Degradation of sulfanilamide by Fenton-like reaction and optimization using response surface methodology

Bacterial community structure analysis of sludge from Taozi lake and isolation of an efficient 17β-Estradiol (E2) degrading strain Sphingobacterium sp. GEMB-CSS-01

Environmental challenges arising from organic pollutants pose a significant problem for modern societies. Efficient microbial resources for the degradation of these pollutants are highly valuable. In this study, the bacterial community structure of sludge samples from Taozi Lake (polluted by urban sewage) was studied using 16S rRNA sequencing. The bacterial phyla Proteobacteria, Bacteroidetes, and Chloroflexi, which are potentially important in organic matter degradation by previous studies, were identified as the predominant phyla in our samples, with relative abundances of 48.5%, 8.3%, and 6.6%, respectively. Additionally, the FAPROTAX and co-occurrence network analysis suggested that the core microbial populations in the samples may be closely associated with organic matter metabolism. Subsequently, sludge samples from Taozi Lake were subjected to enrichment cultivation to isolate organic pollutant-degrading microorganisms. The strain Sphingobacterium sp. GEMB-CSS-01, tolerant to sulfanilamide, was successfully isolated. Subsequent investigations demonstrated that Sphingobacterium sp. GEMB-CSS-01 efficiently degraded the endocrine-disrupting compound 17β-Estradiol (E2). It achieved degradation efficiencies of 80.0% and 53.5% for E2 concentrations of 10 mg/L and 20 mg/L, respectively, within 10 days. Notably, despite a reduction in degradation efficiency, Sphingobacterium sp. GEMB-CSS-01 retained its ability to degrade E2 even in the presence of sulfanilamide concentrations ranging from 50 to 200 mg/L. The findings of this research identify potential microbial resources for environmental bioremediation, and concurrently provide valuable information about the microbial community structure and patterns within Taozi Lake.

Denim industry wastewater treatment by a heterogeneous solar-Fenton process catalyzed by Fe supported on recycled polyethylene terephthalate (PET) by ultrasonic modification

The textile industry is an important economic sector; however, its wastewater generates a great impact on the environment. A heterogeneous solar Fenton (HSF) process was evaluated for denim wastewater treatment. The catalyst was obtained through ultrasonic modification of recycled polyethylene terephthalate (PET) with Fe nanoparticles (PET/NPs- Fe3O4). The SFH process was optimized using surface response methodology with a face-centered central composite design considering the effects of the hydraulic retention time (10, 25, and 40 min), hydrogen peroxide dosage (500, 1000, and 1500 mg/L), and mass of the packed catalyst (4, 6 and 8 g) on the color, COD, and turbidity removal efficiencies. The operating conditions for maximum COD removal were H2O2 541.7 mg/L, HRT 33.9 min, and PET/NPs- Fe3O4 dose 7.9 g with solar radiation. The removal of 91.2% COD, 86.2% color, 90.4% turbidity, and 81.9% TOC was obtained at 14.2 kJ/L QUva. PET modification yielded 1.6 mg Fe/g PET, and the modification method does not allow Fe leaching. The effluent obtained from the SFH process complies with the maximum permissible limits in Mexican legislation in terms of COD, TOC, turbidity, and color and allows the reuse of PET.

Evaluation of the photodegradation activity of bismuth oxoiodide/bismuth sub-carbonate nanocatalyst: Experimental design and the mechanism study

In this study, a binary BiOI/(BiO)2CO3 catalyst was prepared and used for sulfasalazine (SSZ) photodegradation in an aqueous phase. The semiconductors were identified by XRD, SEM-EDX, and UV-Vis diffuse reflectance spectroscopy (DRS) methods. Applying the Kubelka-Munk model on DRS results, the band gap energies of 2.09, 3.5, and 2.07 eV were obtained for BiOI, (BiO)2CO3, and BiOI/(BiO)2CO3 samples. pHpzc values of 6.3, 10.1, and 8.1 were estimated for BiOI, (BiO)2CO3, and BiOI/(BiO)2CO3, respectively. After observing the boosted photocatalytic activity by the coupled system, the interaction effects of the influencing variables in SSZ photodegradation were evaluated via the response surface methodology (RSM) approach. The optimal RSM-run conditions were 8.5 ppm SSZ at pH 8, which contained 0.28 g/L of the BiOI/(BiO)2CO3 catalyst and 29 min illumination time, resulting in 87% SSZ photodegradation. The effects of some scavenging agents were also studied to elucidate the relative roles of the reactive species in the SSZ photodegradation by the proposed catalyst, that is, hydroxyl radicals ∼ photoinduced electrons > superoxide radicals ∼ photoinduced holes. The proposed catalyst retained good activity after 5 successive reusing runs.

Insight into n-CaO2/SBC/Fe(II) Fenton-like system for glyphosate degradation: pH change, iron conversion, and mechanism

Glyphosate has significant adverse effects on creature and ecological balance. Therefore, the efficient treatment of glyphosate wastewater is of great significance. In this study, nano calcium peroxide (n-CaO₂) was loaded onto activated sludge biochar (SBC), and then Fe(II) was added to construct a Fenton-like system (n-CaO₂/SBC/Fe(II)). SBC played the role of both a dispersant and catalyst, which greatly improved the removal capability of glyphosate. The removal efficiency of glyphosate in the n-CaO₂/SBC/Fe(II) system was as high as 99.6%. The persistent free radicals (PFRs) on SBC can promote the conversion of Fe(III) to Fe(II) in the reaction system, and Fe(II) can be maintained at about 15 mg L^-1 until the reaction reached equilibrium. Due to the synergistic effect of Fe(II) hydrolysis and SBC catalysis, n-CaO₂/SBC/Fe(II) system can effectively remove glyphosate in a wide initial pH range (4.0-10.0), and the pH of the reaction system can be remained in a suitable environment (4.0-6.0) for Fenton-like reaction. Advanced oxidation and chemical precipitation were the main mechanisms for the removal of glyphosate. Most of glyphosate could be oxidized into H₂PO^-₄ anions by breaking the bonds of C-P and C-N, and the H₂PO^-₄ can be further adsorbed and bounded on the surface of the composites. This system overcomes the shortcomings of pH rising and Fe(III) precipitation in the CaO₂-based oxidation systems, and realizes the efficient and complete degradation for glyphosate.

