3) to characterize the structure and optical properties of powdery BiOI microspheres and BiOI films using a suite of instrumental analysis techniques, and (4) to evaluate the photocatalytic performance of BiOI films in the degradation of Bisphenol A (BPA) under white LED light irradiation. ...
Bismuth oxyiodide (BiOI) films were prepared through the Layer-by-Layer (LbL) method for the first time using powdery BiOI microstructures previously synthesized by a solvothermal method. BiOI films and powdery samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV–vis diffuse reflectance spectroscopy. The chemical composition and morphology of the powdery BiOI microstructures was not affected by the deposition process. The photocatalytic activity of prepared BiOI films and powdery samples was evaluated in the degradation of bisphenol A under white LED (Light emitting diode) light irradiation. The BiOI film composed by 1 layer (BiOI-1) of BiOI flower-like microspheres exhibited the highest photocatalytic activity in comparison with BiOI as powder and BiOI films composed by 3 (BiOI-3) and 5 layers (BiOI-5). The probable reasons for the highest photocatalytic performance of BiOI-1 may be related to its larger surface area, morphological characteristics, and fractal geometry. The results obtained in this work demonstrate that the LbL method can be a suitable technique to fabricate BiOI films with photocatalytic properties for water treatment.
... A category of appearing new noxious pollutants comprised of EDCs (Endocrine disrupting compounds), having a destructive effect on the ecosystem especially on the aquatic animals, water bodies, and humans (Rathi et al. 2019;Usha Vipinachandran et al. 2020). The unrestrained discharge of toxic chemicals into the water bodies due to huge urban industrialization, agricultural activities, and many human actions, causes a serious threat to the earth's ecosystem (Usha Vipinachandran et al. 2020;Rathi et al. 2021). ...
... A category of appearing new noxious pollutants comprised of EDCs (Endocrine disrupting compounds), having a destructive effect on the ecosystem especially on the aquatic animals, water bodies, and humans (Rathi et al. 2019;Usha Vipinachandran et al. 2020). The unrestrained discharge of toxic chemicals into the water bodies due to huge urban industrialization, agricultural activities, and many human actions, causes a serious threat to the earth's ecosystem (Usha Vipinachandran et al. 2020;Rathi et al. 2021). These substances disturb the normal functioning of the endocrine systems by binding with the receptors site and start mimicking their functions which leads to unwanted responses (antagonizing effect/blocking effect) like neurological, reproductive, metabolic, and cardiovascular disorders in the human species (Aanchal et al. 2020;Sharma and Basu 2021). ...
Endocrine disruptors are toxic substances having adverse effects on the endocrine system even in very fewer amounts which appeared to be a serious concern for human health and water quality. EDCs (Endocrine disrupting compounds) behave like natural hormones in human beings that cause an interruption in endogenous hormonal activities like decreased fertility, changed sexual behavior, inflate abnormalities, and cancers in humans or animals. There are growing concerns about the effects of EDCs on drinking water or human health which are the key environmental problems worldwide. They can be removed from wastewater by many methods such as absorption, adsorption, oxidation, chemical degradation, photocatalytic degradation, membrane separation, biological degradation, transformation, and volatilization. The toxic effect of some EDCs is not fully known and needs further investigations. Detailed treatment methodology for each process is discussed for a better understanding of the scientific community for mitigation and handling these EDCs. The effect of influential operational parameters on the eradication of EDCs from aqueous media via various processes has been highlighted. Finally, the future perspective of the various water treatment techniques along with the key challenges to be faced by the next generation researchers towards expulsion of EDCs is discussed.
... A category of appearing new noxious pollutants comprised of EDCs (Endocrine disrupting compounds), having a destructive effect on the ecosystem especially on the aquatic animals, water bodies, and humans (Rathi et al. 2019;Usha Vipinachandran et al. 2020). The unrestrained discharge of toxic chemicals into the water bodies due to huge urban industrialization, agricultural activities, and many human actions, causes a serious threat to the earth's ecosystem (Usha Vipinachandran et al. 2020;Rathi et al. 2021). ...
... A category of appearing new noxious pollutants comprised of EDCs (Endocrine disrupting compounds), having a destructive effect on the ecosystem especially on the aquatic animals, water bodies, and humans (Rathi et al. 2019;Usha Vipinachandran et al. 2020). The unrestrained discharge of toxic chemicals into the water bodies due to huge urban industrialization, agricultural activities, and many human actions, causes a serious threat to the earth's ecosystem (Usha Vipinachandran et al. 2020;Rathi et al. 2021). These substances disturb the normal functioning of the endocrine systems by binding with the receptors site and start mimicking their functions which leads to unwanted responses (antagonizing effect/blocking effect) like neurological, reproductive, metabolic, and cardiovascular disorders in the human species (Aanchal et al. 2020;Sharma and Basu 2021). ...
Exponential growth in industrialization, urbanization, and commercialization activities in last three decades have contributed to the increasing number of bio-refractory contaminants in the wastewater and this continuous admittance of toxic and persistent organic pollutants in the wastewater are imparting hazardous impacts on the environment. The conventional physical and biological treatment technologies are not very efficient in treating the wastewater having toxic and refractory pollutants and researchers worldwide are working to develop more efficient and sustainable technologies for the same. In recent years, advanced oxidation processes (AOPs) have emerged to be efficient, promising and environmental-friendly methods for the treatment of wastewater having high degree of pollution in comparison to conventional wastewater treatment methods. AOPs have appeared as an important avenue of technologies involving treatment of recalcitrant pollutants through different pathways such as “Enhanced Electrolysis”, “Ultraviolet radiation”, “Ozonation”, “Sonolysis”, etc. Many AOPs are based on the in-situ generation of strong oxidants like hydroxyl radicals which can completely mineralize or degrade the organic pollutants into harmless products. This chapter reports the details about various AOPs including theirbasic principle, mechanism, advantages, and limitations of each method to gain better scientific understanding of the most feasible approach to treat industrial wastewater. The authors have tried to summarize some recent AOPs too, which are being practiced seeing the disadvantages of the conventional AOPs. The contents will help to understand the future sustainable challenges for wastewater treatment (WWT).
... Ingestion of such polluted water will lead to several health issues including thyroid, infertility, allergies, neurological, and carcinogenic problems [1,2]. Endocrine disruptors (EDs) belong to a class of colorless pollutants and these are commonly used in plasticizers, agricultural fields, pharmaceutical and personal care products, food sweetening etc. [3]. Finally, these compounds ran-off, meet with aquatic sources and remain stable depending on their lifetime. ...
... During the thermal treatment, brown color powder was obtained indicating the formation of CN nanosheets. On the other hand, a mixture of Bi(NO 3 ) 3 and Na 2 WO 4 was heated hydrothermally to get white colored suspension. Nanoplates of BW were obtained by calcining the white powder at 400 • C for 3 h. ...
Colorless endocrine disruptors (EDs) are generally known as interference chemicals with the hormonal system. Widespread usage of such pollutants in daily life leads to the hike in the level of EDs in water resources as well as drinking water resulting in various health issues upon ingestion unknowingly. Thus, it is a challenging issue to efficiently degrade colorless EDs under visible light in spite the report of several photocatalysts. Herein, we fabricated a composite comprising metal-free graphitic carbon nitride (g-C3N5) with Bi2WO6 that exhibits visible light-induced efficient degradation of colorless EDs. A simple hydrothermal polymerization method was adopted to prepare nanosheets of g-C3N5 loaded with Bi2WO6 nanoplates and the resulting heterostructure efficiently degrade tetracycline, 2-mercaptobenzothiazole, and chlorpyrifos under cheap visible light irradiation in a short period of time. The synergistic effect of g-C3N5 and Bi2WO6 components in the composite leads to efficient separation of photogenerated charge carriers via Z-scheme pathway and resulting in remarkable photocatalytic activity compared to individuals.
... Apart from energy, wastewater pollution is another threat to the world. There are miscellaneous pollutants such as pharmaceutical products [3,4], textile industry dyes [5], endocrine disruptors (ED) [6], heavy metals [7], and pesticides [8] which can potentially bring harm to the public. For example, United Nations (UN) environment specialists were advised that the thoughtless disposal of antibiotic wastes could produce "ferocious superbugs" [9]. ...
Rapid industrialization and overpopulation have led to energy shortages and environmental pollution, accelerating research to solve the issues. Currently, metal-free photocatalysts have gained the intensive attention of scientists due to their environmental-friendly nature and ease of preparation. It was noticed that g-C3N4 (GCN) consists of a few outstanding properties that could be used for various applications such as water treatment and clean energy production. Nonetheless, bare GCN contains several drawbacks such as high charge recombination, limited surface area, and low light sensitivity. Several solutions have been applied to overcome GCN limitations. Co-doping, tri-doping, and rare-earth-doping can be effective solutions to modify the GCN structure and im-prove its performance toward photocatalysis. This review highlights the function of multi-elemental and rare-earth dopants in GCN structure, mechanisms, and performance for photocatalytic ap-plications as well as the advantages of co-doping, tri-doping, and rare-earth-doping of GCN. This review summarizes the different roles of dopants in addressing the limitations of GCN. Therefore, this article critically reviewed how multi-elemental and rare-earth-doping affect GCN properties and enhanced photoactivity for various applications.
... Photocatalysis is a low-cost and versatile green technology widely used for the degradation of organic pollutants such as EDCs [33][34][35][36]. Photocatalytic processes need a semiconductor acting as photocatalyst that absorbs light radiation in a specific wavelength range, thus resulting in the excitation of electron (e − ) from the valence band (VB) to the conduction band (CB). ...
Endocrine Disrupting Compounds (EDCs) comprise a class of natural or synthetic molecules and groups of substances which are considered as emerging contaminants due to their toxicity and danger for the ecosystems, including human health. Nowadays, the presence of EDCs in water and wastewater has become a global problem, which is challenging the scientific community to address the development and application of effective strategies for their removal from the environment. Particularly, catalytic and photocatalytic degradation processes employing nanostructured materials based on metal oxides, mainly acting through the generation of reactive oxygen species, are widely explored to eradicate EDCs from water. In this review, we report the recent advances described by the major publications in recent years and focused on the degradation processes of several classes of EDCs, such as plastic components and additives, agricultural chemicals, pharmaceuticals, and personal care products, which were realized by using novel metal oxide-based nanomaterials. A variety of doped, hybrid, composite and heterostructured semiconductors were reported, whose performances are influenced by their chemical, structural as well as morphological features. Along with photocatalysis, alternative heterogeneous advanced oxidation processes are in development, and their combination may be a promising way toward industrial scale application.
