Ecological Structure Activity Relationships Research Articles

Robust advantage of MXene/g-C3N4 loaded on Fe2WO6/BiIO4 nano-platform for chemo-peroxidase colorimetric detection of uranyl ions, antifungal properties, photocatalytic degradation of p-chlorophenol, and eco-toxicity studies

In this study, we have designed a nanocomposites based on MXene/g-C3N4 (MX/CN) loaded on Fe2WO6/BiIO4 (FWO/BIO) for different applications. The nanocomposites were identified by using the structural and morphological studies including XRD, FESEM, EDS, DLS, TGA, BET, UV–vis, XPS techniques. The average sizes of BIO, FWO/BIO, and MX/CN/FWO/BIO were 44, 46, and 58 nm, respectively. The synthesized MX/CN/FWO/BIO nanocomposites was utilized for the peroxidase colorimetric identification of uranyl ions (UO22+) with the excellent selectivity and sensitivity properties (LOD: 3.21 nM). The antifungal efficiency of the as-fabricated nanomaterials was investigated and the inhibition zone at high concentration 2.5 mg/mL of MX/CN/FWO/BIO nanocomposites were 19.74, 17.91, 24.25, and 21.32 mm against Aspergillus spp., Penicillum spp., Candida spp. and Fusarium spp., respectively. The MX/CN/FWO/BIO nanocomposites was utilized in photocatalysis process for decomposition of p-chlorophenol under visible light lamp. The findings showed that the MX/CN/FWO/BIO nanocomposites can be degrade p-chlorophenol (100.0 %) under visible light irradiation (80 min). The photocatalytic response was decreased about 2 % after 5th cycle times, and showed the best stability of the MX/CN/FWO/BIO nanocomposites. The quenching test shows the mechanism of p-chlorophenol degradation was conducted by •O2−, and •OH species. Additionally, the ecological structure activity relationships ECOSAR software was utilized to evaluate the toxicity of the p-chlorophenol and the intermediates produced.

Periodate activation by MnFe2O4 spinel for sulfamethoxazole degradation: Iodate radical dominance, degradation pathway, DFT calculation and toxicity assessment

This study synthesized spinel MnFe2O4 at different temperatures, which was applied to activate periodate (PI) for sulfamethoxazole (SMX) degradation. It was found that the 500-MFO (MnFe2O4 calcined at 500 ℃) demonstrated superior activity in PI activation, with notable sustainability but strong substrate selectivity. Furthermore, a comprehensive analysis, including quenching experiment, electron paramagnetic resonance (EPR) technique, X-ray photoelectron spectroscopy (XPS) analysis, metal ions leaching detection, homogeneous PI activation, and methyl phenyl sulfoxide (PMSO) probe test, revealed that homo- and heterogeneous pathways as well as free and non-free radical routes coexisted in the 500-MFO/PI system. Multiple active species, including iodate radical (IO3•), hydroxyl radical (•OH), superoxide radical (O2•-), singlet oxygen (1O2), and Mn(IV) were identified, with IO3• from heterogeneous activation being the primary species. When PMSO and SMX coexisted, PMSO could react with Mn(IV), promoting the regeneration of Mn reaction sites and the production of IO3•, thereby being beneficial for the degradation of SMX. The degradation pathways of SMX were elucidated through high-performance liquid chromatography-mass spectrometry (HPLC-MS) and density functional theory (DFT) calculation. The acute and chronic toxicity of thirteen by-products to aquatic organisms were predicted using the Ecological Structure Activity Relationships (ECOSAR) software, with the corresponding results revealing that although the toxicity of intermediates fluctuated, the final products were environmentally benign. Therefore, this investigation provides a viable method for SMX degradation in wastewater treatment.