Enhanced degradation of emerging contaminants by percarbonate/Fe(II)-ZVI process: case study with nizatidine

Pharmaceuticals have recently emerged as a significant environmental concern due to the growth of population, expansion of industry, and the shift in modern lifestyles. Herein, we present a Fe(II)/percarbonate (SPC) process with dramatically enhanced efficiency by the introduction of zerovalent iron (ZVI). After the addition of ZVI, the removal rate of nizatidine (NZTD) went up from 71.7 to 84.2%. The removal rate of NZTD decreases with rising pH and speeds up with increasing temperature. It was found that under the condition of pH = 7 and T = 25 °C, the molar ratio of the optimal concentration of NZTD degradation in the system was [NZTD]₀:[SPC]₀:[Fe(II)]₀:[ZVI]₀ = 1:8:24:16, with a degradation rate of 99.8%. At the same time, target pollutants can also be successfully eliminated from actual water bodies. Moreover, we test for toxicity using luminescent bacteria, and the results demonstrate that the system is capable of effectively decreasing the toxicity of NZTD. The research findings can contribute to the clarification of the migration and transformation law of NZTD in the oxidation process, thereby providing a scientific basis and technical support for the removal of NZTD in the tertiary water treatment for a water source.

Degradation of organic compounds in hypersaline wastewater concentrate by a supercritical oxidation approach

Hypersaline wastewater is a typical industrial wastewater produced by iron and steel metallurgy, food material processing and other industries. Aiming at a waste liquid produced by mechanical vapour recompression evaporation and concentration in Tianjin coastal industrial zone, an environment-friendly supercritical water oxidation technology was used to efficiently remove the high-content organic matter in the hypersaline wastewater concentrate (HWC). A comparison of the degradation effects of various oxidants in the supercritical state showed that hydrogen peroxide (H₂O₂) could be used as a suitable agent for processing the HWC. The reaction parameters were systematically optimised by single-factor experiment and response surface design. The degradation mechanism and reaction characteristics were analyzed using gas chromatography mass spectrometry. Solid residues were characterised by field emission scanning electron microscope. The results indicated that when the dosage of hydrogen peroxide was 6.39%, the reaction temperature was 380°C, the reaction time was about 90 min and the optimal total organic carbon removal rate was 96.22%. Furthermore, it was found that hydroxyl radicals produced by hydrogen peroxide initiated the bond breaking and ring-opening reactions in organic matter, which eventually degraded organic matter into water and carbon dioxide.

The role of MnO2 crystal morphological scale and crystal structure in selective catalytic degradation of azo dye

MnO₂, as a representative manganese-based catalyst with many kinds of crystal forms, has been widely used to activate PMS. However, the role of morphological scale and crystal structures on the catalytic capability of MnO₂ still lacks further study. In this study, four different crystal forms of MnO₂ (α-MnO₂, β-MnO₂, γ-MnO₂, and δ-MnO₂) are succeeded in being fabricated via hydrothermal processes and evaluated by activating PMS for the removal of Reactive Yellow X-RG, typical azo dye. Experiment results indicate that α-MnO₂ with a one-dimensional structure exhibits the best catalytic performance among the four as-prepared MnO₂, which can be attributed to its broadest crystal interplanar distance (0.692), the highest portion of Mn (III)/Mn (IV) (4.194), and lowest value of average oxidation state AOS (2.696). Correlation analysis confirms that interplanar distance is the most relative factor with the catalytic activity of MnO₂ among the three studied factors (R² = 0.99715). Meanwhile, the morphological scale structure of α-MnO₂ can also account for its highest catalytic ability among the four as-prepared MnO₂, including its large specific area and advantageous one-dimensional nanostructure. Furthermore, according to the response surface methodology, when the dosage of PMS is 2.369 g/L, the dosage of α-MnO₂ is 0.991 g/L, and the initial dye concentration is 1025 mg/L, the maximum removal rate of Reactive Yellow X-RG is up to 97.38%.

Optimization of Methyl Anthranilate Synthesis Process by Response Surface Methodology and Its Reaction Mechanism

In this paper, a unique process for the production of methyl anthranilate (MA) was investigated. The factors of the phthalimide/sodium hypochlorite/methanol molar ratio, reaction temperature, hydrolysis temperature, and water consumption on the yield and purity of MA were analyzed. Response surface methodology (RSM) was used to optimize conditions for the semi-batch synthesis process of MA. The best synthetic conditions for the formation of MA were reaction temperature 0.5 °C, hydrolysis temperature 70 °C and n(phthalimide)/n(sodium hypochlorite)/n(methanol) = 1:2.03:5.87, and water consumption m(H2O)/m(phthalimide) = 7.16:1. The yield of MA could reach 90% under the optimal conditions, which is more than 10% higher than that of the previous semi-batch process. Furthermore, the reaction mechanism was investigated by infrared spectroscopy analysis, and the mechanism of ester group formation and the structure of intermediate products are proposed. The byproduct of the reaction was studied by GC-MS analysis, a byproduct called 2-cyanobenzoic acid has been discovered. Therefore, an unprecedented reaction mechanism of the whole synthesis process is proposed.

Electrocatalytic degradation of sulfamethylthiadiazole by GAC@Ni/Fe three-dimensional particle electrode

In this work, GAC@Ni/Fe particle electrodes were prepared and employed for the degradation of sulfamethylthiadiazole (SMT) by three-dimensional electrocatalytic technology. The effects of particle electrode bi-metal loading ratio, cell voltage, particle electrode dosage, electrode plate spacing, and SMT initial concentration on SMT removal were studied. In addition, GAC@Ni/Fe particle electrode was analyzed by the scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), and Fourier transform infrared spectrometer (FTIR) to characterize which indicated that a significant amount of iron-nickel oxide was formed on the surface of GAC@Ni/Fe particle electrode. The results indicated that when the nickel-iron loading ratio is 1:1, the SMT removal effect is the best, and the removal rate can reach 90.89% within 30 min. Compared with the granular activated carbon without bimetal, the removal efficiency is increased by 37.58%. The degradation of SMT in the GAC@Ni/Fe particle three-dimensional electrode reactor is the joint result of both direct oxidation and indirect oxidation. The contribution rates of direct oxidation of anode and particle electrode and indirect oxidation of ·OH in the degradation are 32%, 27%, and 41%, respectively. Based on the intermediate detected by ultra-high liquid chromatography and the calculation of bond energy of SMT molecule by Gauss software, the degradation pathway of SMT in the GAC@Ni/Fe three-dimensional electrode reactor is proposed. This research provides a green, healthy, and effective method for removing sulfonamide micro-polluted wastewater.

