Degradation of ketoprofen by sulfate radical-based advanced oxidation processes: Kinetics, mechanisms, and effects of natural water matrices

Overlooked role of CO3·- reactivity with different dissociation forms of organic micropollutants in degradation kinetics modeling: A case study of fluoxetine degradation in a UV/peroxymonosulfate system

Selective oxidizing agent carbonate radical (CO3•-) is an important secondary radical in radical-based advanced oxidation technology for wastewater treatment. However, the role of CO3•- in removing ionizable organic micropollutants (OMs) under environmentally relevant conditions remains unclear. Herein we investigated CO3•- effect on degradation kinetics of fluoxetine in UV/peroxymonosulfate (PMS) system based on a built radical model considering CO3•- reactivity differences with its different dissociation forms. Results revealed that the model, which incorporated CO3•- selective reactivity (with determined second-order rate constants, ksrc,CO3·-, of 7.33 ×106 and 2.56 ×108 M-1s-1 for cationic and neutral fluoxetine, respectively) provided significantly more accurate predictions of fluoxetine degradation rates (k). A good linear correlation was observed between ksrc,CO3·- from experiments and literatures for 24 ionizable OMs and their molecular orbital energy gaps and oxidation potentials, suggesting the possible electron transfer reaction mechanism. Cl- slightly reduced the degradation rates of fluoxetine owing to rapid transformation of Cl• with HCO3- into CO3•-, which partially compensated for the quenching effects of Cl- on HO• and SO4•-. Dissolved organic matter significantly quenched reactive radicals. The constructed kinetic model successfully predicted fluoxetine degradation rates in real waters, with CO3•- being the dominant contributor (∼90 %) to this degradation process.

A review on recent advancements in the treatment of polyaromatic hydrocarbons (PAHs) using sulfate radicals based advanced oxidation process

Polyaromatic hydrocarbons (PAHs) are the most persistent compounds that get contaminated in the soil and water. Nearly 16 PAHs was considered to be a very toxic according US protection Agency. Though its concentration level is low in the environments but the effects due to it, is enormous. Advanced Oxidation Process (AOP) is an emergent methodology towards treating such pollutants with low and high molecular weight of complex substances. In this study, sulfate radical (SO4‾•) based AOP is emphasized for purging PAH from different sources. This review essentially concentrated on the mechanism of SO4‾• for the remediation of pollutants from different sources and the effects caused due to these pollutants in the environment was reduced by this mechanism is revealed in this review. It also talks about the SO4‾• precursors like Peroxymonosulfate (PMS) and Persulfate (PS) and their active participation in treating the different sources of toxic pollutants. Though PS and PMS is used for removing different contaminants, the degradation of PAH due to SO4‾• was presented particularly. The hydroxyl radical (•OH) mechanism-based methods are also emphasized in this review along with their limitations. In addition to that, different activation methods of PS and PMS were discussed which highlighted the performance of transition metals in activation. Also this review opened up about the degradation efficiency of contaminants, which was mostly higher than 90% where transition metals were used for activation. Especially, on usage of nanoparticles even 100% of degradation could be able to achieve was clearly showed in this literature study. This study mainly proposed the treatment of PAH present in the soil and water using SO4‾• with different activation methodologies. Particularly, it emphasized about the importance of treating the PAH to overcome the risk associated with the environment and humans due to its contamination.

Tailoring CuOx loading on CoFe2O4 nanocubes photocatalyst for superior photocatalytic degradation of triclosan pollutants under VL irradiation and toxicological evaluation

In this study, we report the development of a novel CuOx(3 wt%)/CoFe2O4 nanocubes (NCs) photocatalyst through simple co-precipitation and wet impregnation methods for the efficient photocatalytic degradation of triclosan (TCS) pollutants. Initially, rod-shaped bare CoFe2O4 was synthesized using a simple co-precipitation technique. Subsequently, CuOx was loaded in various percentages (1, 2, and 3 wt%) onto the surface of bare CoFe2O4 nanorods (NRs) via the wet impregnation method. The synthesized materials were systematically characterized to evaluate their composition, structural and electrical characteristics. The CuOx(3 wt%)/CoFe2O4 NCs photocatalyst exhibited superior photocatalytic degradation efficiency of TCS (89.9%) compared to bare CoFe2O4 NRs (62.1 %), CuOx(1 wt%)/CoFe2O4 (80.1 %), CuOx(2 wt%)/CoFe2O4 (87.0 %) under visible light (VL) irradiation (λ ≥ 420 nm), respectively. This enhanced performance was attributed to the improved separation effectiveness of photogenerated electron (e-) and hole (h+) in CuOx(3 wt%)/CoFe2O4 NCs. Furthermore, the optimized CuOx(3 wt%)/CoFe2O4 NCs exhibited strong stability and reusability in TCS degradation, as demonstrated by three successive cycles. Genetic screening on Caenorhabditis elegans showed that CuOx(3 wt%)/CoFe2O4 NCs reduced ROS-induced oxidative stress during TCS photocatalytic degradation. ROS levels decreased at 30, 60, and 120-min intervals during TCS degradation, accompanied by improved egg hatching rates. Additionally, expression levels of stress-responsible antioxidant proteins like SOD-3GFP and HSP-16.2GFP were significantly normalized. This study demonstrates the efficiency of CuOx(3 wt%)/CoFe2O4 NCs in degrading TCS pollutants, offers insights into toxicity dynamics, and recommends its use for future environmental remediation.

Elucidating the enhanced role of carbonate radical in propranolol degradation by UV/peroxymonosulfate system

Carbonate radical (CO3•-) has been proved to be an important secondary radical in advanced oxidation processes due to various radical reactions involved HCO3-/CO32-. However, the roles and contributions of CO3•- in organic micropollutant degradation have not been explored systematically. Here, we quantified the impact of CO3•- on the degradation kinetics of propranolol, a representative pollutant in the UV/peroxymonosulfate (PMS) system, by constructing a steady-state radical model. Substantially, the measured values were coincident with the predictive values, and the contributions of CO3•- on propranolol degradation were the water matrix-dependent. Propranolol degradation increased by 130% in UV/PMS system containing 10 mM HCO3-, and the contribution of CO3•- was as high as 58%. Relatively high pH values are beneficial for propranolol degradation in pure water containing HCO3-, and the contributions of CO3•- also enhanced, while an inverse phenomenon was shown for the effects of propranolol concentrations. Dissolved organic matter exhibited significant scavenging effects on HO•, SO4•-, and CO3•-, substantially retarding the elimination process. The developed model successfully predicted oxidation degradation kinetics of propranolol in actual sewage, and CO3•- contribution was up to 93%, which in indicative of the important role of CO3•- in organic micropollutant removal via AOPs treatment.

