Review on the hazardous applications and photodegradation mechanisms of chlorophenols over different photocatalysts

Comparative evaluation of biodegradation of chlorpyrifos by various bacterial strains: Kinetics and pathway elucidation

The present study focused on the isolation and identification of CP and TCP bacteria degrading bacteria from the rhizospheric zone of aromatic grasses i.e. palmarosa (Cymbopogon martinii (Roxb. Wats), lemongrass (Cymbopogon flexuosus) and vetiver (Chrysopogon zizaniodes (L.) Nash.). So that these isolates alone or in combination with the vegetation of aromatic grasses will be used to clean up CP-contaminated soils. The study also explored enzymatic activities, CO2 release, dechlorination potential, and degradation pathways of bacterial strains. A total of 53 CP-tolerant bacteria were isolated on their physical characteristics and their ability to degrade CP. The ten highly CP-tolerant isolates were Pseudomonas aeruginosa Pa608, three strains of Pseudomonas hibiscicola R4-721 from different rhizosphere, Enterococcus lectis PP2a, Pseudomonas monteilii NBFPALD_RAS131, Enterobacter cloacae L3, Stenotrophomonas maltophilia PEG-390, Escherichia coli ABRL132, and Escherichia coli O104:H4 strain FWSEC0009. The CO2 emission and phosphatase activities of the isolates varied from 3.1 to 8.6 μmol mL-1 and 12.3 to 31 μmol PNP h-1, respectively in the CP medium. The degradation kinetics of CP by these isolates followed a one-phase decay model with a dissipation rate ranging from 0.048 to 0.41 d-1 and a half-life of 1.7-14.3 days. The growth data fitted in the SGompertz equation showed a growth rate (K) of 0.21 ± 0.28 to 0.91 ± 0.33 d-1. The P. monteilii strain had a faster growth rate while E. coli ABRL132 had slower growth among the isolates. The rate of TCP accumulation calculated by the SGompertz equation was 0.21 ± 0.02 to 1.18 ± 0.19 d-1. The Pseudomonas monteilii showed a lower accumulation rate of TCP. Among these, four highly effective isolates were Pseudomonas aeruginosa Pa608, Pseudomonas monteilii NBFPALD_RAS131, Stenotrophomonas maltophilia PEG-390, and Pseudomonas hibiscicola R4-721. Illustrations of the degradation pathways indicated that the difference in metabolic pathways of each isolate was associated with their growth rate, phosphatase, dehydrogenase, oxidase, and dechlorination activities.

Synergistically enhanced photocatalytic properties of Co3O4-G/GO nanocomposites: unravelling their interactions and charge-transfer dynamics using XAS

Metal oxide composites with graphene/graphene oxide have increasingly gained popularity in enhancing the photocatalytic degradation of several existing harmful dyes. Moreover, identifying the role of carbon networks and their interactions in composite formation would assist in the design and development of photocatalysts. In the present study, we investigated the role of carbon networks in improving photocatalytic properties. Electronic structure analysis of cobalt oxide-graphene (C2)/graphene oxide (C3) nanocomposites using XAS suggested possible charge transfer from cobalt oxide nanoparticles to the carbon network during composite formation. The photocatalytic degradation of C3 towards phenol dye (1 × 10-3 M) was >50% and improved the degradation rate with k = 0.231 h-1.In the quest to understand the mechanism unfolding on its surface, in situ XAS under UV-visible irradiation was performed, which shed light on delayed excitonic recombination in the synthesized nanocomposites. This enabled hydroxy radicals (˙OH) to play a preeminent role in the cleavage of the phenol ring and its intermediaries. Based on these observations, a detailed mechanism for charge transfer occurring during nanocomposite formation and the mechanism involved in the enhanced photocatalytic activity of the nanocomposite photocatalyst towards phenol degradation under the influence of UV-visible irradiation are discussed.

Electrocatalytic denitrification biofilter for advanced purification of chlorophenols via ceramsite-based Ti/SnO2-Sb particle electrode: Performance, microbial community structure and mechanism

In response to the demand for advanced purification of industrial secondary effluent, a new method has been developed for treating chlorophenol wastewater using the novel ceramsite-based Ti/SnO2-Sb particle electrodes (Ti/SnO2-Sb/CB) enhanced electrocatalytic denitrification biofilter (EDNBF-P) to achieve removal of chlorophenols (CPs), denitrification, and reduction of effluent toxicity. The results showed that significantly improved CPs and TN removal efficiency at low COD/N compared to conventional denitrification biofilter, with CPs removal rates increasing by 0.33%-59.27% and TN removal rates increasing by 12.53%-38.92%. Under the conditions of HRT = 2h, 3V voltage, charging times = 12h, and 25 °C, the concentrations of the CPs in the effluent of EDNBF-P were all below 1 mg/L, the TN concentration was below 15 mg/L, while the effluent toxicity reached the low toxicity level. Additionally, the Ti/SnO2-Sb/CB particle electrodes effectively alleviated the accumulation of NO2--N caused by applied voltage. The Silanimonas, Pseudomonas and Rhodobacter was identified as the core microorganism for denitrification and toxicity reduction. This study validated that EDNBF-P could achieve synergistic treatment of CPs and TN through electrocatalysis and microbial degradation, providing a methodological support for achieving advanced purification of chlorophenol wastewater with low COD/N in industrial applications.

UV-induced photodegradation of emerging para-phenylenediamine quinones in aqueous environment: Kinetics, products identification and toxicity assessments

Substituted para-phenylenediamine quinones (PPD-quinones) are a class of emerging contaminants frequently detected in the aqueous environment. One of them, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q), was found to cause acute toxicities to aquatic species at extremely low environmental levels. The ubiquitousness and ecotoxicity of such pollutants underscore the importance of their transformation and elimination. In this work, we demonstrated effective removals of five PPD-quinones in aqueous environments under UV irradiation, with up to 94% of 6PPD-Q eliminated after a 40-min treatment. By applying high-resolution mass spectrometry (HRMS) non-targeted screening in combination with isotope labeling strategies, a total of 22 transformation products (TPs) were identified. Coupling with the time-based dynamic patterns, potential transformation mechanisms were identified as an •OH-induced photocatalysis reaction involving bond cleavage, hydroxylation, and oxidation. Computational toxicity assessment predicted lower aquatic toxicity of the TPs than their parent PPD-quinones. Our results in parallel evidenced an obvious reduction of PPD-quinones accompanied by the presence of their TPs in the effluent after UV disinfection in real municipal wastewater. This work builds a comprehensive understanding of the fate, transformation products, and related toxicological characteristics of emerging PPD-quinone contaminants in the aqueous environment.

