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The design of bioelectrochemical system based on the principle of niche construction, offers a prospective pathway for achieving efficient and thorough biodechlorination in groundwater. This study designed a single-chamber microbial electrolysis cell, with porous three-dimensional (3D) electrodes introduced, to accelerate the niche construction process of functional communities. This approach allowed the growth of various bacteria capable of simultaneously degrading 2,4-dichlorophenol (DCP) and its refractory intermediates, 4-chlorophenol (4CP). The 3D-electrodes provided abundant attachment sites for diverse microbes with a high initial Shannon index (3.4), and along the degradation progress, functional bacteria (Hydrogenoanaerobacterium and Rhodococcus erythropolis for DCP-degrading, Sphingobacterium hotanense for 4CP-degrading and Delftia tsuruhatensis for phenol-degrading) constructed their niches. Applying an external voltage (0.6 V) further increased the selective pressure and niche construction pace, as well as provided 'micro-oxidation' site on the electrode surface, thereby achieving the degradation of 4CP and mineralization of phenol. The porous electrodes could also adsorb contaminants and narrow their interaction distance with microbes, which benefited the degradation efficiency. Thus a 10-fold increase in the overall mineralization of DCP was achieved. This study constructed a novel bioelectrochemical system for achieving efficient and thorough biodechlorination, which was suitable for in situ bioremediation of groundwater.

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Chlorophenols are one of the major organic pollutants responsible for the contamination of water bodies. This study explores the application of Ni-Zn/CeO2 nanocomposites, synthesized via the aqueous co-precipitation method, as effective adsorbents for the 4-chlorophenol removal from aqueous solutions. The nanocomposites' chemical and structural characteristics were assessed using different physical characterization methods, viz. X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, zeta potential, using a Box-Behnken design within response surface methodology, optimal conditions of pH 3, temperature 20 °C, contact time 120 min, adsorbent dosage 0.05 g, and 4-chlorophenol concentration 50 ppm are identified. Among the nanocomposites tested, NZC 20:10:70, with 20% Ni and 10% Zn, achieves enhanced performance, removing 99.1% of 4-chlorophenol within 2 h. Adsorption kinetics follow the pseudo-second-order model and equilibrium data fit the Freundlich isotherm. Thermodynamic analysis indicates an exothermic and spontaneous process. The adsorption capacity of NZC 20:10:70 shows significant enhancement, growing from 19.85 mg/g at 10 ppm to 96.33 mg/g at 50 ppm initial concentration. Physical characterization confirms NZC 20:10:70's superior properties, including a high surface area of 118.471 m2/g. Evaluating economic viability, NZC 20:10:70 demonstrates robust reusability, retaining 85% efficiency over eight regeneration cycles. These results highlight NZC 20:10:70 as a promising adsorbent for effective and sustainable chlorophenol removal in water treatment.

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Ammonia monooxygenase (AMO)-mediated cometabolism of organic pollutants has been widely observed in biological nitrogen removal process. However, its molecular mechanism remains unclear, hindering its practical application. Furthermore, conventional nitrification systems encounter significant challenges such as air pollution and the loss of ammonia-oxidizing bacteria, when dealing with wastewater containing volatile organic pollutants. This study developed a nitrifying membrane-aerated biofilm reactor (MABR) to enhance the biodegradation of volatile 4-chlorophenol (4-CP). Results showed that 4-CP was primarily removed via Nitrosomonas nitrosa-mediated cometabolism in the presence of NH4+-N, supported by the increased nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP) content, AMO activity and the related genes abundance. Hydroquinone, detected for the first time and produced via oxidative dechlorination, as well as 4-chlorocatechol was primary transformation products of 4-CP. Nitrosomonas nitrosa AMO structural model was constructed for the first time using homology modeling. Molecular dynamics simulation suggested that the ortho-carbon in the benzene ring of 4-CP was more prone to metabolismcompared to the ipso-carbon. Density functional theory calculation revealed that 4-CP was metabolized by AMO via H-abstraction-OH-rebound reaction, with a significantly higher rebound barrier at the ipso-carbon (16.37 kcal·mol-1) as compared to the ortho-carbon (6.7 kcal·mol-1). This study fills the knowledge gap on the molecular mechanism of AMO-mediated cometabolism of organic pollutants, providing practical and theoretical foundations for improving volatile organic pollutants removal through nitrifying MABR.