Aquatic photolysis of high-risk fluorinated liquid crystal monomers: Kinetics, toxicity evaluation, and mechanisms

Despite the frequent detection of fluorinated liquid-crystal monomers (FLCMs) in the environment, the level of understanding of their fate, toxicity, and transformation remains insufficient. Herein, we investigated the degradation kinetics and mechanism of an FLCM (4-cyano-3-fluorophenyl 4-ethylbenzoate, CEB-F) under ultraviolet (UV) photolysis in aquatic environment. Our findings demonstrated that the UV photolysis of CEB-F followed first-order kinetics. Photodegradation products were identified using liquid chromatography with mass spectrometry, and detailed reaction pathways were proposed. It is postulated that through the attack of reactive oxygen species, hydroxylation, and CO/C-F bond cleavage, CEB-F gradually degraded into small molecular compounds, releasing fluorine ions. Acute immobilization tests with Daphnia magna (D. magna) revealed significant acute toxicity of CEB-F, with LC50 values ranging from 1.023 to 0.0536 μM over 24 to 96 h, emphasizing the potential high risk of FLCMs in aquatic ecosystems if inadvertently discharged. Interestingly, we found that the toxicity of CEB-F photolysis reaction solutions was effectively reduced. Through catalase and acetylcholinesterase activities analysis along with molecular docking simulation, we proposed differences in the underlying toxicity mechanisms of CEB-F and its photolysis products to D. magna. These findings highlight the potential harmful effects of FLCMs on aquatic ecosystems and enrich our understanding of the photolysis behavior of FLCMs.

Electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4 to activate persulfate (E/oxygen-vacancy CuFe2O4/PS) for separation of Ebselen from wastewater

To enhance the catalytic activity of CuFe2O4 on PS, a nanoscale oxygen-vacancy CuFe2O4 was prepared by hydrogenation reduction technique to construct an advanced oxidation system of electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4-activated persulfate. Using Ebselen (EBS) as a model pollutant, the degradation efficiency, activation mechanism and degradation pathway were studied. The oxygen-vacancy CuFe2O4 was characterized and analysed by FESEM, EDS and XPS. The results show that under the optimal reaction conditions (PS = 0.8 g/L, oxygen-vacancy CuFe2O4 = 0.3 g/L, initial pH = 6.5), the removal rate of 20 mg/L EBS can reach 92% after reaction for 60 min, which proves that the formation of oxygen-vacancy changed the catalytic inertness of CuFe2O4 on PS. It is speculated that in the E/oxygen-vacancy CuFe2O4/PS system, the existence of oxygen holes enhances the electron transfer ability and reducibility of the catalyst, so the oxygen-vacancy CuFe2O4 can efficiently activate PS to degrade EBS. The quenching experiments show that both SO 4 ⋅ - and ⋅ OH are involved in the oxidation reaction as reactive radicals in the system, with SO 4 ⋅ - being the main reactive radical. In addition, both dissolved oxygen (DO) and anions in the solution inhibit the oxidative degradation of EBS by oxygen-vacancy CuFe2O4/PS system. Through GC-MS detection, a possible degradation pathway is proposed.

Phosphorous nitride dots induced efficient advanced oxidation with intrinsic chemiluminescence for organic pollutant degradation

In this work, we introduced new metal-free catalysts, phosphorus nitride dots (PNDs), into an environmentally friendly H2O2-SO32- system to generate abundant reactive oxygen species (O2˙-, ˙OH and SO4˙-) with strong intrinsic chemiluminescence (CL). The excellent catalytic ability of PNDs not only improved the degradation efficiency of organic pollutants, but also provided a promising prospect for deeply probing the mechanism of advanced oxidation processes (AOPs) by combining with CL.

Advanced oxidation and biological integrated processes for pharmaceutical wastewater treatment: A review

The stress of pharmaceutical and personal care products (PPCPs) discharging to water bodies and the environment due to increased industrialization has reduced the availability of clean water. This poses a potential health hazard to animals and human life because water contamination is a great issue to the climate, plants, humans, and aquatic habitats. Pharmaceutical compounds are quantified in concentrations ranging from ng/Lto μg/L in aquatic environments worldwide. According to (Alsubih et al., 2022), the concentrations of carbamazepine, sulfamethoxazole, Lutvastatin, ciprofloxacin, and lorazepam were 616-906 ng/L, 16,532-21635 ng/L, 694-2068 ng/L, 734-1178 ng/L, and 2742-3775 ng/L respectively. Protecting and preserving our environment must be well-driven by all sectors to sustain development. Various methods have been utilized to eliminate the emerging pollutants, such as adsorption and biological and advanced oxidation processes. These methods have their benefits and drawbacks in the removal of pharmaceuticals. Successful wastewater treatment can save the water bodies; integrating green initiatives into the main purposes of actor firms, combined with continually periodic awareness of the current and potential implications of environmental/water pollution, will play a major role in water conservation. This article reviews key publications on the adsorption, biological, and advanced oxidation processes used to remove pharmaceutical products from the aquatic environment. It also sheds light on the pharmaceutical adsorption capability of adsorption, biological and advanced oxidation methods, and their efficacy in pharmaceutical concentration removal. A research gap has been identified for researchers to explore in order to eliminate the problem associated with pharmaceutical wastes. Therefore, future study should focus on combining advanced oxidation and adsorption processes for an excellent way to eliminate pharmaceutical products, even at low concentrations. Biological processes should focus on ideal circumstances and microbial processes that enable the simultaneous removal of pharmaceutical compounds and the effects of diverse environments on removal efficiency.

CuS/Bi2O3 composites activating PMS under visible light for efficient degradation of antibiotic tetracycline

CuS/Bi2O3 composite photocatalyst was prepared by calcination and in situ precipitation, and peroxymonosulfate (PMS) was applied to the degradation of tetracycline (TC) wastewater under visible light. The microscopic morphology, chemical composition, and optical properties of the composites were investigated by characterization means of XRD, FTIR, SEM, XPS, and UV-Vis DRS. The results showed that the introduction of CuS increased the specific surface area of Bi2O3 and increased the visible absorption boundary of Bi2O3 from 455 to 524 nm, which effectively inhibited the complexation of photogenerated electron-hole pairs. The experimental results showed that the introduction of PMS strengthened the removal of TC from the composites, and 95% of TC could be removed under visible light irradiation, and the reaction rate was 8.22 times higher than that of the unspiked PMS, indicating that the BC-15+vis/PMS catalytic system could degrade the pollutants efficiently. The radical capture experiments showed that several radicals, including ·OH, SO4·-, ·O2-, h+, and 1O2, were present in the catalytic system as the main active species to degrade TC, and the mechanism of photocatalytic activation of PMS by Z-type heterostructures of CuS/Bi2O3 composites was proposed. The present study showed that BC-15 has excellent degradation performance and stability, which provides new ideas for the treatment of antibiotic wastewater.