... The catalytic reactor setup was kept inside a black chamber. The diameter and height of the cylindrical batch reactor are 10.2 and 18.5 cm, respectively, and the volume of inserted TiO 2 -coated quartz tube is 130 cm 3 . The volume of the reactor (V R ) is 1510 mL, in that 1100 mL of 8.3 μM RhB dye solution (∼4 mg/L) was taken for the degradation reaction. ...
Silica‐based nanomaterials have attracted huge attention for maximizing their safety and efficacy due to their nontoxicity, chemical and thermal stability, size tunability, and versatile functionality. Nanosilica with ZnO or carbon in a composite has excellent usage as an electrochemical sensor. Recent technological progression in nanotechnology and nanoscience has seen a number of applications of zinc oxide (ZnO) nanomaterials ranging from electronics, and sensing to environmental, and biomedical applications because of its various applications, multifunction, high specific surface area, stability, biocompatibility, nontoxicity, electrochemical activities, and so on. Carbon also has various advantageous properties like renewability, low ohmic resistance, and very stable response due to which carbon paste electrodes have attracted attention in the fabrication of electrochemical sensors. Electrochemical sensors are inexpensive, portable, and have excellent ability in detecting water contaminants, pesticides, disinfectants, pathogens, and different molecules. Artificial dyes are usually mixed with vegetable sauces, drinks, and other food items, which can cause cancer in human body. Voltametric methods with electrochemical sensors can be used to detect them in food samples. In this review, the present applications of ZnO and carbon nanomaterial‐based chemical sensors are meticulously studied to detect water contaminants and food dyes where nanosilica plays an important role as a sensor modifier.
A ternary composite by combining g-C 3 N 5 and Gd-MOF adorned with AgNCs has been fabricated for the efficient reduction of Cr ⁶⁺ and neomycin degradation.
The use of efficacious and cost‐effective pesticides (OP and OC) has undoubtedly proven to be a blessing and a baron because these pesticides are safeguarding the world from food insecurity. Unfortunately, their presence in aquatic bodies brings about an upsurge in water pollution. Amazingly, the photocatalytic degradation approach utilizing biogenic nanoparticles (BNPs) is a trendy state‐of‐the‐art approach and has been established to be a sustainable methodology for the complete mineralization of contaminants into harmless molecules. Thus, this work holistically explores the use of BNPs for photocatalytic degradation of OP and OC. Based on the review, it was found that the least amount of time needed for degradation was less than 5 minutes, while the maximum degradation efficiency was >80 %. The dominant radicals participating in the degradation are ⋅OH and O2⋅ and this radical dominance was enhanced by the oxygenated functional groups present in the biogenic entities employed for the biosynthesis of BNPs. The photocatalytic degradation data fits the pseudo‐first‐order and Langmuir isotherm models (R² > 0.9), which indicates that the main adsorption mechanisms involved during electron‐hole pair formation and photocatalytic degradation are physisorption and monolayer at the surface of the BNPs. BNPs can sustain a >80 % degradation efficiency for approximately 5 cycles and are reusable for up to 8 cycles. It was also revealed that plants constitute 80 % of the engaged biogenic entities for BNP synthesis. Ultimately, this work offers novel avenues and future research hotspots that might accelerate the use of BNPs for sustainable agricultural and wastewater management practices.
The detection and removal of Pb2+ is of utmost importance for environmental protection and human health due to its toxicity, persistent pollution, and bioaccumulation effects. To address the limitations associated with organic small molecule-based fluorescence probes such as poor water solubility and single functionality in detecting Pb2+, a fluorescence probe based on halloysite nanotubes was developed. This probe not only enables specific, rapid, and reliable detection of Pb2+ but also facilitates efficient removal of it from water. The development of this bifunctional fluorescent probe provides a valuable insight for designing more advanced probes targeting heavy metal ions.
This work presents a simple yet selective fluorometric protocol for the quantification of vancomycin, an important antibiotic for treating infections caused by Gram-positive bacteria. A novel ratiometric fluorometric method for the determination of vancomycin is developed based on dual emissive carbon dots (DECDs) with emission at 382 nm and 570 nm in combination with Co²⁺ ions. Upon addition of Co²⁺ions, the fluorescence at 382 nm of DECDs is enhanced while emission at 570 nm remains constant. In the presence of vancomycin, it complexes with Co²⁺ leading to quenching of the 382 nm fluorescence due to strong binding with Co²⁺ in the Co@DECDs system. The DECDs are fully characterized by TEM and different spectroscopic techniques. The proposed ratiometric method is based on measuring fluorescence ratio (F570/F382) against vancomycin concentration and the method exhibits a good linearity range from 0.0 to 120.0 ng mL⁻¹ with a low limit of detection (S/N = 3) of 0.31 ng mL⁻¹. The method shows good selectivity with minimal interference from potential interfering species. This ratiometric fluorometric approach provides a promising tool for sensitive and specific vancomycin detection in clinical applications.
The green synthesized gold nanoparticles (Au Nps) and medicinal plants have both proven to be reliable sources of management for diabetes mellitus. To assess the antidiabetic characteristics of produced Au Nps in vitro and in vivo, the current study focused on the green synthesis of Au Nps from the Hemidesmus indicus root extract (Hire). The aqueous Hemidesmus indicus root extract (Hire) was used as the starting material for the biological synthesis of the Au Nps, which was then examined using spectroscopic techniques and microscopic techniques. By inhibiting α-amylase and α-glucosidase, the Hire-Au Nps in vitro antidiabetic activity was demonstrated. Also antioxidant and antibacterial properties of Hire-Au Nps were explored. Furthermore, Albino Wistar rats given streptozotocin were used to test the in vivo antidiabetic activity. Hire-Au Nps (50 µg/kg) were administered to rats for 48 days. Albino Wistar rats were killed after treatment in order to perform biochemical parameters and to collect organ samples, including liver, pancreas, heart, kidney, and adipose tissue, for histological investigation. When albino Wistar rats were given Hire-Au Nps, the levels of blood sugar were significantly reduced. The biologically synthesized Hire-Au Nps have antidiabetic action, according to the results of in vitro and in vivo tests on rats administered the Hire-Au Nps. Due to the Hire-Au Nps potent antidiabetic activity in the type 2 diabetes model in Albino Wistar rats, they may be developed for use in the management for diabetes mellitus.
The present scenario of water insecurity (poor availability and accessibility to clean and healthy water when needed) denotes the preponderance of environmental damage caused by effluents or waste runoff from industries, such as the dye and textile industries. The polluted waters have led to terrible and sonorous negative impacts on the eco‐system and eco‐networking, thus, urging for a sustainably suitable substitute to tackle and annul the noxious environmental constraint posse by the hazardous dye effluent. Several chemical and physical methods for treating dye effluent are now in use, but they are time‐consuming, expensive, and inefficient. Interestingly, nanoparticles have egressed as a superior answer for efficient dye removal and degradation, because of their chemical reactivity and exceptional surface characteristics. As a result, the use of metal nanomaterials in the treatment of dye runoffs has been thoroughly investigated. The study used major scientific databases such as SciFinder, Scopus, PubMed, Google Scholar, and Science Direct to conduct a comprehensive review of publicly available literature. Degradation, dye effluent, green metal nanoparticles, and water pollution were the keywords used to find scholarly papers. Efforts were made to figure out and explain the mechanism of dye effluent degradation, how long the degradation will take and how effective the use of plant biosynthesized metal nanoparticles for dye removal is. In addition, the role of bimetallic nanoparticles has also been investigated with remarkable feat from literature. The current level of knowledge about the mechanism and the use of plant biogenic metal nanoparticles in common dye effluent treatment is summarized in this paper.
Exposure to constituent hazardous chemicals in medical products has become a threat to environmental health across the globe. Excessive medication and the mishandling of pharmaceutical drugs can lead to the increased presence of chemicals in the aquatic environment, causing water pollution. Only a few nanomaterials exist for the detection of these chemicals and they are limited in use due to their adverse toxicity, instability, cost, and low aqueous solubility. In contrast, carbon dots (C-dots), a member of the family of carbon-based nanomaterials, have various beneficial properties including excellent biocompatibility, strong photoluminescence, low photobleaching, tunable fluorescence, and easy surface modification. Herein, we summarize recent advancements in various synthetic strategies for high-quality tunable fluorescent C-dots. The root of fluorescence has been briefly explained via the quantum confinement effect, surface defects, and molecular fluorescence. The surface functional moieties of C-dots have been investigated in depth to recognize the various types of pharmaceutical drugs that are used for the treatment of patients. The modulation of C-dot fluorescence in the course of their interactions with these drugs has been carefully explained. Different types of interaction mechanisms behind the C-dot fluorescence alteration have been discussed. Finally, the challenges and future perspectives of C-dots have been proposed for the vibrant field development of C-dot-based drug sensors.
Iron–carbon (Fe–C) microelectrolysis has attracted considerable attention in wastewater treatment due to its excellent ability to remove contaminants. Herein, novel Fe–C granules were synthesized by simple calcination method for removing organic contaminations, and a cost–effective and environmentally friendly method, namely pre–magnetization, was used to improve the micro–electrolysis performance of Fe–C. Batch experiments proved that premagnetized iron–carbon (pre-Fe–C) could significantly improve the removal of methyl orange (MO) at different Fe–C mass ratios (1:2–2:1), material dosages (1.0–2.5 g/L), initial pH values (3.0–5.0), and MO concentrations (10.0–50.0 mg/L). Electrochemical analysis showed that premagnetization could increase the current density and reduce the charge transfer resistance of the microelectrolysis system, making Fe–C more susceptible to electrochemical corrosion. Characterizations confirmed that the corrosion products of the materials included FeO, Fe2O3, and Fe3O4, and more corrosion products were formed in the pre-Fe–C system. Radical quenching experiments and electron spin resonance spectroscopy verified that •OH, ¹O2, and O2−• were all involved in pollutant removal, and premagnetization could promote the generation of more reactive oxygen species. Overall, the pre-Fe–C process could effectively remove various organic pollutants, exhibit good adaptability to complex water environments, and hold potential for industrial applications.