Formation and toxicity contribution of chlorinated and dechlorinated halobenzoquinones from dichlorophenols after ozonation

Halobenzoquinones (HBQs) are a class of disinfection byproducts with high cytotoxicity and potential carcinogenicity, which have been widely detected in chlorination of drinking water and swimming pool water. However, to date, the formation of HBQs upon ozonation and the HBQ precursors have been overlooked. This study investigated the formation of chlorinated and dechlorinated HBQs from six dichlorophenol (DCP) isomers. The monomeric and dimeric HBQs were identified in all the ozonation effluents, exhibiting 1-100 times higher toxicity levels than their precursors. The sum of detected HBQs intensity had a satisfactory linear relation with the maximum toxic unit (R2 = 0.9657), indicating the primary toxicity contribution to the increased overall toxicity of effluents. Based on density functional theory calculations, when ozone attacks the para carbon to the hydroxyl group of 2,3-DCP, the probability of producing chlorinated HBQs is 80.41 %, indicating that the para carbon attack mainly resulted in the formation of monomeric HBQs. 2,3-dichlorophenoxy radicals were successfully detected in ozonated 2,3-DCP effluent through electron paramagnetic resonance and further validated using theoretical calculation, revealing the formation pathway of dimeric HBQs. The results indicate that chlorinated phenols, regardless of the positions of chlorine substitution, can potentially serve as precursors for both chlorinated and dechlorinated HBQs formation during ozonation.

Charge transfer in TiO2-based photocatalysis: fundamental mechanisms to material strategies

Semiconductor-based photocatalysis has attracted significant interest due to its capacity to directly exploit solar energy and generate solar fuels, including water splitting, CO2 reduction, pollutant degradation, and bacterial inactivation. However, achieving the maximum efficiency in photocatalytic processes remains a challenge owing to the speedy recombination of electron-hole pairs and the limited use of light. Therefore, significant endeavours have been devoted to addressing these issues. Specifically, well-designed heterojunction photocatalysts have been demonstrated to exhibit enhanced photocatalytic activity through the physical distancing of electron-hole pairs generated during the photocatalytic process. In this review, we provide a systematic discussion ranging from fundamental mechanisms to material strategies, focusing on TiO2-based heterojunction photocatalysts. Current efforts are focused on developing heterojunction photocatalysts based on TiO2 for a variety of photocatalytic applications, and these projects are explained and assessed. Finally, we offer a concise summary of the main insights and challenges in the utilization of TiO2-based heterojunction photocatalysts for photocatalysis. We expect that this review will serve as a valuable resource to improve the efficiency of TiO2-based heterojunctions for energy generation and environmental remediation.

Degradation and metagenomic analysis of 4-chlorophenol utilizing multiple metal tolerant bacterial consortium

Chlorophenols are persistent environmental pollutants used in synthesizing dyes, drugs, pesticides, and other industrial products. The chlorophenols released from these processes seriously threaten the environment and human health. The present study describes 4-chlorophenol (4-CP) degradation activity and metagenome structure of a bacterial consortium enriched in a 4-CP-containing medium. The consortium utilized 4-CP as a single carbon source at a wide pH range, temperature, and in the presence of heavy metals. The immobilized consortium retained its degradation capacity for an extended period. The 4-aminoantipyrine colorimetric analysis revealed complete mineralization of 4-CP up to 200 mg/L concentration and followed the zero-order kinetics. The addition of glycerol and yeast extract enhanced the degradation efficiency. The consortium showed both ortho- and meta-cleavage activity of catechol dioxygenase. Whole genome sequence (WGS) analysis revealed the microbial compositions and functional genes related to xenobiotic degradation pathways. The identified genes were mapped on the KEGG database to construct the 4-CP degradation pathway. The results exhibited the high potential of the consortium for bioremediation of 4-CP contaminated sites. To our knowledge, this is the first report on WGS analysis of a 4-CP degrading bacterial consortium.

A heterostructural MoS2QDs@UiO-66 nanocomposite for the highly efficient photocatalytic degradation of methylene blue under visible light and simulated sunlight

The development of recyclable photocatalysts with high activity and stability has piqued the interest of researchers in the field of wastewater treatment. In this study, an ultrasonic probe approach was used to immerse a sequence of heterojunctions formed by metal-organic frameworks (UiO-66) and different amounts of molybdenum disulfide quantum dots (MoS2QDs), resulting in a highly recyclable MoS2QDs@UiO-66 photocatalyst. Multiple advanced techniques, such as XPS, XRD, TEM, XRF, and UV-vis spectrophotometry, were used to characterize and confirm the successful preparation of UIO-66 impregnated with MoS2QDs. The results indicated that the best heterostructure catalyst exhibited superior efficiency in the photocatalytic degradation of methylene blue (MB) in water, achieving approximately 99% removal within 30 minutes under simulated sunlight, while approximately 97% removal under visible light. The outstanding photocatalytic performance is predominantly attributed to the photoinduced separation of carriers in this heterostructure system. This study proposes a unique, simple, and low-cost method for improving the degradation performance of organic contaminants in water.

Degradation of Pesticides Using Semiconducting and Tetrapyrrolic Macrocyclic Photocatalysts-A Concise Review

Exposure to pesticides is inevitable in modern times, and their environmental presence is strongly associated to the development of various malignancies. This challenge has prompted an increased interest in finding more sustainable ways of degrading pesticides. Advanced oxidation processes in particular appear as highly advantageous, due to their ability of selectively removing chemical entities form wastewaters. This review provides a concise introduction to the mechanisms of photochemical advanced oxidation processes with an objective perspective, followed by a succinct literature review on the photodegradation of pesticides utilizing metal oxide-based semiconductors as photosensitizing catalysts. The selection of reports discussed here is based on relevance and impact, which are recognized globally, ensuring rigorous scrutiny. Finally, this literature review explores the use of tetrapyrrolic macrocyclic photosensitizers in pesticide photodegradation, analyzing their benefits and limitations and providing insights into future directions.

Degradation of 2,4-DCP by immobilized laccase on modified biochar carrier

Rape straw was used as the raw material for the biochar in this study, which was then changed using acid, alkali, and magnetic techniques. The laccase was attached using the adsorptions-crosslinking process, and the three modified biochars served as the carriers. The ideal circumstances for laccase immobilization were explored, and both biochar and immobilized laccase's characteristics were examined. The removal of 2,4-dichlorophenol (2,4-DCP) by immobilized laccase from modified biochar and its degradation products were researched. The main conclusions are as follows: the optimal concentration of glutaraldehyde (GLU) was 4%, and the pH was four, and the enzyme dosage was 1.75 mg/mL for the immobilized laccase of acid-modified biochar (SBC@LAC). The optimal concentration of GLU was 5%; the pH was four, and the enzyme dosage was 2 mg/mL for immobilized laccase from alkali-modified biochar (JBC@LAC). The optimal concentration of GLU was 5%; the pH was four, and the enzyme dosage was 1.75 mg/mL for immobilized laccase from magnetically modified biochar (CBC@LAC). SEM images could show the changes in the surface morphology of biochar caused by three modification methods. The BET results demonstrated that acid and magnetic modification increased the specific surface area of biochar, and alkali modification mainly expanded the pore size of biochar. FT-IR and XRD showed that modification and laccase loading had little effect on the structure of biochar. The stability of immobilized laccase was better than that of free laccase in acid-base, heat, and storage. Among the three modified biochar immobilized laccases, JBC@LAC showed the best acid-base stability and thermal stability, and the relative enzyme activity changed the least when pH and temperature conditions changed. The storage stability of SBC@LAC is the best. After 30 days of storage, the relative enzyme activity is still 83%. The removal rates of 2,4-DCP were 57, 99, and 63%, respectively, by SBC@LAC, JBC@LAC, and CBC@LAC. After five reuses, the removal rates of 2,4-DCP by SBC@LAC, JBC@LAC and CBC@LAC were 26, 42, and 27%, respectively. The intermediate products of 2,4-DCP degradation by immobilized laccase were p-phenol, p-benzoquinone and maleic acid.