Recent progress in mineralization of emerging contaminants by advanced oxidation process: A review

Emerging contaminants are chemicals generated due to the usage of pesticide, endocrine disrupting compounds, pharmaceuticals, and personal care products and are liberated into the environment in trace quantities. The emerging contaminants eventually become a greater menace to living beings owing to their wide range and inhibitory action. To diminish these emerging contaminants from the environment, an Advanced Oxidation Process was considered as an efficient option. The Advanced Oxidation Process is an efficient method for mineralizing fractional or generous contaminants due to the generation of reactive species. The primary aim of this review paper is to provide a thorough knowledge on different Advanced Oxidation Process methods and to assess their mineralization efficacy of emerging contaminants. This study indicates the need for an integrated process for enhancing the treatment efficiency and overcoming the drawbacks of the individual Advanced Oxidation Process. Further, its application concerning technical and economic aspects is reviewed. Until now, most of the studies have been based on lab or pilot scale and do not represent the actual scenario of the emerging contaminant mineralization. Thus, the scaling up of the process was discussed, and the major challenges in large scale implementation were pointed out.

Efficient degradation and detoxification of antibiotic Fosfomycin by UV irradiation in the presence of persulfate

Fosfomycin (FOS) as a widely used antibiotic has been found in abundance throughout the environment, but little effort has been devoted to its treatment. In this study, we systemically looked into the degradation of FOS by ultraviolet-activated persulfate (UV/PS) in aqueous solutions. Our findings demonstrated that FOS can be degraded efficiently under the UV/PS, e.g., >90 % of FOS was degraded with 19,200 mJ cm-2 of UV irradiance and 20 μM of PS. HO was the dominant radical responsible for FOS degradation. FOS degradation increased as PS dosage increased, and higher degradation efficiency was observed at neutral pH. Natural water constitutes either promoted (e.g., Cu2+, Fe3+, and SO42-) or inhibited (e.g., humic acid, HCO3-, and CO32-) FOS degradation to varying degrees. Hydroxyl substitution, CP bond cleavage, and coupling reactions were the major degradation pathways for FOS degradation. Finally, the toxicity evaluation revealed that FOS was toxic to E. coli and S. aureus, but the toxicity of the intermediate products of FOS to E. coli and S. aureus rapidly decreased over time after UV/PS treatment. Therefore, these findings provided a fundamental understanding of the transformation process of FOS and supplied useful information for the environmental elimination of FOS contamination and its toxicity.

Targeted degradation of naphthalene by peroxymonosulfate activation using molecularly imprinted biochar

Polycyclic aromatic hydrocarbons (PAHs) in aquatic environments are threatening ecosystems and human health. In this work, an effective and environmentally friendly catalyst based on biochar and molecular imprinting technology (MIT) was developed for the targeted degradation of PAHs by activating peroxymonosulfate. The results show that the adsorption amount of naphthalene (NAP) by molecularly imprinted biochar (MIP@BC) can reach 82% of the equilibrium adsorption capacity within 5 min, and it had well targeted adsorption for NAP in the solution mixture of NAP, QL and SMX. According to the comparison between the removal rates of NAP and QL by MIP@BC/PMS or BC/PMS system in respective pure solutions or mixed solutions, the MIP@BC/PMS system can better resist the interference of competing pollutants (i.e., QL) compared to the BC/PMS system; that is, MIP@BC had a good ability to selectively degrade NAP. Besides, the removal rate of NAP by MIP@BC/PMS gradually decreased as pH increased. The addition of Cl- greatly promoted the targeted removal of NAP in the MIP@BC/PMS system, while HCO3- and CO32- both had an inhibitory effect. Furthermore, SO4•-, O2•- and 1O2 produced by BC activating PMS dominated the NAP degradation, and it was inferred that the vacated imprinted cavities after NAP degradation can continue to selectively adsorb NAP and this could facilitate the reusability of the material. This study can promote the research on the targeted degradation of PAHs through the synergism of biochar/PMS advanced oxidation processes and MIT.

Efficient degradation of tetrabromobisphenol A using peroxymonosulfate oxidation activated by a novel nano-CuFe2O4@coconut shell biochar catalyst

In this study, a novel bimetallic complexation-curing nucleation-anaerobic calcination method was developed to synthesize a nano-CuFe2O4@coconut shell biochar (CuFe2O4@CSBC) catalyst to activate peroxymonosulfate for degradation of tetrabromobisphenol A (TBBPA). The reaction processes of the TBBPA on CuFe2O4@CSBC have been investigated using in situ characterization and metal leaching. The effects of initial reaction conditions and degradation mechanism were investigated. Greater than 99% degradation of TBBPA at 10 mg L-1 was achieved in 30 min under the condition of pH 11, a total organic carbon removal rate of up to 70.67% was achieved and the degradation efficiency was 90% after 5 cycles of CuFe2O4@CSBC use. The degradation was in a second-order reaction at a constant of 0.797 M-1 min-1 (R2 = 0.993). The degradation was attributed to the main active species (SO4·-≈·OH < 1O2), and the surface active site of CuFe2O4@CSBC was the key role. The degradation process involved three main degradation pathways. Path A: ·OH attacked the C-Br bonds (TBBPA→TriBBPA→DBBPA→MBBPA→BPA); Path B: Hydroxylation and decarboxylation; Path C: Dehydrocoupling of TBBPA. What's more, the practical application of the system was very positive, achieved >77% degradation in sewage and industrial wastewater.

Merits and Limitations of Radical vs. Nonradical Pathways in Persulfate-Based Advanced Oxidation Processes

Urbanization and industrialization have exerted significant adverse effects on water quality, resulting in a growing need for reliable and eco-friendly treatment technologies. Persulfate (PS)-based advanced oxidation processes (AOPs) are emerging as viable technologies to treat challenging industrial wastewaters or remediate groundwater impacted by hazardous wastes. While the generated reactive species can degrade a variety of priority organic contaminants through radical and nonradical pathways, there is a lack of systematic and in-depth comparison of these pathways for practical implementation in different treatment scenarios. Our comparative analysis of reaction rate constants for radical vs. nonradical species indicates that radical-based AOPs may achieve high removal efficiency of organic contaminants with relatively short contact time. Nonradical AOPs feature advantages with minimal water matrix interference for complex wastewater treatments. Nonradical species (e.g., singlet oxygen, high-valent metals, and surface activated PS) preferentially react with contaminants bearing electron-donating groups, allowing enhancement of degradation efficiency of known target contaminants. For byproduct formation, analytical limitations and computational chemistry applications are also considered. Finally, we propose a holistically estimated electrical energy per order of reaction (EE/O) parameter and show significantly higher energy requirements for the nonradical pathways. Overall, these critical comparisons help prioritize basic research on PS-based AOPs and inform the merits and limitations of system-specific applications.