To improve the performance of graphitic carbon nitride (g-C3N4), a hotly researched metal-free photocatalyst, for better application in the efficient removal of organic pollutants, adsorption synergistically enhanced photocatalysis mechanism was thoroughly explored. Based on KOH pore-forming activated biochar (ACB) and K⁺ doped g-C3N4 (K-gC3N4), the novel activated biochar-based K-gC3N4 composite (ACB-K-gC3N4) was synthesized via the innovative ultrasonic-milling method. Rhodamine B (RhB), tetracycline (TC), norfloxacin (NOR), and chloramphenicol (CAP) were selected as target pollutants, and the effects of environmental factors, recycling and actual wastewater tests, disinfection effects, and various enhancement strategies were investigated. The results showed that K-gC3N4 was successfully composited with ACB by various characterizations, where the loading mass ratio of 1:2 exhibited the best performance. ACB-K-gC3N4 possessed a larger specific surface area, richer functional groups, suitable band gap (2.29 eV), and broader visible light absorption (~716 nm) than K-gC3N4. ACB-K-gC3N4 presented effective removal efficiency over K-gC3N4 for four pollutants, in which the removal efficiency of RhB reached 93.26%, and the degradation rate constant of 0.0119 min⁻¹ was four times higher than K-gC3N4 (0.0029 min⁻¹). Moreover, ACB-K-gC3N4 was superior to K-gC3N4 in disinfecting S. aureus and E. coli, with a sterilization rate of exceeding 90% for 12 h. The photodegradation activity was dominated by ·O2⁻, h⁺, and ·OH, and the mechanisms involved in the three stages. This was attributed to the unique structure and surface properties (defects and persistent free radicals) of ACB, as evidenced by improved adsorption stage and transfer of degradation intermediates, facilitated the generation of active species, accelerated migration of photogenerated electrons, and inhibited photogenerated carriers recombination by the heterojunction. The good reusability and stability, enhancement strategies (blowing air and heating), and satisfactory feasibility for actual wastewater allow ACB-K-gC3N4 possible to promote high-concentration wastewater treatment and disinfection.
The occurrence of acetaminophen in surface water has been reported worldwide, indicating the need of alternative wastewater treatments. Activated hydrochar (AHC) is efficient for pharmaceuticals removal. Powdered AHC presents challenges that hamper its expansion. However, these issues can be overcome by adding polymers, such as alginate, in composite beads. Therefore, the present study aimed to develop and characterize alginate/brewer's spent grain AHC beads, applying them to acetaminophen adsorption in batch and fixed-bed experiments. The adsorbent presented a high surface area (533.42 m² g–1) and Fourier-transform infrared spectroscopy (FTIR) showed that alginate assigned new functional groups to the composite. Batch studies revealed an endothermic behavior and maximum adsorption capacity of 165.94 mg g⁻¹, with an equilibrium time of 240 min. The fixed-bed maximum adsorption capacity was 127.01 mg g⁻¹, with a mass transfer zone of 5.89 cm. The importance of alginate for the adsorbent development has been successfully proven.
A novel flower-like Co3O4 QDs/Bi2WO6 p-n heterostructure photocatalyst was prepared by hydrothermal and ultrasonic synthesis strategies with uniformly dispersing zero-dimensional (0D) Co3O4 QDs on the three-dimensional (3D) flower-like Bi2WO6 nanosheets. The structural morphology and optical properties analysis confirmed the successful combination of the Co3O4 QDs/Bi2WO6 composite photocatalyst. Photodegradation experiments results proved that 10%-Co3O4 QDs/Bi2WO6 showed the optimum rate constant (0.017 min⁻¹) for the degradation of TC, which was about 3.40 and 1.55 times higher than Co3O4 QDs (0.005 min⁻¹) and Bi2WO6 (0.011 min⁻¹), respectively. The significant improvement in the photocatalytic performance of Co3O4 QDs/Bi2WO6 was mainly attributed to the enhancement of visible light absorption capacity and the formation of p-n heterojunction, which effectively inhibited the recombination of electron/holes (e⁻/h⁺) pairs. Radical trapping experiments and electron spin resonance (ESR) spectrum demonstrated that O2⁻ radicals were the leading active species in photocatalytic degradation. Furthermore, three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) and Liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF MS) techniques results revealed the degradation pathway and mechanism of efficient visible-light-driven photocatalytic tetracycline antibiotics. The outstanding photocatalytic performance makes the 0D/3D Co3O4 QDs/Bi2WO6 p-n heterojunction photocatalyst a promising photocatalyst for the degradation of tetracycline antibiotics.
Inorganic nanotubes with unique and well-defined porous structures show promising applications in diverse functional materials. However, it remains a challenge to fabricate inorganic nanotubes with precise length controllability. Herein, we report the synthesis of block copolymers consisting of a crystalline π-conjugated oligo(p-phenylenevinylene) (OPV) block, a hydrophilic poly(2-vinylpyridine) (P2VP) segment and a photo-cleavable o-nitrobenzyl (ONB) junction. By taking advantage of crystallinity of OPV segment, self-seeding approach of living crystallization-driven self-assembly was employed to generate uniform fiber-like micelles composed of an OPV core and a P2VP corona. The P2VP corona was then used to host the formation of silica, titania and Pt(0)-embedded silica shell. After the photo-cleavable OBN junctions were broken under light irradiation, the OPV core can be removed in a good solvent for OPV segments to give silica, titania and Pt(0)-embedded silica nanotubes. Significantly, the Pt(0)-embedded silica nanotubes exhibited much higher catalytic activity toward the reduction of p-nitroaniline than Pt(0)-embedded silica nanofibers with the same Pt content, probably owing to the presence of porous channel for nanotubes. This work opens a new avenue to fabricate inorganic nanotubes of controlled length.
In this study, superparamagnetic β-CD-MnFe2O4 with a large surface area was synthesized via a facile co-precipitation method, with β-cyclodextrin (β-CD) acting as a coating agent. The as-prepared β-CD-MnFe2O4 exhibited better catalytic performance than bare MnFe2O4 in terms of activating peroxymonosulfate (PMS) to degrade 2,4-dichlorophenol (2,4-DCP) over a broad pH range of 5–11. Electron spin resonance spectroscopy (ESR) and free radical quenching experiments indicate that various active species (SO4•−/•OH/O2•−/¹O2) are generated in the β-CD-MnFe2O4/PMS system and that pollutants trapped in the cyclodextrin cavity are quickly degraded. Various reaction parameters of the β-CD-MnFe2O4/PMS system and the stability of β-CD-MnFe2O4 were also investigated. The results indicate that β-CD-MnFe2O4 is promising for use in water purification owing to its excellent magnetic separation and recovery properties and good resistance to humic acid (HA).
The presence of bisphenol A (BPA) in various water sources has potentially led to numerous adverse effects in human such as increased in blood pressure and derangement in liver function. Thus, a reliable treatment for the removing BPA is highly required. This present work aimed to study the efficiency of visible light driven photocatalytic dual-layer hollow fiber (DLHF) membrane for the removal of BPA from water and further investigated its detrimental effects by using an in-vivo model. The prepared membranes were characterized for their morphology, particles distribution, surface roughness, crystallinity and light absorption spectra. The removal of 81.6% and 86.7% in BPA concentration was achieved for N-doped TiO2 DLHF after 360 min of visible and UV light irradiation, respectively. No significant changes for all three groups were observed in liver function test meanwhile the rats-exposed to untreated BPA water shows significance blood pressure increment contrary to rats-exposed to treated BPA water. Similarly, the normal morphology in both jejunum and ileum were altered in rats-exposed to untreated BPA water group. Altogether, the presence of N-doped TiO2 in DLHF are shown to significantly enhance the photocatalytic degradation activity under visible irradiation, which effectively mitigates the effect of BPA in an in-vivo model.
Atrazine (ATZ) is a known herbicide used in agriculture and caused many concerns according to its toxicity. Herein, we have prepared NiCo2O4 nanorods that can work as a photocatalyst under visible light exposure by Ag loading through a simple route. The characterizations revealed the role of Ag for improving the structural, optical and optoelectronic properties of the produced photocatalyst. The Ag loading with 5 wt% confirms the minimization of the bandgap from 3.6 down to 2.57 eV with enhanced visible light absorption and sustaining the magnetic properties. The Ag/NiCo2O4 nanorods showed a superior photodegradation of ATZ within 20 min at 2.0 g L–1 with excellent recyclability. The enhancement of the photocatalytic activity is referred to the local surface plasmon resonance of Ag-loaded photocatalyst. This reduces the electron-hole recombination and outperforms the unloaded sample. This work is highlighting the application of magnetically separable spinel photocatalysts for the removal of herbicides and water remediation.
In this paper, we report a layer-by-layer approach for the preparation of a concentric recyclable composite (CoxNi1−xFe2O4/SiO2/TiO2; x = 0.9) designed for wastewater treatment. The prepared composite was investigated by X-ray diffraction spectroscopy, high-resolution transmission electron microscopy and scanning electron microscopy (SEM) supported with energy dispersive X-ray (EDX) spectroscopy to analyze crystallinity, average particle size, morphology and elemental composition, respectively. The antimicrobial activities of the prepared composite have been investigated against multi-drug-resistant bacteria and pathogenic fungi using a variety of experiments, such as zone of inhibition, minimum inhibitory concentration, biofilm formation and SEM with EDX analysis of the treated bacterial cells. In addition, the effects of gamma irradiation (with different doses) and UV irradiation on the antibacterial abilities of the prepared composite have been evaluated. Moreover, the effect of gamma irradiation on the crystallite size of the prepared composite has been studied under varying doses of radiation (25 kGy, 50 kGy and 100 kGy). Finally, the photocatalytic efficiency of the prepared composite was tested for halogen-lamp-assisted removal of pyridine (artificial wastewater). Various parameters affecting the efficiency of the photocatalytic degradation, such as photocatalyst dose, pyridine concentration, pH, point of zero charge and the presence of hydrogen peroxide, have been studied. Our results show that the synthesized composite has a well-crystallized semi-spherical morphology with an average particle size of 125.84 nm. In addition, it possesses a high degree of purity, as revealed by EDX elemental analysis. Interestingly, the prepared composite showed promising antibacterial abilities against almost all the tested pathogenic bacteria and unicellular fungi, and this was further improved after gamma and UV irradiation. Finally, the prepared composite was very efficient in the light-assisted degradation of pyridine and its degradation efficiency can be tuned based on various experimental parameters. This work provides a revolutionary nanomaterial-based solution for the global water shortage and water contamination by offering a new wastewater treatment technique that is recyclable, cost effective and has an acceptable time and quality of water.