Spinel ferrite nanoparticles as potential materials in chlorophenol removal from wastewater

Persistent organic pollutants (POPs) including chlorophenols (CPs) are increasing in water effluents, creating serious problems for both aquatic and terrestrial lives. Several research attempts have considered the removal of CPs by functionalised nanomaterials as adsorbents and catalysts. Besides the unique crystal structure, spinel ferrite nanomaterials (SFNs) own interesting optical and magnetic properties that give them the potential to be utilised in the removal of different types of CPs. In this review, we highlighted the recent research work that focused on the application of SFNs in the removal of different CP substances based on the number of chlorine atom attached to the phenolic compound. We have also discussed the structure and properties of SFN along with their numerous characterisation tools. We demonstrated the importance of identifying the structure, surface area, porosity, optical properties, etc. in the efficiency of the SFN during the CP removal process. The reviewed research efforts applied photocatalysis, wet peroxide oxidation (WPO), persulfate activated oxidation and adsorption. The studies presented different paths of enhancing the SFN ability to remove the CPs including doping (ion substitution), oxide composite structure and polymer composite structure. Experimental parameters such as temperature, dosage of CPs and SFN structure have shown to have a major effect in the CP removal efficiency. More attention is needed to investigate the different properties of SFN that can be tailored through different techniques and expected to have major role in the removal mechanism of CPs.

Tailored chitosan-based entrapped catalyst for dyes removal by highly active, stable, and recyclable nanoparticles toughened hydrogel

Functional catalytic hydrogels were a promising catalyst carrier with the advantages of low cost, high efficiency and environmental friendliness. However, conventional hydrogels suffered from mechanical defects and brittleness. Acrylamide (AM) and lauryl methacrylate (LMA) were used as raw materials, SiO₂-NH₂ spheres as toughening agents, and chitosan (CS) as stabilizers to form hydrophobic binding networks. p(AM/LMA)/SiO₂-NH₂/CS hydrogels exhibited superior stretchability and withstood strains up to 14,000 %. In addition, these hydrogels exhibited exceptional mechanical properties, including a tensile strength of 213 kPa and a toughness of 13.1 MJ/m³. Surprisingly, the introduction of chitosan into hydrogels showed excellent antibacterial activity against S. aureus and E. coli. At the same time, the hydrogel served as a template for the formation of Au nanoparticles. This resulted in high catalytic activity for methylene blue (MB) and Congo red (CR) on p(AM/LMA)/SiO₂-NH₂/CS-8 %-Au hydrogels with K_app of 1.038 and 0.76 min^-1, respectively. The catalyst was also found to be reusable for 10 cycles while maintaining an efficiency of over 90 %. Therefore, innovative design strategies can be used to develop durable and scalable hydrogel materials for catalysis in the wastewater treatment industry.

A PdPt nanoparticle-decorated thiol-functionalized MOF with high peroxidase-like activity for colorimetric sensing of D-glucose and chlorophenol isomers

The peroxidase (POD)-like catalytic activity of various nanozymes was extensively applied in many significant fields. In this study, a thiol-functionalized MOF-loaded PdPt nanocomposite (UiO-66-(SH)₂@PdPt) was fabricated, which possesses superior and selective POD-like activity with strong affinity towards H₂O₂ and 3,3',5,5'-tetramethylbenzidine under mild conditions. The POD-like property of UiO-66-(SH)₂@PdPt was used to sensitively detect the concentration of D-glucose under near-neutral (pH = 6.5) conditions. The detection limit of D-glucose was as low as 2.7 μM, and the linear range of D-glucose was 5-700 μM. In addition, UiO-66-(SH)₂@PdPt could accelerate the oxidative coupling chromogenic reaction of chlorophenol (CP) and 4-aminoantipyrine (4-AAP) in the presence of H₂O₂. Based on this phenomenon, a simple and visualized sensing array for the identification of chlorophenol contaminant isomers was further constructed to finally achieve the effective differentiation of three monochlorophenol isomers and six dichlorophenol isomers. Furthermore, a colorimetric detection method for 2-chlorophenol and 2,4-dichlorophenol was established. This work provides an effective means to improve the catalytic activity and selectivity of nanozymes by introducing an ideal carrier, which will be of significant value for the design of efficient nanozymes.

Hydroxylation of some emerging disinfection byproducts (DBPs) in water environment: Halogenation induced strong pH-dependency

In this work, the hydroxylation mechanisms and kinetics of some emerging disinfection byproducts (DBPs) have been systematically investigated through theoretical calculation methods. Five chlorophenols and eleven halogenated pyridinols were chosen as the model compounds to study their pH-dependent reaction laws in UV/H₂O₂ system. For the reactions of HO^• with 37 different dissociation forms, radical adduct formation (RAF) was the main reaction pathway, and the reactivity decreased with the increase of halogenation degree. The k_app values (at 298 K) increased with the increase of pH from 0 to 10, and decreased with the increase of pH from 10 to 14. Compared with phenol, the larger the chlorination degree in chlorophenols was, the stronger the pH sensitivity of the k_app values; compared with chlorophenols, the pH sensitivity in halogenated pyridinols was further enhanced. As the pH increased from 2 to 10.5, the degradation efficiency increased at first and then decreased. With the increase of halogenation degree, the degradation efficiency range increased, the pH sensitivity increased, the optimal degradation efficiency slightly increased, and the optimal degradation pH value decreased. The ecotoxicity and bioaccumulation of most hydroxylated products were lower than their parental compounds. These findings provided meaningful insights into the strong pH-dependent hydroxylation of emerging DBPs on molecular level.