Role of direct current on thermal activated peroxydisulfate to degrade phenanthrene in soil: Conversion of sulfate radical and hydroxyl radical to singlet oxygen, accelerated degradation rate and reduced efficiency

Electrokinetic (EK) delivery followed by thermal activated peroxydisulfate (PS) has turned out to be a potential in situ chemical oxidation technology for soil remediation, but the activation behavior of PS in an electrical coupled thermal environment and the effect of direct current (DC) intervention on PS in heating soil has not been explored. In this paper, a DC coupled thermal activated PS (DC-heat/PS) system was constructed to degrade Phenanthrene (Phe) in soil. The results indicated that DC could force PS to migrate in soil, changing the degradation rate-limiting step in heat/PS system from PS diffusion to PS decomposition, which greatly accelerated the degradation rate. In DC/PS system, ¹O₂ was the only reactive species directly detected at platinum (Pt)-anode, confirming that S₂O₈^2- could not directly obtain electrons at the Pt-cathode to decompose into SO₄^•-. By comparing DC/PS and DC-heat/PS system, it was found that DC could significantly promote the conversion of SO₄^•- and •OH generated by thermal activation of PS to ¹O₂, which was attributed to the hydrogen evolution caused by DC that destroys the reaction balance in system. It was also the fundamental reason that DC leaded to the reduction of oxidation capacity of DC-heat/PS system. Finally, the possible degradation pathways of phenanthrene were proposed on the basis of seven detected intermediates.

Electrochemical oxidation of carbamazepine in water using enhanced blue TiO2 nanotube arrays anode on porous titanium substrate

In this study, a blue TiO₂ nanotube arrays anode on porous titanium substrate (Ti-porous/blue TiO₂ NTA) was successfully fabricated by facile anodization and in situ reduction, and was used to investigate the electrochemical oxidation of carbamazepine (CBZ) in aqueous solution. The surface morphology and crystalline phase of the fabricated anode were characterized by SEM, XRD, Raman spectroscopy and XPS, and the electrochemical analysis confirmed that blue TiO₂ NTA on Ti-porous substrate had larger electroactive surface area, better electrochemical performance and higher ⋅OH generation ability than that on Ti-plate substrate. The removal efficiency of 20 mg L^-1 CBZ in 0.05 M Na₂SO₄ solution reached 99.75% at 8 mA cm^-2 after 60 min electrochemical oxidation, and the rate constant was 0.101 min^-1 with low energy consumption. EPR analysis and free radical sacrificing experiments showed that ⋅OH played a key role in the electrochemical oxidation. The possible oxidation pathways of CBZ were proposed through the identification of degradation products, and the main reactions may involve deamidization, oxidization, hydroxylation and ring-opening. Compared with Ti-plate/blue TiO₂ NTA anode, Ti-porous/blue TiO₂ NTA anode displayed excellent stability and reusability, and is promising to be used in the electrochemical oxidation of CBZ in wastewater.

Core-shell magnetic CFO@COF composites toward peroxymonosulfate activation for degradation of sulfamethoxazole from aqueous solution: A comparative study and mechanistic consideration

A core-shell covalent organic framework encapsulated Co1.2Fe1.8O4 magnetic particles (CFO@COF) was designed and prepared successfully to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation. It displays amazing catalytic reactivity since the unique interior structure and synergistic effect between COF shell and CFO core, reaching 99.8% removal of SMX (10 mg/L) within 30 min and 90.8% TOC removal. The synergy between bimetals vests high reactivity to CFO core. And the outer COF shell can stabilize the CFO core under intricate reaction conditions to restrain the leaching of Co ions (decreased from 0.75 to 0.25 mg/L). Further investigation compared the activation mechanism in two different system, CFO/PMS system and CFO@COF/PMS system. The result showed that the radical mechanism controlled by SO4⋅- guided the SMX degradation in CFO/PMS system whereas the 1O2 played a pivotal role in CFO@COF/PMS system called non-radical leading. The influences of various factors on degradation experiments and SMX degradation pathway were also studied. Most importantly, risk assessment in CFO@COF/PMS/SMX system was estimated via "ecological structure activity relationships". In most case, the toxicities of intermediates were lower than the initial samples, which confirmed the effectiveness of CFO@COF/PMS/SMX system in the reduction of toxicity of SMX.

Phase transformation-driven persulfate activation by coupled Fe/N-biochar for bisphenol a degradation: Pyrolysis temperature-dependent catalytic mechanisms and effect of water matrix components

Fe-N co-doped biochar is recently an emerging carbocatalyst for persulfate activation in situ chemical oxidation (ISCO). However, the involved catalytic mechanisms remain controversial and distinct effects of coexisting water components are still not very clear. Herein, we reported a novel N-doped biochar-coupled crystallized Fe phases composite (Fe@N-BC₈₀₀) as efficient and low-cost peroxydisulfate (PDS) activators to degrade bisphenol A (BPA), and the underlying influencing mechanism of coexisting inorganic anions (IA) and humic constituent. Due to the formation of graphitized nanosheets with high defects (AI index>0.5, I_D/I_G = 1.02), Fe@N-BC₈₀₀ exhibited 2.039, 5.536, 8.646, and 23.154-fold higher PDS catalytic activity than that of Fe@N-BC₆₀₀, Fe@N-BC₄₀₀, N-BC, BC. Unlike radical pathway driven by carbonyl group and pyrrolic N of low/mid-temperature Fe@N-BCs. The defective graphitized nanosheets and Fe-Nx acted separately as electron transfer and radical pathway active sites of Fe@N-BC₈₀₀, where π-π sorption assisted with pyrrolic N and pore-filling facilitated BPA degradation. The strong inhibitory effects of PO₄^3- and NO₂^- were ascribed to competitive adsorption of phosphate (61.11 mg g^-1) and nitrate (23.99 mg g^-1) on Fe@N-BC₈₀₀ via electrostatic attraction and hydrogen bonding. In contrast, HA competed for the pyrrolic-N site and hindered electron delivery. Moreover, BPA oxidation pathways initiated by secondary free radicals were proposed. The study facilitates a thorough understanding of the intrinsic properties of designed biochar and contributes new insights into the fate of degradation byproducts formed from ISCO treatment of micropollutants.