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This current study explored the effect of pyrite on the treatment of chlorophenolic compounds (CP) by Fenton process with micron-sized zero-valent iron (ZVI) as the catalyst. The experiments were conducted in batch reactors with 100 mg L-1 CP, 0-0.02 M H2O2, and variable pyrite and ZVI doses (0-1 g L-1). Our findings show that while the reactor with 1 g L-1 ZVI as the only catalyst achieved only 10% CP removal efficiency due to rapid ZVI surface passivation and ZVI particle aggregation, the CP removal efficiency increased with increasing pyrite dose and reached 100% within couple of minutes in reactors with 0.8 g L-1 pyrite and 0.2 g L-1 ZVI. The CP removal was mainly driven by the oxidative treatment of CPs with some strong radicals such as hydroxyl radicals (•OH) while the adsorption onto the catalyst surface was only responsible for 10 to 25% of CP removals, depending on the type of CP studied. The positive impact of pyrite on CP removal by the ZVI/H2O2 system could be attributed to the ability of pyrite to (1) create an acidic environment for optimum Fenton process, (2) provide support material for ZVI to minimize ZVI particle agglomeration, and (3) stimulate iron redox cycling for improved surface site generation. Following oxidative Fenton treatment, the degradation intermediate products of CPs, including some aromatic compounds (benzoquinone, hydroquinone, etc.) and organic acids (e.g., acetic acid), became more biodegradable in comparison to their mother compounds. Overall, the treatment systems with a mixture of ZVI and pyrite as catalyst materials could offer a suitable cost-effective technology for the treatment of wastewater containing biologically non- or low-degradable toxic compounds such as chlorophenols.

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Pesticide micropollutants like 4-chlorophenol (4CP) and E. coli bacteria represent a substantial hazard, impacting both the environment and human health. This study delves into the effectiveness of Ag-doped TiO2 (Ag@TiO2) in removing both 4CP and E. coli. Ag@TiO2 has demonstrated remarkable effectiveness in removing 4CP under both solar and visible light conditions, earning degradation efficiencies of 91.3% and 72.8%, respectively. Additionally, it demonstrates outstanding photodegradation efficiency for 4CP (98.8%) at an initial concentration of 1 mg L-1. Moreover, Ag@TiO2 exhibited substantially higher removal performance for 4CP (81.6%) compared to TiO2 (27.6%) in wastewater. Analysis of the radicals present during the photodegradation process revealed that ·O2- primarily drives the decomposition of 4CP, with h+ and ·OH also playing significant roles in the oxidation reactions of the pollutant. Interestingly, even under dark conditions, Ag@TiO2 exhibited the capability to eliminate approximately 20% of E. coli, a percentage that increased to over 96% under solar light. In addition, the prospects for environmental and health impacts of utilizing Ag@TiO2 for pesticide micropollutant removal and bacteria were discussed.

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Rational reuse of municipal sludge to produce electro-Fenton electrode can not only save resources, but also produce superior peroxide and degradation pollutants simultaneously. Herein, a novel electro-Fenton electrode derived from sludge biochar loaded on Ni foam (SBC@Ni) was constructed via high temperature pyrolysis and chemical coating for efficient H2O2 evolution and pollutant degradation. Systematic experiments and density functional theory calculations (DFT calculation) explained that the production of graphite C and graphite N during high-temperature pyrolysis of municipal sludge can greatly enhance the oxygen reduction reaction of SBC@Ni electrode and promote the evolution of H2O2. And the hybrid heterojunctions, such as FeP, also played a key role in electrocatalytic processes. Notably, the electrode still exhibited excellent performance after 1000 linear scans and 12 h of continuous current stimulation, which demonstrated the excellent stability of the electrode. Moreover, SBC@Ni electrode can not only effectively oxidize 4-chlorophenol through the electro-Fenton effect, but also fully mineralize organic matter, indicating promising environmental application. The free radical quenching experiment also revealed that the ·OH is the main active species for 4-CP degradation in SBC@Ni electro-Fenton system.