Enhanced peroxymonosulfate activation for degradation of iodinated contrast media by microwave-induced bimetallic carbon-based catalysts: Insight into the synergistic mechanism between microwaves and bimetallic sites

Microwave-assisted catalytic oxidation process was a promising wastewater treatment technology for the disposal of refractory organic contaminants. Nevertheless, its practical implementation was limited by the high energy consumption of microwaves and the poor sustainable reactivity of catalysts. To address these issues, the microwave-assisted dielectric-activation double-responsive Co/Fe carbon-based catalyst (CoFe/NC-3) was used to activate peroxymonosulfate (PMS) for oxidative degradation of refractory diatrizoate (DTZ). The results showed that the DTZ was completely degraded within 6 min in the MW/CoFe/NC-3/PMS reaction system, and the degradation efficiency increased by 82.38 % compared with the MW/Fe/NC/PMS system. It was attributed to the enriched active sites and prolonged redox cycling capability of the bimetallic catalysts. Moreover, microwave enhanced electron migration ability to accelerate the circulation of Fe3+/Fe2+/Fe0 and Co3+/Co2+ and generate more reactive oxygen species (ROSs) for the high-efficiency degradation of DTZ. The degradation pathways of DTZ were elucidated by LC-MS in combination with DFT calculation and the product toxicity was evaluated using ecological structure–activity relationship software (ECOSAR). The results showed that the majority of intermediate degradation products were not acute or chronic toxicity to fish, daphnia, and green algae. Overall, these results revealed that the MW/CoFe/NC-3/PMS system was a cost-effective and stable method for wastewater treatment.

Myricetin Inhibits Photodegradation of Profenofos in Water: Pathways and Mechanisms

Profenofos is a detectable insecticide in the environment with strong toxicity to non-targeted organisms. Photodegradation is a main transformation of profenofos in the environment. Myricetin is a flavonoid that strongly scavenges free radicals. The effect of myricetin on the photodegradation of profenofos was studied. The half-lives (T1/2) of profenofos were 1.7–7.0 and 90 h under artificial light and sunlight. The photolysis rate of profenofos decreased by 1.87–4.72 and 7.62 times with the addition of 20 ratios of myricetin. Free radicals reacting with profenofos were •OH and 1O2, and the key free radical was •OH. Myricetin strongly scavenged •OH and 1O2 which rapidly reacted with profenofos. O-(2-Chlorophenyl)-O-ethyl-S-propyl phosphorothioate (M3) and O-(2-chlorophenyl)-O-ethyl phosphorothioate (M4) were major and new photoproducts of profenofos. According to the Ecological Structure Activity Relationships, photodegradation of profenofos was a detoxification process, but myricetin inhibited the photodegradation of profenofos and its photoproducts. These results highlight the implication of myricetin on the fate and potential risk of profenofos in the environment.

Green synthesis of Mn2O3 activated PDS to degrade estriol in medical wastewater and its degradation pathway

While green synthesized Mn2O3 has been used to activate peroxydisulfate (PDS) to degrade estrogens, effective application in real wastewater is less common due to variation in environmental matrices in wastewater. Here, green synthesized Mn2O3 was used as a Fenton-like catalyst to activate PDS for estriol (E3) degradation in wastewater. The results show that the high concentration of K+ and humic acid in wastewater could inhibit the activation process of the Mn2O3/PDS system, resulting in low removal efficiency of E3 in wastewater. However, when the concentration of PDS was increased to 15 mM, the removal efficiency of E3 in medical wastewater can reach 100 %, because the high PDS concentration increases the main reactive oxygen species singlet oxygen (1O2) in medical wastewater. XRD and SEM-EDS analysis indicate that the crystal structure of Mn2O3 is stable, with a consistent rice grain-like morphology before and after reaction. XPS results show no obvious changes in the percentages of Mn(II), Mn(III) and Mn(IV) before and after reaction, indicating that Mn2O3 has good stability when degrading E3 in medical wastewater. Based on density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS), and ecological structure–activity relationship (ECOSAR) modeling data analysis, the reactive oxygen species produced by the Mn2O3/PDS system mainly attack the benzene ring structure of E3, where the toxicity of its intermediate products declines significantly after breaking the benzene ring structure. Overall, this work provides greater understanding of the E3 degradation pathway and the toxicity of its degradation products.