Thermally activated persulfate oxidation of ampicillin: Kinetics, transformation products and ecotoxicity

The heat-activated persulfate system showed encouraging results for the destruction of the widely used antibiotic Ampicillin (AMP). AMP removal follows exponential decay, and the observed kinetic constant was enhanced with persulfate (PS) dosage at the range 50-500 mg L^-1 and temperature (40-60 °C), while AMP thermolysis at 60 °C was almost negligible. The apparent activation energy was estimated to 124.7 kJ mol^-1_. Alkaline conditions, water matrix constituents like bicarbonates, humic acid, and real water matrices retarded AMP oxidation. Experiments performed with tert-butanol and methanol as scavengers demonstrated the contribution of sulfate radicals as the dominant reactive species. Seven transformation products (TPs) of AMP have been identified from AMP destruction. An EC₅₀ value equal to 187 mg L^-1 was calculated for 72 h of exposure of the microalgae Chlorella sorokiniana to AMP. According to the ecotoxicity experiments that conducted after treatment of AMP with PS for different reaction times, no important inhibition of microalgae was noticed for contact time of 72 h and 10 d. These results indicate the formation of no toxic AMP by-products for the applied experimental conditions.

Impact of water matrices on oxidation effects and mechanisms of pharmaceuticals by ultraviolet-based advanced oxidation technologies: A review

The binding between water components (dissolved organic matters, anions and cations) and pharmaceuticals influences the migration and transformation of pollutants. Herein, the impact of water matrices on drug degradation, as well as the electrical energy demands during UV, UV/catalysts, UV/O₃, UV/H₂O₂-based, UV/persulfate and UV/chlorine processes were systemically evaluated. The enhancement effects of water constituents are due to the powerful reactive species formation, the recombination reduction of electrons and holes of catalyst and the catalyst regeneration; the inhibition results from the light attenuation, quenching effects of the excited states of target pollutants and reactive species, the stable complexations generation and the catalyst deactivation. The transformation pathways of the same pollutant in various AOPs have high similarities. At the same time, each oxidant also can act as a special nucleophile or electrophile, depending on the functional groups of the target compound. The electrical energy per order (EEO) of drugs degradation may follow the order of EEO_UV > EEO_UV/catalyst > EEO_UV/H2O2 > EEO_UV/PS > EEO_UV/chlorine or EEO_UV/O3. Meanwhile, it is crucial to balance the cost-benefit assessment and toxic by-products formation, and the comparison of the contaminant degradation pathways and productions in the presence of different water matrices is still lacking.

Heat-activated persulfate for the degradation of micropollutants in water: A comprehensive review and future perspectives

This work is a critical review of the most important studies that have dealt with heat-activated persulfate to degrade persistent micropollutants in the last six years. The effect of the different operating parameters is discussed, wherein in all cases, the efficiency was favored at higher temperatures and oxidant concentrations. Particular emphasis was given to the effect of the aqueous matrix. Since heat activation is a homogeneous process based on the production of free radicals, in most of the studies presented, the removal of pollutants decreases as the complexity of the aqueous matrix increases except in cases where secondary oxidative species are produced that are selective with specific pollutants. It has also been observed that the change in toxicity usually follows the removal of the parent compound despite the formation of several by-products. Nowadays, combining different processes for the simultaneous activation of persulfate seems to be gaining ground. A hybrid process is an interesting strategy to reduce costs and increase efficiency, especially in real wastewater. In this light, the most interesting studies of hybrid systems for the destruction of micropollutants in recent years based on thermally activated persulfate are also summarized. Finally, some steps are proposed for future research towards the industrial application, including the study of chemical mixtures, the integrated toxicity assessment, the examination of simultaneous disinfection and decomposition of pollutants into real wastewater, the estimation of the required costs, and energy the combination of processes and their coupling with renewable sources, and the design of pilot plants and the scale-up of the hybrid processes.

Chemiluminescence based on UV-assisted persulfate activation for sensitive detection of triphenyl phosphate

Triphenyl phosphate (TPHP), a typical kind of organophosphorus flame retardants (OPFRs) with aryl groups, has been recognized as an emerging contaminant that causes environmental and health hazards. It is a pervasive threat that can be frequently detected in the environment and living organisms. Hence, establishing an efficient analytical method for TPHP is an urgent issue. In this work, a heteropolyacid (HPA)-luminol chemiluminescence strategy coupled with UV-assisted persulfate (PS) activation was proposed for the sensitive and selective detection of TPHP. The UV-assisted PS oxidation pretreatment could decompose the water-insoluble TPHP into smaller orthophosphates, which were further converted into HPA with the subsequently introduced vanadium‑molybdenum acid. The formed HPA served as a catalyst to oxidize luminol, and strong chemiluminescence at 425 nm was generated immediately. Furthermore, the degradation process of TPHP and chemiluminescence mechanism were also investigated. The results demonstrated that some reactive oxygen radicals such as SO₄^-, OH, ¹O₂, and O₂^-, were involved in the degradation and chemiluminescence reaction. Notably, this proposed chemiluminescence analytical strategy realized a highly sensitive detection for TPHP, and granted the limit of detection down to 0.38 ppt. This study provides an attractive perspective for the detection of emerging OPFRs.

Accelerate sulfamethoxazole degradation and detoxification by persulfate mediated with Fe2+&dithionite: Experiments and DFT calculation

Advanced oxidation process (AOPs) is one of the most effective technologies for organic pollutants removal. In this study, diverse reactive species generation and enhanced sulfamethoxazole (SMX) degradation were investigated based on persulfate (PDS) activated by Fe²⁺&dithionite (DTN). When involving Fe²⁺&dithionite in PDS, SMX degradation efficiency reached 84 % within 30 min following a pseudo-first-order kinetic, which was higher than those in Fe²⁺/PDS (50.4 %) and Fe²⁺/O₂/DTN (41.3 %). SO₄^•- and ^•OH were identified as dominant reactive species with a crucial role of FeSO₃⁺ based on quenching experiment and electron spin resonance (ESR). The contributions of SO₄^·-, ^·OH, and other species to SMX degradation were 60.1 %, 33.9 %, and 6 %, respectively. In Fe²⁺/DTN/PDS system, SMX was effectively degraded under nearly neutral pH (5.0-9.0), with activation energy of 96.04 kJ·mol^-1. The experiments and density functional theory (DFT) calculation demonstrated that three functional groups (benzenesulfonamido, benzene ring, and oxazole ring) were attacked for SMX degradation. Moreover, acute toxicity to Vibrio fischeri has enhanced in the earlier degradation process due to the intermediates and weaken with the continuous reaction. This work not only provides a high-activity SO₄^·--AOP for refractory pollutant treatment with possible dual radical generation resources, but elucidated diverse reactive species formation with Fe²⁺&dithionite.