Nanobiohybrids: Synthesis strategies and environmental applications from micropollutants sensing and removal to global warming mitigation

Micropollutants contamination and global warming are critical environmental issues that require urgent attention due to natural and anthropogenic activities posing serious threats to human health and ecosystems. However, traditional technologies (such as adsorption, precipitation, biodegradation, and membrane separation et al.) are facing challenges of low utilization efficiency of oxidants, poor selectivity, and complex in-situ monitoring operations. To address these technical bottlenecks, nanobiohybrids, synthesized by interfacing the nanomaterials and biosystems, have recently emerged as eco-friendly technologies. In this review, we summarize the synthesis approaches of nanobiohybrids and their utilization as emerging environmental technologies for addressing environmental problems. Studies demonstrate that enzymes, cells, and living plants can be integrated with a wide range of nanomaterials including reticular frameworks, semiconductor nanoparticles and single-walled carbon nanotubes. Moreover, nanobiohybrids demonstrate excellent performance for micropollutant removal, carbon dioxide conversion, and sensing of toxic metal ions and organic micropollutants. Therefore, nanobiohybrids are expected to be environmental friendly, efficient, and cost-effective techniques for addressing environmental micropollutants issues and mitigating global warming, benefiting both humans and ecosystems alike.

Insights into the mechanism of persulfate activation with carbonated waste metal adsorbed resin for the degradation of 2,4-dichlorophenol

Superabsorbent resin (SAR) saturated with heavy metals poses a threat to surrounding ecosystem. To promote the reutilization of waste, resins adsorbed by Fe²⁺ and Cu²⁺ were carbonized and used as catalysts (Fe@C/Cu@C) to activate persulfate (PS) for 2,4-dichlorophenol (2,4-DCP) degradation. The heterogeneous catalytic reaction was mainly responsible for 2,4-DCP removal. The synergistic effect of Fe@C and Cu@C was propitious to 2,4-DCP degradation. Fe@C/Cu@C with a ratio of 2:1 showed the highest performance of 2,4-DCP removal. 40 mg/L 2,4-DCP was completely removed within 90 min under reaction conditions of 5 mM PS, pH = 7.0 and T = 25 °C. The cooperation of Fe@C and Cu@C facilitated the redox cycling of Fe and Cu species to supply accessible PS activation sites, enhancing ROS generation for 2,4-DCP degradation. Carbon skeleton enhanced 2,4-DCP removal via radical/nonradical oxidation pathways and via its adsorption to 2,4-DCP. SO₄˙-, HO˙ and O₂^•- were the dominate radical species involved in 2,4-DCP destruction. Meanwhile, the possible pathways of 2,4-DCP degradation were proposed based on GC-MS. Finally, recycling tests proved catalysts exhibited recyclable stability. Aiming to resource utilization, Fe@C/Cu@C with satisfactory catalysis and stability, is promising catalyst for contaminated water treatment.

Recent progress on plant extract-mediated biosynthesis of ZnO-based nanocatalysts for environmental remediation: Challenges and future outlooks

The plant extract mediated green synthesis of nanomaterials has attracts enormous interest due to its cost-effectiveness, greener, and environmentally friendly. It is also considered as an alternative and facile method in which the phytochemicals can be used as a natural capping and reducing agents and helped to produce nanomaterials with high surface area, different sizes, and shapes. One of the materials fabricated using green methods is zinc oxide (ZnO) semiconductor due to its enormous applications in different field areas. In this review, an overview of recent progress on green synthesized ZnO-based catalysts and various modification methods for the purpose of enhancing the catalytic activity of ZnO and the corresponding structural-activity and interactions towards the removal of pollutants are highlighted. Particularly, the plant extract mediated ZnO-based photocatalysts application for the removal of pollutants via photocatalytic degradation, reduction reaction, and adsorption mechanism are demonstrated. Besides, the opportunities, challenges, and future outlooks of ZnO-based materials for environmental remediation with green and sustainable methods are also included. We believe that this review is a timely and comprehensive review on the recent progress related to plant extract mediated ZnO-based nanocatalysts synthesis and applications for environmental remediation.

Biochar-supported sulfurized nanoscale zero-valent iron facilitates extensive dechlorination and rapid removal of 2,4,6-Trichlorophenol in aqueous solution

Nanoscale zero-valent iron (NZVI) has been widely used in rapid remediation of contaminants. However, several obstacles such as aggregation and surface passivation hampered NZVI from further application. In this study, sulfurized nanoscale-zero valent iron supported by biochar (BC-SNZVI) was successfully synthesized and utilized for highly efficient 2,4,6-Trichlorophenol (2,4,6-TCP) dechlorination in aqueous solution. SEM-EDS analysis revealed the even distribution of SNZVI on the surface of BC. FTIR, XRD, XPS and N₂ Brunauer-Emmett-Teller (BET) adsorption analyses were carried out to characterize the materials. Results showed that BC-SNZVI with S/Fe molar ratio of 0.088, Na₂S₂O₃ as sulfurization agent, and pre-sulfurization as the sulfurization strategy exhibited the superior performance for 2,4,6-TCP removal. The overall removal of 2,4,6-TCP was well described with the pseudo-first-order kinetics (R² > 0.9), and the observed kinetics constant K_obs was 0.083 min^-1 with BC-SNZVI, which was one order of magnitude higher than that of BC-NZVI (0.0092 min^-1) and SNZVI (0.0042 min^-1), and two orders of magnitude higher than that of NZVI (0.00092 min^-1). Moreover, the removal efficiency of 2,4,6-TCP reached 99.5% by BC-SNZVI with dosage of 0.5 g·L^-1, initial 2,4,6-TCP concentration of 30 mg·L^-1 and initial solution pH of 3 within 180 min. The removal of 2,4,6-TCP by BC-SNZVI was acid-promoted and the removal efficiencies of 2,4,6-TCP decreased with the increase of initial 2,4,6-TCP concentrations. Furthermore, more extensive dechlorination of 2,4,6-TCP was achieved with BC-SNZVI and complete dechlorination product phenol became predominant. The facilitation of sulfur for Fe⁰ utilization and electron distribution in the presence of biochar remarkably enhanced the dechlorination performance of BC-SNZVI for 2,4,6-TCP. These findings provide insights into BC-SNZVI as an alternative engineering carbon based NZVI material for treating chlorinated phenols.

Intensification of the photodegradation efficiency of an emergent water pollutant through process conditions optimization by means of response surface methodology

Heterogeneous photocatalysis has been increasingly investigated during the past years and has been recognized as a promising technique for clean and safe water purification. The current study exploits the advantage of this technique demonstrating that the removal of a biorefractory water pollutant named clofibric acid can be really improved by photocatalysis through a parametric comprehensive investigation and optimization study based on response surface methodology. Its novelty comes from the approach used to enhance the efficiency of the photocatalytic degradation of clofibric acid. A custom central composite design consisting of 49 trials was applied for process modeling and a quadratic robust model was derived based on the analysis of variance for the optimization of the process parameters. The effective removal of the target molecule with about 70% carbon mineralization was achieved under optimal photocatalytic conditions: 1.5 mg/L as the initial concentration of pollutant, 0.61 g/L catalyst, and an irradiation time of 190 min. Further, it was provided that nitrates play a positive role in the removal of this pollutant, while hydrogenocarbonates slow down its elimination. The ecotoxicity evaluation at different trophic levels confirmed the low toxicity of photodegradation by-products. Data analysis demonstrated that response surface methodology is a reliable approach for the optimization of the interactive effects of photocatalytic process parameters and is able to enhance their performance for the complete elimination of this hardly removed water pollutant.