Green synthesis of Ag2O nanoparticles using Punica granatum leaf extract for sulfamethoxazole antibiotic adsorption: characterization, experimental study, modeling, and DFT calculation

Silver oxide (Ag₂O) nanoparticles (NPs) were generated by synthesizing green leaf extract of Punica granatum, and afterwards they were used as adsorbent to remove the antibiotic additive sulfamethoxazole (SMX) from aqueous solutions. Prior of their use as adsorbent, the Ag₂O NPs were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX), and transmission electron microscopy (TEM). The Ag₂O NPs were found to be spherically shaped and stabilized by the constituents of the extract. Further, at SMX antibiotic concentration of 100 mg L^-1, the Ag₂O NPs achieved almost complete removal of 98.93% within 90 min, and by using 0.8 g L^-1 of adsorbent dose at pH=4 and temperature T=308 K. In addition, the experimental data were well fitted with the theoretical Langmuir model indicating homogeneous adsorbed layer of the SMX antibiotic on the Ag₂O NPs surface. The maximum uptake capacity was 277.85 mg g^-1. A good agreement was also found between the kinetic adsorption data and the theoretical pseudo-second-order model. Regarding the thermodynamic adsorption aspects, the data revealed an endothermic nature and confirmed the feasibility and the spontaneity of the adsorption reaction. Furthermore, the regeneration study has shown that the Ag₂O NPs could be efficiently reused for up to five cycles. The geometric structures have been optimized and quantum chemical parameters were calculated for the SMX unprotonated (SMX^+/-) and protonated (SMX⁺) using density functional theory (DFT) calculation. The DFT results indicated that the unprotonated SMX^+/- reacts more favorably on the Ag₂O surface, as compared to the protonated SMX⁺. The SMX binding mechanism was predominantly controlled by the electrostatic attraction, hydrogen bond, hydrophobic, and π-π interactions. The overall data suggest that the Ag₂O NPs have promising potential for antibiotic removal from wastewater.

Surface mechanism and optimization of catalytic ozonation with CoxFe oxides as catalyst for degradation of sodium p-toluenesulfonate in water

In this study, the removals of sodium p-toluenesulfonate (NaTSA) by catalytic ozonation with two different cobalt-iron compounds, Co_xFe oxides prepared by co-precipitation/calcination (CPO) and Co_xFe oxides prepared by direct calcination (DCO), as the catalysts, had a difference of about 12%. It was found that the CPO surface contained active type c water, which was generally adsorbed on the oxygen vacancy. The test of oxygen temperature-programmed desorption (O₂-TPD) showed that the surface of CPO was rich in oxygen vacancy. Through the electrochemical oxygen evolution reaction (OER) detection, a pair of Co valence redox peaks were detected from the CV curves, and the results of XPS test showed the replacement of octahedral Co³⁺ with Fe^{3 +} in the Co₃O₄ during preparation of CPO. The enriched oxygen vacancy could be used as active sites for ozone adsorption and improve the charge transfer capacity. The number of hydroxyl radicals was detected by electron spin resonance (EPR) and it indicated that CPO contained more hydroxyl radicals, so it had higher effect in catalytic ozonation for organic pollutant degradation. In this paper, the relationship between oxygen vacancy and reactive center in the microstructure of the catalysts was established to discuss their working mechanism. The influence of the initial pH value, catalyst dosage, and ozone concentration on the removal of NaTSA was investigated by response surface design, and the optimal experimental conditions were predicted and verified.

Optimization of Biodegradation Characteristics of Sphingopyxis sp. YF1 against Crude Microcystin-LR Using Response Surface Methodology

Sphingopyxis sp. YF1 has proven to be efficient in biodegrading microcystin (MC)-leucine (L) and arginine (R) (MC-LR); however, the optimal environmental factors to biodegrade the toxin have not been investigated. In this study, the biodegrading characteristics of strain YF1 against MC-LR were assessed under diverse environmental factors, including temperature (20, 30 or 40 °C), pH (5, 7 or 9) and MC-LR concentration (1, 3 or 5 µg/mL). Data obtained from the single-factor experiment indicated that MC-LR biodegradation by strain YF1 was temperature-, pH- and MC-LR-concentration-dependent, and the maximal biodegradation rate occurred at 5 µg/mL/h. Proposing Box-Behnken Design in response surface methodology, the influence of the three environmental factors on the biodegradation efficiency of MC-LR using strain YF1 was determined. A 17-run experiment was generated and carried out, including five replications performed at the center point. The ANOVA analysis demonstrated that the model was significant, and the model prediction of MC-LR biodegradation was also validated with the experimental data. The quadratic statistical model was established to predict the interactive effects of the environmental factors on MC-LR biodegradation efficiency and to optimize the controlling parameters. The optimal conditions for MC-LR biodegradation were observed at 30 °C, pH 7 and 3 µg/mL MC-LR, with a biodegradation efficiency of 100% after 60 min. The determination of the optimal environmental factors will help to unveil the detailed biodegradation mechanism of MC-LR by strain YF1 and to apply it into the practice of eliminating MC-LR from the environment.

Insights into the role of nanoscale zero-valent iron in Fenton oxidation and its application in naphthalene degradation from water and slurry systems

Few researches have focused on the role of nanoscale zero-valent iron (nZVI) in Fenton-like process for polycyclic aromatic hydrocarbons (PAHs) removal. In this study, the naphthalene (NAP) degradation tests in ultrapure water showed that nZVI addition could enhance NAP degradation from 79.7% to 99.0% in hydrogen peroxide (H2 O2 )/Fe (II)/nZVI/NAP system at the molar ratio of 10/5/3/1, showing the excellent role of nZVI in promoting NAP removal. Multiple linear regression analysis found that the correlation coefficient between H2 O2 consumption and NAP degradation was converted from -9.17 to 0.48 with nZVI and 1-mM H2 O2 , indicating that nZVI could decompose H2 O2 more beneficially for NAP degradation. Multiple Fe (II)-dosing and iron leaching tests revealed that nZVI could gently liberate Fe (II) and promote Fe (II)/Fe (III) redox cycle to enhance the NAP degradation. When the H2 O2 /Fe (II)/nZVI/NAP molar ratios of 10/5/3/1 and 50/25/15/1 were applied in the simulated NAP contaminated actual groundwater and soil slurry, respectively, 75.0% and 82.9% of NAP removals were achieved. Based on the major degradation intermediates detected by GC/MS, such as 1,4-naphthalenedione, cinnamaldehyde, and o-phthalaldehyde, three possible NAP degradation pathways were proposed. This study provided the applicable potential of nZVI in Fenton process for PAHs contaminated groundwater and soil remediation. PRACTITIONER POINTS: nZVI enhanced the NAP degradation in Fenton-like process. Three schemes of NAP degradation pathway were proposed. nZVI performed well in the remediation of the simulated NAP contamination.