Oxidative degradation of nitroguanidine (NQ) by UV-C and oxidants: Hydrogen peroxide, persulfate and peroxymonosulfate

Nitroguanidine (NQ), a component used in insensitive munitions formulations, has high solubility which often leads to highly contaminated wastewater streams. In this work, batch experiments were conducted to investigate and compare the NQ degradation by UV-based advanced oxidation processes (AOPs); hydrogen peroxide (H₂O₂), persulfate (PS) and peroxymonosulfate (PMS) were selected as oxidants. A preliminary evaluation of AOPs kinetics, byproducts, and potential degradation pathways were carried out and compared to NQ degradation by direct UV-C photolysis. The effects of oxidant dosage, NQ concentrations and pH were evaluated by determining the respective kinetic constants of degradation. Among the treatments applied, UV/PS showed to be a promising and effective alternative leading to faster rates of degradation respect to both oxidant dosage (25 mM) and initial NQ concentrations (≤24 mM). Nevertheless, the degradation rate of NQ by UV/PS appeared to be affected strongly by the initial pH compared to UV/H₂O₂ and UV/PMS, with the lowest rate overall at pH ≥ 8.0. In addition, the main byproducts from NQ degradation, guanidine and cyanamide, showed to be involved in further degradation steps only with UV/PS and UV/PMS suggesting higher degradation effectiveness of these oxidants compared UV/H₂O₂ and UV alone.

Degradation of Ibuprofen by the Electro/Fe3+/Peroxydisulfate Process: Reactive Kinetics, Degradation Products and Mechanism

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO4•− generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO4•− generated from the electron transfer reaction. The radical scavenging experiments indicated that SO4•− and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

Amlodipine removal via peroxymonosulfate activated by carbon nanotubes/cobalt oxide (CNTs/Co3O4) in water

Amlodipine (AML) is an effective drug that has been widely used for hypertension and angina. However, AML is frequently detected in aqueous environments, posing potential risks to human and ecological health. In this study, the degradation of AML via peroxymonosulfate (PMS) activated by CNTs/Co₃O₄ was investigated. CNTs/Co₃O₄ was prepared via a facile method, and multiple characterizations suggested that Co₃O₄ were uniformly dispersed on the surface of MWCNTs-COOH. Experimental results indicated that complete removal of 10 μM AML was achieved within 30 min by using 2 mg/L CNTs/Co₃O₄ and 4 μM PMS at 25 °C in PBS buffered solution (pH 7.0). The observed pseudo-first-order rate constant was calculated to be 0.1369 min^-1. Interestingly, the presence of 100 mM Cl^- resulted in a slight enhancement of AML removal rate from 0.0528 to 0.0642 min^-1. The addition of 100 mM HCO₃^-, 5 mg/L Pony Lake fulvic acid (PLFA), or Suwannee River humic acid (SRHA) retarded AML degradation by 15.5, 0.7, and 1.6 times, respectively. As per the quenching experiments, SO₄^⦁- rather than ⦁OH were verified to be the dominant reactive oxygen species (ROS). Additionally, ten major intermediates were identified using TOF-LC-MS and three associated reaction pathways including ether bond broken, H-abstraction, and hydroxylation were proposed. We outlook these findings to advance the feasibility of organic contaminants removal via CNTs/Co₃O₄ + PMS systems that have extremely low-level PMS.

Manganese oxide OMS-2 loaded on activated carbon fiber: a novel catalyst-assisted UV/PMS process for carbamazepine treatment in water

A novel catalyst was prepared by loading OMS-2 onto activated carbon fiber (ACF) via a one-step hydrothermal method, which was further adopted for carbamazepine treatment.

Cephalexin removal by persulfate activation using simulated sunlight and ferrous ions

This study presents the main results related to the use of activated persulfate (PS) in the elimination of the beta-lactam antibiotic cephalexin (CPX). Experiments were done using K₂S₂O₈ and simulated sunlight. A face-centered central composite experimental design was used to analyze the effects of the solution pH and the PS concentration on the reaction, and to determine the optimized conditions that favor the CPX elimination. The results indicated that the removal of CPX is promoted by an acidic pH and under the higher evaluated PS dose (7.5 mg L^-1). CPX total removal was achieved in 30 min. The analysis of the effect of the pollutant initial concentration indicated that a pseudo-first-order kinetics model can be used to describe the reaction. Likewise, the use of Fe²⁺ ions for PS activation (in the dark) was evaluated and established that a higher concentration of ions favors the pollutant removal. Control tests and under the presence of scavenger agents indicated that both HO• and SO₄^-• radicals would be present in the solution and promote the CPX elimination. The assessment of the solution dissolved organic carbon, nitrates and sulfates was also carried out, and indicated that a portion of the organic matter was mineralized.

UVA/persulfate-driven nonylphenol polyethoxylate degradation: effect of process conditions

UV/persulfate (UV/PS) technologies have gained increased attention as efficient alternatives for removing pollutants from different classes, although processes based on the UVA-driven S2O82- (PS) activation have not yet been discussed in the literature for the removal of the nonionic surfactant nonylphenol polyethoxylate (NPEO). The present study investigated the simultaneous effect of the initial persulfate concentration ([PS]₀) and specific photon emission rate (E_P,0) on NPEO degradation by UVA/PS following a Doehlert experimental design. The results for [NPEO]₀ = (4.65 ± 0.15) mg L^-1 indicated more than 97.8% NPEO removal after 2 h, with pseudo first-order specific degradation rate (k_obs) of 0.0320 min^-1, for [PS]₀ = 7.75 mmol L^-1 and E_P,0 = 0.437 μmol photons L^-1 s^-1. Under these conditions, NPEO half-life time was about 22 min, and the EC₅₀-48 h (% v/v) values for Daphnia similis before and after treatment did not differ significantly. Higher values of E_P,0 would influence NPEO removal for [PS]₀ not higher than 8-10 mmol L^-1, although lower degradation efficiencies were obtained with higher [NPEO]₀ or real wastewater, except for longer reaction times. Additionally, UVA/PS showed to be efficient for tensoactivity removal, despite the negligible total organic carbon (TOC) removal achieved. Finally, UVC and UVA resulted in NPEO degradation higher than 96% and similar tensoactivity removals when UVA/PS was conducted under optimal conditions ([PS]₀ = 10 mmol L^-1; E_P,0 = 0.324 μmol photons L^-1 s^-1), suggesting that UVA radiation available in solar light could be advantageously employed for NPEO removal at concentrations usually found in wastewater.