Enhanced degradation of atrazine through UV/bisulfite: Mechanism, reaction pathways and toxicological analysis

Atrazine residue in the environment continues to threaten aquatic ecosystem and human health owing to its adverse effect. However, limited researches focused on degradation mechanism of atrazine by UV/bisulfite, especially risk of intermediates at cellular and molecular level has not been seriously elaborated. In current work, transformation patterns and residual toxicity of intermediates of atrazine by UV/bisulfite were systematically investigated. The atrazine degradation was described by a pseudo first-order kinetic model (K_obs = 0.1053 min^-1). The presence of H₂PO₄^-, HCO₃^- and HA had a powerful inhibition. Scavenging test of radicals illustrated that SO₄^•-, •OH and O₂^•- existed in UV/bisulfite system, SO₄^•- and •OH were mainly responsible for atrazine degradation. Eight degradation intermediates were identified, which were involved in dealkylation, alkyl oxidation, dechlorination-hydroxylation, and alkylic-hydroxylation. E. coli as a model microorganism was selected to assess the risk of degradation intermediates. The levels of reactive oxygen species, MDA and Na⁺/K⁺-ATPase were declined, suggesting that oxidative damage induced by these intermediates was weakened. According to differential metabolites expression analysis, several key metabolites including aspartate, L-tryptophan, L-asparagine, cytidine, cytosin, stearic acid, behenic acid, were up-regulated, and glutathione, cadaverin, L-2-hydroxyglutaric acid and phytosphingosine were downregulated, clarifying that effective detoxification of atrazine can be performed by UV/bisulfite.

Miniaturized ternary deep eutectic solvent-based matrix solid-phase dispersion: A green sample preparation method for the determination of chlorophenols in river sediment

New ternary deep eutectic solvents were prepared and applied as efficient green dispersing solvents in miniaturized matrix solid-phase dispersion to extract chlorophenols from river sediments for the first time. High-performance liquid chromatography coupled with a photodiode array detector was used to analyze the target analytes. The significant factors affecting the extraction were optimized as follows: dispersant (100 mg), sample (100 mg), ternary eutectic solvents (150 μl), grinding for 1 min, 450 μl of acetonitrile as the elution solvent, and vortex mixing for 20 s. Under the optimal conditions, the method exhibited excellent linearity (correlation coefficient > 0.9980), low limits of detection between 1.039-2.478 μg/g, and extraction recoveries between 93.9% and 99.2%. Furthermore, the method demonstrated excellent precision in the intra- and inter-day analysis with a relative standard deviation below 6%. When compared to conventional extraction techniques, the miniaturized matrix solid-phase dispersion considerably reduced samples and solvent usag, offering important environmental benefits. The green profile of the method was assessed using the complementary green analytical procedure index tool confirming its eco-friendship. The technique was finally employed to evaluate sediment samples from three distinct locations along the Zuibaiji River, indicating its applicability for monitoring environmental samples.

Heterogeneous Catalytic Ozonation: Solution pH and Initial Concentration of Pollutants as Two Important Factors for the Removal of Micropollutants from Water

There are several publications on heterogeneous catalytic ozonation; however, their conclusions and the comparisons between them are not always consistent due to the variety of applied experimental conditions and the different solid materials used as catalysts. This review attempts to limit the major influencing factors in order to reach more vigorous conclusions. Particularly, it highlights two specific factors/parameters as the most important for the evaluation and comparison of heterogeneous catalytic ozonation processes, i.e., (1) the pH value of the solution and (2) the initial concentration of the (micro-)pollutants. Based on these, the role of Point of Zero Charge (PZC), which concerns the respective solid materials/catalysts in the decomposition of ozone towards the production of oxidative radicals, is highlighted. The discussed observations indicate that for the pH range 6–8 and when the initial organic pollutants’ concentrations are around 1 mg/L (or even lower, i.e., micropollutant), then heterogeneous catalytic ozonation follows a radical mechanism, whereas the applied solid materials show their highest catalytic activity under their neutral charge. Furthermore, carbons are considered as a rather controversial group of catalysts for this process due to their possible instability under intense ozone oxidizing conditions.

Enhanced Photocatalytic Degradation of P-Chlorophenol by ZnIn2S4 Nanoflowers Modified with Carbon Quantum Dots

The removal of chlorophenol (CP) contaminants from water is a great challenge owing to their natural robustness and the toxic chlorinated by-products generated in degradation processes. In this work, a series of three-dimensional nanoflower-like structured photocatalysts (CQDs/ZnIn2S4-x, x = 1, 2, or 3 wt%) were fabricated via a facile hydrothermal approach. Excellent photocatalytic abilities toward 4-CP degradation under Xe lamp irradiation were achieved over the as-prepared composites. The removal efficiency of total organic carbon for 4-CP on the optimized CQDs/ZnIn2S4-2 was 49.1%, which was 16.0% higher than that of ZnIn2S4. The presence of CQDs could not only be used to adjust controllable band structures for enhancing light absorption, but it could also serve as an electron acceptor to promote the transition of electron–hole pairs. Moreover, a possible degradation mechanism of 4-CP was also proposed according to the analyses of active species, electron paramagnetic resonance characterization, degradation products, and attacked sites. Overall, this work unveils a superior function of an efficient photocatalyst for refractory organic pollutants.

Existence of Ti3+ and dislocation on nanoporous CdO-TiO2 heterostructure applicable for degrading chlorophenol pollutant

This study addresses the significance of wastewater recuperation by a simple and facile treatment process known as photocatalyst technology using visible light. Titanium di-oxide (TiO₂) is the most promising photocatalyst ever since longing decades, has good activity under UV light, owing to its small band gap. Hence, TiO₂ has been modified with metal oxides for the positive response against visible light. Since this is an efficient process, the novelty has been made on nanometal oxide CdO (cadmium oxide) combined with TiO₂ to acquire the best efficiency of degrading organic chlorophenol contaminant. Initially, the composites were synthesized by sol-gel and thermal decomposition methods and investigated for their various outstanding properties. The characterized outcomes have exhibited heterostructures with reduced crystallite size from the X-ray diffraction studies. Then, the determination of nanoporous feature was recognized through HR-TEM analysis which was also detected with some dislocations. The EDX spectrum was identified the perfect elemental composition. The nitrogen adsorption-desorption equilibrium was attained that offers many pores measured with high surface area. The XPS result convinced that Ti³⁺ was accessible along with TIO₂/CdO composite. Further the absorption towards higher wavelength was obtained from UV-vis spectra. Finally, for the photocatalytic application of chlorophenol, the composite shows higher percentage of degrading efficiencies than the pristine TiO₂. The photocatalytic mechanism was discussed in detail.