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Halogenated aromatic compounds possess bidirectional effects on denitrifying bio-electron behavior, providing electrons and potentially interfering with electron consumption. This study selected the typical 4-chlorophenol (4-CP, 0-100 mg/L) to explore its impact mechanism on glucose-supported denitrification. When COD(glucose)/COD(4-CP)=28.70-3.59, glucose metabolism remained the dominant electron supply process, although its removal efficiency decreased to 73.84-49.66 %. When COD(glucose)/COD(4-CP)=2.39-1.43, 4-CP changed microbial carbon metabolism priority by inhibiting the abundance of glucose metabolizing enzymes, gradually replacing glucose as the dominant electron donor. Moreover, 5-100 mg/L 4-CP reduced adenosine triphosphate (ATP) by 15.52-24.67 % and increased reactive oxygen species (ROS) by 31.13-63.47 %, causing severe lipid peroxidation, thus inhibiting the utilization efficiency of glucose. Activated by glucose, 4-CP dechlorination had stronger electron consumption ability than NO2--N reduction (NO3--N > 4-CP > NO2--N), combined with the decreased nirS and nirK genes abundance, resulting in NO2--N accumulation. Compared with the blank group (0 mg/L 4-CP), 5-40 mg/L and 60-100 mg/L 4-CP reduced the secretion of cytochrome c and flavin adenine dinucleotides (FAD), respectively, further decreasing the electron transfer activity of denitrification system. Micropruina, a genus that participated in denitrification based on glucose, was gradually replaced by Candidatus_Microthrix, a genus that possessed 4-CP degradation and denitrification functions after introducing 60-100 mg/L 4-CP.

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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.

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This study introduces the UV/glucose-oxidase@Kaolin (GOD@Kaolin) coupled organic green rust (OGR) system (UV/OGR/GOD@Kaolin) to investigate the promotion of glucose oxidase activity by UV light and its synergistic degradation mechanism for photosensitive pollutants, specifically targeting the efficient degradation of 4-chlorophenol (4-CP). The enzyme system demonstrates its ability to overcome drawbacks associated with traditional Fenton systems, including a narrow pH range and high localized concentration of H2O2, by gradually releasing hydrogen peroxide in situ within a neutral environment. In the presence of UV radiation under specific conditions, enhanced enzyme activity is observed, resulting in increased efficiency in pollutant removal. The gradual release of hydrogen peroxide plays a crucial role in preventing unwanted reactions among active substances. These unique features facilitate the generation of highly reactive species, such as Fe(IV)O, •OH, and •O2-, tailored to efficiently target the organic components of interest. Additionally, the system establishes a positive iron cycle, ensuring a sustained reactive capability throughout the degradation process. The results highlight the UV/OGR/GOD@Kaolin system as an effective and environmentally friendly approach for the degradation of 4-CP, and the resilience of the enzyme extends the system's applicability to a broader range of scenarios.

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In this research, graphitic carbon nitride/zinc oxide-copper denoted as GCN/ZnO-Cu nanocomposite photocatalysts were synthesized using a novel facile synthesis process, the co-exfoliation method involving ultrasonic exfoliation of the mixture of GCN and ZnO-Cu in ethanol and then thermal exfoliation. Different characterization techniques such as X-ray diffraction (XRD), mean crystallite size (MCS), BET surface area, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), particle size distribution (PSD), Fourier transform-infrared spectroscopy (FT-IR), photoluminescence (PL) spectra, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were conducted to study the crystallinity, morphology, elemental composition, chemical structure, and optoelectronic properties. The band gap was estimated using the UV-Vis DRS results and Tauc plots. The photocatalytic activity of the GCN/ZnO-Cu3% nanocomposites was evaluated in the degradation of 4-chlorophenol (4-CP), and the disinfection of wastewater primary influent under a narrowband visible light source, royal blue LED (λ = 450 nm). GCN/0.1ZnO-Cu3% nanocomposite showed the best performance in the degradation of 4-CP and the disinfection of municipal wastewater primary influent. For 4-CP degradation, GCN/0.1ZnO-Cu3% was 2.2 times better than GCN, 9.4 times better than ZnO-Cu3%, and 1.8 times better than the sum of the individual GCN and ZnO-Cu3%. A 5.5 log reduction was achieved for the disinfection of total coliforms in wastewater primary influent in 360 min. This enhanced photocatalytic activity of GCN/ZnO-Cu3% nanocomposite can be attributed to the synergistic of GCN and the ZnO-Cu3%, resulting in a large surface area and improved bandgap.