Microbially-mediated synthesis of activated carbon derived from cottonseed husks for enhanced sulfanilamide removal

This study provided a novel pathway to develop activated carbon with enhanced adsorption performance via feedstock pretreatment by fungi. The growth of Pleurotus ostreatus on cottonseed husks offered this feedstock an advantageous pore size for porous carbon making. The prepared activated carbons derived from cottonseed husks (CSH-ACs) during different fungal growth periods exhibited extraordinary performance than commercial activated carbon for sulfanilamide adsorptive removal. Their experimental data of adsorption capacities for sulfanilamide were 139.43, 146.15, and 146.16 mg g^-1, respectively. The adsorption behaviors of sulfanilamide on CSH-ACs were evaluated by kinetic, isotherm and thermodynamic models. Pore filling, hydrogen-bond forming and π-π staking interactions all contributed to the rapid sulfanilamide removal. The microporous-mesoporous structure, stronger hydrophilicity, and richer functional groups moieties owing to the lignocellulose decomposition in the plant wall significantly strengthened the adsorption process on the microbial-mediated activated carbon. The effects of pH and water impurities (H₂PO₄^-, CO₃^2-, SO₄^2-, Cl^-, and humic acid) on sulfanilamide removal were investigated by a single factor experimental design. Results indicated that CSH-ACs were suitable for sulfanilamide removal in actual wastewater treatment with wide pH adaptability and resilience to interference.

Development of a horseradish peroxidase-Fenton-like system for the degradation of sulfamethazine under weak acid condition

Both horseradish peroxidase (HRP) and ferrous ion (Fe²⁺) can degrade organic micropollutants (e.g., sulfamethazine) in the presence of hydrogen peroxide (H₂O₂), but they have their own disadvantages, such as low degradation efficiency and low pH condition, respectively. In order to overcome the above shortcomings, this study is to develop a HRP-Fenton-like system for sulfamethazine (SMR) efficient degradation by analyzing the optimal reaction conditions, degradation mechanisms, and effect of ions. Results show that HRP and Fe²⁺ achieve effective coupling by adding trace Fe²⁺ (≤ 10 μmol/mL) to the HRP system at pH = 5, and the degradation rate of SMR increased by 20.7-42% depending on Fe²⁺ concentration compared with single HRP treatment. Consumption of H₂O₂ and quenching of hydroxyl radicals confirmed that HRP dominated SMR removal in the HRP-Fenton-like system. HPLC-MS analysis shows that SMR was degraded by C-S bond breaking, N-S bond breaking, hydroxyl substitution, and rearrangement. Furthermore, Cl^-, HCO₃^-, and NO₃^- exhibit an acceptable negative effect, while SO₄^2- shows a positive effect on the degradation of SMR.

Comparison of naphthalene removal performance using H2O2, sodium percarbonate and calcium peroxide oxidants activated by ferrous ions and degradation mechanism

The presence of polycyclic aromatic hydrocarbons (PAHs) in groundwater is making a great threat to human health in the world which has received an increasing environmental concern. Among various Fenton oxidation processes, 97.6%, 92.1% and 89.4% naphthalene (NaP) removals were observed using hydrogen peroxide (H₂O₂), sodium percarbonate (SPC) and calcium peroxide (CP) as oxidants activated by Fe(II) in ultrapure water tests, respectively. While, the inhibitory effect on NaP degradation caused by the weak alkaline solution pH and the presence of HCO₃^- in actual groundwater could be compensated by doubling dosages of oxidants and Fe(II) to different extent. 98.0%, 49.8% and 11.5% of NaP were degraded by using H₂O₂, SPC and CP, respectively, strongly suggesting the best H₂O₂ performance among them. It was observed that 83.3% and 9.6% inhibition on NaP degradation in H₂O₂/Fe(II)/NaP system occurred in the presence of isopropyl alcohol and chloroform, confirming that both hydroxyl radical (HO) and superoxide anion radical () contributed to NaP degradation in Fenton process and HO was the prominent radical. The presence of HO was further demonstrated by electro-spin resonance spectrometer analysis. The identification of transformation products of NaP revealed that hydroxylation and ring rupture were the main NaP degradation pathways.

The Fenton-like reaction for Arsenic removal from groundwater: Health risk assessment

In this paper, the heterogeneous Fenton like-reaction for Arsenic-contaminated groundwater remediation based on the performance of FeSO₄ as an efficient and green catalyst and CaO₂ as a source of H₂O₂ was investigated. To intensify the heterogeneous Fenton process, three oxidants were tested: sodium percarbonate (SPC), sodium persulfate (SPS), and calcium peroxide (CP). The results showed that CP and SPC had a synergetic effect on the rate of Arsenic degradation, while SPS had an antagonistic effect. On the other hand, inorganic ions such as Na⁺, Mg²⁺ have a very low impact on the Arsenic removal efficiency, while the anions Cl^- and NO₃^- exhibited significant inhibition of Arsenic degradation. This effect may be imputed to the reaction and conversion of hydroxyl (HO^•) radicals to less reactive. Thus, HCO₃^- and humic acid dramatically raised the degradation rate. Also, the response Surface method based on Box-Behnken design was applied to examine the suitable modeling, and optimized condition of the Fenton like-reaction process, the maximum Arsenic removal efficiency of 94.91% is obtained when [Fe³⁺]₀ = 1.97 mM, [CaO₂]₀ = 1.74 mM and initial pH = 4.67. The obtained results showed that the Fenton-like reaction is an effective and reliable process for arsenic removal from groundwater with low non-carcinogenic risk (HQ) and carcinogenic risk (CR) values.

