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An efficient magnetic nanoadsorbent based on functionalized graphene oxide with gellan gum hydrogel embedded with MnFe layered double hydroxide for adsorption of Indigo carmine from water
Abstract
The primary objective of this investigation was to synthesize a novel antibacterial nanocomposite consisting of natural gellan gum (GG) hydrogel, MnFe LDH, GO, and Fe3O4 nanoparticle, which was developed to adsorb Indigo carmine (IC). The GG hydrogel/MnFe LDH/GO/Fe3O4 nanocomposite was characterized through different analytical, microscopic, and biological methods. The results of adsorption experiments reveal that 0.004 g of the nanocomposite can remove 98.38 % of IC from a solution with an initial concentration of 100 mg/L, within 1 h at room temperature and under acidic pH conditions. Moreover, the nanocomposite material effectively suppressed the in vitro growth of both E. coli and S. aureus strains, with inhibitory rates of 62.33 % and 53.82 %, respectively. The isotherm data obtained in this investigation were fitted by linear and non-linear forms of Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms equations. The results of the adsorption kinetics study indicated that the pseudo-second-order model best described the experimental data. The findings of this study suggest that the synthesized nanocomposites hold great potential as effective adsorbents for removing IC and bacteria from aqueous solutions.
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This study aimed to explore a test method for evaluating the effective cross-linking density of hydrogels. A guar gum–epichlorohydrin hydrogel (GEH) was prepared using guar gum (GG) as the raw material and epichlorohydrin (ECH) as the cross-linking agent. The thermal and mechanical properties, equilibrium swelling rate (ESR), water uptake (WU), and mass cross-linking degree of the hydrogels were assessed. Furthermore, the diffusion behavior of water molecules in the freeze-dried GEH was investigated. The experimental results showed the significance of the initial decomposition temperature (Ti) and final decomposition temperature (Tf) of the freeze-dried GEHs in determining the effective cross-linking density. The water uptake kinetics of the freeze-dried GEH was consistent with the linear fitting of the pseudo-second-order kinetic model and nonlinear fitting of the Fickian diffusion model, suggesting that chemisorption dominated the water absorption process in the GEH. Therefore, the effective cross-linking density of the hydrogels could be determined from the thermodynamic analysis and the diffusive behavior of water molecules in the gels. The thermal stability and water diffusion kinetics of the hydrogels were closely linked to the effective cross-linking density and pendant modification.
The increased discharge of water pollutants drives the development of new and effective wastewater remediation methods. Herein, a magnetic nanocomposite of chitosan-graphene oxide (GO) decorated with copper ferrite (MCSGO) was synthesized under ultrasound agitation and applied to the effective removal of Safranin O (SAF) and indigo carmine (IC) dyes from wastewater. The structural, magnetic, and physicochemical features of the as-prepared MCSGO nanocomposite have been thoroughly investigated using various characterization techniques. The operational parameters such as MCSGO mass, contact time, pH, and initial dye concentration were investigated. The effects of diverse coexisting species on both dye elimination processes were examined. The experimental results demonstrated that the adsorption capacity of MCSGO nanocomposite for IC and SAF was 112.6 and 66.15 mg g −1 , respectively. Five different adsorption isotherms were investigated using two-parameter (Langmuir, Tekman, and Freundlich) and three-parameter (Sips, and Redlich-Peterson) models. Thermodynamic studies revealed that the elimination of both dyes on MCSGO nanocomposite was endothermic and spontaneous, with anionic and cationic dye molecules randomly arranged onto the adsorbent nanoparticles. Moreover, the mechanism of dye elimination was deduced. Furthermore, even after five cycles of adsorption and desorption, the as-prepared nanocomposite showed no significant loss in the dye removal efficiency, indicating that it has superior stability and recycling potential.
As a novel functional nanomaterial, Fe3O4 magnetic nanoparticles (MNPs) modified by different surfactants have attracted and are attracting worldwide interest. In this research, we introduced two different silane coupling agents to modify Fe3O4 MNPs instead of a single surfactant to achieve complete coating and functionalization. The modification mechanism was also explained. Techniques such as TEM, XRD, FT-IR, TG-DSC, and VSM were applied to characterize the obtained modified Fe3O4 sample. From these techniques, the following information is obtained: The characteristic bands of TEOS and KH-792 were present in the FT-IR spectra and in the XPS plots of modified Fe3O4 MNPs, demonstrating that the silane coupling agents were present in the sample obtained after the modification. The TG analysis of the modified sample showed complete decomposition at 228°C. The mass ratio of the sample obtained before and after the modification was close to 29:65. The XRD patterns show that the modified Fe3O4 MNPs possessed an identical reverse spinel crystal structure as an unmodified Fe3O4 sample. The modification decreased the saturation magnetization of Fe3O4 MNPs from 70.04 emu/g to 57.41 emu/g and the coating did not change the superparamagnetism of Fe3O4 MNPs.
The β-carotene emulsion system using high-acyl gellan gum (HA) as an emulsifier was fabricated and systematically studied. The stability and stabilizing mechanism of the emulsion using medium-chain triglyceride as oil phase with a water-oil mass ratio of 9:1 under different physicochemical conditions of heat, pH, and ions were investigated by analyzing mean particle size (MPS), emulsion yield (EY), and dynamic stability. The effects of the HA-β-carotene emulsion system on the bioaccessibility of β-carotene in vitro were conducted. During the simulated oral digestion stage (SODP) and simulated gastric digestion stage (SGDP), the emulsion systems stabilized with different HA contents showed good stability, and the changes of MPS and zeta potential (ZP) were within 2.5 μm and 3.0 mV, respectively. After entering the simulated intestinal digestion phase (SIDP), β-carotene was released from oil droplets and formed micelles with bile salts, phospholipids, etc. HA-β-carotene emulsion can enhance the release rate of free fatty acid (FFA), which ultimately affects the β-carotene bioaccessibility. These results indicate that HA can be used to prepare carotene emulsion and improve its bioavailability. The study provides a reference for the application of HA as a natural emulsifier and the delivery of β-carotene.
Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties (e.g., stiffness, pore size, viscoelasticity, microarchitecture, degradability, ligand presentation, stimulus-responsive properties, etc.) and influence cell signaling cascades and fate. In the past few decades, a plethora of pioneering studies have been implemented to explore the cell–hydrogel matrix interactions and figure out the underlying mechanisms, paving the way to the lab-to-clinic translation of hydrogel-based therapies. In this review, we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely. Subsequently, the comprehensive description and deep discussion were elucidated, wherein the influences of different hydrogels properties on cell behaviors and cellular signaling events were highlighted. These behaviors or events included integrin clustering, focal adhesion (FA) complex accumulation and activation, cytoskeleton rearrangement, protein cyto-nuclei shuttling and activation (e.g., Yes-associated protein (YAP), catenin, etc.), cellular compartment reorganization, gene expression, and further cell biology modulation (e.g., spreading, migration, proliferation, lineage commitment, etc.). Based on them, current in vitro and in vivo hydrogel applications that mainly covered diseases models, various cell delivery protocols for tissue regeneration and disease therapy, smart drug carrier, bioimaging, biosensor, and conductive wearable/implantable biodevices, etc. were further summarized and discussed. More significantly, the clinical translation potential and trials of hydrogels were presented, accompanied with which the remaining challenges and future perspectives in this field were emphasized. Collectively, the comprehensive and deep insights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes, which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.
The need to minimize surfactant adsorption on rock surfaces has been a challenge for surfactant-based, chemical-enhanced oil recovery (cEOR) techniques. Modeling of adsorption experimental data is very useful in estimating the extent of adsorption and, hence, optimizing the process. This paper presents a mini-review of surfactant adsorption isotherms, focusing on theories of adsorption and the most frequently used adsorption isotherm models. Two-step and four-region adsorption theories are well-known, with the former representing adsorption in two steps, while the latter distinguishes four regions in the adsorption isotherm. Langmuir and Freundlich are two-parameter adsorption isotherms that are widely used in cEOR studies. The Langmuir isotherm is applied to monolayer adsorption on homogeneous sites, whereas the Freundlich isotherm suites are applied to multilayer adsorption on heterogeneous sites. Some more complex adsorption isotherms are also discussed in this paper, such as Redlich–Peterson and Sips isotherms, both involve three parameters. This paper will help select and apply a suitable adsorption isotherm to experimental data.
Hydrogels are attractive biomaterials with favorable characteristics due to their water uptake capacity. However, hydrogel properties are determined by the cross-linking degree and nature, the tacticity, and the crystallinity of the polymer. These biomaterials can be sorted out according to the internal structure and by their response to external factors. In this case, the internal interaction can be reversible when the internal chains are led by physicochemical interactions. These physical hydrogels can be synthesized through several techniques such as crystallization, amphiphilic copolymers, charge interactions, hydrogen bonds, stereo-complexing, and protein interactions. In contrast, the internal interaction can be irreversible through covalent cross-linking. Synthesized hydrogels by chemical interactions present a high cross-linking density and are employed using graft copolymerization, reactive functional groups, and enzymatic methods. Moreover, specific smart hydrogels have also been denoted by their external response, pH, temperature, electric, light, and enzyme. This review deeply details the type of hydrogel, either the internal structure or the external response. Furthermore, we detail some of the main applications of these hydrogels in the biomedicine field, such as drug delivery systems, scaffolds for tissue engineering, actuators, biosensors, and many other applications.
Layered double hydroxides (LDHs), shown as the general formula of [M2+1-xM3+x(OH)2]x+(An-)x/n∙yH2O, are useful for various applications such as anion exchangers/adsorbents, catalysts and catalysts' supports, and drug/gene carriers due to their structural, compositional and morphological characteristics and their variation. The x value (M3+/(M2+ + M3+) ratio) in layered double hydroxides (LDHs), corresponding to the layer charge density, is one of the important parameters for controlling the properties of LDHs. The x values in commonly available LDHs are limited (0.2 < x < 0.3). In order to obtain LDHs with x < 0.2, Mg2+ Ga3+-LDHs with interlayer iodide were examined. The linear correlation between lattice parameter a and x value in the products with x of 0.06-0.24 was seen, suggesting the successful substitution of Mg2+ in the brucite-like sheet with Ga3+. Carbonate and dodecyl sulfate types MgGa-LDH were prepared by ion exchange with carbonate anion and reconstruction in aqueous solution of sodium dodecyl sulfate. The products with x of 0.06 were dispersed in water and hexanol better than those with x of 0.24 for MgGa-LDHs containing carbonate and dodecyl sulfate, respectively, suggesting effects of the lower layer charge density on the dispersion.
A novel material named Fe/Mn-C layered double hydroxide composite (Fe/Mn-C-LDH) was synthesized to remove arsenic from an aqueous solution. The removal performance of the composite toward arsenic ions was studied through the batch experiments. The experiment results showed that Fe/Mn-C-LDH exhibited a high adsorption capacity of 46.47 mg/g for As(III) and 37.84 mg/g for As(V) at 318 K, respectively. In addition, the investigation of the release of Fe3+ and Mn2+ in the process of arsenic adsorption revealed that the Fe/Mn-C-LDH exhibited better stability than Fe/Mn-layer double hydroxide (Fe/Mn-LDH) with fewer Mn2+ and Fe3+ releasing under the same condition. The BET results showed that the specific surface area of Fe/Mn-C-LDH decreased after adsorption of As (III) and As (V). Furthermore, the Density Functional Theory (DFT) calculation results proved that the adsorbent combining arsenic by T-site to produce a better adsorption effect for arsenic. Possessing better stability and adsorption capacity, Fe/Mn-C-LDH could potentially serve as a perfect adsorbent for arsenic removal from an aqueous environment. It would provide a promising approach for removing heavy metal from the aquatic environment in the future.