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In this work, a simple g-C3N4 quantum dots enriched MoO3 nanohybrid was formulated for the synergistic photocatalytic degradation of an industrially active organic pollutant, p-chlorophenol (PCP) and a widely prescribed antibiotic, rifampicin (RIF). The nanohybrid was synthesised via a facile ultrasonic assisted hydrothermal method and characterized using various characterization analysis. The efficient Z-scheme charge transfer of the nanohybrid resulted in the elimination of 98% PCP and 89% RIF under visible light with a rate constant of 0.012 and 0.006 min-1 respectively. The photocatalysis was attributed to the formation of both hydroxyl (OH•) and superoxide (O2•-) radicals in the resulting nanohybrid. The intermediates formed in the course of reaction were estimated through gas chromatography-mass spectroscopy/mass spectroscopy (GC-MS/MS) analysis and a suitable degradation pathway was constructed. The structural stability and reusability of the nanohybrid was affirmed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis to outweigh the industrial potential of the catalyst, with 85% PCP and 80% RIF removal efficiency after six cycles of degradation. In addition, the mineralization of the pollutants was confirmed by total organic carbon analysis. Further, the toxicity of the drug and the formed intermediates was determined using ecological structure activity relationships (ECOSAR) software. On the whole, this work provides an excellent insight for the development of environment-friendly materials in a large scale for the degradation of water-based pollutants.

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The present study highlights the treatment of industrial effluent, which is one of the most life-threatening factors. Herein, for the first time, two types of NiO (green and black) photocatalysts were prepared by facile chemical precipitation and thermal decomposition methods separately. The synthesized NiO materials were demonstrated with various instrumental techniques for finding their characteristics. The X-ray diffraction studies (XRD) and X-ray photoelectron spectroscopy (XPS) revealed the presence of Ni2O3 in black NiO material. The transmission electron microscopic (TEM) images engrained the nanospherical shaped green NiO and nanoflower shaped black NiO/Ni2O3 materials. Further, the band gap of black NiO nanoflower was 2.9 eV compared to green NiO having 3.8 eV obtained from UV-vis spectroscopy. Meanwhile, both NiO catalysts were employed for visible light degradation, which yields a 60.3% efficiency of black NiO comparable to a 4.3% efficiency of green NiO within 180 min of exposure. The higher degrading efficiency of black NiO was due to the presence of Ni2O3 and the development of pores, which was evident from the Barrett-Joyner-Halenda (BJH) method. Type IV hysteresis was observed in black NiO nanoflowers with high surface area and pore size measurements. This black NiO/Ni2O3 synthesized from the thermal decomposition method has promoted better photocatalytic degradation of 4-chlorophenol upon exposure to visible light and is applicable for other industrial pollutants.

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Chlorophenols frequently occur alongside salinity in industrial wastewater; thus, the effects of low concentrations of salinity (NaCl, 100 mg/L) on sludge performance, microbial community, and functional genes were deeply analyzed among 4-chlorophenol (4-CP, 2.4-4.0 mg/L) wastewater treatment. The influent 4-CP was effectively degraded, but the efficiencies for PO43--P, NH4+-N, and organics reduction were slightly inhibited by NaCl stress. Long-term NaCl and 4-CP stress significantly stimulated the secretion of extracellular polymeric substances (EPS). The abundances of predominant microbes at different taxonomic levels were affected by NaCl, and the increased relative abundances of functional genes encoding proteins contributed to resist NaCl and 4-CP stress. The functional genes associated with phosphorus metabolism and nitrogen metabolism in nitrification were unaffected, but the functional genes in denitrification increased in diversity under NaCl stress in 4-CP wastewater treatment. This finding acquires useful insight into the wastewater treatment with low chlorophenols and low salinity.