Predicting environmental risks of pharmaceutical residues by wastewater surveillance: An analysis based on pharmaceutical sales and their excretion data

Pharmaceutical residues are increasingly becoming a significant source of environmental water pollution and ecological risk. This study, leveraging official national pharmaceutical sales statistics, predicts the environmental concentrations of 33 typical pharmaceuticals in the Tianjin area. The results show that 52 % of the drugs have a PEC/MEC (Predicted Environmental Concentration/Measured Environmental Concentration) ratio within the acceptable range of 0.5–2, including atenolol (1.21), carbamazepine (1.22), and sulfamethoxazole (0.91). Among the selected drugs, tetracycline, ciprofloxacin, and acetaminophen had the highest predicted concentrations. The EPI (Estimation Programs Interface) biodegradation model, a tool from the US Environmental Protection Agency, is used to predict the removal efficiency of compounds in wastewater treatment plants. The results indicate that the EPI predictions are acceptable for macrolide antibiotics and β-blockers, with removal rates of roxithromycin, spiramycin, acetaminophen, and carbamazepine being 14.1 %, 61.2 %, 75.1 %, and 44.5 %, respectively. However, the model proved to be less effective for fluoroquinolone antibiotics. The ECOSAR (Ecological Structure-Activity Relationships) model was used to supplement the assessment of the potential impacts of drugs on aquatic ecosystems, further refining the analysis of pharmaceutical environmental risks. By combining the concentration and detection frequency of pharmaceutical wastewater, this study identified 9 drugs with significant toxicological risks and marked another 24 drugs as substances of potential concern. Additionally, this study provides data support for addressing pharmaceutical residues of priority concern in subsequent research.

Trace Analysis of Five Androgens in Environmental Waters by Optimization of Enzymolysis and Solid-Phase Extraction Ultra-Performance Liquid Chromatography-Mass Spectrometry and its Risk Assessment.

Steroid hormones (SHs) have received widespread attention in recent years. However, current studies of SHs have primarily focused on estrogenic substances, with androgen-related studies being quite limited. We optimized the solid-phase extraction (SPE) pretreatment method, as well as the enzymolysis conditions of five androgens (androstenedione, boldenone, methandienone, nandrolone, and testosterone), to simultaneously determine their concentrations in the effluent from wastewater treatment plants and surface water samples. Then we evaluated the ecological risks of the five androgens in the effluent and Pearl River basin of Guangzhou (PR China) using the risk quotient method. The recovery rates of the targets were 90% to 99% in water samples when digested with β-glucosidase for 90 min before solid-phase extraction, extracted with a Poly-Sery HLB column, and washed with 15% methanol aqueous solution and 2% ammonia. The established instrument's limit of detection was between 0.02 and 0.39 μg/L, and the limit of quantification was between 0.05 and 1.29 μg/L. Androstenedione, boldenone, methandienone, nandrolone, and testosterone were detected in all samples from the 2018 and 2022 wastewater influent and the 2018 surface water, with concentrations of 3.06 × 101 ng/L to 1.33 × 103 ng/L, 1.03-8.15 × 102 ng/L, and 0.93 × 101 ng/L to 5.50 × 102 ng/L, respectively. The ecological risks of androgens in wastewater influent and surface water were medium to high and low to medium, respectively. Moreover, the biotoxicity of androgens was predicted by the Ecological Structure Activity Relationships model, with methandienone and androstenedione having the highest and lowest acute and chronic toxicities, respectively. These results suggest that the risk of environmental androgens should not be ignored and that further research should be carried out. Environ Toxicol Chem 2024;43:915-925. © 2023 SETAC.

Constructing oxygen defect-rich Bi2WO6/CeO2 S-scheme heterojunction for boosted photocatalytic antibiotic removal

Efficient photocatalytic eradication of antibiotic contaminant from water is of significance for the sustainability of the aquatic environment. Oxygen defective Bi2WO6/CeO2 S-scheme heterojunctions were obtained by two-step hydrothermal processes. The optimal Bi2WO6/CeO2 heterostructure (BC-10) delivered degradation efficiencies of 86.6 % and 87.1 % for tetracycline (TC) and ciprofloxacin (CIP), respectively. The boosted photocatalytic performance of BC-10 was attributed to the increased specific surface area, S-scheme construction and the formed oxygen-defect energy level which promoted the fast charge transfer and separation of photoinduced h+/e– pairs. In addition, experiments confirmed that BC-10 possessed a good catalytic performance for other organic pollutants. The toxic behavior of the TC-removal solution was verified via the Ecological Structure-Activity Relationship (ECOSAR) model and hemp-pea growth experiment, and the possible photocatalytic degradation mechanism of TC and CIP on BC-10 was proposed. This work offers an applicable construction concept of advanced photocatalysts with high redox capacity for wastewater remediation.