A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditions (pH 3). The sorption isotherms revealed that the sorption followed a monolayer/homogenous behavior. The sorption kinetic data were well fitted by the pseudo-second-order kinetic model, and were consistent with those derived from sorption isotherms. The intraparticle diffusion was considered to be the rate-determining step. Two main sorption mechanisms for Zn (II) were identified namely, ion exchange at low pH values, and both ion exchange and chemisorption in weekly acidic conditions.
p>The use of the c hicken eggshell with its membrane as low-cost adsorbent had been done to the removal of synthetic dyes in aqueous solution. Adsorption method in the batch system was done to adsorb Methylene Blue and Indigo Carmine as the cationic and anionic dyes. Some parameters were studied such as pH, contact time, initial concentration of dyes and mass of ES+M to find the optimum adsorption. The functional group of ES+M like hydroxyl, amine, carboxyl and thiol were used to binding the dyes. The characteristics of ES+M were determined by FTIR and XRF to analyzed functional group and elements composition before and after adsorption. The adsorption capacity optimum of ES+M to adsorb Methylene Blue was 11.54 mg/g with % RE 92.34 % in 30 minutes, and Indigo Carmine was 8.04 mg/g with % RE 64.34 % in 15 minutes.</p
Mesoporous magnesium oxide–graphene oxide composite (MGC) has been synthesized using a facile post-immobilization method by mixing pre-synthesized magnesium oxide (MgO) with graphene oxide (GO). MgO used for fabrication of the composite has been synthesized using an environment-friendly method involving gelatin as a template. XRD, Raman and EDX analyses have confirmed the presence of MgO and GO in the composite. FTIR and SEM analyses of synthesized MGC have further elucidated the surface functionalities and morphology, respectively. Using N2 adsorption–desorption isotherm, BET surface area of MGC has been calculated to be 55.9 m² g⁻¹ and BJH analysis confirmed the mesoporous nature of MGC. The application of synthesized MGC as a selective adsorbent for various toxic anionic dyes has been explored. Batch adsorption studies have been carried out to investigate the influence of different adsorption parameters on the adsorption of two anionic dyes: indigo carmine (IC) and orange G (OG). The maximum adsorption capacities exhibited by MGC for IC and OG are 252.4 and 24.5 mg g⁻¹, respectively. Plausible mechanism of dye adsorption has been explained in detail using FTIR analysis. In a mixture of cationic and anionic dyes, MGC selectively adsorbs anionic dyes with high separation factors, while in binary mixtures of anionic dyes, both dyes are adsorbed efficiently. Thus, MGC has been shown to be a potential adsorbent for the selective removal of anionic dyes from wastewater.
By means of in situ melt polycondensation of polyethylenterephathalate accompanied with simultaneous reduction of introduced graphene oxide, the composite of polyethylenterephathalate filled with reduced graphene oxide was prepared. Melting and crystallization of the reduced graphene oxide – polyethyleneterephthalate composite was studied by the differential scanning calorimetry method, and the rheological test was carried out by rotational rheometry and compared to the pristine polyethylenterephathalate. The morphology of the reduced graphene oxide – polyethyleneterephthalate composite was studied using optical microscopy. The reduced graphene oxide was isolated from the reduced graphene oxide – polyethyleneterephthalate composite and characterized by thermogravimetry, X-ray photoelectron spectroscopy and X-Ray diffraction methods. Since a part of polymer could not be removed from reduced graphene oxide particles by trifluoroacetic acid, the hypothesis about probable grafting of polyethyleneterephthalate on reduced graphene oxide sheets was suggested. Rheological behaviour of the reduced graphene oxide – polyethyleneterephthalate composite melt confirms this suggestion. According to the calculations based on thermogravimetry, the reduced graphene oxide, isolated from the reduced graphene oxide – polyethyleneterephthalate composite, consists of about 80% polyethyleneterephthalate.
2D conductive nanosheets are central to electronic applications because of their large surface areas and excellent electronic properties. However, tuning the multifunctions and hydrophilicity of conductive nanosheets are still challenging. Herein, a green strategy is developed for fabricating conductive, redox‐active, water‐soluble nanosheets via the self‐assembly of poly(3,4‐ethylenedioxythiophene) (PEDOT) on the polydopamine‐reduced and sulfonated graphene oxide (PSGO) template. The conductivity and hydrophilicity of nanosheets are highly improved by PSGO. The nanosheets are redox active due to the abundant catechol groups and can be used as versatile nanofillers in developing conductive and adhesive hydrogels. The nanosheets create a mussel‐inspired redox environment inside the hydrogel networks and endow the hydrogel with long‐term and repeatable adhesiveness. This hydrogel is biocompatible and can be implanted for biosignals detection in vivo. This mussel‐inspired strategy for assembling 2D nanosheets can be adapted for producing diverse multifunctional nanomaterials, with various potential applications in bioelectronics. Inspired by redox reactions in nature, a green and cost‐effective strategy is developed for designing hydrophilic, conductive, and redox‐active sandwich‐like 2D nanosheets via the self‐assembly of poly(3,4‐ethylenedioxythiophene) (PEDOT) on a functional graphene oxide (PSGO) template. The 2D nanosheet can be used as a versatile nanofiller in the development of a conductive and adhesive hydrogel for bioelectronic applications.
The rapid development of electrochemical energy storage (EES) systems requires novel electrode materials with high performance. A typical 2D nanomaterial, layered transition metal dichalcogenides (TMDs) are regarded as promising materials used for EES systems due to their large specific surface areas and layer structures benefiting fast ion transport. The typical methods for the preparation of TMDs and TMD‐based nanohybrids are first summarized. Then, in order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium‐ion batteries, lithium–sulfur batteries, sodium‐ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD‐based electrode materials are discussed. Furthermore, the applications of layered TMD‐based nanomaterials in supercapacitors, especially in untraditional supercapacitors, are presented. Finally, the existing challenges and promising future research directions in this field are proposed.