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Hydrodechlorination (HDC) is a reaction that involves the use of hydrogen to cleave the C-Cl bond in chlorinated organic compounds such as chlorophenols and chlorobenzenes, thus reducing their toxicity. In this study, a palladium (Pd) catalyst, which is widely used for HDC due to its advantageous physical and chemical properties, was immobilized on alumina (Pd/Al) and graphene-based materials (graphene oxide and reduced graphene oxide; Pd/GO and Pd/rGO, respectively) to induce the HDC of 4-chlorophenol (4-CP). The effects of the catalyst dosage, initial 4-CP concentration, and pH on 4-CP removal were evaluated. We observed that 4-CP was removed very rapidly when the HDC reaction was induced by Pd/GO and Pd/rGO. The granulation of Pd/rGO using sand was also investigated as a way to facilitate the separation of the catalyst from the treated aqueous solution after use, which is to improve practicality and effectiveness of the use of Pd catalysts with graphene-based support materials in an HDC system. The granulated catalyst (Pd/rGOSC) was employed in a column to induce HDC in a continuous flow reaction, leading to the successful removal of most 4-CP after 48 h. The reaction mechanisms were also determined based on the oxidation state of Pd, which was observed using X-ray photoelectron spectroscopy. Based on the results as a whole, the proposed granulated catalyst has the potential to greatly enhance the practical applicability of HDC for water purification.

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The response characteristic and performance stabilization of anammox process under the stress of the potential organic pollutants support the application of ammonia-nitrogen wastewater treatment. In the present study, nitrogen removal performance was significantly suppressed with the addition of 4-chlorophenol. The activity of anammox process was inhibited by 14.23% (0.1 mg/L), 20.54% (1 mg/L) and 78.15% (10 mg/L), respectively. Metagenomic analysis revealed a significant decrease in the abundance of KEGG pathways associated with carbohydrate and amino acid metabolism with increasing 4-chlorophenol concentration. Metabolic pathway profiles suggest that putrescine is down-regulated at high 4-chlorophenol stress due to inhibition of nitrogen metabolism processes, while it is up-regulated to reduce oxidative damage. In addition, the presence of 4-chlorophenol induced an enhancement of EPS and bacterial debris decomposition, and a partial conversion of 4-chlorophenol to p-nitrophenol. This study unravels the mechanism of effect on anammox consortia in response to 4-CP, which could provide supplementary to facilitate its full-scale application.

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Bismuth oxide (BiO2-x) with oxygen vacancies was created using a hydrothermal process and was found to exhibit good catalytic oxidation performance under low-temperature heating without the addition of external oxidants. The catalytic activity of BiO2-x was tested using 4-chlorophenol (4-CP) as the target aqueous pollutant. We observed that 10 ppm of 4-CP was completely degraded within 40 min at a reaction temperature of 65 °C. The effective elimination of 4-CP was attributed to active oxygen species produced by the release of lattice oxygen. Furthermore, the low-temperature thermal catalytic activity of BiO2-x was affected by the electron transfer characteristics of pollutants, leading to the rapid degradation of electron-rich pollutants. This study reveals the unique application of BiO2-x as a catalyst for removing phenolic pollutants under low-temperature thermal catalysis, thereby expanding its catalytic application scenarios and offering a new approach for the degradation of phenolic pollutants.

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Natural manganese-containing mineral (NMM) was used as a catalyst in heterogeneous catalytic ozonation for 4-chlorophenol (4-CP) degradation. The surface and structural properties of NMM were modified by the hydrothermal aging process and called H-NMM. The catalytic activity of NMM and H-NMM were evaluated for the catalytic ozonation process (COP). The synergistic effect of NMM and H-NMM in ozonation processes for 4-CP degradation under optimal conditions (pH of 7, 1 g/L of NMM and H-NMM, 0.85 mg/min of O3, and 15 min of reaction time) was measured by 3.04 and 4.34, respectively. During the hydrothermal process, Mn4+ and Fe2+ were converted to Mn2+ and Fe3+, which caused better performance of the H-NMM than the NMM. During the catalytic ozonation process, Mn2+ is completely oxidized, which increases the production of Hydroxyl radical (•OH). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging experiments. •OH, superoxide radical (•O2-), and singlet oxygen (1O2) represented the dominant reactive species for 4-CP degradation. The O3/H-NMM process indicated a powerful ability in the mineralization of 4-CP (66.31% of TOC degradation). H-NMM exhibited excellent stability and reusability in consecutive catalytic cycles, and the NMM exhibited desirable performance. This study offers NMM and H-NMM as effective, stable, and competitive catalysts for hastening and enhancing the ozonation process to mitigate environmentally related pollutants of high concern.