In this study, a series of Ag3PO4/graphene oxide (GO) films were dip-coated on a metal nickel foam. The immobilized catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy and photoluminescence spectroscopy. The results show that Ag3PO4/GO was successfully supported on a nickel foam. The photocatalytic activity of the film catalyst under visible light was investigated by the degradation of norfloxacin, an antibiotic. Photocatalytic stability of this catalyst was also investigated. An optimized film exhibited superior activity and stability, the degradation rate of norfloxacin was about 83.68% in 100 min and the reaction rate constant k was 1.9 times that of pristine Ag3PO4. Further investigation found that photo-generated holes (h⁺) and superoxide anion radicals (·O2⁻) are the main active species in the photodegradation process. The result indicates that the addition of GO inhibits the recombination of photogenerated electron–hole pairs, and thus has improved the photocatalytic activity and cyclic stability under visible light. The photocatalytic mechanism of the film catalyst was proposed. The prepared Ag3PO4/GO film catalyst is a promising candidate for treatment of wastewater containing antibiotics.
In today’s global scenario, development of novel materials for wastewater treatment has drawn the synthetic pursuit of academic and industrial researchers as it ensures a reliable access to clean water. Herein, we report the development of an economic and sustainable bimetallic nanocatalytic system comprising of polymeric magnetic chitosan support decorated with redox couple Co-Ni nanoparticles for the first time and highlight its role in the in-situ generation of hyroxyl radical species that effectively catalyze the degradation of toxic water contaminants including pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) as well as azo dye methyl orange (MO). Coumarin fluorescence probe and radical scavenging studies provided valuable insight into the mechanistic pathway by indicating the in-situ generation of hydroxyl radicals that were responsible for expediting the degradation process. Kinetic studies revealed that the degradation process followed pseudo first order kinetics in both the cases (with the kinetic constant value of 0.07517 min-1 for 2,4-D and 0.03352 min-1 for MO at room temperature under neutral pH conditions). The reusability studies in addition suggested that the Co-Ni@CS@Fe3O4 nanocatalyst maintained its degradation efficiency even after eight consecutive cycles. Notably, this is the first report which effectively exploits the synergistic combination of two transition metals Co and Ni anchored onto the surface of chitosan coated Fe3O4 nanoparticles that effectively catalyze the degradation of hazardous contaminants in presence of a green oxidant under neutral and ambient conditions.
An efficient visible-light driven three components photocatalyst for carbamazepine (CBZ) degradation has been assembled by co-loading reduction cocatalyst Pt and oxidation cocatalyst Co3O4 (MnOx) on BiVO4. The apparent rate constant of the three components photocatalyst Pt/BiVO4/Co3O4 for degradation of CBZ is 54 times that of Co3O4/BiVO4 and 2.5 times that of Pt/BiVO4, which shows a synergetic effect in the photocatalytic activity. The same synergetic effect is also observed for Pt/BiVO4/MnOx. The spatial separation of the reduction and oxidation cocatalysts could reduce the recombination of the photogenerated charges, which mainly accounts for the high photocatalytic activity of the three components photocatalyst. The photocatalytic intermediates of CBZ were detected by HPLC-ESI-MS, and a deductive degradation pathway of CBZ was proposed.
Photolysis and photocatalysis of typical phthalic acid esters (dimethyl phthalate, DMP; diethyl phthalate, DEP; dibutyl phthalate, DBP) were carried out in UV, UV/TiO2, and UV-Vis/Bi2WO6 systems. All of the selected phthalic acid esters and their decomposition byproducts were subjected to qualitative and quantitative analysis through HPLC and GC-MS. The results of 300 min of photolysis and photodegradation reaction were that each system demonstrated different abilities to remove DMP, DEP, and DBP. The UV/TiO2 system showed the strongest degradation ability on selected PAEs, with removal efficiencies of up to 93.03, 92.64, and 92.50% for DMP, DEP, and DBP in 90 min, respectively. UV-Vis/Bi2WO6 had almost no ability to remove DMP and DEP. However, all of the systems had strong ability to degrade DBP. On the other hand, the different systems resulted in various byproducts and PAE degradation pathways. The UV system mainly attacked the carbon branch and produced o-hydroxybenzoates. No ring-opening byproducts were detected in the UV system. In the photocatalytic process, the hydroxyl radicals produced not only attacked the carbon branch but also the benzene ring. Therefore, hydroxylated compounds and ring-opening byproducts were detected by GC-MS in both the UV/TiO2 and UV-Vis/Bi2WO6 photocatalytic systems. However, there were fewer products due to direct hole oxidation in the UV-Vis/Bi2WO6 system compared with the UV/TiO2 system, which mainly reacted with the pollutants via hydroxyl radicals.
The removal of organic pollutants by heterogeneous photocatalysts is still faced with several challenges including the catalyst activity in the visible light range and its recovery. In relation to that, the synthesis of N-doped TiO2/SiO2-based nanomagnetic photocatalyst (NTiO2@
SiO2@Fe3O4) was successfully made through a simple sol-gel method in this study. The morphology of the nanocomposite was then identified and confirmed by XRD, FT-IR, EDX, SEM, XPS and BET analytical techniques. After that, the influential factors affecting
the removal efficiency of PQ was investigated in detail and the optimal conditions were established. Under the conditions of visible light and 180 min of reaction time, the TOC removal efficiency of 84.71% was accomplished. Furthermore, the synthesized photocatalyst almost maintained its efficiency after a run of eight cycles with a negligible loss of 7.88% in the removal efficiency of PQ. Finally, the results revealed that the photocatalyst could be potentially used in treatment technology.
BACKGROUND
Photocatalysis is one of the effective ways to solve the problem of water and gas pollution. An excellent photocatalyst should have the following advantages: efficient photocatalytic activity for gas and water pollutants, recyclable and stable characteristics, non‐toxic and low‐cost. Constructing heterojunctions and introducing oxygen vacancies (OVs) are two effective measures to achieve these targets.
RESULTS
It is found that the 1.0% Pd/PdO/β‐Bi2O3 exhibits the best photocatalytic activity with an efficiency of 97.4% for Bisphenol A (BPA) degradation and 47.6% for nitric oxide (NO) removal within 30 min. The 1.0% Pd/PdO/β‐Bi2O3 composite shows 23.3% efficiency in the photodegradation of BPA under 595 nm monochromatic light irradiation, while β‐Bi2O3 tends to be invalid. Moreover, the OVs promote the removal of NO without irradiation.
CONCLUSION
In this work, a novel ternary Pd/PdO/β‐Bi2O3 material as high‐performance photocatalyst for the BPA degradation and NO removal was synthesized. The presence of OVs promotes the activation of the oxygen molecule, thereby facilitating the photocatalytic process. The p‐n junction of PdO/β‐Bi2O3 and the Schottky barrier of Pd/β‐Bi2O3 significantly limit the recombination of photoinduced electron–hole pairs in the composite. Furthermore, an artifact in the electron spin resonance (ESR) spectrum obtained by spin trapping with 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) as adducts confirms that both hydroxyl radical (•OH) and superoxide radical (•O2⁻) species are involved in the photocatalytic process. The present work offers a new perspective for developing the composite photocatalysts with high efficiency through loading of metal nanoparticles and creating an heterojunction. © 2019 Society of Chemical Industry
In this study, activated carbon (AC) coated with a green silicone surfactant (SS) was further incorporated with magnetite particles (Fe3O4) via a co-precipitation method to enhance the separation of the newly designed magnetic AC–SS (Fe3O4@AC–SS) in a magnetic field. The properties of this magnetic adsorbent were characterized via Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The adsorption characteristics of the Fe3O4@AC–SS adsorbent were examined using 2,4-nitrophenol and 2,4-dichlorophenol as adsorbates. Experiments were performed to investigate the adsorption kinetics, isotherms, thermodynamics as well as the effects of adsorption dosage and solution pH on the removal of both analytes. The kinetic data were well-fitted by the pseudo-second order model and the Freundlich model best described the adsorption isotherm for both analytes. The maximum adsorption capabilities for 2,4-dinitrophenol and 2,4-dichlorophenol reached 43 and 98 mg g⁻¹, respectively. The analysis was further validated using real industrial effluent, and a removal efficiency of 62.2–98.1% and relative standard deviation value less than 7.2% were attained for both analytes. Thus, the multifunctional adsorbent has potential to function as an adsorbent for the fast, convenient, economical and highly efficient removal of pollutants from wastewater, which is significant for the purification of natural water and industrial effluent.
The present study focuses on the effects of nitrogen (N) ion implantation in vertically aligned ZnO nanorod arrays (NRAs) and the photocatalytic degradation of acetaminophen. The X-ray diffraction of these NRAs exhibit a wurtzite structure with a predominant (002) diffraction peak that shifts slightly after N-ion implantation. The field emission scanning electron microscopic images of as-prepared NRAs show a length of ∼4 μm and diameter of ∼150 nm. UV–visible spectroscopy reveals that the band gap of pristine ZnO NRAs decreases from 3.2 to 2.18 eV after N-ion implantation. Under visible irradiation, the N-ion-implanted ZnO catalyst exhibits significant enhancement of the photocatalytic degradation of acetaminophen from 60.0 to 98.46% for 120 min.
Advanced oxidation processes (AOPs) including heterogeneous photocatalysis has proven as one of the best technique for waste-water treatment. Photocatalytic process using semiconductor like TiO2 based heterogeneous photocatalysis is a promising method for the treatment of toxic pollutants. In the present study, visible-light photoactive cobalt and nitrogen co-doped TiO2 nanoparticles were synthesized via wet impregnation method. The photocatalysts were characterized using X-ray diffraction (XRD), Raman Spectra, Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis spectrophotometer and X-ray photoelectron spectrophotometer (XPS). The photocatalytic activitiy of prepared (N, Co)-codoped TiO2 on the mineralization of Bisphenol-A (BPA) under visible light irradiation was studied and the results were compared to commercial TiO2 (Degussa P25). The results demonstrated that 1.5% Co and 0.5% N – codoped TiO2 samples revealed higher activity than commercial TiO2. Total organic carbon (TOC) removal was observed to be 97%, which indicate the complete mineralization of BPA. GC-MS analysis was carried to find out the possible intermediates formed and reaction pathway.