With the rapid growth of industrialization, water bodies are polluted with heavy metals and toxic pollutants. In pursuit of removal of toxic pollutants from the aqueous environment, researchers have been developed many techniques. Among these techniques, magnetic separation has caught research attention, as this approach has shown excellent performance in the removal of toxic pollutants from aqueous solutions. However, magnetic graphene oxide based nanocomposites (MGO) possess unique physicochemical properties including excellent magnetic characteristics, high specific surface area, surface active sites, high chemical stability, tunable shape and size, and the ease with which they can be modified or functionalized. As results of their multi-functional properties, affordability, and magnetic separation capability, MGO's have been widely used in the removal of heavy metals, radionuclides and organic dyes from the aqueous environment, and are currently attracting much attention. This paper provides insights into preparation strategies and approaches of MGO's utilization for the removal of pollutants for sustainable water purification. It also reviews the preparation of magnetic graphene oxide nanocomposites and primary characterization instruments required for the evaluation of structural, chemical and physical functionalities of synthesized magnetic graphene oxide nanocomposites. Finally, we summarized some research challenges to accelerate the synthesized MGO's as adsorbents for the treatment of water pollutants such as toxic and radioactive metal ions and organic and agricultural pollutants.
This research work undertook a comparative study of the promoting effects of graphene in TiO 2 photoanodes. The aim of this work was to investigate the effects of the types and concentration of reduced graphene oxides (rGO) on structure properties and the photovoltaic performance of TiO 2 based electrodes. Graphene oxide (GO) was prepared by using modified Hammer’s method. Next, GO was reduced by using two different approaches, which were the chemical reduction with vitamin C and thermal reduction. The latter approach was also carried out in situ during the fabrication and heat treatment processes of the dye-sensitized solar cells (DSSCs). From the results, it was found that the photovoltaic performance of the DSSCs containing the GO/TiO 2 electrode, in which the GO phase experienced an in situ thermal reduction, was superior to those containing rGO/TiO 2 . It was also found that the power conversion efficiency of the DSSCs changed with the concentration of graphene in a nonlinear fashion. The optimum concentrations of graphene, corresponding to the highest PCE values of the GO/TiO 2 based DSSC (3.69%) and that of the rGO/TiO 2 based cell (2.90%), were 0.01 wt% and 0.03 wt%, respectively.
Graphene oxide/polyaniline/manganese oxide ternary nanocomposites (GO/PANI/Mn2O3) have been successfully synthesized in one-pot method by in situ chemical oxidative polymerization of aniline in acidic medium using MnO2 as an oxidant. The obtaining nanocomposites have been characterized by transmission electron microscope, Fourier transform infrared, X-ray powder diffraction, and thermogravimetric analysis. The adsorption isotherms of indigo carmine (IC) onto; PANI, GO/PANI, PANI/MnO2, and GO/PANI/Mn2O3 have been evaluated under different adsorption conditions. The adsorption isotherm models of Langmuir, Freundlich, and Temkin were applied and the fit linear was obtained with Langmuir model. It was found that adsorption capacities followed the order: GO/PANI > GO/PANI/Mn2O3 > PANI > PANI/MnO2 with the values of 88.73, 76.40, 60.45 and 22.52 mg/g. Moreover, the kinetics of the adsorption process was investigated and fit linear was obtained with pseudo-second-order model. The adsorption process was exothermic and spontaneous as revealed from the thermodynamic studies.
In this work, we synthesized graphene oxide–glycine (GO–G) nanocomposite. To produce this nanocomposite with GO surface, glycine with known concentration was added
to GO suspension in
ethanol solvent. Nanocomposites provided were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. Thermogravimetric analysis (TGA) was employed to investigate the thermal stability of these nanocomposites. Results of characterization by SEM and FT-IR showed that nanocomposite was created by the reaction between GO and G. Study of thermal stability by TGA showed that thermal stability of GO was more than that of the GO–G nanocomposite.
Novel-morphological Fe3O4 nanosheets with magnetochromatic property have been prepared by a modified solvothermal method. Such nanosheets could form one-dimension photonic crystal under an external magnetic field. The Fe3O4 nanosheets suspension could strongly diffract visible light and display varied colors with changing the intensity of the magnetic field. The photonic response is rapid, fully reversible and widely tunable in the entire visible spectrum. Excellent magnetic properties of these Fe3O4 nanosheets are exhibited with a high saturation magnetization (82.1 emu/g), low remanence (13.85 emu/g) and low coercive force (75.95 Oe). The amount of the solvent diethylene glycol (DEG) plays a key role in the formation of the sheet-shaped morphology. When the ratio of the DEG reaches 100%, the growing of the crystal plane (111) of Fe3O4 is inhibited and the sheet-like Fe3O4 crystals are formed.
A novel biopolymer-based semi interpenetratin network (IPN) superabsorbent polymer (SAP) hydrogel was synthesized through chemical crosslinking by graft copolymerization of 2-hydroxy ethyl methacrylate (HEMA) and acrylic acid on to starch in presence of gum arabic, N,N'-methylene-bis-acrylamide (MBA) as crosslinker and benzoyl peroxide (BPO) as initiator. The structures of the copolymers were confirmed by FTIR. Morphological examination of SAP by SEM confirms the macro porous nature of the copolymer. The high char yield, up to 12.5wt%, at 600 ºC observed in thermogram indicates the thermal stability of the SAP. Because of its super absorbency, pH sensitivity, good swelling and re swelling ability, it can be concluded that the prepared polymer system may be useful in extending the delivery of entrapped drug in the form of formulations for predetermined period of time, in future.
