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![FIGURE 3. Degradation pathway of dichlorvos. [35]](profile/Paramjeet-Sidhu/publication/254216551/figure/fig1/AS:348296448102405@1460051754313/Degradation-pathway-of-dichlorvos-35_Q320.jpg)
This review is an attempt to summarize the research carried out on heterogeneous photocatalytic treatment of selected organophosphates present invariably in shallow and ground water supplies. The basic principle of semiconductor mediated photocatalytic process, experimental conditions used, optimization of the parameters affecting the efficiency an...
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Context 1
... pesticides are synthetic compounds and are usually esters, amides, or thiol derivatives of phosphoric, phosphonic, phosphorothioic, or phosphonothioic acids. The classification of organophosphate pesticides on the basis of their structure is shown in Table 1 and the physicochemical characteristics of the pesticides which provides the information about the persistence and fate of organophosphate pesticides in the environment are reported in Table 2. [10,67] 3. HETEROGENEOUS PHOTOCATALYSIS ...
Context 2
... pesticides, having four oxygen atoms attached to the phospho- rus atom of the compound as shown in Table 1, are reviewed in this paper include chlorfenvinphos, dichlorvos, mevinphos, monocrotophos, and tetra- chlorvinphos. Chemical structures and formula weights of these compounds are shown in Figure 2. ...
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Citations
... With the increase of OPE emissions in water, many studies have focused on the harm in recent years [13,14]. Although triphosphate compounds had not been found to be bioaccumulative, certain monoesters and diesters of their degradation intermediates had been found to be endocrine disrupting and neurotoxic [15,16]. ...
As a substitute for banned brominated flame retardants (BFRs), the use of organophosphate esters (OPEs) increased year by year with the increase in industrial production and living demand. It was inevitable that OPEs would be discharged into wastewater in excess, which posed a great threat to the health of human beings and aquatic organisms. In the past few decades, people used various methods to remove refractory OPEs. This paper reviewed the photocatalysis method, the adsorption method with wide applicability, and the biological method mainly relying on enzymolysis and hydrolysis to degrade OPEs in water. All three of these methods had the advantages of high removal efficiency and environmental protection for various organic pollutants. The degradation efficiency of OPEs, degradation mechanisms, and conversion products of OPEs by three methods were discussed and summarized. Finally, the development prospects and challenges of OPEs’ degradation technology were discussed.
... Metal oxides have received a great deal of attention as catalysts for the degradation of OPs, both thermally and by means of photodegradation [6]. In particular, titaniabased photocatalysts have gained particular interest for the remediation of contaminated waters and air [7,8]. The high affinity of phosphates and phosphonates for metal oxides is well-known, and adsorption and photo-degradation have been studied for a number of photocatalytic metal oxides, including iron oxides [9], ceria [10,11], zinc oxide [12,13], and titanium dioxide [14][15][16]. ...
The adsorption and photocatalytic degradation of trimethyl phosphate (TMP) and triethyl phosphate (TEP), two environmentally relevant model pollutants, have been studied on commercial anatase TiO2 and sulfate-terminated anatase TiO2 nanoparticles by means of operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and 2D correlation spectroscopy (2D COS). It is concluded that both TMP and TEP adsorb dissociatively on anatase TiO2, while on the sulfate-terminated anatase TiO2, TMP and TEP adsorb associatively. Upon UV illumination, TMP and TEP are completely oxidized on sulfate-terminated anatase TiO2, as evidenced by the evolution of the IR bands characteristic for water and carbon dioxide. In contrast, on anatase TiO2, UV illumination leads to the formation of stable surface-coordinated carboxylate products, which impedes complete oxidation. 2D COS analysis suggests that parallel reaction pathways occur during oxidation under UV illumination, viz. methoxide/ethoxide (ads) → carboxylates (ads) and methoxide/ethoxide (ads) → aldehydes (ads) → carboxylates (ads). A parallel reaction occurs on sulfated TiO2 that yields CO2 and H2O by direct radical reactions with the methoxide groups with little, or no, formation of surface-coordinated intermediates. Sulfated TiO2 favor the formation of aldehyde intermediates, with reaction rates 10 times and 30 times faster for TMP and TEM, respectively, compared with commercial anatase TiO2. About 37% (33%) and 32% (24%) of TMP (TEP) were degraded on sulfated-terminated TiO2 and pure TiO2, respectively, after the first 9 min of UV illumination. We show that the sulfate-functionalization of TiO2 has two main functions. First, it prevents the formation of strongly bonded bridging carboxylates, thereby alleviating deactivation. Second, it promotes full oxidation of the organic side-chains into carbon dioxide and water. Improved electron-hole separation by the electrophilic S(VI) in combination with the blocking of bridging reaction intermediates is proposed to contribute to the improved activity. The presented results give insights into how acidic surface modifications change adsorbate surface chemistries, which can be used to increase the sustained activity of low-temperature photocatalysts.