The objective of this study was to determine toxicities of four parabens (methyl paraben, MP; ethyl paraben, EP; n-propyl paraben, PP; and n-butyl paraben; BP) and their mixtures to two aquatic microorganisms, Daphnia magna and Aliivibrio fischeri. Parabens are one of the widely used preservatives for personal care products, such as cosmetics, pharmaceuticals and food also. First, each paraben was treated to D. magna to measure the toxicity levels as LC20 and LC50. The results showed their value of MP (25.2 mg/L, 73.4 mg/L), EP (18.4 mg/L, 43.7 mg/L), PP (10.4 mg/L, 21.1 mg/L) and BP (3.3 mg/L, 11.2 mg/L). Then, each of the parabens was treated to A. fischeri and calculated their EC20 and EC50 by bioluminescence inhibition test. The results showed the values of MP (2.93 mg/L, 16.8 mg/L), EP (1.18 mg/L, 6.74 mg/L), PP (0.51 mg/L, 5.85 mg/L) and BP (0.21 mg/L, 2.34 mg/L). These four parabens belong to the group classified as being ‘harmful to aquatic organisms’ (above 10 mg/L, below 100 mg/L). After measuring the toxicity, EC20 values of two or more parabens were tested in order to investigate their toxicity. A total of ten combinations of four parabens were tested. As a result, the bioluminescence inhibition test of A. fischeri showed that the toxicity of mixture parabens was stronger than that of a single compound and combinations of three parabens showed the highest bioluminescence inhibition. These results showed that independent toxicity of paraben was maintained. Therefore, it can be predictable that the toxicity of paraben is getting stronger by the addition of other parabens.
A symmetric double Z-scheme BiFeO3/CuBi2O4/BaTiO3 with enhanced solar photocatalytic performance was fabricated, and employed in the photodegradation of norfloxacin. The photocatalytic performances of BiFeO3/CuBi2O4/BaTiO3, BiFeO3, CuBi2O4 and BaTiO3 were compared. Also, the mechanism on the symmetric double Z-scheme BiFeO3/CuBi2O4/BaTiO3 photocatalytic system was proposed. The results display that BiFeO3/CuBi2O4/BaTiO3 has more superior photocatalytic performance, which results from the construction of the symmetric double Z-scheme photocatalyst. Its light absorption range is extended to UV-vis and near-infrared (NIR) light, which effectively utilizes the whole solar light spectrum. Especially, the large VB oxidation surface of this composite photocatalyst promotes e--h⁺ separation and improves the oxidation-reduction ability. Also, BiFeO3/CuBi2O4/BaTiO3 can be recycled with superior stability for 5 cycles. Furthermore, in the photodegradation, the h⁺ and •OH play major roles, while the •O2⁻ plays little role. Hence, the BiFeO3/CuBi2O4/BaTiO3/solar light technology has great application prospects in the treatment of contaminated wastewater with antibiotics.
Layered double hydroxides (LDHs) are excellent adsorbent for removal of organic and inorganic contaminates from water and wastewater. In this aspect, extrudates of LDHs are of great importance for water/wastewater treatment through fixed-bed column operations. The present study reports preparation of biopolymer modified LDH extrudates by one-pot co-precipitation and extrusion method for their effective application in column-based water/wastewater treatment systems. The microstructural properties of the LDH extrudates were studied by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen adsorption-desorption analysis. The adsorption performance of the prepared LDH extrudates was studied through batch system and fixed-bed column experiments for the adsorption of acid orange II dye in aqueous medium. The adsorbent extrudates are found to be stable between a solution pH of 5 and 10. The adsorption kinetics followed a pseudo-second order kinetic model. These LDH-starch-cellulose extrudates found to be user friendly adsorbent for column-based water purification systems.
In order to improve the catalytic activity and recycling performance of heterogeneous Fenton catalyst, a heterogeneous Fenton catalyst Fe/TiO2 based on TiO2 supported visible light response was prepared by a simple method using TiO2 synthesized by sol-gel method as carrier and ferric nitrate as Fe source. It was characterized by SEM, EDX, XRD, UV–vis instruments. The influencing factors of catalytic degradation of atrazine by visible light heterogeneous Fenton of Fe/TiO2 were studied and the reaction kinetics were fitted. The mineralization degree of atrazine was reflected by the removal rate of TOC. The intermediate products by the degradation of the catalytic system was analyzed and the reaction mechanism of Fe/TiO2–H2O2 visible light system was discussed. The XRD results showed that Fe was highly dispersed on the surface of TiO2 in the form of α-Fe2O3. The Fe/TiO2 catalyst with heterogeneous Fenton and visible light photocatalytic activity was successfully optimized, forbidden bandwidth of Fe/TiO2 after Fe supported was narrower, the scope of light absorption red-shifted, the electron-hole pairs were more generated, and there was a significant synergistic effect between the carrier TiO2 and the supported Fe, which exhibited good oxidation capacity for degradation of 10 mg L⁻¹ atrazine in pH of 3, the concentration of H2O2 was 1.6 mM, and the catalyst was added at 1 g L⁻¹, achieving over 95% removal efficiency within 30 min, and, in the range of pH 3–7, the degradation rate of the reaction for 30 min can be maintained above 75%, which greatly broadened the range of pH application and had good recycling performance. The degradation process conformed to the quasi-first-order kinetic model. Through LC-MS analyzed, 12 intermediate products were formed during the degradation of atrazine, the final products were all cyanuric acid, and then the triazine ring was mineralized into inorganic substances such as CO2, H2O and NO3⁻ by oxidation of ·OH, and the possible degradation pathways were inferred.
The removal mechanisms of ciprofloxacin (CIP) in an aqueous solution using the persulfate (PS) oxidation system activated by zero-valent metals (ZVMs), such as zero-valent iron (ZVI), zero-valent aluminum (ZVA), and zero-valent copper (ZVC), were compared. The CIP removal followed the pseudo-first-order kinetics in all the PS oxidation processes mediated by the ZVMs. The influence of factors of the PS oxidation system, such as pH, and concentrations of both ZVMs and PS, was analyzed. Our results indicate that ZVI/PS process resulted in the highest removal of CIP at 84.5 ± 1.3 % (k obs = 29.8 × 10 −3 min-1) within 60 min with pH o of 3.0, a molar dosage of PS at 2.25 mM and concentration of ZVI at 126 mg L-1. However, CIP was only removed to the extent of 73.3 ± 2.5 % with k obs = 21.9 × 10 −3 min-1 by ZVA/PS with pH o of 3.0, [PS] o = 2.25 mM and concentration of ZVA at 81 mg L-1. Finally, for ZVC/PS system, the removal efficiency of CIP was lowest at 59.9 ± 3.2 % with constant rate k obs = 15 × 10 −3 min-1 when optimum conditions were initial pH of 4.0, [PS] o = 2.25 mM and dosage of ZVC at 192 mg L-1. Based on X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) spectra, Fe 2+, and Fe 3+ ions from ZVI, Al 3+ ions from ZVA, and Cu + and Cu 2+ ions from ZVC were released by PS oxidation. Moreover, active radicals (HO*, SO 4 *-) determined as primary agents to total oxidation performance, were generated through the activation of PS by intermediate ion metals.
The efficient removal of endocrine-disrupting pollutants (EDCs) from water is a crucial issue for improving the quality of drinking water. Herein, hierarchical structures carbon composites (HCCs), which is composed of carbon-polyhedron decorated carbon nanosheet, were fabricated using zeolite imidazole framework-8 (ZIF-8) as precursor under the presence of molten NaCl. The as-prepared hierarchical carbon composites showed higher specific surface areas, high defects, high N-doping, and hydrophilicity compared with the NaCl-free ZIF-8 derived carbon polyhedrons (CPs). Additionally, the as-prepared HCCs exhibited boosted adsorption performance for the removal of model EDC, carbamazepine (CBZ), surpassing CPs and commercial powdered activated carbon (AC). The adsorption kinetics showed that HCCs possessed a higher sorption rate than CPs and AC. In the initial 5 min, the adsorption amount of CBZ on HCCs reached 94.9% of adsorption quantity at equilibrium. Furthermore, the maximum adsorption capacity of CBZ on HCCs is 248.7 mg/g, which is superior to that of CPs and AC. X-ray photoelectron spectroscopy characterizations indicated that the predominant factors to control the adsorption of CBZ on HCCs are π-π electron donor-acceptor interaction and hydrogen bonding, though, some of the adsorbed CBZ molecules were decomposed by oxidation. Finally, a fixed-bed experiment demonstrated that the HCCs have great potential as a filler for the purification of tap water.
The performance of trichloroethene (TCE) removal was initially investigated in sodium persulfate (SPS) or potassium monopersulfate triple salt (PMS) oxidative environment by reduced graphene oxide (rGO) supported nZVI (nZVI-rGO) catalyst and further the role of sulphur by anchoring nano FeS on nZVI-rGO (FeS@nZVI-rGO) was evaluated. The high usage of oxidants and stability of FeS@nZVI-rGO catalyst were significantly improved due to the insoluble nature of this innovative catalyst by involvement of nano FeS which limited the rapid iron loss caused by the corrosion of active sites and mitigated rapid oxidants decomposition in FeS@nZVI-rGO/SPS and FeS@nZVI-rGO/PMS systems. The tests for target contaminant removal showed that over 95 % TCE could be removed at 100 mg L-1 FeS@nZVI-rGO and 1.2 mM SPS or 0.3 mM PMS dosages, in which over 85 % TCE could be dechlorinated. The reactive oxygen radicals (ROSs) generation mechanisms and their contribution to TCE removal were investigated through radical scavenge tests in both systems, indicating that both HO and SO4- were the major ROSs rather than O2-. In conclusion, this study revealed the well function and fundamental mechanism of this innovative catalyst by anchoring nano FeS and worth of further demonstration of this technique in TCE contaminated groundwater remediation application.