Fe 3 O 4 nanoparticles and non aqueous stable magnetic fluid (MF) containing Fe 3 O 4 nanoparticles with mean diameters of 10 nm, which are in the range of super-paramagnetism, are prepared. Magnetite nanoparticles are synthesized via co-precipitation method from ferrous and ferric solutions. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) are used to study the physical properties of the (MF) and powder. The band gap parameters of the magneto-nanopowders such as the direct, indirect-band gap energies, Fermi energy and Urbach energy are determined.
Conductive hydrogels have emerged as promising materials for flexible electronics due to their integrated conductivity and mechanical flexibility. However, they turn to rigid and poorly conductive at subzero temperature because of inevitable water freezing. Besides, they also suffer from poor water retention ability and cannot self-regenerate to their original state after dehydration. Herein, a novel ionic conductive poly (sulfobetaine-co-acrylic acid) hydrogel possessing antifreezing, water retention and self-regeneration abilities was developed by introducing a highly hydratable salt-lithium chloride. The hydrogel could endure ultralow temperature (-80 ℃) over 30 days without freezing and retain ∼100% of its initial water content after storage at ambient temperature (25 ℃, 54% humidity) for one week. Moreover, after vacuum drying, the dehydrated hydrogel could self-regenerate by spontaneously harvesting water molecules from surrounding environments even at -40 ℃, which had not been achieved by previously reported conductive hydrogels. These properties enabled the hydrogel with a wide working temperature range and extended lifespan for the development of more advanced and sustainable flexible electronics.
The development of functional hydrogel materials for applications in catalysis has attracted great research interest, especially in aqueous phase catalysis. However, preparation of new structural hydrogel catalysts with enhanced catalytic activity still remains a challenge. In this study, a series of Pd nanoparticles (PdNPs) doped chitosan (CS)-based composite hydrogels were successfully prepared by adding graphene oxide (GO), carbon nanotubes (CNTs) and layered double hydrotalcites (LDHs) to CS hydrogel with glutaraldehyde as a cross-linking agent and in situ growing PdNPs. The structure and morphology analysis indicated that chitosan-based composite hydrogels could be used as carriers to load PdNPs and effectively prevent the agglomeration of PdNPs. Subsequently, 4-nitrophenol (4-NP) catalytic reaction was used as a typical model to evaluate catalytic performances of chitosan (CS)-based composite hydrogel catalysts. The obtained chitosan-based composite hydrogel catalysts exhibited better catalytic activity than that of PdNPs doped CS hydrogel catalyst (CS-PdNPs) and reusability for the reduction of 4-nitrophenol in water. The catalytic process conformed to the pseudo-first-order kinetic equation. Moreover, chitosan-based composite hydrogel catalysts containing CNTs had the best catalytic performance since the particle size of PdNPs was the smallest among three kinds of chitosan-based composite hydrogel catalysts. This work provides new ideas for the preparation of stable and efficient precious metal nanoparticle catalysts for applications in aqueous phase catalysis.
Graphene oxide/locust bean gum (GO/LBG) aerogels, synthesized in an ice crystal template without using any chemical modifiers, were used for the treatment of water pollution. Various characterization results showed that GO/LBG aerogel exhibited a network-like three-dimensional (3D) structure with large specific surface area. The adsorption data revealed that GO/LBG aerogels with GO/LBG mass ratio of 1:4 (GO/LBG-1 aerogels) exhibited more prominent adsorption properties for Rhodamine-B (RhB, 514.5 mgg⁻¹) than Indigo Carmine (IC, 134.6 mgg⁻¹). Simultaneously, GO/LBG-1 aerogels could selectively remove RhB from a binary mixed solution of RhB-IC dyes. Furthermore, GO/LBG-1 aerogels also displayed excellent reusability and could still reach 92.4 % after ten cycles. Based on the above results, GO/LBG-1 aerogel could be considered as an ideal adsorbent with potential application value for removing water-soluble RhB from wastewater.
Clean water is not only essential for drinking but it also important for other activities of living beings. Unfortunately, two‐third of the world population largely in India and China faces severe water scarcity. The economic burden of contaminated and impure water is much higher than the required cost of safe drinking water across the globe. Various techniques have been developed to achieve the goal of safe drinking water. Nanotechnology holds great potential for improving the efficiency of water purification and decontamination. The effectiveness of nanomaterials for the removal of heavy metals, organic and inorganic pollutants from water and for killing microorganisms in the wastewater has been established. Therefore, they can be used for the purification of ground water, surface water, and wastewater. This chapter focuses mainly on purification of drinking water using nanomaterials. Nanocomposites have also been developed to overcome some of the demerits of nanoparticles for the scaled‐up application. It is expected that the use of nanomaterials for water purification at large‐scale may soon become a reality if some inherent bottlenecks including aggregation of nanoparticles, leakage into drinking water and subsequent environmental outcomes are satisfactorily addressed. Strong legal framework regulating wise utilization of the nanomaterials is also required.
Recently, antibiotic resistance of pathogens has grown given the excessive and inappropriate usage of common antimicrobial agents. Hence, producing novel antimicrobial compounds is a necessity. Carbon nanomaterials (CNMs) such as carbon nanotubes, graphene/graphene oxide, and fullerenes, as an emerging class of novel materials, can exhibit a considerable antimicrobial activity, especially in the nanocomposite forms suitable for different fields including biomedical and food applications. These nanomaterials have attracted a great deal of interest due to their broad efficiency and novel features. The most important factor affecting the antimicrobial activity of CNMs is their size. Smaller particles with a higher surface to volume ratio can easily attach onto the microbial cells and affect their cell membrane integrity, metabolic procedures, and structural components. As these unique characteristics are found in CNMs, a wide range of possibilities have raised in terms of antimicrobial applications. This study aims to cover the antimicrobial activities of CNMs (both as individual forms and in nanocomposites) and comprehensively explain their mechanisms of action. The results of this review will present a broad perspective, summarizes the most remarkable findings, and provides an outlook regarding the antimicrobial properties of CNMs and their potential applications.