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Lower back pain is a universal dilemma leaving a negative effect on both health and life quality. It was found that a fixed dose combination of chlorzoxazone and ibuprofen gave a higher efficiency than analgesic alone in treatment of acute lower back pain. Based on the significant benefit of that combination, a green, sensitive, rapid, direct, and cost-effective method is created for concurrent determination of ibuprofen and chlorzoxazone in presence of 2-amino para chlorophenol (a synthetic precursor and potential impurity of chlorzoxazone) adopting the synchronous spectrofluorimetric technique. Synchronous spectrofluorimetric technique is adopted to avoid the highly overlapped native spectra of both drugs. The synchronous spectrofluorometric method was applied at Δλ = 50 nm, ibuprofen was measured at 227 nm while chlorzoxazone was measured at 282 nm with no hindering from one to another. The various experimental variables affecting the performance of the suggested technique were explored and adjusted. The suggested technique showed good linearity from 0.02 to 0.6 and 0.1 to 5.0 µg/mL for ibuprofen and chlorzoxazone, respectively. The produced detection limits were 0.27 × 10-3 and 0.03, while the quantitation limits were 0.82 × 10-3 and 0.09 µg/mL for ibuprofen and chlorzoxazone, respectively. The suggested approach was successfully applied for the analysis of the studied drugs in the synthetic mixture, different pharmaceutical preparations, and spiked human plasma. The suggested technique was validated with respect to the International Council of Harmonization (ICH) recommendations. The suggested technique was found to be simpler and greener with lower cost compared to the earlier reported methods which required complicated techniques, longer time of analysis, and less safe solvents and reagents. Green profile assessment for the developed method compared with the reported spectrofluorometric method was performed using four assessment tools. These tools confirmed that the recommended technique attained the most possible green parameters, so it could be used as a greener option in routine quality control for analyzing the two drugs in genuine form and pharmaceutical preparations.

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The Fenton process is a widely used to remedy organic wastewaters, but it has problems of adding H2O2, low utilization efficiency of H2O2 and low mineralization efficiency. Here, a new photocatalysis-self-Fenton process was exploited for the removal of persistent 4-chlorophenol (4-CP) pollutant through coupling the photocatalysis of 4-carboxyphenylboronic acid edge covalently modified g-C3N4 (CPBA-CN) with Fenton. In this process, H2O2 was in situ generated via photocatalysis over CPBA-CN, the photogenerated electrons assisted the accelerated regeneration of Fe2+ to improve the utilization efficiency of H2O2, and the photogenerated holes facilitated the enhancement of 4-CP mineralization. Under the conjugation of CPBA, the electronic structure of CN was optimized and the molecular dipole was enhanced, resulting in the deepening valence band position, accelerated electron-hole pair separation, and improved O2 adsorption-activation. Therefore, the incremental 4-CP degradation rate in the CPBA-CN photocatalysis-self-Fenton process was approaching 0.099 min-1, by a factor of 3.1 times compared with photocatalysis. The parallel mineralization efficiency increased to 74.6% that was 2.1 and 2.6 times than photocatalysis and Fenton, respectively. In addition, this system maintained an excellent stability in the recycle experiment and can be potentially applied in a wide range of pHs and under the coexistence of various ions. This study would provide new insights for improving Fenton process and promote further development of Fenton in organic wastewater purification.

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Photo-Fenton processes activated by biodegradable Fe(III)-EDDS complexes have attracted huge attention from the scientific community, but the operative mechanism of the photo-activation of H2O2 in the presence of Fe(III)-EDDS has not been fully clarified yet. The application of the Fe(III)-EDDS complex in Fenton and photo-Fenton (mainly under UV-B light) processes, using 4-chlorophenol (4-CP) as a model pollutant was explored to give insights into the operative mechanism. Furthermore, the potential synergistic contribution of soybean peroxidase (SBP) was investigated, since it has been reported that upon irradiation of Fe(III)-EDDS the production of H2O2 can occur. SBP did not boost the 4-CP degradation, suggesting that the possibly produced H2O2 reacts immediately with the Fe(II) ion with a quick kinetics that does not allow the diffusion of H2O2 into the bulk of the solution (i.e., outside the solvent cage of the complex). So, a concerted mechanism in which the photochemically produced H2O2 and Fe(II) react inside the hydration sphere of the Fe(III)-EDDS complex is proposed.

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