Response surface methodology for strontium removal process optimization from contaminated water using zeolite nanocomposites

The effective removal of strontium from polluted water is an emerging issue worldwide, especially in Japan, after the destruction of Fukushima's Daiichi Nuclear Power Plant. In the strontium removal process, statistical optimization of associated factors is needed to reduce the quantity of chemicals and the number of experimental trials. In this study, response surface methodology based on the central composite design was employed for assessing the influence of different factors and their interaction effects on the efficiency of strontium removal. We have considered nanoscale zero-valent iron-zeolite (nZVI-Z) and nano-Fe/Cu zeolite (nFe/Cu-Z) as adsorbents for the effective removal of strontium. The results suggested that the studied three factors such as pH, contact time, and concentration are positively related to the adsorption of strontium. That is, the maximum strontium removal occurred at pH, initial concentration, and contact time of 12, 200 mg L^-1, and 30 min, respectively. The experimental maximum strontium adsorption capacity of nZVI-Z and nFe/Cu-Z adsorbents is 32.5 mg/g and 34 mg/g, respectively. The present study also showed that the most statistically significant potential contributor was initial concentration, followed by contact time in the removal process. The study indicated that the interaction effect between contact time and initial concentration was statistically important, suggesting the need for a multi-mechanism technique in the removal phase of strontium. Tόth, Langmuir, Dubinin-Astakhov (D-A), Freundlich, and Hill isotherm models were also fitted with the experimental strontium adsorption data, in which the Tόth model fitted best compared to the other models based on the RMSD and R².

A review on percarbonate-based advanced oxidation processes for remediation of organic compounds in water

Sodium percarbonate (SPC) is considered a potential alternative to liquid hydrogen peroxide (H₂O₂) in organic compounds contaminated water/soil remediation due to its regularly, transportable, economical, and eco-friendly features. The solid state of SPC makes it more suitable to remediate actual soil and water with a milder H₂O₂ release rate. Apart from its good oxidative capacity, alkaline SPC can simultaneously remediate acidized solution and soil to the neutral condition. Conventionally, percarbonate-based advanced oxidation process (P-AOPs) system proceed through the catalysis under ultraviolet ray, transition metal ions (i.e., Fe²⁺, Fe³⁺, and V⁴⁺), and nanoscale zero-valent metals (iron, zinc, copper, and nickel). The hydroxyl radical (^•OH), superoxide radical (^•O₂^-), and carbonate radical anion (^•CO₃^-) generated from sodium percarbonate could attack the organic pollutant structure. In this review, we present the advances of P-AOPs in heterogeneous and homogeneous catalytic processes through a wide range of activation methods. This review aims to give an overview of the catalysis and application of P-AOPs for emerging contaminants degradation and act as a guideline of the field advances. Various activation methods of percarbonate are summarized, and the influence factors in the solution matrix such as pH, anions, and cations are thoroughly discussed. Moreover, this review helps to clarify the advantages and shortcomings of P-AOPs in current scientific progress and guide the future practical direction of P-AOPs in sustainable carbon catalysis and green chemistry.

Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate (SPC) and peroxymonocarbonate (PMC) have been widely used in modified Fenton reactions because of their multiple superior features, such as a wide pH range and environmental friendliness. This broad review is intended to provide the fundamental information, status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades. Both SPC and PMC can directly decompose various pollutants. The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC. The most commonly used catalysts for SPC activation are iron compounds while cobalt compositions are applied to activate PMC in homogenous and heterogeneous catalytical systems. The generation and participation of hydroxyl, superoxide and/or carbonate radicals are involved in the activated SPC and PMC system. The reductive radicals, such as carbon dioxide and hydroxyethyl radicals, can be generated when formic acid or methanol is added in the Fe(II)/SPC system, which can reduce target contaminants. SPC can also be activated by energy, tetraacetylethylenediamine, ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition. The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment. The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.

Optimization of microcystin biodegradation by bacterial community YFMCD4 using response surface method

The increasing production of microcystin-LR (MC-LR) causing animal and human health issues is found in eutrophic water bodies, marine habitats and desert environments. The health threat posed by MC-LR has led to the establishment of World Health Organization's water guideline value of 1 μg/mL. Combating this has increased the search for cost-effective approach to degrade MC-LR. The study aimed to optimize the MC-degrading environmental factors of bacterial community YFMCD4. Response surface methodology (RSM) was employed to evaluate the influence of varying temperatures, pH and initial MC-LR concentration on the biodegradation efficiency of MC-LR by bacterial community YFMCD4. The optimal MC-LR biodegradation environmental factors were found to be 30 °C, pH 7 and 2 μg/mL initial MC-LR. The biodegradation rate reached 100% after 10 h. YFMCD4 mainly consisted of genera Alacligenes, Sphingobacterium and Pseudomonas using High-throughput pyrosequencing technology. The mlrA gene encoding MlrA enzyme considered most important for MC-LR biodegradation was obtained from YFMCD4. Data demonstrated that the bacterial structure and biodegradation efficiency of YFMCD4 varied with the change of environmental factors including temperature, pH and MC-LR concentrations. RSM is considered a good method to examine the optimal biodegradation environmental conditions for MC-LR. To date, RSM and High-throughput pyrosequencing technology are employed to optimize the biodegradation conditions (30 °C, pH 7 and 2 μg/mL initial MC-LR) and analyze the structure of bacterial community for the first time.

Magnetic cotton textile wastes pyrolyzed by ferric cerium oxide for degradation of p-nitrophenol by catalytic ozonation

In this paper, magnetic cotton textile wastes pyrolyzed by ferric cerium oxide (Fe_xCe_y oxide/PC) were synthesized for degradation of p-nitrophenol by catalytic ozonation, and the optimal Fe-Ce ratio was 10:1. Compared to Fe₁₀Ce₁ oxide, the Fe₁₀Ce₁ oxide/PC not only greatly improved the degradation efficiency of PNP, but also reduced the dosage of catalyst. Through the BET test, the Fe₁₀Ce₁ oxide/PC has a high specific surface area to absorb part of the pollutants. VSM test shows that the material is magnetic and easy to recycle. Response surface methodology (RSM) was applied to optimize the experimental condition, and the optimal removal rate was 90% when the initial pH was 9, the catalyst dosage was 0.4 g/L, and the ozone addition was 1.77 L/min (5.9 mg/L). Finally, the mechanism of PNP degradation was explored utilizing inhibitor and ESR free radical detection. The adsorption capacity of the material and electron-absorbing property of PNP jointly determined the high catalytic efficiency with Fe₁₀Ce₁ oxide/PC in catalytic ozonation.