The objective of this study was to design a versatile and reusable pesticide detection surface-enhanced Raman scattering (SERS) substrate in combination with SERS enhancement and self-cleaning properties. In this paper, we present an inexpensive way to synthesize three-dimensional tilted ZnO micron rods with an Ag hierarchical structure (ZMRs/Ag arrays). Although expensive materials and complex methods were not used, the detection limit of thiram residue was 10-11 M, with a quantitative relationship (R2 = 0.9929) between the thiram concentration and the intensity of the SERS peaks. Additionally, the substrates exhibited fast and efficient photocatalytic activity for the degradation of adsorbed thiram, and the degradation rate in 30 min was close 100 % under visible-light irradiation. The enhancement and photocatalytic mechanism of this substrate were meticulously analyzed in detail. Furthermore, the residues of several mixed pesticides (e.g., thiram and methamidophos compounds) in various juices (such as grape, pear, orange, apple, and cherry juices) were quickly detected using ZMRs/Ag substrates. The main advantages of this substrate are recyclability, stability, selectivity, handiness, and cost-eff ;ectiveness. The substrate can prevent single-use problems associated with conventional SERS substrates and can be applied in pesticide residue and food security.
Water is essential in all aspects of life, being the defining characteristic of our planet and even our body. Regrettably, water pollution is increasingly becoming a challenge due to novel anthropogenic pollutants. Of particular concern are emerging organic contaminants (EOCs), the term used not only to cover newly developed compounds but also compounds newly discovered as contaminants in the environment. Aside from anthropogenic contamination, higher temperature and more extreme and less predictable weather conditions are projected to affect water availability and distribution. Therefore, wastewater treatment has to become a valuable water resource and its reuse is an important issue that must be carried out efficiently. Among the novel technologies considered in water remediation processes, metal-organic frameworks (MOFs) are regarded as promising materials for the elimination of EOCs since they present many properties that commend them in water treatment: large surface area, easy functionalizable cavities, some are stable in water, and synthesized at large scale, etc. This review highlights the advances in the use of MOFs in the elimination (adsorption and/or degradation) of EOCs from water, classifying them by the nature of the contaminant.
A recyclable magnetic waste tyre activated carbon-chitosan composite was synthesized as a suitable adsorbent material in the adsorptive parabens removal from model solutions and real wastewater samples. Characterization techniques such as, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy as well as X-ray diffraction confirmed the formation of adsorbent material. The results of Brunauer–Emmett–Teller isotherms showed that the adsorbent has a specific surface area of 1281 m² g⁻¹ and pore size of 4.05 nm. These results offer relatively high adsorption capacity for the parabens. Under optimised conditions, kinetics results demonstrated that the adsorption fitted the pseudo-second-kinetic model. While, the simultaneous adsorption of methylparaben and propylparaben was described better by Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacity for monolayer adsorption from the Langmuir model as 85.9 mg.g⁻¹ and 90.0 mg.g⁻¹ for methylparaben and propylparaben, respectively. It was observed that the composite was stable after seven cycles of adsorption-desorption with obvious loss of adsorption efficiency (>95%). Therefore, it was concluded that as-prepared composite had considerable reusability properties which could make it a cost-effective adsorbent for the removal of parabens from various media. Furthermore, the eco-friendly and cost-effective magnetic adsorbent was used for remediation of parabens from wastewater samples and up to 100% removal was achieved.
Magnetically separable visible-light response Ag/AgBr/ZnFe2O4 plasmonic composite photocatalyst was synthesized and characterized by XRD, XPS, SEM, EDS, N2 Adsorption-Desorption (BET), VSM and, UV–Vis Diffuse Reflectance Spectra (DRS). Inductively Coupled Plasma (ICP) analysis was performed for measurement of leaching amount of Ag from catalyst to solution. The visible-light photocatalytic activity of the as-prepared Ag/AgBr/ZnFe2O4 was evaluated by the degradation of pharmaceutical drug, Carbamazepine (CBZ), and the Z-scheme mechanism of Ag/AgBr/ZnFe2O4 heterostructure photocatalyst was explained by the conduction and valance bands levels of semiconductors. The photocatalytic activity was also performed with the addition of oxidants of H2O2 and persulfate (PS). Addition of PS increased the photocatalytic activity of catalyst, however, H2O2 addition caused a decrease in photocatalytic activity. According to results of radical scavengers runs, the O2⁻ and SO4⁻ were confirmed to be the main active species in photocatalytic process both in the absence and in the presence of oxidants. Besides, Ag/AgBr/ZnFe2O4 is superparamagnetic and can be recycled by external magnet after photocatalytic reaction. Toxicity tests were also performed and the results showed that the intermediates formed in the photocatalytic oxidation of CBZ were less toxic compared to the parent CBZ molecule under the experimental conditions used.
Excitation of metal-free graphitic carbon nitride (g-C3N4) under visible light can successfully achieve efficient activation of peroxymonosulfate (PMS). Synergistic effects and involved mechanism were systematically investigated using a light-inert endocrine disrupting compound, dimethyl phthalate (DMP), as the target pollutant. Under visible light irradiation, DMP could not be degraded by direct g-C3N4-mediated photocatalysis, while in the presence of PMS, the dominant radicals were converted from •O2 to SO4•⁻ and •OH, resulting in effective DMP degradation and mineralization. Results showed that higher dosage of PMS or g-C3N4 could increase the activation amount of PMS and corresponding DMP degradation efficiency, but the latter approach was more productive in terms of making the most of PMS. High DMP concentration hindered effective contact between PMS and g-C3N4, but could provide efficient use of PMS. Higher DMP degradation efficiency was achieved at pH lower than the point of zero charge (5.4). Based on intermediates identification, the DMP degradation was found mainly through radical attack (•OH and SO4•⁻) of the benzene ring and oxidation of the aliphatic chains.
In this work, the shuttle-like CeO2 modified g-C3N4 composite was synthesized and was combined with persulfate (PS) for the efficient photocatalytic degradation of norfloxacin (NOR) under visible light. Scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) emission spectra were used to characterize the structural and optical properties of the as-prepared catalysts. Active species trapping experiments demonstrated that additional sulfate radicals (·SO4-) formed upon the addition of PS which could cooperate with superoxide radicals (O2-), holes (h+) and hydroxyl radicals (OH) to decompose NOR. Singlet oxygen (1O2) was also formed during the reaction and acted as an important active species. The degradation products of NOR were also identified and analyzed by using LC-MS technology, and the possible degradation mechanism and pathways were proposed and discussed. This work indicated that the shuttle-like CeO2 modified g-C3N4 coupled with PS displayed promising applications in the field of pharmaceutical wastewater purification.
In this work, the Z-scheme Cu2S/Bi2WO6 photocatalysts were prepared through a three-step synthetic route. The structural, electronic, and optical properties of the as-prepared photocatalysts have been investigated. The as-prepared Cu2S/Bi2WO6 composites display a hierarchical flower-like agglomeration of nanosheets, in which the Cu2S nanoparticles are deposited on the surface of Bi2WO6 nanosheets. The photocatalytic activities of glyphosate degradation over the Cu2S/Bi2WO6 composites were investigated under a 44 W light emitting diode lamp irradiation (λ > 400 nm). The 1%Cu2S/Bi2WO6 sample shows the best photocatalytic activity of glyphosate degradation under visible light irradiation. The enhancement of photocatalytic activity is ascribed to hierarchical structure, strong visible light absorption and Z-scheme mechanism. This work could offer a new insight into the design and construction of Z-scheme materials for photocatalytic applications.
Hierarchical copper sulfide/bismuth tungstate (CuS/Bi2WO6) p-n junction with two-dimensional (2D) interfacial coupling were prepared through a two-step hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, photocurrent and electrochemical impedance spectroscopy. CuS nanoplates anchored on the surface of hierarchical Bi2WO6 microspheres consisting of Bi2WO6 nanosheets to form a CuS/Bi2WO6 p-n junction photocatalyst. The photocatalytic activity of glyphosate degradation over CuS/Bi2WO6 under 44 W light-emitting diode (LED) light irradiation (λ > 400 nm) was investigated. The results indicate that the CuS/Bi2WO6 heterojunctions display higher photocatalytic activity than pure CuS and Bi2WO6. The improved photocatalytic activity of the CuS/Bi2WO6 heterostructures can be attributed to strong visible light absorption and enhanced separation of photogenerated charge carriers by the internal electric field near the interface of the p-n junction. In addition, the CuS/Bi2WO6 p-n junction photocatalysts consisting of nanosheets are beneficial for the transport of photoexcited charge carriers, thus resulting in the increase of the photocatalytic activity of glyphosate degradation. This work provides the new avenue for the development and design p-n junction materials for photocatalytic applications.
Photocatalytic degradation of toxic pollutants is an efficient technique to completely remove the toxic pollutants from water bodies. In the present investigation, photocatalytic degradation of pollutants was studied over porous g-C3N4/H-ZSM-5 nanocomposite under visible light irradiation. The composite g-C3N4/H-ZSM-5 was synthesized by mixing an aqueous solution of H-ZSM-5 zeolite (increases surface area and provides active sites for degradation) with melamine (precursor of g-C3N4) for 10-12 h followed by calcinations at 550 °C. The photocatalyst was characterized by XRD, BET, HRTEM, FESEM, EDS and elemental mapping analysis. These techniques confirmed that, g-C3N4/H-ZSM-5 composite have layered and porous structure with uniform distribution of g-C3N4 on H-ZSM-5 surface. The BET N2 adsorption-desorption analysis verified that the catalyst has high surface area (∼175 m2/g) having mesopores and micropores. The prepared catalyst was then used for the photodegradation of a model dye, Methylene Blue (MB) and an endocrine disrupting compound, Fipronil (FIP). Effects of various parameters such as pH, catalyst dose and scavengers were also studied. The % photocatalytic degradation of MB and FIP were around ∼92% and ∼84% with a high rate constants of 0.00997 and 0.00875 min-1, respectively. From the scavenger study, OH (hydroxyl radical) and radical was found to be the major reactive species for MB and FIP degradation. From these studies it is revealed that, the catalyst is visible active, easy to prepare and an efficient photocatalyst for toxic pollutant degradation.