Degradation of pharmaceuticals in UV/H2O2 process: EEM-based kinetic model, transformation products and corresponding toxicity evaluation

Advanced oxidation process (AOP) by UV/H2O2 presented excellent performance on removing trace pharmaceuticals in wastewater. Monitoring the removal efficiency of pharmaceuticals rapidly can evaluate the effectiveness of UV/H2O2 process. And evaluating the potential risks of this technology is essential to facilitate its engineering application. In this study, diclofenac, ibuprofen, naproxen, carbamazepine and citalopram, which have potential biological effect to ecological environment, were degraded by UV/H2O2 in wastewater. Results suggested that UV/H2O2 could degrade 5 pharmaceuticals effectively. An EEM-based degradation kinetic model was constructed by combining pseudo first-order kinetic patterns of pharmaceuticals degradation and multiple exponential decay pattern of fluorescence degradation. This model could estimate the removal of pharmaceuticals rapidly and exhibited excellent predictive capability (R2 values > 0.90). Based on suspect and untargeted screening, 40 transformation products (TPs) were identified, with hydroxylation, (de)methylation and decarboxylation being the dominant pathways. Among them, 20 TPs were newly discovered. Furthermore, the predicted toxicity results from Ecological Structure-Activity Relationship (ECOSAR) model suggested that 37.5%− 42.5% of TPs exhibited higher toxicity than parent compounds. The increased toxicity of TPs of DCF and IBP could be attributed to decarboxylation. This study provides a promising and rapid method for monitoring the degradation of pharmaceuticals and estimating the toxicity of TPs. These findings facilitate further evaluation of the practicality and risks associated with the UV/H2O2 process for pharmaceutical removal in wastewater.

Accelerated removal of sulfadiazine by heterogeneous electro-Fenton system with Pt-FeOX/graphene single-atom alloy cathodes

Heterogeneous electro-Fenton (EF) process is emerging as an attractive treatment technology for removal of sulfadiazine (SDZ), in which in situ generation of H2O2 and Fe(II) are crucial steps. In this study, Pt-FeOX/G was synthesized as a heterogeneous EF catalyst by incorporating Pt single atoms into a FeOX nanocrystal. The optimized Pt1-FeOX/G cathode exhibited an SDZ conversion of >90% within 30 min over a broad pH range (3–11). The Pt1-FeOX/G cathode under a strong alkaline medium exhibited very prominent selectivity to H2O2 via 2e− oxygen reduction reaction with a maximum H2O2 concentration of 211.93 mg L−1. The hydroxyl radicals in the cathodic chamber were mainly derived from the in situ conversion of generated H2O2 in the heterogeneous EF system. The structure-activity results of Pt-FeOX/G suggested that the SDZ removal efficiency was closely related to the decentralized morphology and electronic configuration of the Pt-FeOX microcrystalline structure. Three possible SDZ degradation pathways, dominated by S–N bond cleavage, were proposed based on the stage products. The toxicity of the major products was determined using the ecological structure-activity relationship model in conjunction with trophic aquatic organisms. This study demonstrated the feasibility of enhancing heterogeneous EF catalysis for antibiotic-polluted water using multifunctional single-atom alloy cathodes.