Carboxyl-functionalized biochar derived from walnut shells with enhanced aqueous adsorption of sulfonamide antibiotics

The novel HNO₃-modifitied biochar (NBC) was synthesized from walnut shell. The NBC was characterized from scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectrum. The NBC was then used in the adsorption of sulfadiazine, sulfamethazine and sulfachloropyridazine from aqueous solution. The material surface has carbon/oxygen-contained groups, which is benefit for the adsorption. The results showed the adsorption ability of NBC on three sulfonamides were 32, 46, and 40 mg g^-1, respectively. The kinetic was found to follow the Elovich model and the isotherm conformed Freundlich. Adsorption was more favorable at weak acidic solution. The interactions mainly include π-π EDA, electrostatic interaction, Lewis acid-base interaction, hydrophobic interaction and H-bond.

Removal of sulfamethoxazole, sulfadiazine, and sulfamethazine by UV radiation and HO• and SO4•- radicals using a response surface model and DFT calculations

In this work, the degradation of sulfamethazine (SMT), sulfadiazine (SMD), and sulfamethoxazole (SMX) by using UV light, UV/H₂O₂, and UV/S₂O₈^-2 was analyzed. Direct photolysis was studied by varying the lamp power and the solution pH. DFT calculations were carried out to corroborate the efficiency of the degradation as a function of the solution pH. The variation of the apparent rate constant, k_ap, was determined in the indirect photolysis by employing an experimental Box-Behnken-type response surface design. The results evidenced that SMX can be efficiently degraded by applying UV radiation independent of the operating conditions. Nevertheless, the quantum yields for SMT and SMD were close to zero, indicating a low energy efficiency for their photochemical transformation. The effect of the solution pH showed that the photodegradation of sulfonamides depends both on the amount of radiation absorbed as the electronic density. Calculations based on density functional theory and supported by the quantum theory of atoms in molecules allowed to describe fragmentation patterns in the systems under study, proving the lability of S₁₄-C₂, N₁₇-C₁₈, and N₂₂-O₂₂ bonds, for SMT, SMD, and SMX, respectively. From response surface methodology, four statistically reliable equations were obtained to determine the k_ap value as a function of the system operating conditions. Finally, SO₄^•- radicals proved to have a higher reactivity to degrade SMT and SMD compared with HO^• radicals regardless of the operating conditions of the system.

Photo-assisted peroxymonosulfate activation via 2D/2D heterostructure of Ti3C2/g-C3N4 for degradation of diclofenac

In this paper, a two dimensional/two dimensional (2D/2D) heterostructure of Ti₃C₂/g-C₃N₄ (T/CN) was constructed and used to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF) in water in the presence of light illumination. Compared with single photocatalytic process by T/CN (0.040/min) and with pure g-C₃N₄ nanosheets in PMS system (0.071/min), 5.0 and 3.0 times enhanced activities were achieved in the T/CN-PMS system at optimum Ti₃C₂ (1.0 wt%) loading under light illumination (0.21/min). Moreover, the decomposing processes of DCF in T/CN-PMS system were applicable in a wide initial pH range (3∼14), therefore, overcoming the limitation of pH dependence in traditional PMS system. Based on the synergistic effect of photocatalysis and PMS oxidation processes, the ¹O₂ was generated as primary reactive species for the removal of DCF in T/CN-PMS system. The DCF degradation mechanism was further proposed through the results of liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations.

Removal of p-aminobenzenesulfanilamide from water solutions by catalytic photo-oxidation over Fe-pillared clay

The catalytic photo-oxidation of p-aminobenzenesulfanilnamide (ABS) with hydrogen peroxide in the presence of Fe-pillared clay as heterogeneous catalyst has been investigated under UV-irradiation (λ_max = 254 nm). Fe-pillared clay was synthesized by intercalating the iron polyhydroxycomplexes into the interlayer space of a natural layered aluminosilicate - montmorillonite and a subsequent heat treatment at 500 °C. The catalyst was characterized by chemical analysis, low temperature nitrogen adsorption and XRD. The kinetics of photocatalytic oxidative degradation of ABS in aqueous solutions under various experimental conditions was studied. The dependence of the photo-oxidation rate on such experimental factors as pH, hydrogen peroxide concentration and catalyst content was established. The conversion of ABS was 100% and the mineralization efficiency was 52.3% at optimal conditions. The intermediate products of ABS photo-oxidation identified by HPLC were a sulfanilic acid, benzenesulfonamide, benzenesulfonic acid, hydroquinone, pyrocatechol, benzoquinone and aliphatic acids. Fe-pillared clay remained highly active in three consecutive catalytic cycles without regeneration. The results of the study suggested that the heterogeneous photo-system «Fe-pillared clay/H₂O₂/UV» was effective in the oxidative degradation of aminobenzenesulfanilnamide. This system may be of interest for use in organic wastewater treatment processes.

Fe3+-sulfite complexation enhanced persulfate Fenton-like process for antibiotic degradation based on response surface optimization

To improve the cycle between Fe³⁺ and Fe²⁺ in persulfate (PS) Fenton-like system, sulfite (Na₂SO₃) was used as the iron complexing agent to enhance the degradation of sulfamethoxazole (SMX) antibiotic in water. Response surface methodology (RSM) was applied to regulate the operation parameters for the Fe³⁺/Na₂SO₃/PS synergistic system. Based on the RSM, the SMX could be completely degraded when the concentration of Fe³⁺, Na₂SO₃, and PS were 0.4, 0.5, and 2.5 mM, respectively. The result showed that the synergistic process represented a high Fe³⁺ utilization rate and SMX degradation efficiency. After 1 h reaction, 100.00% of SMX and 27.80% of total organic carbon were removed under the ambient conditions containing the initial SMX concentration of 10 μM and initial pH of 5.96. Free radical masking and electron spin-resonance tests proved that hydroxyl radical (HO) and oxysulfur radicals (SO_x^-, x = 3, 4, 5) were all played the significant role in the antibiotic removal, and the primary active radical was HO. The SMX decomposition pathways based on the formed intermediates was proposed through the high-performance liquid chromatography and mass spectrum analyses. The toxicity assessment prediction indicated that the toxicities of decomposed SMX byproducts were reduced after the coupling treatment.