Hydrothermal synthesis of magnetic nano-CoFe2O4 catalyst and its enhanced degradation of amoxicillin by activated permonosulfate

Advanced oxidation process (AOP) has attracted widespread attention because it can effectively remove antibiotics in water, but its practical engineering application is limited by the problems of the low efficiency and difficult recovery of the catalyst. In the study, nano-spinel CoFe₂O₄ was prepared by hydrothermal method and served as the peroxymonosulfate (PMS) catalyst to degrade antibiotic amoxicillin (AMX). The reaction parameters such as CoFe₂O₄ dosage, AMX concentration, and initial pH value were also optimized. The reaction mechanism was proposed through free radical capture experiment and possible degradation pathway analysis. In addition, the magnetic recovery performance and stability of the catalyst were evaluated. Results showed that 85.5% of AMX could be removed within 90 min at optimal conditions. Sulfate radicals and hydroxyl radicals were the active species for AMX degradation. Moreover, the catalyst showed excellent magnetism and stability in the cycle experiment, which has great potential in the AOP treatment of antibiotic polluted wastewater.

Mechanism, Kinetics, and Ecotoxicity Assessment of ·OH-Initiated Oxidation Reactions of Sulfoxaflor

The ·OH-initiated reaction mechanism and kinetics of sulfoxaflor were investigated by using electronic structure calculations. The possible hydrogen atom and cyano group abstraction reaction pathways were studied, and the calculated thermochemical parameters show that the hydrogen atom abstraction from the C7 carbon atom is the more favorable reaction pathway. The subsequent reactions for the favorable intermediate (I4) with other atmospheric reactive species, such as O₂, H₂O, HO₂·, and NO_x· (x = 1, 2), were studied in detail. The products identified from the subsequent reactions could contribute to secondary organic aerosol (SOA) formation in the atmosphere. The intermediates and products formed from the initial and subsequent reactions are equally as toxic as the parent sulfoxaflor. At 298 K, the rate constant calculated for the formation of the favorable intermediate I4 is 2.54 × 10^-12 cm³ molecule^-1 s^-1, which shows that the lifetime of sulfoxaflor is 54 h. The excited-state calculation performed through time-dependent density functional theory shows that the photolysis of the title molecule is unlikely in the atmosphere. The global warming potentials (GWPs) for different time horizons, photochemical ozone creation potential (POCP), and ecotoxicity analysis were also studied for the insecticide sulfoxaflor.

The pH-dependent degradation of sulfadiazine using natural siderite activating PDS: The role of singlet oxygen

Occurring naturally siderite (FeCO₃) was used as the heterogeneous catalyst to activate peroxodisulfate (PDS) for the degradation of sulfadiazine under different initial pH values. The findings of this system exhibited various ROS (e.g. ¹O₂, SO₄^- and OH) present during a wide range of pH values. Among them, ¹O₂ could significantly facilitate the initial degradation rate, and the increased pH enhanced the role of ¹O₂. The factors including initial pH values, siderite dosage, PDS concentration, initial contaminants concentration, and water matrix were discussed. The role of each ROS was investigated through quenching test and electron paramagnetic resonance (EPR). Furthermore, the comprehensive degradation process was proposed based on the LC-MS results. And the cycle test demonstrates the reusability of siderite at a pH of 3. Accordingly, this study is of great significance for understanding the degradation of such sulfonamide pollutants in the siderite/PDS system.

Electrocatalytic oxidation of ciprofloxacin by Co-Ce-Zr/γ-Al2O3 three-dimensional particle electrode

In this work, Co-Ce-Zr/γ-Al₂O3₃ particle electrodes were prepared for the efficient degradation of ciprofloxacin (CIP). Co-Ce-Zr/γ-Al₂O₃ particle electrodes were analyzed with a scanning electron microscope (SEM), X-Ray Diffraction (XRD), X-Ray Fluorescence Spectrometer (XRF), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). According to the results, significant amounts of Co₃O₄, CeO₂, and ZrO₂ were formed on the Co-Ce-Zr/γ-Al₂O₃ particle electrodes. It was shown that when the conditions of the reaction system were at pH=6, conductivity of 4 ms/cm, current of 0.2 A, initial pollutant concentration of 100 mg/L, and material dosage of 15 g, CIP could be completely degraded within 40 min, and the energy consumed in the reaction was 41.3 kWh/kg CIP. The rate of total organic carbon (TOC) removal by Co-Ce-Zr/γ-Al₂O₃ particle electrodes was recorded to be approximately 52.6%. Using a response surface methodology, we explored the optimal operating conditions. At the same time, we also explored the influence of inorganic anions in water and actual water medium on the rate of CIP removal. In addition, the ESR data proved that the main active substance in the reaction system was ·OH. The degradation intermediates were investigated, and the possible mechanism was proposed. Thus, this research provided a new solution for the treatment of antibiotic-containing wastewater.

Electrochemical degradation of DCF by boron-doped diamond anode: degradation mechanism, pathways and influencing factors

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been widely detected in wastewater and surface water, indicating that the removal of NSAIDs by wastewater treatment plants was not efficient. Electrochemical advanced oxidation technology is considered to be an effective process. This study presents an investigation of the kinetics, mechanism, and influencing factors of diclofenac (DCF) degradation by an electrochemical process with boron-doped diamond anodes. Relative operating parameters and water quality parameters are examined. It appears that the degradation follows the pseudo-first-order degradation kinetics. DCF degradation was accelerated with the increase of pH from 6 to 10. The degradation was promoted by the addition of electrolyte concentrations and current density. Humic acid and bicarbonate significantly inhibited the degradation, whereas chloride accelerated it. According to the quenching tests, hydroxyl radicals (•OH) and sulfate radicals contributed 76.5% and 6.5%, respectively, to the degradation. Sodium sulfate remains a more effective electrolyte, compared to sodium nitrate and sodium phosphate, suggesting the quenching effect of nitrate and phosphate on •OH. Major DCF transformation products were identified. According to the degradation products detected by liquid chromatography-mass spectrometry, hydroxylation and decarboxylation are the main pathways of DCF degradation; while dechlorination, chlorination, and nitro substitution are also included in this electrochemical degradation process.