... According to the summary of published studies, the degradation pathways of dichlorvos can be broadly classified into four types, of which hydrogen uptake (Fig. 5, Pathway D1-1), addition-elimination (Fig. 5, Pathway D1-2) and unsaturated bond addition (Fig. 5, Pathway D3) are the key pathways, while most reactions are initiated by electron transfer and • OH. In the study of Sud and Kaur (2012), dichlorvos were attacked by • OH, e − and H + , resulting in the intermediate (l), (m) and (i). Eventually, CO 2 , H 2 O and Cl − are formed under a series of actions of • OH. ...
... The degradation pathways for TiO 2 -mediated photocatalytic degradation of dichlorvos(Sud and Kaur, 2012). Possible removal pathways during the degradation of DT (DT1, DT2, DT3-1 and DT3-2-TiO 2 suspensions; DT3-2 and DT4-Vis/Ag@CNG/sulfite system; DT5simulated sunlight). ...
Organophosphorus pollutants (OPs), which are compounds containing carbon‑phosphorus bonds or phosphate derivatives containing organic groups, have received much attention from researchers because of their persistence in the aqueous environment for long periods of time and the threat they pose to human health. Heterogeneous photocatalysis has been widely applied to the removal of OPs from aqueous solutions due to its better removal effect and environmental friendliness. In this review, the removal of OPs from aqueous matrices by heterogeneous photocatalysis was presented. Herein, the application and the heterogeneous photocatalysis mechanism of OPs were described in detail, and the effects of catalyst types on degradation effect are discussed categorically. In particular, the heterojunction type photocatalyst has the most excellent effect. After that, the photocatalytic degradation pathways of several OPs were summarized, focusing on the organophosphorus pesticides and organophosphorus flame retardants, such as methyl parathion, dichlorvos, dimethoate and chlorpyrifos. The toxicity changes during degradation were evaluated, indicating that the photocatalytic process could effectively reduce the toxicity of OPs. Additionally, the effects of common water matrices on heterogeneous photocatalytic degradation of OPs were also presented. Finally, the challenges and perspectives of heterogeneous photocatalysis removal of OPs are summarized and presented.
... AOP may be a good option for this problem. This process uses highly reactive transitory species like ⋅ OH, ⋅ O 2 − , O 3 , and H 2 O 2 to oxidize the organic effluents under ambient conditions into comparatively harmless end products such as CO 2 , H 2 O, and inorganic anions [13][14][15][16]. Fenton oxidation is an important AOP process, where H 2 O 2 is decomposed catalytically by ferrous ion and the resultant ⋅ OH oxidize the organic pollutant non-selectively. ...
Persistent organic substances in wastewater are creating serious problems to the living world as well as to the environment, thereby creating a hugely detrimental impact on the ecosystem. Given the critical situation, the removal of the persistent organic substances from wastewater effluent holds a great promise to balance the ecosystem and sustain societal impact value. Among the several wastewater treatment techniques, the advanced oxidation processes (AOPs) employing solar energy is the acceptable one and is considered one of the promising alternative methods to work on. Organic pollutants like dye-contaminated wastewater, pharmaceutical waste-water, petroleum wastewater, municipality wastewater, etc. are treated for purification purposes by these techniques. This review article aims to provide an overview on the importance of the above techniques, from their origin to their recent modification, progress, and the probable scopes for further improvement. The modification of the Fenton process has been processed to overcome several weaknesses including high bandgap, recombination of electron-hole pair, lower light intensity in solar light, operation under visible light, and natural pH conditions. The photo-catalysts with novel properties are functioning as an emergent class of smart materials with recently introduced promising materials like graphene, g-C 3 N 4 , metal-organic framework, quantum dots, etc. The review will spark the kinetic study and role of scavengers to investigate the mechanistic insights for the development of value-added photo-catalysts. The study also evaluates the prospects and future challenges to follow strict regulations.
... There are various chemical methods used for the degradation of OPs. Photocatalytic degradation and chlorination are the different methods for the degradation of OPs (Kamel et al. 2009;Sud and Kaur 2012). Chemical agents such as DS2, sodium hydroxide, and hypochlorite can be used for decontamination of OPs (Kitamura et al. 2014). ...
... Heterogeneous photocatalysis includes use of semiconductor catalysts such as TiO 2 , ZnO, and ZrO 2 in combination with UV/solar radiation. The most evolving degrading technology is heterogeneous photocatalysis using TiO 2 as photocatalyst (Sud and Kaur 2012;Mirmasoomi et al. 2017). However, the mechanism of photocatalytic degradation depends on experimental conditions such as concentration of oxygen, dose of catalyst, temperature, and pH (Sud and Kaur 2012). ...