This paper gives a comprehensive review of the recent progress on electrochemical energy storage devices using graphene oxide (GO). GO, a single sheet of graphite oxide, is a functionalised graphene, carrying many oxygen-containing groups. This endows GO with various unique features for versatile applications in batteries, capacitors and fuel cells. Specific applications are considered principally including use in electrodes as the active materials to enhance the performance or as substrates to diversify the structures, in solid-state electrolytes and membranes to improve the ionic conductivity and mechanical properties, and in interlayers to protect the electrodes, membranes or current collectors. Furthermore, the challenges and future prospects are discussed in the paper for encouraging further research and development of GO applications.
Graphene oxide, silver and copper oxide nanoparticles display photoactivated antibacterial behavior owing to their ability to generate charge carriers via light exposure. In this work, silver nanoparticles (AgNPs) and copper oxide nanoparticles (CuONPs) were embedded through graphene oxide (GO) using laser ablation technique. The microstructural behavior of the synthesized compositions has been investigated via XRD and TEM. The optical properties were studied by (UV–Vis), while the antibacterial properties were investigated in addition to the cell viability towards normal cell line (HFB4) in vitro. The antibacterial activity of GO was enhanced significantly with addition nanoparticles; by meaning, the inhibition zone enlarged from 5.4 mm with pure GO to be around 11.2 mm against E. coli with contribution of CuONPs. This trend of enhancement suggests that GO could be a great platform for different kinds of photo-activated antibacterial to be recommended for versatile biomedical applications.
Adsorption to date is the most effective and utilized technology globally to remove several pollutants in wastewater. In this approach, many adsorbents have been synthesized, tested and used for the elimination and separation of the contaminants such as radionuclides, heavy metals, dyes and pharmaceutical compounds both at lab and industrial scale. However, there are many challenges to adsorption processes such as reducing the high cost, through means of separation of suspending adsorbents to be used again, as well as the ease to synthesize. Two methods that have shown promising results and gained significant interest is that of magnetic nanomaterials and biosorbents due to their effective, safe, eco-friendly, low cost and low-energy intensive material properties. Magnetic nanomaterials act as efficient adsorbents due to their ease of removal of contaminants from wastewater using an applied magnetic field but also their advantageous surface charge and redox activity characteristics. On the other hand, biosorbents have a synergistic effect with their efficient adsorption capacity to remove contaminants, high abundance and participation in waste minimization, helping alleviate ecological and environmental problems. This review highlights, discusses and reports on the state-of-the-art of these two promising routes to adsorp-tion and provides indications as to what are the optimum materials for utilization and insight into their efficiency, reusability and practicality for the removal of pollutants from wastewater streams. Some of the main material focuses are zero-valent iron, iron oxides, spinel ferrites, natural and waste-based biosorbents.
Nuclear medicine imaging has been developed as a powerful diagnostic approach for cancers by detecting gamma rays directly or indirectly from radionuclides to construct images with beneficial characteristics of high sensitivity, infinite penetration depth and quantitative capability. Current nuclear medicine imaging modalities mainly include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that require administration of radioactive tracers. In recent years, a vast number of radioactive tracers have been designed and constructed to improve nuclear medicine imaging performance toward early and accurate diagnosis of cancers. This review will discuss recent progress of nuclear medicine imaging tracers and associated biomedical imaging applications. Radiolabeling nanomaterials for rational development of tracers will be comprehensively reviewed with highlights on radiolabeling approaches (surface coupling, inner incorporation and interface engineering), providing profound understanding on radiolabeling chemistry and the associated imaging functionalities. The applications of radiolabeled nanomaterials in nuclear medicine imaging-related multimodality imaging will also be summarized with typical paradigms described. Finally, key challenges and new directions for future research will be discussed to guide further advancement and practical use of radiolabeled nanomaterials for imaging of cancers.
Graphene oxide (GO), which have many different oxygen-having groups (hydroxyl, carboxyl) is a tremendous graphene derivative and two dimensional carbon molecule. It was believed as a superb catalyst support and promoter for its large specific surface, carrier mobility and high optical transmittance. Explorers across multiple disciplines were paid huge concentration to it owing to the unique physiochemical characteristics. In this review, hybrids of graphene oxide and semiconductors promise photocatalysts owing to their flexible properties and the large number of synthesis variables obtainable for modifications. Recent developments were confirmed that the GO supported semiconductors based photocatalysts can be predictable as the most privileged and hopeful novel photocatalysts in the photocatalytic applications. Furthermore, we were discussed important progresses in an efficient GO supported semiconductors based nanocomposites, including the common preparation approaches and development mechanisms, as well as their recent applications such as, removal of contaminates, H2 evolution and CO2 reduction. This significant review ends with an outline and some perceptions on the challenges and new instructions in investigating GO supported semiconductors based photocatalysts. It is also believed that this review will encourage further exploration and will inaugurate new possibilities to increase new hybrid GO based semiconductors photocatalysts with new and inspiring applications.
The Hummers' method, in which concentrated sulfuric acid (H2SO4) acts as the intercalator and potassium permanganate serves as the oxidant, is a commonly used method to prepare graphene oxide (GO). The amounts of intercalator and oxidant along with the particle size of graphite are important factors that affect the structure and properties of GO. In this study, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, thermogravimetric analysis, and atomic force microscopy were used to characterize the effects of these factors on the structure and properties of GO. The results show that the amount of intercalator and oxidant clearly affect the types of oxygen-containing functional groups in the GO structure along with the oxidation degree of GO. Increasing the dosages of intercalator and oxidant can improve the oxidation degree of GO, facilitating the preparation of typical GO. Sodium nitrate (NaNO3) has a synergistic effect with H2SO4 during the process of graphite oxidation, which is helpful for the intercalation and oxidation of graphite. Increasing the oxidation degree of graphite can increase the interlayer spacing, which is conducive to the exfoliation of GO. However, the use of excessive NaNO3 is not conducive to improving GO oxidation. The effect of graphite particle size on GO interlayer spacing is greater than that of NaNO3. The obtained results provide a reference for the preparation of GO with controllable structure.