Degradation of ciprofloxacin using magnetite nanoparticle-activated periodate: Kinetic, mechanistic and toxicity evaluation

In this study, the activation mechanisms of periodate (IO4−) by magnetite (Fe3O4) were investigated for the degradation of ciprofloxacin (CIP). Compared to standalone IO4− (PI) and Fe3O4, the combined Fe3O4/IO4− system exhibited superior degradation efficiency, especially at elevated pH levels, such as 11. Scavenger experiments revealed IO3· and IO4· as critical radicals at pH 6.5, while ·OH was the key reactive species at pH 11. X-ray photoelectron spectroscopy (XPS) identified electron transfer between Fe(II)/Fe(III) species as the main mechanism resulting in the partial reduction of Fe3O4. The study confirmed the high thermal stability of periodate and found that N2 purging reduced the degradation efficiency of the Fe3O4/PI system. High degradation efficiency was maintained in real wastewater and tap water, with Fe3O4 showing minimal structural and performance changes during repeated oxidation processes. Its magnetic properties allow for easy collection and reuse, thus minimizing costs and environmental harm. Liquid chromatography high-resolution mass spectrometry (LC-QTOF-MS) identified CIP degradation products and degradation pathways at different pH values (i.e., 3, 6.5, and 11), with piperazine ring opening and decarboxylation as the main mechanisms. Ecological Structure Activity Relationships (ECOSAR) predicted low acute and chronic toxicity to fish, daphnids and green algae for most CIP degradation products. Overall, the Fe3O4/IO4− systemoffers an efficient alternative for treating effluents containing CIPacross various water media.

Amoxicillin degradation in the heat, light, or heterogeneous catalyst activated persulfate systems: Comparison of kinetics, mechanisms and toxicities

Various activated persulfate (PS) technologies have been investigated and implemented to eliminate antibiotic contaminants from water. The investigation and evaluation of different activation systems are essential for the application of PS techniques. The degradation of amoxicillin (AMX) by heat, light, or heterogeneous catalyst of Fe–AC composite activated PS was investigated, and the kinetics, mechanisms and toxicities were compared in this work. The apparent activation energy of the Fe–AC system was lower than that of the heat system. Hydroxyl and sulfate radicals were demonstrated by electron paramagnetic resonance (EPR) spectroscopy and quenching tests. There were 22, 21 and 13 types of degradation intermediates detected in heat, light and Fe–AC system, respectively. Six pathways of AMX degradation were proposed and compared in the three activated PS systems. The toxicity prediction of degradation intermediates under different treatment processes was estimated by ecological structure-activity relationship model and toxicity estimation software tool. The genotoxicity of the AMX degradation solution was tested by Acinetobacter baylyi ADP1_recA, which indicated that the AMX solution after treatment in the Fe–AC system had almost no genotoxicity. The Fe–AC/PS system shows apparent advantages over the heat or light activated PS system in most cases, demonstrating that the Fe–AC/PS system is suitable for AMX-contaminated remediation in aqueous solution.

Waste coconut shell-derived carbon monolith as an efficient binder-free cathode for electrochemical advanced oxidation treatment of endocrine-disrupting compounds

Discharge of endocrine-disrupting compounds such as methylparaben (MePa) into natural water bodies deteriorates the aquatic ecosystem. In this regard, electrochemical oxidation (EO) and electro-Fenton (EF) processes are acknowledged as effective methods to eliminate biorecalcitrant compounds from different wastewater matrices. In these systems, the H2O2-producing ability of carbon-based cathodes is put to advantage for producing homogenous hydroxyl radicals by simulating Fenton's reaction, which dramatically augments the contaminant removal efficiency. However, commercial carbon based cathodes are not economically affordable, especially for voluminous treatment. Hence in the present work, waste-derived carbonised coconut shell (CCS) monolith was employed as a cathode in EO and EF treatment of MePa. Almost the entire MePa with initial concentration of 10 mg/L was removed in 60 min by EO and 45 min by EF process at neutral pH, applied current density of 7.5 mA/cm2, NaCl concentration of 1.0 g/L and 10 mg/L of Fe2O3 dosing. The MePa removal efficiency of the CCS cathode-fitted system after 60 min was better than the commercial graphite plate and Ti-based mixed metal oxide employing system due to higher H2O2 electrosynthesis (H2O2 = 9.0 ± 0.6 mg/L after 60 min). Moreover, the same setup was used for treating 10 mg/L of MePa-spiked real sewage and demonstrated MePa and total organic carbon removal efficiency of 80.16 ± 2.31% and 37.42 ± 3.50%, respectively, in 45 min. Further, the CCS-mediated EF treatment achieved >90% removal of MePa for eight continuous batch cycles and recorded a current density drop of just 0.23% per cycle. The degradation pathway and toxicity assessment of the intermediates using the Ecological Structure Activity Relationships (ECOSAR) tool supported the eco-friendliness of the current treatment scheme.