... The most evolving degrading technology is heterogeneous photocatalysis using TiO 2 as photocatalyst (Sud and Kaur 2012;Mirmasoomi et al. 2017). However, the mechanism of photocatalytic degradation depends on experimental conditions such as concentration of oxygen, dose of catalyst, temperature, and pH (Sud and Kaur 2012). Chlorination of water is another chemical-based method reported to oxidize OPs. ...
Environment is everything surrounding human beings. Biotic and abiotic contributors of environment affect natural, build, and social aspects of human beings. For healthy livelihood, human beings are dependent on environment. The increase in population, urbanization, and industrialization is having severe effect on world environment. Climate change further aggravates the situation. Despite several laws drafted for the awareness and reduction of environmental degradation, no profound results have been obtained. Environmental issues induce several negative externalities and contribute to market failure, thus affecting economic growth; this becomes a serious problem in developing and underdeveloped countries where there are no strong rules for reducing these negative externalities. Pakistan is ranked fifth among the most affected countries in terms of climate change despite the contribution of less than 01% in emissions. The air quality index of Pakistan is getting poor with every passing day; Lahore and Faisalabad were ranked as most polluted cities all over the world in terms of air quality index. The government of Pakistan
has taken some time to realize environmental degradation and has initiated projects like billion tree tsunami and air quality laws to address climate change and environmental degradation.
... a Fenton reagent, ferrous iron (Fe 3+ ), and sodium hypochlorite , either alone or in combination with light, to generate free radicals, which attack the organic pollutants to trigger the redox reactions. The heterogeneous photocatalysis process utilizes semiconductor catalysts, which may be transition metal oxides/sulfides such as TiO 2 , ZnO, In 2 S 3 , CdS, CoS 2 , and WO 3 under UV/solar radiation to accomplish the degradation process (24). AOPs depend on the photo-assisted formation of highly reactive intermediate free radicals such as hydroxyl radicals ( • OH), superoxide radicals ( • O 2 -), and positively charged holes (h + ). ...
... There are various chemical methods used for degradation of OPs. Photocatalytic degradation and chlorination are different methods for the degradation of OPs (Kamel et al. 2009;Sud and Kaur 2012). Chemical agents such as DS2, sodium hydroxide, and hypochlorite can be used for decontamination of OPs (Kitamura et al. 2014). ...
... Heterogeneous photocatalysis include the use of semiconductor catalyst such as TiO 2 , ZnO, and ZrO 2 in combination with UV/solar radiation. The most evolving degrading technology is heterogeneous photocatalysis using TiO 2 as photocatalyst (Sud and Kaur 2012;Mirmasoomi et al. 2017). Photocatalysis of dimethoate involves oxidation, dealkylation, and reduction reactions as observed by Evgenidou et al. (2006) and Chen et al. (2007). ...
... Evgenidou et al. (2006) also revealed that the secondary intermediates produced through photocatalysis were more toxic than the dimethoate itself. However, mechanism of photocatalytic degradation depends on experimental conditions such as concentration of oxygen, dose of catalyst, temperature, and pH (Sud and Kaur 2012). The chlorination of water is another chemicalbased method reported to oxidize OPs. ...
Organophosphate pesticides (OPs) are used extensively for crop protection worldwide due to their high water solubility and relatively low persistence in the environment compared to other pesticides, such as organochlorines. Dimethoate is a broad-spectrum insecticide that belongs to the thio-organophosphate group of OPs. It is applied to cash crops, animal farms, and houses. It has been used in Pakistan since the 1960s, either alone or in a mixture with other OPs or pyrethroids. However, the uncontrolled use of this pesticide has resulted in residual accumulation in water, soil, and tissues of plants via the food chain, causing toxic effects. This review article has compiled and analyzed data reported in the literature between 1998 and 2021 regarding dimethoate residues and their microbial bioremediation. Different microorganisms such as bacteria, fungi, and algae have shown potential for bioremediation. However, an extensive role of bacteria has been observed compared to other microorganisms. Twenty bacterial, three fungal, and one algal genus with potential for the remediation of dimethoate have been assessed. Active bacterial biodegraders belong to four classes (i) alpha-proteobacteria, (ii) gamma-proteobacteria, (iii) beta-proteobacteria, and (iv) actinobacteria and flavobacteria. Microorganisms, especially bacterial species, are a sustainable technology for dimethoate bioremediation from environmental samples. Yet, new microbial species or consortia should be explored.
... Physicochemical properties of organophosphate pesticides[19],[20][21]. ...
... The Half-life of some organophosphates[19][22]. ...