Overpopulation day by day promotes industrial revolution, and manufacturing processes have become more efficient and productive, science has become much more advanced, and our life has changed a great deal. For water pollution and scarcity, many sources are responsible such as industrial wastewater, domestic sewage, storm water runoff, septic tanks water and agricultural practices. Out of which, industries play a key role and also release various toxic chemicals, organic and inorganic matters or sludge, radioactive sludge, sulphur, asbestos, poisonous solvents, polychlorinated biphenyl, lead, mercury, nitrates, phosphates, acids, alkalies, dyes, pesticides, benzene, chlorobenzene, carbon tetrachloride, toluene and volatile organic chemicals. These wastes when discharged into the water ecosystem without adequate treatment become very unhealthy for any type of human and other use. The industrial wastewater is responsible for many diseases such as anaemia, low blood platelets, headaches, risk for cancer, many skin diseases, etc. To prevent such type of issues, effective treatment technology, adequate treatment, water reuse, desalination, infrastructure repair and maintenance, water conservation and also strict pollution control law and legislation and their proper implementation do play an important role.
Pectin is one of the finest natural polymer which has drawn great attention because of its applications in different fields. Due to the quintessential structure of pectin, it can be transformed into variety of useful products. It can be utilized as a blend in many polymers to make a mixture or a composite material. Owing to considerable collection in chemical conformation and cross-linking mechanism, different pectin based hydrogels have been prepared for different characteristics in pharmaceutical and bio-medical sites. Inventive properties of hydrogels like volubility, swellability, solvability and hydrophilicity make them better alternative for wastewater treatment. Recently, pectin based hydrogels have demonstrated excellent performance to eliminate various metal ions and dyes from the polluted water. The adsorption characteristics of pectin based hydrogels can be upgraded by using nanoparticles, which prompts to the development of hydrogel nano-composites. In this review article, we have summarized a comprehensive assessment in the direction of using pectin based hydrogels to remove toxic pollutants from aqueous solution. Sodium acrylate-co-N-isopropylacrylamide based pectin hydrogel has demonstrated the maximum adsorption capacities of 265.49, 137.43, 54.86, 53.86, 51.72 and 50.01 mg g ⁻¹ for the adsorption of methyl violet, methylene blue, Pb(II), Cu(II), Co(II) and Zn(II) respectively. We have also discussed the pectin structure, properties and applications in this article.
Graphene, graphene oxide (GO), and their composites have been prominently utilized for wastewater purification because of their adsorption, oxidation, and catalytic properties. Graphene and GO and its composites naturally have significant pore volume, high conductivity, rich surface chemistry, and an exceptionally large aspect ratio which make it favorable for adsorption and catalysis of organic pollutants from wastewater. The sheet-like, resonating, polyaromatic π-system of graphene subsidiaries play a significant role in π-π interactions, hydrogen bonding, and/or electrostatic interactions with organic pollutants that include dyes, pharmaceutical waste, and agricultural and industrial effluents whose base structure consists of notably reactive unsaturated aromatic rings and oxygen-rich functional groups. The adsorption capacities of pollutants have been widely researched and catalogued by considering the adsorption isotherm (Langmuir, Freundlich, Temkin, DR model) they fit, the kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion) they follow, the parameters that affect the process (pH, temperature, etc.) and the reusability of the adsorbent. The photocatalytic efficiency has been anthologized with the viewpoint of the radicals being involved in photocatalysis and the light source used for the process. This review focuses on adsorption, advanced oxidation, and catalysis of various emerging organic pollutants using graphene subsidiaries, graphene-based composites, and hybrids; proves their efficacy as multifunctional materials for the expulsion of toxic aqueous phase pollutants; and presents new prospects for designing advanced water treatment strategies.
On account of high oxidation ability of sulfate radical-based advanced oxidation processes (AOPs), the eco-friendly catalysts for peroxymonosulfate (PMS) activation have received considerable attentions. Previous studies mainly focused on Cobalt-based catalyst due to its high activation efficiency, such as Co3O4/MnO2 and FeCo-layered double hydroxide (LDH), whereas Cobalt-based catalyst usually has serious risk to environment. To avoid this risk, MnFe-LDH was primarily synthesized in this research by simple co-precipitation and subsequently utilized as an effective catalyst for peroxymonosulfate (PMS) activation to degrade organic pollutants. The experimental results demonstrated that MnFe-LDH with a lower dosage (0.20 g/L) could efficiently activate PMS to achieve 97.56% removal of target organic pollutants Acid Orange 7 (AO7). The AO7 degradation process followed the pseudo-first-order kinetic well with an activation energy of 21.32 kJ/mol. The intrinsic influencing mechanism was also investigated. The quenching experiment and electron spin resonance (ESR) indicated that sulfate and hydroxyl radicals were produced by the effective activation of PMS by MnFe-LDH, resulting in a high rate of decolorization. The possible AO7 removal pathway in the constructed MnFe-LDH/PMS system was presented on the basis of UV–vis spectrum analysis and GC–MS, which suggested that the AO7 degradation was firstly initiated by breaking azo linkages, then generated phenyl and naphthalene intermediates and finally presented as ring-opening products. This effective MnFe-LDH/PMS system showed great application potential in the purification of wastewater contaminated by refractory organic pollutants.