Naproxen (NPX) as one of the typical pharmaceuticals and personal care products (PPCPs) has been constantly detected in aquatic environment recently which has potentially hazard to the human health and ecosystem. However, the practical applicability of photocatalysts in degradation of NPX is still restricted by challenges that most nanomaterials need to be stimulated by ultraviolet light and their limited photocatalytic activity under visible light. Therefore, we synthesized bismuth titanate nanobulks (Bi-TNB) through the two-step method of hydrothermal-calcining. The crystal structure, morphology, UV–vis diffuse reflectance spectra and surface adsorption performance of the as-prepared were investigated by XRD, SEM, UV–vis and BET. Several parameters which might influence the degradation efficiency were studied including initial NPX concentration, catalyst dosage, solution pH and concentration of anions, cations and humus. The results indicated that more than 99.9% of NPX (0.25 mg/L) was removed by Bi-TNB (0.5 g/L) at pH = 7. Reactive species scavenging experiments indicated that h⁺ and O2·− were the dominant active species involved the degradation of NPX. In photodegradation process, NPX was firstly decarboxylated and then further photocatalytic oxidized to form carboxylic acids of lower molecular weights and would be finally transformed into CO2 and H2O. PPCPs coexistence experiment showed that acetaminophen would hinder the removal of NPX by Bi-TNB. Both the reaction in different water matrices and degradation under the condition of sunlight indicated that Bi-TNB could be applied in degradation of NPX in environmental water systems. This study provides a new strategy for enhancing material photocatalytic performance to be used in practical applications.
An innovative advanced oxidation process was successfully developed to photocatalytic-degradation of estrone through the synergistic effect of biochar and Bi/Bi2O3 in bismuth-containing photocatalytic biochar (BiPB). The highest reaction rate constant (kobs) of estrone degradation by BiPB was 0.045 min-1 under the conditions of initial concentration of estrone =10.4 μmol L-1, [BiPB] =1 g L-1, pH = 7.0. The kobs was almost tenfold and more than 20 times than that of biochar without bismuth impregnation and pristine Bi/Bi2O3, respectively. The best photocatalytic performance of BiPB composites for the degradation of estrone was primarily attributed to generation of OH radicals. Impregnation of bismuth helped control the concentration of persistent free radicals (PFRs) and develop a hierarchical porous structure of biochar. The presence of biochar facilitated pre-concentration estrone on BiPB and improved the separation and transfer efficiency of charge carriers. The synergistic effect between biochar and Bi/Bi2O3 contributed to the generation of OH radicals for estrone degradation under neutral pH conditions. The transformation pathway of estrone was also proposed based on the measured transformation products in the presence of BiPB. The high efficiency of BiPB composites indicated that this easily-obtained material was promising for estrone-wastewater treatment applications as a low-cost composite photocatalyst.
In this study, Pd-BiVO4 bearing highly dispersed Pd nanoparticles was prepared from pure BiVO4 using an impregnation method. The pure BiVO4 and Pd-BiVO4 catalysts were characterized by X-ray diffraction, scanning electron microscopy, UV-visible diffuse reflection, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that the prepared catalysts had a monoclinic scheelite structure and exhibited a flake-like morphology. Pd-BiVO4 showed a distinct response in the visible light region, with an extended absorption edge at 550 nm. According to the Scherrer formula, the nanocrystal particle sizes of the BiVO4 and Pd-BiVO4 catalysts were 35 and 28 nm, respectively. Highly dispersed Pd nanoparticles with sizes of 2.5 ± 0.5 nm were observed on the BiVO4 surface. Two Pd valence states, Pd(II) and Pd(0), were identified in a 2:1 ratio. Pd-BiVO4 exhibited excellent activity for paracetamol (PCT) degradation, with 100% removal achieved in 1 h under visible light irradiation. During degradation, the mineralization ratio reached up to 40% total organic carbon removal. Two highly active species, namely, hydroxyl and superoxide radicals, were determined by electron spin resonance (ESR). Furthermore, the potential degradation of PCT in this system was proposed based on intermediate information obtained using HPLC-MS and Gauss analysis. The high dispersion and small size of Pd nanoparticles might favor the removal of emerging contaminants using the Pd-BiVO4 photocatalytic system.
To develop techniques like photocatalytic degradation of toxic-pollutants to reduce water pollution is essential as every human being has the right to have an access to safe water. Metal oxide monoliths have a huge significance regarding this due to their easy-to-separate nature. Porous WO3/SiO2 monoliths were synthesized by vacuum-impregnation of sodium tungstate in silica monoliths and calcination. The XRD spectra confirmed the successful formation of monolith and the morphological studies were done by FESEM exhibiting a connected porous network structure. The elemental-state and uniform elemental-distribution were analyzed by XPS and EDS. BET analysis showed that monoliths displayed multimodal porosity with pore-diameter of 0.70–14.71 nm and high surface area (82 m²/g). DRS revealed that the monolith had a narrow band gap (2.5 eV), which is suitable for visible light photocatalysis. The photocatalytic performance of monolith was estimated by degradation of model-pollutant methylene blue (MB) under visible-light illumination. High photocatalytic efficiency (91%) and rate constant (0.013 min⁻¹) was observed at natural pH of the dye (pH 7.5). The effect of pH and catalyst concentration was explored which revealed that best degradation occurred at pH 3 (97.5%) and catalyst concentration 0.4 g/L (96%). The trapping experiments suggested that the holes were governing reactive-species in the reaction. The photocatalyst was reused for 5 consecutive cycles (80% degradation). The characterization-results of monolith after 2nd cycle of photodegradation explicated its stability. A colorless-pollutant (Imidacloprid) was also degraded to distinguish between direct and indirect photocatalysis. A comparative study was also done with reported catalysts in literature regarding MB degradation.
BiOBr-based composite photocatalysts had attracted extensive attention for efficient photocatalytic degradation aqueous organic pollutants in the past decade. However, the catalysis ability of photocatalyst is greatly limited by their intrinsic high recombination rate of photo-generated charge carriers. Herein, we solve this problem by constructing a novel 2D/3D Bi5O7Br/BiOBr heterojunction photocatalyst that was prepared via one-step facile hydrolysis process. The pure Bi5O7Br and pure BiOBr photocatalysts were also obtained by only adjusting the pH value of the mixed solution. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical and electric property analysis and etc. The results suggested that 2D Bi5O7Br nanosheets tightly attached to the surface of BiOBr 3D structure with nanoflakes self-assembled microsphere, which could increase the transfer and separation efficiency of photogenerated charges. Furthermore, the 2D/3D Bi5O7Br/BiOBr heterojunction exhibited superior visible light photocatalytic performance for carbamazepine (CBZ) degradation than pure BiOBr and pure Bi5O7Br, which owing to the enhanced separation of photoinduced electrons and holes. At last, the underlying photocatalytic mechanism is elucidated based on the band structure and radical scavenging experiments. This work provided a feasible design idea to one-step construct 2D/3D nanocomposite for pharmaceutical wastewater purification.
Titanate nanomaterials (TNs) have been widely used in organic degradation and photocatalysis due to their large specific surface area, high activity and outstanding ion exchange capacity. However, TNs has a weak response to visible light, and the mechanism of photodegradation of PPCPs by various TNs under visible light is still
poorly understood. At the same time, metal modified TNs have a potential secondary pollution problem in aquatic environment. Here, we report on an efficient TNs photocatalyst modified by the H2O2 (HTNM), which exhibited an enhanced photoresponse to visible light and a highly improved photocatalytic activity. The prepared samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Brunauer-Emmet-Teller (BET) surface area, UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and X-ray photoelectron spectroscopy (XPS). The degradation effect, influencing factors, quantum yield, reaction kinetics and intermediate products transformation pathways of naproxen (NPX) degraded by HTNM were systematically studied, and the degradation mechanism of NPX by HTNM was also investigated. The results show that the
absorption of visible light and the photocatalytic activity can be improved remarkably
by H2O2-modification of TNs. Under visible light, the removal rate of NPX by HTNM
can reach 99.9% within 180 min, the degradation rate was fit with pseudo-first-order
kinetic model, and the catalytic activity was stable. The photodegradation of NPX was
inhibited by Cl-, CO32-, SO42- and NO3-in aqueous solution. Among hese ions, theNO3-had the greatest impact on the degradation of NPX, and the following were CO32-, SO42- and Cl-. The common humus in water, fulvic acid (FA), would decreasethe degradation rate of NPX, while humic acid (HA), could promote thephotocatalytic degradation of NPX. The mechanism study showed that ·OH and O2·-Catalysis Science & Technology Page 2 of 462were mainly involved in the photodegradation of NPX by HTNM, and decarboxylation and hydroxylation were the main pathways of NPX degradation. In
summary, HTNM proposes a better photocatalytic degradation route compared with pristine titanate for removing NPX in aquatic environment, which provides a new idea for wastewater treatment contaminated with NPX and has a broad application prospect in aquatic environment.
In this study, we designed and successfully prepared all solid state 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite by embedding 3D Fe2O3 nanoparticles on 2D g-C3N4 nanosheets to for 3D/2D Fe2O3/g-C3N4 followed by the addition of 2D rGO nanosheets via a simple hydrothermal technique with the support of response surface methodology for the first time. The formation of this unique 2D/3D/2D heterojunction leads to generate several nanochannels in their interfacial contact for high-speed photoinduced charge transfer. The considerable enhancement in photoinduced charge transportation and migration efficiency resulted in significant visible-light-driven degradation of emerging pharmaceutical condemnations. The 3D/2D Fe2O3/g-C3N4 nanocomposite was optimized by various concentrations of Fe2O3 in g-C3N4, followed by the optimization of rGO concentration in 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite to obtain maximum degradation efficiency. We observed that the 3% of rGO in 4% Fe2O3/g-C3N4 nanocomposite exhibited superior photocatalytic ability, nearly 22 times and 16 times higher than pristine g-C3N4 nanosheets towards tetracycline and ciprofloxacin degradation, respectively. The synergistic effect between 2D/3D/2D g- rGO/Fe2O3/g-C3N4 nanocomposites and the photocatalytic mechanism was well studied through various characterization techniques like XRD, FTIR, SEM-EDX-mapping, HR-TEM, UV–vis DRS, PL, XPS and EPR. In addition, the 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite exhibits excellent recyclability and stability, establishing a promising application in environmental remediation. This research would provide a noteworthy platform for the extensive photocatalytic properties of 2D/3D/2D heterojunction nanocomposite system with enhanced charge migration and separation.