Pesticides are synthetic compounds that may become environmental contaminants through their use and application. The high productivity achieved in the agricultural industry can be credited to the use and application of pesticides by way of pest and insect control. As much as pesticides have a positive impact on the agricultural industry, some disadvantages come with their application in the environment because they are intentionally toxic, and this is more towards non-target organisms. They are grouped into chlorophenols, organochlorines, synthetic pyrethroid, car-bamates, and organophosphorus based on their structure. The symptoms of exposure to carbamate (CM) and organophosphates (OP) are similar, although poisoning from CM is of a shorter duration. The analytical evaluation of carbamate and organophosphate pesticides in human and environmental matrices are reviewed using suitable extraction and analytical methods.
... This process is based on the use of semiconductor material as a catalyst and UV/solar radiation to activate the catalyst to initiate a redox reaction for the intended contaminants [23,51]. A semiconductor material has an electronic band structure that consists of the highest and lowest energy levels, known as the valence band (VB) and conduction band (CB), respectively that are separated by band gap energy [88,89]. When a photon of energy equal or greater than the band gap energy is absorbed by a semiconductor photocatalyst, an electron from the valence band is excited to the conduction band with simultaneous production of a hole in the valence band (h VB + ) [11]. ...
... Compared to individual methods, sonophotocatalysis offers substantial advantages such as improvement in the light penetration, uniform distribution of catalyst particles, acceleration of the cleavage of H 2 O 2 , and more generation of highly reactive radicals [95][96][97]. Moreover, the acoustic cavitation process increases the catalyst surface due to particle fragmentation and deagglomeration and continuously cleans the photocatalyst surface during the operation [11,88,98]. Schematic representation of degradation mechanism by photocatalytic and sono-photocatalytic processes are shown in Figs. 3 and 4, respectively. ...
Over the past few decades, the indiscriminate use of a large variety of synthetic dyes and their continuous input into aquatic environments has constituted a serious risk to human health and ecological systems. Among a variety of treatment methods for dye removal from the aqueous environment, sonophotocatalysis has recently received a lot of attention due to its green and environmental-friendly properties. The aim of this review is to present an in-depth study of the sonophotocatalytic process for the degradation of various dyes in aqueous matrices. In the present study, the fundamentals of sonolysis and photocatalysis for wastewater treatment and their merits and drawbacks are explained in detail, along with a detailed discussion on the benefits that can be obtained using the combined approach. Additionally, operational parameters, the pathway, and kinetics of the sonophotocatalytic dye degradation, the cost estimation as well as the application of sonophotocatalysis for the textile wastewater treatment are discussed based on recently published works. It is observed that sonophotocatalysis indeed results in the remarkable enhancement of the oxidation intensity and thus the degradation rates of dyes, however, its applicability in large-scale wastewater treatment is limited. According to findings, most of the sonophotocatalytic optimization processes can achieve high removal efficiency with low concentrations of dyes (i.e., 0.1–100 μM), low ultrasound frequencies (i.e., 20–200 kHz), and acidic pH values over a temperature range of 20–40 °C, though the exact recommended value would be dependent on the compound characteristics and the reactor geometry.
... a Fenton reagent, ferrous iron (Fe 3+ ), and sodium hypochlorite , either alone or in combination with light, to generate free radicals, which attack the organic pollutants to trigger the redox reactions. The heterogeneous photocatalysis process utilizes semiconductor catalysts, which may be transition metal oxides/sulfides such as TiO 2 , ZnO, In 2 S 3 , CdS, CoS 2 , and WO 3 under UV/solar radiation to accomplish the degradation process (24). AOPs depend on the photo-assisted formation of highly reactive intermediate free radicals such as hydroxyl radicals ( • OH), superoxide radicals ( • O 2 -), and positively charged holes (h + ). ...
The discharge of dyestuff from various industries (e.g., textiles, paper or printing, and leather-tanning industries), food technology, and hair coloring in water has a negative impact on the aqueous system and human life. With continual industrial development, the increasing release of synthetic dyes into the aquatic system is of public concern. Traditional water-treatment methods based on physical, chemical, and biological approaches, such as ion exchange, coagulation, flocculation, adsorption, and biological processes, suffer from high operational costs and produce secondary toxic pollutants. Photocatalysis utilizes semiconductor catalysts that may be transition metal oxides or sulfides, such as TiO2, ZnO, Fe2O3, CdS, GaP, and ZnS, to degrade a wide range of synthetic dyes into biodegradable or less toxic organic compounds. However, the low separation efficiency, easy agglomeration, and low solar energy consumption efficiency of these semiconductor catalysts restrict their large-scale applications. Therefore, this research explores new photocatalysts, focusing on the aforementioned concerns for the degradation of dyes. Remarkably, photoactive metal-organic frameworks (MOFs) utilize solar energy and continuously fascinate researchers around the world because of their large surface area and porous nature, high mechanical stability, and reusability. This chapter principally summarizes the design strategy and versatile synthesis methodologies that have been adopted to construct MOFs and highlights the research progress in the application of MOFs as a means of photocatalytic degradation of synthetic dyes.