GOx/Fe3O4/TiO2 on natural kissiris support was produced by consecutive preparation of TiO2/kissiris and Fe3O4/TiO2/kissiris followed by immobilization of Glucose Oxidize (GOx). This magnetic biocatalyst was used for continuous elimination of Malachite Green (MG) from aqueous solution in a packed bed reactor through bio-Fenton reaction. The biocatalyst was characterized by FT-IR, EDX and SEM analyses. Residence time distribution (RTD) of MG in the reactor was measured and parameters of the Langmuir-Hinshelwood kinetics model were obtained for the decolorization process. Hydrodynamics of the packed bed reactor were investigated via a thorough computational fluid dynamics (CFD) simulation using Eulerian approach in axisymmetric space and results were validated using experimental RTD curves and decolorization efficiencies. Ultimately, process simulation was utilized to obtain design parameters of the packed bed reactor in recirculating mode with 99.1% decolorization efficiency. The knowledge obtained through this study can be used to design and scale-up continuous and efficient bioreactors for treatment of wastewater.
With increasing urbanization and advancement of science, researches in nanotechnology and nanomaterial development are experiencing unprecedented expansion. Nanoparticle pollution is considered to be the most difficult pollution being managed and controlled. This chapter briefly describes the different types of water pollutants with a more detailed discussion on nanoparticle pollution. The chapter also gives an effort to visualize the challenges associated with dealing with nanoparticle waste. © Springer International Publishing AG, part of Springer Nature 2018.
Novel gellan gum incorporated TiO2 nanotubes (GG+TiO2-NT) film was successfully fabricated using solvent casting method for skin tissue engineering. The physicochemical properties of the film was investigated by FTIR, XRD and SEM. FTIR studies show the existence of interactions between TiO2 nanotubes and GG polymer matrix. XRD analysis revealed that the film was in amorphous state and the presence of TiO2 nanotubes on the surface of film was proved by SEM images. Cell proliferation studies demonstrated that, no sign of toxicity and the number of cells were found to be increased, thus exhibiting an ideal characteristic in skin tissue engineering applications.
Cellulose nanowhiskers (CNWs, 90% crystalline) were used to enhance the adsorption capacity of chitosan-g-poly(acrylic acid) hydrogel. The composites up to 20 w/w-% CNWs showed improved adsorption capacity towards methylene blue (MB) as compared to the pristine hydrogel. At 5 w/w-% CNWs the composite presented the highest adsorption capacity (1968 mg/g). The maximum removal of MB (>98% of initial concentration 2000 mg/L) was achieved quickly (60 min) at room temperature, pH 6, and at low ionic strength (0.1 M). Adsorption mechanism was explained with the Langmuir type I model suggesting the formation of a MB monolayer on the adsorbent surface. The interaction between the adsorbent and MB molecules was explained by chemisorption, as suggested by the pseudo-second-order kinetic model. Desorption experiments showed that 75% of loaded-MB could be recovered from the adsorbent by its immersion in a pH 1 solution. Additional experiments showed the post-utilized composite could be regenerated and reused for at least 5 consecutive adsorption/desorption cycles with minimum efficiency loss (∼2%).
A new approach for removal of indigo carmine blue (IC) dye which is extensively used in jeans manufacture was successfully performed on novel mesoporous [LDH] nanoparticles prepared by sol-gel route using CTAB as shape and pore directing agent. The physicochemical features were monitored by X-ray diffraction (XRD), Fourier transformer infra-red (FTIR), N2 adsorption-desorption isotherm, Field emission electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). The influence of reaction parameters affecting dye adsorption including contact time, initial dye concentration, pH and temperature were investigated. Textural analysis and HRTEM images indicate the existence of mesoporous spherical nanoparticles of size = 26 nm connected to each other's and embedded large numbers of mesopores of average pore radius = 43.5 Å. A successful adsorption of IC on LDH nanoparticles of surface area = 85.6 m(2)/g at various pH with maximum adsorption capacity = 62.8 mg/g at pH = 9.5. Langmuir model is more favorable to describe the adsorption of IC rather than Freundlich model which reflecting the preferential formation of monolayer on the surface of LDH. Both film diffusion and the intraparticle diffusion affect the dye adsorption. The values of enthalpy change (ΔH) for and (ΔS) are + 28.18 and + 0.118 kJ/mol, respectively indicating that the removal process is endothermic. The results indicated that LDH nanoparticles conserved a good activity even after five consecutive cycles of reuse. Our results suggest that mesoporous LDH nanoparticles are considered a potential novel adsorbent for remediation of wastewater containing IC.
A new hazardous azocoumarin dye has been synthesized and characterized using different spectroscopic techniques. The adsorption of hazardous azocoumarin dye onto low cost rice straw based carbons (RSC) was investigated in an aqueous solution in a batch system with respect to initial dye concentration, contact time, solution pH and temperature. Surface modification of rice straw using scanning electron microscopy (SEM) was obtained. The surface area and pore volume of RSC were determined by nitrogen adsorption/desorption experiments at 77 K and found to be 67.4 m2 g− 1 and 0.134 cm3 g− 1, respectively. Experimental data indicated that the adsorption capacity of RSC for azocoumarin dye was higher in acidic rather than in basic solutions. Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The activation energy of adsorption was also evaluated and found to be + 15.56 kJ mol− 1 indicating that the adsorption is physisorption. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The dynamic data fitted the pseudo-second-order kinetic model well. The thermodynamics of the adsorption indicated spontaneous and exothermic nature of the process. The results indicate that RSC could be employed as low-cost material for the removal of acid dyes from an aqueous solution.
Advances in nanoscale science and engineering suggest that many of the current problems involving water quality could be resolved or greatly ameliorated using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes and nanoparticle enhanced filtration among other products and processes resulting from the development of nanotechnology. Innovations in the development of novel technologies to desalinate water are among the most exciting and promising. Additionally, nanotechnology-derived products that reduce the concentrations of toxic compounds to sub-ppb levels can assist in the attainment of water quality standards and health advisories. This article gives an overview of the use of nanomaterials in water purification. We highlight recent advances on the development of novel nanoscale materials and processes for treatment of surface water, groundwater and industrial wastewater contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses. In addition, we discuss some challenges associated with the development of cost effective and environmentally acceptable functional nanomaterials for water purification.
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