A series of direct Z-scheme α-Fe2O3/MIL-101(Cr) hybrids were successfully prepared through a facile hydrothermal method in this work. And, the materials were characterized by some technologies including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, photoluminescence (PL) spectroscopy, Ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy (DRS) and electron spin resonance (ESR). The photocatalytic activities of the hybrids were evaluated by degradation of carbamazepine (CBZ) under visible light irradiation. It is found that 100% of CBZ was able to be removed after 180 min irradiation over the optimum α-Fe2O3 (0.3)/MIL-101(Cr) hybrid. The superior activity was engendered from good textural properties and the formation of a direct Z-scheme heterojunction in the hybrid. The decomposition process of CBZ and the formation of intermediate products were analyzed through liquid chromatography-tandem mass spectrometry (LC–MS) and a possible photodegradation pathway of the CBZ was proposed. Also, the possible mechanism for the photodegradation process was provided to illustrate the excellent performance. The work has paved a new way for the application of MOF materials in the design of efficient Z-scheme system for organic pollution degradation in wastewater.
In this work, samples consisting of BiVO 4 with exposed (040) facets coupled with Bi 2 S 3 (Bi 2 S 3 /BiVO 4 ) were prepared through a one-pot hydrothermal method, using ethylenediaminetetraacetic acid as directing agent and L-cysteine as sulfur source and soft template. X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy measurements indicated that the Bi 2 S 3 content had a significant influence on the growth of (040) and (121) facets as well as on the morphology of the Bi 2 S 3 /BiVO 4 samples. When the Bi 2 S 3 content reached 1 mmol, the Bi 2 S 3 /BiVO 4 samples exhibited a peony-like morphology. The results of transient photocurrent tests and electrochemical impedance spectroscopy measurements confirmed that a more effective charge separation and a faster interfacial charge transfer occurred in Bi 2 S 3 /BiVO 4 than BiVO 4 . The enhanced photocatalytic activity of the Bi 2 S 3 /BiVO 4 samples could be attributed to the improved absorption capability in the visible light region and the enhanced electron-hole pair separation efficiency due to the formation of the Bi 2 S 3 /BiVO 4 heterostructure. In addition, the Bi 2 S 3 /BiVO 4 samples showed relative stability and reusability. The simple method presented in this work could be used to fabricate composite photocatalysts with high activity for different applications, such as photocatalytic degradation of organic pollutants, photocatalytic splitting of water, and photocatalytic reduction of carbon dioxide. © 2019 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences
Environmental pollution and its after effects has become a huge global concern in recent years. Among all type of pollutions, water pollution has been considered as one of the major threat in recent year and this problem will be even worse in near future. In the 21st century, water recycling has become a crucial issue as more and more regions across the globe are witnessing water crisis. Detoxification of wastewater via adsorptive removal or photocatalytic degradation for achieving purified and drinkable water has come forth as environmentally benign, energy economic and cost-effective methods. In this context, porous materials have gained enormous research consideration in the recent past for detection of contaminants in effluents and for treatment of wastewater. A combination of high porosity, robustness and structural tunibility makes these nanosorbents stand out materials in environmental remediation. Metal-organic frameworks(MOFs), Covalent-organic frameworks (COFs) and Porous-organic solids are among the recently emerged versatile porous materials that are extensively investigated toward clean environment application. This review intends to provide a summarized compilation of recent research progress in sensing and sequestration of organic pollutants in advanced porous materials.
Fipronil (FIP), an endocrine disrupter pesticide is a hazardous broad spectrum insecticide which needs to eliminate from wastewater effluent. The present investigation explores the performance of cerium-modified H-ZSM-5 zeolite as adsorbent for removal of FIP from its aqueous solution. The H-ZSM-5 zeolite was modified with ceric ammonium nitrate salt by a simple refluxing method. The zeolite was modified with 5%, 10%, 15%, 20%, 25% and 30% (wt%) of cerium nitrate solution are designated as Ce 5 ZSM-5, Ce 10 ZSM-5, Ce 15 ZSM-5, Ce 20 ZSM-5, Ce 25 ZSM-5 and Ce 30 ZSM-5 respectively. The modified zeolite was characterized with XRD, N 2 -adsorption, HRTEM, FESEM, EDS and XPS techniques. The metal-modified zeolite Ce 25 ZSM-5 was proved to be a capable adsorbent for efficient removal of FIP from aqueous solution (>90% FIP removal). The batch adsorption experiments were carried out to study various parameters like pH (2−10), temperature (25–40 °C), adsorbent amount (0.5–4 g/L), stirring speed (50–300 rpm) and initial adsorbate concentration (400–900 mg/L) for elimination of FIP by Ce 25 ZSM-5. The maximum adsorption capacity of 598.80 mg/g was found for Ce 25 ZSM-5 sample in 120 min. The Langmuir isotherm model fitted well to the experimental data whereas the adsorption process obeyed pseudo-second order kinetics. Thermodynamic parameters (ΔG°), (ΔH°) and (ΔS°) predicted the exothermic nature, randomness, spontaneity and feasibility of the adsorption process.
Carbamazepine (CBZ) is one of most frequently detected pharmaceutical contaminants in water ecosystem, which cannot be removed efficiently by traditional techniques. Degradation of CBZ by peroxymonosulfate (PMS) activated with organo-montmorillonite supported nCoFe 2 O 4 (nCoFe 2 O 4 /OMt) was investigated in this study. The degradation efficiency of CBZ (5 mg L ⁻¹ ) was 93% within 60 min in the presence of 0.4 g L ⁻¹ nCoFe 2 O 4 /OMt and 0.5 mM PMS at pH 6.8 and 25 °C, following a pseudo-first order kinetics. High PMS concentration and low initial pH could enhance CBZ degradation. The presence of Cl ⁻ , NO 3⁻ and HCO 3⁻ showed marked enhancement, slight suppression and obvious inhibition of CBZ degradation, respectively. High concentration of humic acid could decrease the CBZ degradation. X-ray photoelectron spectroscopy of nCoFe 2 O 4 /OMt before and after reaction revealed that both Co ²⁺ /Co ³⁺ and Fe ²⁺ /Fe ³⁺ were involved in PMS activation during the CBZ degradation. Electron paramagnetic resonance and radical scavenger experiments confirmed that both [rad] OH and SO 4[rad]− played a predominant role on the CBZ degradation. The degradation products were identified by LC–MS/MS to understand the possible pathways.
Glyphosate is a highly effective non-selective organophosphorous herbicide with wide global usage. The increasing presence of glyphosate and its byproducts has raised considerable concerns about its potential impact on the aquatic environment and human health. In this research, magnetic BiOBr/Fe 3 O 4 nanocomposites photocatalysts, were successfully prepared through a facile solvothermal process. The photocatalysts were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy. The catalysts exhibited excellent photocatalytic activity toward glyphosate degradation in water under visible light irradiation. The rate of glyphosate degradation reached 97%, which was higher than that of the pure BiOBr (85%) within 60 min. Quenching experiments were done to study the degradation mechanism of glyphosate. Photo-generated holes (h ⁺ ) were determined to be the major reactive species in the photodegradation process. Ion chromatography was used to monitor the reaction intermediates to clarify the photodegradation pathway of glyphosate. Moreover, the BiOBr/Fe 3 O 4 photocatalysts have magnetic recyclability properties. After five repeated trials, the percent of degradation of glyphosate was still more than 90%, indicating that the BiOBr/Fe 3 O 4 nanocomposites have excellent reusability and great potential in the treatment of industrial wastewater.
A heterojunction nanocomposite NiWO4@g-C3N4 photocatalyst was designed by simple hydrothermal method and followed by sonication method. The structure, optical, surface area and morphological properties of the as synthesized photocatalyst were broadly investigated by UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Brunauer Emmet Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL) and fourier transform infrared (FT-IR) spectroscopy. The photocatalytic performance of the as-designed samples was studied based on the photodegradation of norfloxacin (NRF) under visible light irradiation. As compared, the photocatalytic activity of NiWO4@g-C3N4 nanocomposite higher than that of single phase of g-C3N4 and NiWO4. The optimal NRF degradation rate of the synthesized nanocomposite was reached at 0.0547, which is 3.59 times higher than that of g-C3N4. Based on the result, enhancement of photocatalytic activity was attributed to the efficient visible light absorption, large surface area and retard charge carriers separation. Hydroxyl radical ([rad]OH) and hole (h⁺) were played crucial role in the photocatalytic degradation process, it systematically explained by trapping experiments.
Inefficient visible light photocatalytic degradation of organic pollutants, such as acetaminophen (ACE) and triclosan (TS), is one of the main limiting factors for implementing cost‐effective metal oxide photocatalyst for large‐scale deployment. Here, a highly efficient CuO thin film photocatalyst is developed through rapid thermal annealing. The CuO thin film is decorated with Pd nanostructures for enhanced visible light degradation of ACE and TS. It is shown that compared to the as‐deposited thin CuO film photocatalyst, the rapid thermal assisted CuO photocatalyst can significantly enhance charge generation and separation efficiency through improvement of crystallinity and reduction of recombination centres. Furthermore, it is demonstrated that the incorporation of Pd nanostructures can considerably increase optical absorption, which further improve the photocatalytic performance through the enhancement of surface plasmon resonance. The CuO film with the 40 s of Pd sputtering (Pd40–CuO) shows the highest performance for photocatalytic degradation of both ACE and TS. The Pd40–CuO film shows good stability and does not show any considerable reduction in photocatalytic activity after five cycles. This indicates the high potential of Pd40–CuO for water and wastewater treatment on industrial scale.
A novel, economical and magnetically separable heterojunction photocatalyst Fe3O4/BiOBr stacked on reed straw biochar (Fe3O4/BiOBr/BC) with visible light response was successfully prepared via a facile modified one-step hydrolysis method for the first time. The target pollutant carbamazepine (CBZ) was used to further investigate the photocatalytic activity of Fe3O4/BiOBr/BC. Compared with BiOBr and Fe3O4/BiOBr, novel photocatalyst Fe3O4/BiOBr/BC owing to the introduction of biochar exhibited better photocatalytic activity (95.51%) of CBZ photodegradation even under 50 W energy-saving visible LED light irradiation. Additionally, effect of pH on CBZ photodegradation using Fe3O4/BiOBr/BC was insignificant meaning wider practical application. Besides, three common anions (Cl⁻, NO3⁻, SO4²⁻) and DOM existing in natural water exhibited beneficial or detrimental effects to some extent. Free radicals trapping experiments results illustrated high carbamazepine removal efficiency could be ascribed to superoxide radicals and hydroxyl radicals. The transformation intermediates of CBZ were determined by HRMS and the possible photodegradation pathways were proposed. Finally, good reusability and stability verified the excellent practicality and feasibility of Fe3O4/BiOBr/BC for removal of organic pollutants in aqueous.