Fe3O4/graphene aerogels: A stable and efficient persulfate activator for the rapid degradation of malachite green

Encapsulation metal oxides into carbon frameworks is a good strategy to synthesis high activity and stable catalyst. Here, Fe₃O₄ nanoparticles (∼20 nm) were firmly encapsulated in the graphene aerogels by a simple and environmentally friendly method (Fe₃O₄/GAs), for activating persulfate (PS) to degrade malachite green (MG) under simulated sunlight. A strong electron conduction was generated between the Fe₃O₄ nanoparticles and graphene sheets to improve the cycle of Fe(II)/Fe(III), and the MG degradation over a wide pH rage (3-9) was enhanced greatly. The MG molecule was decomposed into 12 intermediates and two possible pathways was proposed. More importantly, toxicity test and Toxicity Estimation Software (T.E.S.T.) proved that the toxicity of MG can be effectively controlled by Fe₃O₄/GAs + PS + light system. In addition to the high catalytic activity, Fe₃O₄/GAs exhibited a good stability and reusability due to the strong interaction between Fe₃O₄ and graphene layers. The degradation efficiency remained above 87% after six cycles, and the leaching amount of iron in each cycle was less than 0.125 wt%. SO₄•^- was the dominate radical for MG degradation and the heterogeneous Fenton-like reaction was mainly performed on the surface of catalyst. This work lay a foundation for applying Fe₃O₄/GAs as a highly efficient, stable and reusable heterogeneous Fenton-like catalyst for future applications.

Removal of atrazine by biochar-supported zero-valent iron catalyzed persulfate oxidation: Reactivity, radical production and transformation pathway

Atrazine is a widely used herbicide whose presence poses a potential threat to agriculture and human living environment. This work studied the degradation performances and mechanisms of zero-valent iron and biochar composite (ZVI/BC) activated persulfate (PS) for atrazine. The results showed that the removal percentage of atrazine reached 73.47% within 30 min. Furthermore, the optimal parameters (175 mg/L ZVI/BC, 2 mM PS and initial pH of 3) were obtained through response surface methodology. Meanwhile, the high atrazine removal percentage (83.77%) was obtained under the optimal conditions. Radical quenching studies and electron spin resonance revealed that active substances produced during PS activation, as well as that SO₄·^- and HO· were dominant active species for the atrazine degradation. According to iron corrosion products and XPS analysis, the reaction mechanism of ZVI/BC-PS system was proposed as that ZVI loaded on the composites further activated PS to produce SO₄·^- and HO· which accompany with the valent changing of iron and finally causing degradation of atrazine. In addition, the degradation pathways of atrazine in ZVI/BC-PS system included dealkylation, alkyl oxidation and dechlorination-hydroxylation by the results of GC-MS and LC-MS. These findings demonstrated that ZVI/BC activated persulfate may be an efficient technique for the degradation of atrazine.

Iron foam combined ozonation for enhanced treatment of pharmaceutical wastewater

In this study, iron foam combined ozonation was employed as an advanced oxidation process to treat the organic contaminants in real pharmaceutical wastewater. It was found that this procedure worked well in a wide range of pH, the existence of iron foam in ozonation system markedly elevated the mineralization level of organic contaminants. Within the reaction time of 120 min, iron foam combined ozonation achieved 53% of DOC removal percentage, which was 21% higher than that of ozone alone. Meanwhile, the biodegradability of the pharmaceutical wastewater was improved, a large part of the organic pollutants containing benzene rings and amino groups were effectively degraded, and a certain amount of phosphate and nitrogen also get removed. In iron foam combined ozonation, zero valent iron played the role as an activator. It was oxidized into iron oxides and oxyhydroxides, the electrons transferring among different valences of iron stimulated the decomposition of ozone and the generation of hydroxyl radicals, which accounted for most of the organic contaminants degradation.

Mechanism and impact of synthesis conditions on the one-step green synthesis of hybrid RGO@Fe/Pd nanoparticles

While a one-step green synthesis of a hybrid material composed of reduced graphene oxide and bimetallic Fe/Pd nanoparticles (RGO@Fe/Pd NPs) was previously successfully reported and evaluated for the removal of organic contaminants, the relationship between the formation of RGO@Fe/Pd and the resulting reactivity was unclear. In this paper the impact of the specific synthetic conditions on the reactivity of RGO@Fe/Pd was investigated in order to enhance the removal efficiency of antibiotics such as rifampicin. The hybrid material (RGO@Fe/Pd) successfully removed 96.1% of rifampicin compared to only 63.5 and 81.0% for Fe nanoparticles and RGO, respectively. The best synthetic conditions for the formation of RGO@Fe/Pd included GO/Fe = 1:1 and Fe/Pd = 100: 5. In addition, GC-MS and FTIR were used to identify the main reducing biomolecules in the green tea extract responsible for the one-step synthesis of RGO@Fe/Pd as Catechol, Caffeine, 1,3,5-Benzenetriol. The morphology, size and surface composition of RGO@Fe/Pd was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-Ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These advanced characterization techniques suggested that during synthesis GO was initially converted to RGO, and thereafter Fe/Pd NPs (10-50 nm) were dispersed on RGO. Finally, a plausible formation mechanism for the one-step synthesis of the hybrid material was proposed.

A novel hollow-sphere cyclodextrin nanoreactor for the enhanced removal of bisphenol A under visible irradiation

A novel hybrid nanoreactor with spatially separated co-catalysts (SH-CD-Au@CdS@MnO_x) was successfully synthesised to remove bisphenol-A (BPA) from water by visible light. The photooxidation intermediates, degradation pathway of BPA and the enhancement mechanism were investigated in particular. Gold (Au) nanoparticles modified with SH-β-cyclodextrin and MnO_x nanoparticles were selectively decorated on the interior and exterior surface of hollow CdS nanoreactors, respectively. The directed migration of photogenerated electrons and holes induced by spatially separated co-catalysts lead to high utilization of light, and SH-β-cyclodextrin modification makes catalytic active sites more accessible for oxidation intermediates. Compared with pristine CdS, the hybrid nanoreactor increased the BPA photooxidation reaction rate and the TOC removal efficiency by 5.6-fold and 3.6-fold, respectively. Moreover, the toxic intermediates, such as phenol, were further degraded by visible light. Molecular orbital calculation predicted that the sites on BPA molecule values of (FED²_HOMO + FED²_LUMO) can be easier attacked by the radical, whereas atoms with higher values of 2FED²_HOMO can easily be extracted into electrons. Thus, SH-CD-Au@CdS@MnO_x can provide a new strategy for the high-efficiency photodegradation of endocrine disrupter compounds in advanced water treatments.