Recent Progress in Photocatalytic Removal of Environmental Pollution Hazards in Water Using Nanostructured Materials

Water pollution has become a critical issue because of the Industrial Revolution, growing populations, extended droughts, and climate change. Therefore, advanced technologies for wastewater remediation are urgently needed. Water contaminants are generally classified as microorganisms and inorganic/organic pollutants. Inorganic pollutants are toxic and some of them are carcinogenic materials, such as cadmium, arsenic, chromium, cadmium, lead, and mercury. Organic pollutants are contained in various materials, including organic dyes, pesticides, personal care products, detergents, and industrial organic wastes. Nanostructured materials could be potential candidates for photocatalytic reduction and for photodegradation of organic pollutants in wastewater since they have unique physical, chemical, and optical properties. Enhanced photocatalytic performance of nanostructured semiconductors can be achieved using numerous techniques; nanostructured semiconductors can be doped with different species, transition metals, noble metals or nonmetals, or a luminescence agent. Furthermore, another technique to enhance the photocatalytic performance of nanostructured semiconductors is doping with materials that have a narrow band gap. Nanostructure modification, surface engineering, and heterojunction/homojunction production all take significant time and effort. In this review, I report on the synthesis and characterization of nanostructured materials, and we discuss the photocatalytic performance of these nanostructured materials in reducing environmental pollutants.

Effect of nanodiamond particles on the structure, mechanical, and thermal properties of polymer embedded ND/PMMA composites

Nanodiamonds (NDs), the allotropic carbon nanomaterials with nanosize, durable inert core, adjustable surface morphology, high thermal constancy, and super mechanical performances, possess the characteristics of promising reinforcement materials for various technological applications. However, ND particles hold a vigorous propensity to aggregate in liquid media, obstructing their implementation in mechanical and thermal sciences. This aggregation is caused by high surface to volume ratio. By reducing the surface energy and lowering cluster formation, the mechanical and thermal properties of NDs can be polished. Herein, we report on the covalent functionalization of NDs with amine moiety through ball milling method. Their dispersion was checked in ethanol and polymethyl methacrylate (PMMA polymer) against nonfunctionalized NDs. The dispersive behavior showed that ball mill functionalized NDs produced preferably stable aqueous dispersions in ethanol media. Furthermore, 0.1, 0.2, and 0.4 wt% ND/PMMA composites were synthesized, and their mechanical and thermal behaviors were studied in terms of hardness, compression, Young`s modulus, flexural strength, tensile strength, and thermogravimetric analysis (TGA). Results revealed that the composites containing 0.2 wt% functionalized ND loaded with PMMA matrix showed outstanding mechanical and thermal performances indicating that 0.2 wt% is the optimum amount for achieving excellent outcomes.

Electrochemical removal of 4-chlorophenol in water using a porous Magnéli-phase (Ti4O7) electrode

Electro-oxidation is a promising technology for removal of refractory organic pollutants. While the appeal of this technology lies in its chemical-free nature, commercially scale-up application may be limited by the availability of electrode materials and mass transport. Here we report the development of a flow-through electro-oxidation system for removal of chlorophenols in water using Magnéli-phase (Ti₄O₇) tubular anode and a 304 stainless steel (SS) tubular cathode. The key to this system was the porous and conductive Magnéli-phase Ti₄O₇ anode, the structure and composition of which was confirmed by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. System efficacy was evaluated by using 4-chlorophenol (4-CP) as a typical refractory contaminant and model chlorophenol. Under optimized conditions, a complete removal of 4-CP could be obtained within 120 min in 0.04 mol L^-1 Na₂SO₄ solution. Electro-produced HO^• and direct electron transfer were both shown to contribute to the 4-CP electro-oxidation process due to the high selectivity and oxygen evolution potential of the Ti₄O₇ anode. The intermediates of 4-CP degradation were identified and a pathway for its electro-oxidation was proposed. When challenged with industrial wastewater containing 4-CP, chemical oxygen demand (COD) and total organic carbon removal efficiencies of 67.5% and 63.1% respectively could be obtained, accounting for energy consumption of 85.1 kWh·kg COD^-1 for degradation of 1 kg of COD in industrial wastewater. This study provides an effective and robust solution for the removal of refractory emerging contaminants from industrial wastewaters using a continuous-flow electro-oxidation system.

New insight into the kinetic study on the different loadings of the CuO/CNT catalyst and its optimization for p-chloroaniline photodegradation

The effect of the copper (Cu) content on Cu oxide loaded onto a carbon nanotube (CuO/CNT) catalyst on the mechanistic, kinetic, and photonic efficiency of the photodegradation of p-chloroaniline (PCA) under visible (Vis) and ultraviolet (UV) light irradiation has been explored. For low-loading (1-5 wt%) CuO/CNTs, photodegradation performed better under UV (>84%) rather than the Vis system; this may be due to the presence of abundant defect sites on both CuO and CNTs, which allowed the multielectron reduction of oxygen at their impurity levels to generate more hydrogen peroxide and subsequent ·OH radicals. The active species under UV were in the following order: h⁺ ≫ e^- > ·OH, while it was vice versa for the Vis system with a well-balanced 50 wt% CuO/CNT catalyst that exhibited a similar performance. The kinetic study showed the transition of the kinetic order from the zeroth to the first order on increasing the PCA concentration under the Vis system and vice versa for the UV system. The Thiele modulus (ϕ) further confirmed that the effect of internal mass transfer was negligible under UV light. In contrast, the transition from mass transfer to kinetic control limitation was observed under the Vis system. The optimum PCA degradation predicted from the response surface analysis was 97.36% at the reaction pH of 7.3, catalyst dosage of 0.45 g L^-1, and initial PCA concentration of 11.02 mg L^-1. The condition obtained was fairly close to the forecasted value with an error of 0.26%.

Fabrication of ZnAl-LDH mixed metal-oxide composites for photocatalytic degradation of 4-chlorophenol

In this work, two different types of ZnAl-layered double hydroxide (LDH) mixed metal-oxide composites (CeO₂ and SnO₂) were synthesized and applied for the photodegradation of 4-chlorophenol (4-CP) in wastewater. The fabricated CeO₂/ZnAl-LDH and SnO₂/ZnAl-LDH were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and theoretical density functional theory (DFT) calculations, suggesting that the band gaps of the synthesized hybrid composites were much lower than those of traditional ZnAl-LDH. In addition, the photocatalytic activity for 4-CP degradation and reaction kinetics were investigated to evaluate the catalytic behavior of the prepared composites. The results indicated that the photocatalytic process in this case followed a pseudo-first-order kinetic model, and SnO₂/ZnAl-LDH illustrated the optimum performance for 4-CP degradation with an efficiency of 95.2% due to its stability and recyclability. Additionally, the reaction mechanism of 4-CP photodegradation was studied over SnO₂/ZnAl-LDH; it presented that 4-CP could be oxidized by hydroxyl radicals, holes, and superoxide radicals, where hydroxyl radicals were identified as the dominant active species during the degradation process. Finally, decomposition intermediates were measured to deduce the reaction pathway of 4-CP, and three tentative pathways were proposed and discussed.