Magnetic CoFe2O4 nanocrystals derived from MIL-101 (Fe/Co) for peroxymonosulfate activation toward degradation of chloramphenicol

In this study, porous magnetic CoFe₂O₄ nanocrystals (NCs) were successfully synthesized by using bimetal-organic framework (MOF) as a precursor, and used as catalysts to activate peroxymonosulfate (PMS) for the removal of chloramphenicol (CAP) in the solution. The structure and physicochemical properties of CoFe₂O₄ NCs were thoroughly examined by a series of characterization techniques. The results revealed as-synthesized CoFe₂O₄ had a nanorod-shaped structure with high specific surface area (83.00 m² g^-1) and pore volume (0.31 cm³ g^-1). Furthermore, the degradation efficiency (100%) and the removal of total organic carbon (68.09%) were achieved after 120 min with 0.1 g/L CoFe₂O₄ NCs, 2 mM PMS and 10 mg/L CAP at pH of 8.20. In addition, effects of catalyst dosage, PMS dosage, initial pH values, CAP concentration and co-existing anions as well as natural organic matters in the solution on the degradation efficiencies were studied and all the removal can be well fitted with pseudo-first-order kinetic model (R² > 0.96). Sulfate radicals (SO₄^•-) and hydroxyl radicals (HO•) were proved to be two main reactive species for CAP removal in CoFe₂O₄/PMS system based on quenching experiments. CAP was degraded by the main pathways of dichlorination, denitration, decarboxylation, hydroxylation, ring cleavage and chain cleavage on CoFe₂O₄/PMS system through high performance liquid chromatograph-mass spectrometry analysis. We believe that this study would be very meaningful to promote the applications of MOFs-derived catalysts on the SO₄^•- based advanced oxidation processes (SR-AOPs) for the environmental remediation.

Sulfate radical-based oxidation of the aminopyralid and picloram herbicides: The role of amino group on pyridine ring

The widespread utilization of pesticides has attracted increasing attention to their environmental impacts and effective removal strategies. In the present study, the degradation of herbicides picloram (PCLO) and aminopyralid (AMP) with similar structures were investigated systematically by thermo activated persulfate. Overweight SO₄^•- was determined to be the predominant oxidizing species by quenching experiment. Obtained by laser-flash photolysis (LFP), reaction rate constants of SO₄^•- towards AMP and PCLO were determined at 1.56 × 10⁹ M^-1s^-1 and 1.21 × 10⁹ M^-1s^-1, respectively. Product analysis revealed that both substances underwent similar oxidation paths, namely, successive oxidation on pyridine ring and formation of coupling-products as well as further hydroxylation and decarboxylation. Amino group on the pyridine ring was identified as the main reactive site, which was further confirmed by DFT calculation. It was susceptible attacked by SO₄^•- to form deamination, nitration, and self-coupling products. These couples could be further oxidatively dehydrated to form azo and a series of azo derivatives. EOCSAR program predicted significant hazards on aquatic species during the formation of these couplings and azo derivatives. Our work emphasized the potential ability and toxicity of contaminates to produce azo substances in the presence of amino groups on the pyridine ring.

Exploring the phototransformation and assessing the in vitro and in silico toxicity of a mixture of pharmaceuticals susceptible to photolysis

The present study comprehensively investigates the phototransformation and ecotoxicity of a mixture of twelve pharmaceutically active compounds (PhACs) susceptible to photolysis. Namely, three antibiotics (ciprofloxacin, levofloxacin, moxifloxacin), three antidepressants (bupropion, duloxetine, olanzapine), three anti-inflammatory drugs (diclofenac, ketoprofen, nimesulide), two beta-blockers (propranolol, timolol) and the antihistamine ranitidine were treated under simulated solar irradiation in ultra-pure and river water. A total of 166 different transformation products (TPs) were identified by ultra-high performance liquid chromatography coupled with Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap HRMS), revealing the formation of twelve novel TPs and forty-nine not previously described in photolytic studies. The kinetic profiles of the major TPs resulting from a series of chemical reactions involving hydroxylation, cleavage and oxidation, dehalogenation, decarboxylation, dealkylation and photo substitution have been investigated and the transformation pathways have been suggested. Additionally, an in vitro approach to the toxicity assessment of daphnids was contrasted with ecotoxicity data based on the Ecological Structure Activity Relationships (ECOSAR) software comprising the in silico tool to determine the adverse effects of the whole mixture of photolabile parent compounds and TPs. The results demonstrated that photolysis of the target mixture leads to a decrease of the observed toxicity.

Efficient activation of peroxymonosulfate by copper sulfide for diethyl phthalate degradation: Performance, radical generation and mechanism

Copper-containing minerals have been extensively used in Fenton-like processes for degradation of pollutants and have exhibited great potential for environmental remediation. This work reports the first use of copper sulfide (CuS), a typical Cu-mineral, for the activation of peroxymonosulfate (PMS) for pollutant degradation; the study also elucidates the underlying mechanism of these processes. Copper sulfide effectively activated PMS to degrade diethyl phthalate (DEP). Electron paramagnetic resonance, free radical quenching, X-ray photoelectron spectroscopy, X-ray diffraction analyses and DFT calculations confirmed that ≡Cu (I)/≡Cu (II) cycling on the surface of CuS provided the main pathway to activate PMS to produce highly oxidative species. Unlike conventional sulfate radical-based PMS activation processes, hydroxyl radical (^•OH) were found to be the dominant radical in the tested CuS/PMS system, which performed more efficiently than an alternative ^•OH-based oxidation system (CuS/H₂O₂) for DEP degradation. In addition, the presence of anions such Cl^- and NO₃^- has limited inhibition effects on DEP degradation. Overall, this study provides an efficient pathway for PMS-based environmental remediation as well as a new insight into the mechanism of PMS activation by Cu-containing minerals.

A Review Study on Sulfate-Radical-Based Advanced Oxidation Processes for Domestic/Industrial Wastewater Treatment: Degradation, Efficiency, and Mechanism

High levels of toxic organic pollutants commonly detected during domestic/industrial wastewater treatment have been attracting research attention globally because they seriously threaten human health. Sulfate-radical-based advanced oxidation processes (SR-AOPs) have been successfully used in wastewater treatment, such as that containing antibiotics, pesticides, and persistent organic pollutants, for refractory contaminant degradation. This review summarizes activation methods, including physical, chemical, and other coupling approaches, for efficient generation of sulfate radicals and evaluates their applications and economic feasibility. The degradation behavior as well as the efficiency of the generated sulfate radicals of typical domestic and industrial wastewater treatment is investigated. The categories and characteristics of the intermediates are also evaluated. The role of sulfate radicals, their kinetic characteristics, and possible mechanisms for organic elimination are assessed. In the last section, current difficulties and future perspectives of SR-AOPs for wastewater treatment are summarized.