Characterization of Protein Hydrolysates from Eel (Anguilla marmorata) and Their Application in Herbal Eel Extracts

The enzymatic hydrolysis of fish proteins is the principle method for converting under-utilized fish into valuable products for the pharmaceutical and health food industries. In this study, three commercial enzymes (alcalase, bromelain, and papain) were tested for their ability to create eel protein hydrolysates (EPHs) from whole eel (Anguilla marmorata). Freeze-dried EPHs had almost more than 80% solubility (p < 0.05) in solutions ranging from pH 2–10. The amino acid profiles of the EPHs showed a high percentage of essential amino acids, including histidine, threonine, valine, isoleucine, and leucine. The emulsion activity index (EAI) of EPH resulted as follows: alcalase group (36.8 ± 2.00) > bromelain group (21.3 ± 1.30) > papain group (16.2 ± 1.22), and the emulsion stability index (ESI) of EPH was: alcalase group (4.00 ± 0.34) > bromelain group (2.62 ± 0.44) > papain group (1.44 ± 0.09). As such, EPH has a high nutritional value and could be used as a supplement to diets lacking protein. EPH showed excellent solubility and processed interfacial properties, which are governed by its concentration. Among of them the alcalase group had the best antioxidant effect at 1,1-diphenyl-2-pyridinohydrazinyl (DPPH) radical method, determination of reducing power and ABTS test compared with other groups. EPH may be useful in developing commercial products like herbal eel extracts that are beneficial to human health.

Dramatic enhancement effects of l-cysteine on the degradation of sulfadiazine in Fe3+/CaO2 system

Excessive sulfonamides accumulated in soil and groundwater seriously menace the ecological environment and human health. The performance of a Fenton-like system applying Fe³⁺ and calcium peroxide (CaO₂) in the presence of l-cysteine(l-cys) for sulfadiazine (SDZ) degradation was investigated. Compared with other chelating agents such as citric acid, butyric acid and Ethylenediaminetetraacetic acid, l-cys could effectively promote the SDZ removal in Fe³⁺/CaO₂ system. With the addition of 0.5 mM l-cys, the SDZ degradation increased from 2.14% to 66.53% in 60 min. High concentration of HCO₃^- inhibited the degradation of SDZ while slightly negative effects on SDZ degradation were observed in the presence of Cl^- or humic acid (HA) in l-cys/Fe³⁺/CaO₂ system. Electron paramagnetic resonance (EPR) analysis and radicals scavenge tests affirmed the generation of OH and O₂- in l-cys/Fe³⁺/CaO₂ system. Possible degradation pathway of SDZ was speculated and the toxicity of SDZ intermediates was further evaluated. l-cys could enhance the reduction of Fe³⁺ to Fe²⁺ and reduced the Fe³⁺ precipitation due to the l-cys could form stable complexes with Fe³⁺. l-cys/Fe³⁺/CaO₂ system exhibited high mineralization ability. Overall, these results indicated that l-cys is a promising chelating agent for sulfadiazine wastewater treatment.

Recent advances for dyes removal using novel adsorbents: A review

Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Numerous researchers have attempted to seek or design alternative materials for dye adsorption. However, using various novel adsorbents to remove dyes has not been extensively reviewed before. In this review, the key advancement on the preparation and modification of novel adsorbents and their adsorption capacities for dyes removal under various conditions have been highlighted and discussed. Specific adsorption mechanisms and functionalization methods, particularly for increasing adsorption capacities are discussed for each adsorbent. This review article mainly includes (1) the categorization, side effects and removal technologies of dyes; (2) the characteristics, advantages and limitations of each sort of adsorbents; (3) the functionalization and modification methods and controlling mechanisms; and (4) discussion on the problems and future perspectives about adsorption technology from adsorbents aspects and practical application aspects.

Conversion of chlorine/nitrogen species and formation of nitrogenous disinfection by-products in the pre-chlorination/post-UV treatment of sulfamethoxazole

Pre-chlorination and UV disinfection are two common processes in drinking water treatment plants. Sulfamethoxazole (SMX), an antibiotic widely detected in source water, was selected as a precursor to study the conversion of chlorine/nitrogen species and DBP formation in pre-chlorination/post-UV process. The combined chlorine (mainly organic chloramines) produced in pre-chlorination of SMX can self-degrade and release free chlorine back again as pre-chlorination time goes on. With free chlorine dose increasing, the self-degradation rate of combined chlorine increased obviously. But the combined chlorine stopped self-degrading and remained stable around 1 mg-Cl₂/L after adding 0.30 mM chlorine for 30 min. Post-UV treatment after pre-chlorination can enhance the degradation and achieve a complete removal of combined chlorine (including organic chloramines). Deamination occurred during pre-chlorination/post-UV process and deamination amount (-NH₂) per SMX concentration was 0.19 M/M. Radicals in this process had no obvious influence on chlorine/nitrogen species conversion. Direct chlorination of SMX had the lowest DBP formation potentials while the application of pre-chlorination and UV enhanced them. Compared with UV treatment only, dichloroacetonitrile formation potential of SMX reduced by 1.58 × 10^-3 mol/mol-SMX (17.37 μg/l) after pre-chlorination/post-UV treatment. During pre-chlorination/post-UV/final-chlorination treatment of SMX, Br^- and natural organic matter can enhance DBP formation and toxicity-weighted values. Acid conditions showed a very high DBP risk, while alkaline conditions could cut this risk obviously, especially for the toxicity-weighted values of these DBPs.

Degradation of 1H-benzotriazole using vacuum ultraviolet: a prospective treatment method for micro-pollutants

Benzotriazoles (BTs) attract increasing concerns because of abundant presence in environmental water bodies. In this study, degradation of 1H-benzotriazole (1H-BT) was performed by a customized vacuum ultraviolet (VUV) device emitting 185 + 254 nm (VUV/UV-C) irradiation. Degradation of 1H-BT presented an apparent rate constant reached 8.17 × 10^-4 s^-1. Degradation mechanisms included 185 + 254 nm photodegradation and radical reaction. The later one may be the predominant one, which presented a k_·OH-1H-BT at (7.3 ± 0.8) × 10⁹ M^-1 s^-1. Effects of anions revealed that VUV interception and radical trapping were the dominant restraining factors. Degradation of 1H-BT can be attributed to VUV induced radical-based oxidation. Radical-induced addition, substitution and fracture generated abundant hydroxylated and open-loop products during 10-45 min. Identification using reactive oxygen species and apoptosis in Escherichia coli was conducted. Variations of these two indicators revealed that the incomplete degradation products presented higher toxicities than 1H-BT, and a further mineralization reduced their toxicities. In the pure water solution with little impurities, VUV can induce efficient degradation of 1H-BT, suggesting its potential for eliminating and detoxifying MPs.