Recent developments in photocatalysis of industrial effluents ։ A review and example of phenolic compounds degradation

Industrial expansion and increased water consumption have created water scarcity concerns. Meanwhile, conventional wastewater purification methods have failed to degrade recalcitrant pollutants efficiently. The present review paper discusses the recent advances and challenges in photocatalytic processes applied for industrial effluents treatment, with respect to phenolic compounds degradation. Key operational parameters including the catalyst loading, light intensity, initial pollutants concentration, pH, and type and concentrations of oxidants are evaluated and discussed. Compared to the other examined controlling parameters, pH has the highest effect on the photo-oxidation of contaminants by means of the photocatalyst ionization degree and surface charge. Furthermore, major phenolic compounds derived from industrial sources are comprehensively presented and the applicability of photocatalytic processes and the barriers in practical applications, including high energy demand, technical challenges, photocatalyst stability, and recyclability have been explored. The importance of energy consumption and operational costs for realistic large-scale processes are also discussed. Finally, research gaps in this area and the suggested direction for improving degradation efficiencies in industrial applications are presented. In the light of these premises, selective degradation processes in real water matrices such as untreated sewage are proposed.

A review on synergistic coexisting pollutants for efficient photocatalytic reaction in wastewater remediation

With the tremendous development of the economy and industry, the pollution of water is becoming more serious due to the excessive chemical wastes that need to remove thru reduction or oxidation reactions. Simultaneous removal of dual pollutants via photocatalytic redox reaction has been tremendously explored in the last five years due to effective decontamination of pollutants compared to a single pollutants system. In a photocatalysis mechanism, the holes in the valence band can remarkably promote the oxidation of a pollutant. At the same time, photoexcited electrons are also consumed for the reduction reaction. The synergistic between the reduction and oxidation inhibits the recombination of electron-hole pairs extending their lifetime. In this review, the binary pollutants that selectively removed via photocatalysis reduction or oxidation are classified according to heavy metal-organic pollutant (HM/OP), heavy metal-heavy metal (HM/HM) and organic-organic pollutants (OP/OP). The intrinsic between the pollutants was explained in three different mechanisms including inhibition of electron-hole recombination, ligand to metal charge transfer and electrostatic attraction. Several strategies for the enhancement of this treatment method which are designation of catalysts, pH of mixed pollutants and addition of additive were discussed. This review offers a recent perspective on the development of photocatalysis system for industrial applications.

Sustainable and effective degradation of aniline by sodium percarbonate activated with UV in aqueous solution: Kinetics, mechanism and identification of reactive species

In recent decades, sodium percarbonate (SPC) has been widely applied as a solid replacement for H₂O₂ in advanced oxidation process (AOPs). In this study, ultraviolet (UV) light was utilized for SPC activation to investigate the aniline degradation performance. The effects of SPC dosages and UV irradiation on aniline degradation were elaborated. The removal efficiency was significantly improved by increasing either the SPC dosage or UV irradiation intensity. Moreover, scavenging experiments showed that •OH, CO₃^•-, and O₂^•- were the predominant reactive species for aniline degradation. Meanwhile, the variation in the amount of •OH in the UV/SPC system was monitored, which revealed the dominant role of •OH. As a result, the mechanism of aniline degradation by the UV/SPC system was demonstrated based on confirmed free radicals. Furthermore, aniline degradation by the UV/H₂O₂ and UV/H₂O₂/Na₂CO₃ system were compared with the UV/SPC system, and an enhancement by the addition of Fe(II) in the UV/SPC system was verified. Aniline degradation was not significantly affected by the initial pH or the presence of Cl^-, SO₄^2- while NO₃^-, HCO₃^- and humid acid (HA) suppressed the reaction. In general, the UV/SPC system is a novel, green, and promising technology for aniline removal from aqueous solutions.

Estimation of 2,4-dichlorophenol photocatalytic removal using different artificial intelligence approaches

Photocatalytic degradation is one of the effective methods to remove various pollutants from domestic and industrial effluents. Several operational parameters can affect the efficiency of photocatalytic degradation. Performing experimental methods to obtain the percentage degradation (%degradation) of pollutants in different operating conditions is costly and time-consuming. For this reason, the use of computational models is very useful to present the %degradation in various operating conditions. In our previous work, Fe3O4/TiO2 nanocomposite containing different amounts of silver nanoparticles (Fe3O4/TiO2/Ag) were synthesized, characterized by various analytical techniques and applied to degradation of 2,4-dichlorophenol (2,4-DCP). In this work, a series of models, including stochastic gradient boosting (SGB), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), the improvement of ANFIS with genetic algorithm (GA-ANFIS), and particle swarm optimization (PSO-ANFIS) were developed to estimate the removal percentage of 2,4-DCP. The model inputs comprised of catalyst dosage, radiation time, initial concentration of 2,4-DCP, and various volumes of AgNO3. Evaluating the developed models showed that all models can predict the occurring phenomena with good compatibility, but the PSO-ANFIS and the SGB models gave a high accuracy with the coefficient of determination (R 2) of 0.99. Moreover, the relative contributions, and the relevancy factors of input parameters were evaluated. The catalyst dosage and radiation time had the highest (32.6%), and the lowest (16%) relative contributions on the predicting of removal percentage of 2,4-DCP, respectively.

Spectroscopic characterization of biosynthesized lead oxide (PbO) nanoparticles and their applications in PVC/graphite-PbO nanocomposites

Extract of Hibiscus rosa-sinensis plants was used for the green synthesis of PbO nanoparticles. The prepared nanoparticles were conformed with the help of SEM, X-ray diffraction, FTIR and UV-visible spectroscopy. The prepared PbO nanoparticles were dispersed in deionized water and mixed with graphite to get graphite-PbO (G-PbO) filler. Seven different nanocomposite membranes with variable compositions (5, 10, 15, 20, 25, 30 and 35%) of PVC/G-PbO were prepared in tetrahydrofuran (THF) solvent using solution casting method. Different physiochemical parameters of the nanocomposite membranes studied included morphology, porosity, density, water uptake, swelling degree, electrical conductivity and proton adsorption capacity. All these physiochemical parameters were compared with pure PVC membranes available in literature. It was found that the addition of G-PbO filler in PVC polymer improved all the physiochemical properties except density. PVC/G-PbO membranes showed 42.65 times more electrical conductivity and 5.90 times more ion adsorption capacities compare to pure PVC membranes.