Unveiling the mechanisms of peracetic acid activation by iron-rich sludge biochar for sulfamethoxazole degradation with wide adaptability

Advanced oxidation processes (AOPs) based on peracetic acid (PAA) has been extensively concerned for the degradation of organic pollutants. In this study, metallic iron-modified sludge biochar (Fe-SBC) was employed to activate PAA for the removal of sulfamethoxazole (SMX). The characterization results indicated that FeO and Fe2O3 were successfully loaded on the surface of the sludge biochar (SBC). Fe-SBC/PAA system achieved 92% SMX removal after 30 min. The pseudo-first-order kinetic reaction constant of the Fe-SBC/PAA system was 7.34 × 10−2 min−1, which was 2.4 times higher than the SBC/PAA system. The degradation of SMX was enhanced with increasing the Fe-SBC dosage and PAA concentration. Apart from Cl−, NO3− and SO42− had a negligible influence on the degradation of SMX. Quenching experiments and electron paramagnetic resonance (EPR) techniques identified the existence of reactive species, of which CH3C(O)OO•, 1O2, and O2•- were dominant reactive species in Fe-SBC/PAA system. The effect of different water matrices on the removal of SMX was investigated. The removal of SMX in tap water and lake water were 79% and 69%, respectively. Four possible pathways for the decay of SMX were presented according to the identification of oxidation products. In addition, following the ecological structure-activity relationship model (ECOSAR) procedure and the germination experiments with lettuce seeds to predict the toxicity of the intermediates. The acute and chronic ecotoxicity of SMX solution was dramatically diminished by processing with Fe-SBC/PAA system. In general, this study offered a prospective strategy for the degradation of organic pollutants.

In-situ electrodeposition of Co/Ce-MOF-derived carbon composites as anode for electrochemical degradation of ceftazidime

Antibiotics cannot be completely removed through traditional treatment technologies, leading to their accumulation in the aquatic environment and posing a serious threat to human health. MOF-derived carbon is a promising material for the degradation of antibiotics. Herein, in this study, a novel Co/Ce-MOF electrode was rapidly prepared by one-step electrodeposition at room temperature. Then the Co/Ce-MOF electrode was carbonized to obtain MOF-derived carbon composite electrode (Co/Ce-C350Air). The ceftazidime (CAZ) degradation efficiency achieved 96.59% within 60 min under the optimum conditions ([CAZ] = 5 mg/L, [Na2SO4] = 50 mM, current density = 0.8 mA/cm2, electrode gap = 2 cm and initial pH = 5.6) and the degradation process of CAZ conformed to first-order reaction kinetics. Furthermore, the removal efficiency of CAZ maintained at 94.92% even recycling for 6 times, demonstrating the good electrochemical stability of the Co/Ce-C350Air composite anode. The synergistic effect between Co and Ce metals improved the catalytic performance and stability of the Co/Ce-C350Air electrode. Radical quenching experiments and electron paramagnetic resonance (EPR) spectra results revealed that surface hydroxyl radicals were the main active species in the degradation of CAZ. The main intermediate products were identified by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and the possible degradation pathway was proposed. In addition, toxicity tests with Ecological Structure Activity Relationships (ECOSAR) software results indicated that the toxicity of the intermediate products was lower than that of CAZ. This work provided a safe and effective strategy for the degradation of antibiotics in the electrochemical oxidation system.