Enhanced bio-photodegradation of p-chlorophenol by CdS/g-C3N4 3D semiconductor-microbe interfaces

p-chlorophenol (p-CP), one of the highly toxic chlorinated organic compounds, is recalcitrant in conventional biodegradation process. This study reported a synergistic degradation protocol of 3D semiconductor-microbe interfaces, in which graphite felts (GF) and CdS/g-C₃N₄ nanocomposites were chosen as the carrier and semiconductor for enhanced p-CP degradation. Based on microstructure, photoelectrochemical and degradation performance analysis, the optimal CdS content in CdS/g-C₃N₄ nanocomposites was 10 wt%. The efficiencies of p-CP and TOC removal in bio-photodegradation system were as high as 95% and 77% without extra electron acceptors/donors, which were far better than those in traditional photodegradation and biodegradation system. High-throughput sequencing analysis suggested that p-CP degradation related species (Chryseobacterium, Stenotrophomonas and Rhodopseudomonas), electroactive species (Chryseobacterium, Stenotrophomonas, Hydrogenophaga and Cupriavidus) and hydrogen-utilizing species (Hydrogenophaga and Cupriavidus) were enriched at 3D semiconductor-microbe interfaces. The enrichment of functional species played a crucial role for p-CP removal and mineralization at 3D semiconductor-microbe interfaces. Moreover, the mechanism of enhanced p-CP bio-photodegradation at 3D semiconductor-microbe interfaces was investigated by utilizing Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2). The results showed that the genes involved in p-CP biodegradation, hydrogen metabolism and extracellular electron transfer were remarkably enriched. Possible mechanism for enhancement of p-CP degradation in bio-photodegradation system was proposed, in which photocatalytic H₂ and photoelectron transfer played an important role for enhancing p-CP mineralization by microbes. 3D semiconductor-microbe interfaces could maintain excellent performance for p-CP degradation after long-term operation, which provide a potential alternative for the enhanced treatment of wastewater containing p-CP.

Production of Chlorine Dioxide Using Hydrogen Peroxide and Chlorates

Chlorine dioxide was produced by the reduction of chlorate with hydrogen peroxide in strongly acidic media. To avoid reaction interference during measuring procedures, UV spectra were acquired to monitor the chlorate reduction. This reduction led to the formation of chlorine dioxide and notable concentrations of chlorite and hypochlorous acid/chlorine, suggesting that the hydrogen peroxide:chlorate ratio is important. Once chlorates are transformed to chlorine dioxide, the surplus hydrogen peroxide promoted the further reaction of the chlorinated species down to less-important species. Moreover, chlorine dioxide was stripped with the outlet gas flow. A linear relationship was established between the amount of limiting reagent consumed and the maximum height of the absorption peak at 360 nm after testing with different ratios of hydrogen peroxide and chlorate, allowing calculations of the maximum amount of chlorine dioxide formed. To verify the reproducibility of the method, a test with four replicates was conducted in a hydrogen peroxide/chlorate solution where chlorine dioxide reduction was not promoted due to the presence of surplus chlorate in the reaction medium after the test. Results confirmed the efficient formation of this oxidant, with maximum concentrations of 8.0 ± 0.33 mmol L−1 in 400–450 min and a conversion percentage of 97.6%. Standard deviations of 0.14–0.49 mmol L−1 were obtained during oxidation (3.6–6.5% of the average), indicating good reproducibility.

Plasmonic semiconductor photocatalyst: Non-stoichiometric tungsten oxide

Semiconductor photocatalysis has attracted increasing attention due to its potential application in solving the problems related to energy crisis and environmental pollution. As a typical plasmonic semiconductor, non-stoichiometric tungsten oxide (WO_3-X) has invoked significant interest for its unique property and excellent photocatalytic performance. In this review, we briefly introduce the fundamental properties of the WO_3-x, and then summarize the synthesis methods such as solvothermal reaction, solid phase reduction and exfoliation treatment, together with the modification strategies such as doping and constructing homo-/hetero-junctions. Additionally, we emphasize the practical applications of WO_3-x in hydrogen evolution, nitrogen fixation, carbon dioxide reduction, and pollutant degradation. Finally, comprehensive conclusions and perspectives on the fabrication of WO_3-x photocatalyst leading to satisfactory performance are given as well.

Extended visible light driven photocatalytic hydrogen generation by electron induction from g-C3N4 nanosheets to ZnO through the proper heterojunction

The alarming energy crises has forced the scientific community to work for sustainable energy modules to meet energy requirements. As for this, ZnO/g-C3N4 nanocomposites with proper heterojunction were fabricated by coupling a proper amount of ZnO with 2D graphitic carbon nitride (g-C3N4) nanosheets and the obtained nanocomposites were applied for photocatalytic hydrogen generation from water under visible light illumination (λ > 420 nm). The morphologies and the hydrogen generation performance of fabricated photocatalysts were characterized in detail. Results showed that the optimized 5ZnO/g-C3N4 nanocomposite produced 70 µmol hydrogen gas in 1 h compare to 8 µmol by pure g-C3N4 under identical illumination conditions in the presence of methanol without the addition of cocatalyst. The much improved photoactivities of the nanocomposites were attributed to the enhanced charge separation through the heterojunction as confirmed from photoluminescence study, capacity of the fabricated samples for •OH radical generation and steady state surface photovoltage spectroscopic (SS-SPS) measurements. We believe that this work would help to fabricate low cost and effective visible light driven photocatalyst for energy production.

Synthesis and physiochemical performances of PVC-sodium polyacrylate and PVC-sodium polyacrylate-graphite composite polymer membrane

Three types (type-A, B, and C) of composite polymeric membranes (CPMs) based on poly vinyl chloride (PVC) and different fillers (sodium polyacrylate and sodium polyacrylate-graphite) soaked in water and 0.5 N HCl were prepared using solvent casting method. Different physicochemical parameters such as microscopic surface study, water uptake, perpendicular swelling, density, porosity (ε), ion exchange capacity, and conductivity of the as the prepared CPMs were evaluated. Interestingly, type-A CPM cast with filler-A has greater values of the above parameters except density and ionic conductivity than those of type-B and C CPMs. The water uptake of type-A, B and C composite membranes was respectively in the range of 220.42–534.70, 59.64–41.65, and 15.94–2.62%. Ion exchange capacity of type-A, B and C CPMs was in the range of 3.669 × 107–2.156 × 107, 5.948 × 107–1.258 × 107, and 1.454 × 107–1.201 × 107 m.eq.g−1 respectively while the conductivity order was type-A < B < C. These types of CPMs may be helpful in many applications including proton exchange membranes, fuel cell like devices, as sensors for different metals, gas purification, water treatment, and battery separators.