Unveiling the traits of dry and wet pre-magnetized zero-valent iron-activated peroxymonosulfate: Degradation of oxytetracycline

It has been previously reported that pre-magnetization could enhance the efficacy of zero-valent iron (ZVI) in removing contaminants. However, little is known about the effects and persistence of different magnetization methods on pre-magnetized ZVI (Pre-ZVI) when used in advanced oxidation processes (AOPs). Gaining a comprehensive understanding of the durability of various pre-magnetization methods in enhancing the removal efficiency of different pollutants will significantly impact the widespread utilization of Pre-ZVI in practical engineering. Herein, we investigated the efficiency of dry and wet Pre-ZVI-activated peroxymonosulfate (PMS) in eliminating oxytetracycline (OTC) and evaluated the durability of Pre-ZVI. Additionally, we examined several factors that influence the degradation process's efficiency. Our results found that the reaction constant k values corresponding to the dry Pre-ZVI/PMS system at the pH values of 3, 7, and 9 varied from approximately 0.0384, 0.0331, and 0.0349 (day 1) to roughly 0.0297, 0.0278, and 0.0314 (day 30), respectively. Meanwhile, the wet Pre-ZVI/PMS system exhibited k values ranging from approximately 0.0392, 0.0349, and 0.0374 (day 1) to roughly 0.0380, 0.0291, and 0.0322 (day 30), respectively. Moreover, we proposed four OTC degradation pathways using LC-MS/MS and density functional theory calculations. The toxicity of the degradation products was assessed using the ecological structure activity relationship and the toxicity estimation software tool. Overall, this study provides insights into the application of Pre-ZVI/PMS that can be selectively used to eliminate tetracycline antibiotics from water.

Unraveling the contribution of Co(IV) and free radicals in Co2+-activated Peroxymonosulfate process: Reaction mechanism, degradation pathway, and DFT calculation

The Co2+ and Peroxymonosulfate (PMS) reaction is a highly regarded advanced oxidation process (AOP) that has been extensively researched. The consensus regarding the relative contribution of reactive species in the Co2+/PMS system under different pH conditions has not been established. In this study, quenching experiments and electron spin resonance (ESR) tests demonstrated the coexistence of Co(IV), sulfate radical (SO4•-), hydroxyl radical (•OH), and singlet oxygen (1O2), and there fell to CBZ degradation were Co(IV) > SO4•->•OH ≈ 1O2 in the optimal conditions, where almost 100% of CBZ was degraded in the Co2+/PMS system within 30 min. Furthermore, Cl− would suppress the formation of Co(IV), SO4•-, and •OH but enhance the yield of 1O2, thereby showing a trend of inhibiting CBZ degradation. The probe compound used in this study was Methyl Phenyl Sulfoxide (PMSO), while methyl phenyl sulfone (PMSO2) as the indicator of Co(IV), the generation efficiency of PMSO2 (η'[PMSO2]) increased with reaction time and reached 70%–98% at 40 min at all set pH values (3, 4, 6, and 8). These results suggest that Co(IV) played a significant role in the Co2+/PMS system and its importance became more pronounced as the reaction progressed. PMSO probe and SO4•- quantification experiments jointly revealed that Co(IV) had the greatest performance at pH 4, and compared to other pH values, SO4•- had the largest contribution in the initial stage of the reaction at pH 6. The Ecological Structure Activity Relationships (ECOSAR) software was utilized to predict the toxicity of the degradation by-products. Additionally, luminescent bacteria experiments were conducted to assess the acute toxicity of the reaction solution. The results of these experiments demonstrated that the Co2+/PMS process exhibited a remarkable ability to detoxify the solution.

Effect of common low-molecular-weight organic acid on the photodegradation of sertraline by ferrihydrite

Sertraline is one of the most commonly used antidepressant pharmaceuticals with ubiquitous distribution in the aqueous environment. However, the environmental behavior of sertraline in the co-presence of low-molecular-weight organic acid (LMWOA) and iron oxide mineral is still poorly understood. In this study, the photodegradation of sertraline was systematically investigated in a common photosensitizing system (ferrihydrite (Fh)-LMWOA). Six LMWOAs, including citrate acid (CA), tartrate acid (TA), malate acid (MA), lactate acid (LA), succinate acid (SA) and malonic acid (MOA) were chosen as the representatives. Our results implied that the different Fe3+ dissolution rates would lead to rather different sertraline degradation patterns following the order of Fh-CA > Fh-TA > Fh-MA > Fh-LA > Fh-SA > Fh-MOA. The reaction was initiated by the interaction between LMWOA and Fh via ligand-promoted-dissolution mechanism. Furthermore, the Fe3+ dissolution rates also showed a strong correlation with the metal-organic complexation constants, indicating that the photodegradation process is strongly related to the complexation ability of LMWOA with Fe3+. •OH, O2•- and CO2•- were detected, indicating that they contributed to the photodegradation of sertraline. •OH was demonstrated to be the dominant Reactive oxygen species (ROS) for the degradation of sertraline, and the detailed transformation pathways were proposed based on the product analysis and theoretical calculation. According to the ecological structure activity relationship estimation, the photodegradation products of sertraline possessed lower toxicity compared to the parent compound. These findings contribute to a more comprehensive understanding of the environmental fate of sertraline and evaluate its potential ecotoxicity in natural systems.

Effective peroxydisulfate activation by CQDs-MnFe2O4@ZIF-8 catalyst for complementary degradation of bisphenol A by free radicals and non-radical pathways

The present study reported fabrication of novel carbon quantum dots-MnFe2O4@ZIF-8 (CQDs-MFO@ZIF-8) by using co-precipitation hydrothermal method for activation of peroxydisulfate (PDS) to degrade bisphenol A (BPA), one of important emerging organic pollutants in water environment. CQDs-MFO@ZIF-8 served as a highly efficient thermal activated PDS catalyst with high catalytic degradation efficiency, reusability and stability. The catalyst achieved almost completely removal of 20.0 mg/L BPA within 5.0 min, and the degradation efficiency remained higher than 83% after 5 consecutive cycles. Free radicals (•OH, SO4•− and •O2−) and non-free radicals (1O2) were generated in the thermal PDS-activation system, in which singlet oxygen (1O2) played a dominant role in the degradation of BPA. The potential toxicity of BPA degradation intermediates was analyzed upon the culture of E. coli and Chlorella sorokiniana by using Ecological Structure-Activity Relationship Model (ECOSAR) program. The catalytic performances of BPA degradation by CQDs-MFO@ZIF-8 were evaluated for treatment of different practical water samples to further verify the feasibility of practical applications. This study provides proof-in-concept demonstration of new nanomaterials for enhanced catalytic water decontamination.

Rapid PFOS mineralization with peroxydisulfate activation process mediated by N modified Fe-based catalyst

As the cheap and efficient catalysts, the iron-based catalysts have been considered as one of the most promising catalysts for peroxydisulfate (PDS) activation and the development of high-performance iron-based catalysts are attracting growing attentions. In this work, a magnetic Fe-based catalysts (Fe/NC-1000) was obtained by using Fe modified ZIF-8 as the precursor and used to activate the PDS for the degradation of perfluorooctane sulphonate (PFOS). Morphology and structure analysis showed that the resulted Fe/NC-1000 catalyst was displayed porous spheres (40–60 nm) and mainly composed of Fe0, FeNx and carbon. When Fe/NC-1000 was employed to activate the PDS (0.1 g/L of catalyst dosage, 0.5 g/L of PDS dosage and at initial pH of 4.6), the Fe/NC-1000/PDS system exhibited excellent efficiency (97.9 ± 0.1) % for PFOS (10 mg/L) degradation within 30 min. The quenching tests and EPR results revealed that the Fe/NC-1000/PDS system degraded PFOS primarily through singlet oxygen (1O2) evolution and electron-transfer process. Besides, based on the degradation byproducts determined by LC-MS-MS, the PFOS first occurred de-sulfonation to form PFOA, and then the resulted PFOA underwent stepwise defluorination in the Fe/NC-1000/PDS system. Density Functional Theory (DFT) calculations and electrochemistry tests strongly confirmed that Fe/NC-1000 exhibited high electron transfer efficiency, resulting in promoted performance on activating PDS. Importantly, the results of Ecological Structure-Activity Relationship (ECOSAR) analysis showed that the intermediates were lowly toxic during the PFOS degradation, manifesting a green process for PFOS removal. This study would provide more understandings for the persulfate activation process mediated by Fe-based catalysts for Perfluorinated alkyl substances (PFAS) elimination.