The impact of wastewater matrix on the degradation of pharmaceutically active compounds by oxidation processes including ultraviolet radiation and sulfate radicals

The impact of plasma-activated water on the process of nickel bioremediation by Neowestiellopsis persica A1387

Cyanobacteria provide an economical, feasible, and environmentally friendly solution for heavy metal removal. In addition, plasma can facilitate the removal of heavy metals across various time frames. In this study, we applied plasma-activated water (PAW) to prepare Neowestiellopsis persica A1387 strain medium culture for 0, 10, 15, and 20 min via an Atmospheric Cold Plasma Jet device (ACPJ-17A). Nickel removal efficiency was evaluated after 48 hours of cultivation under controlled conditions at 0, 10, 30, 60, and 90 min. Further investigation was performed through FTIR, GC-MS, and XRD techniques. Statistical analysis of ANOVA and Tukey's test indicated that the samples treated for 15 min had the highest biomass dry weight, polysaccharide content, and nickel removal rate (p ≤ 0.05). The GC-MS analysis presented elevated concentrations of ethanol, 1,3-dimethylbenzene, acetic acid, 3-methylbutyl ester, aromatic chemicals, 2-methyl-1-propanol, and 3-octen-2-ol in all samples treated with plasma. The functional group analysis using the FT-IR approach showed increased peak intensities with more extended treatment periods, indicating the addition of methyl, methylene, and hydroxyl groups to the cyanobacterium cell wall. Furthermore, a peak at 468 cm⁻¹ wavelength was observed, correlating to the Ni-O stretching mode after absorption of Ni on the cyanobacterium surface. The XRD data exhibited prominent peaks in all diffraction patterns angles below 20 degrees, suggesting the presence of amorphous and non-crystalline chemical structures within the cyanobacterial structures. The peak intensity increased with longer treatment durations. The 15-min plasma treatment optimized Ni removal, but the efficiency decreased with prolonged exposure due to adverse effects such as increased reactive oxygen species (ROS) production.

Ultrathin BiOCl-OV/CoAl-LDH S-scheme heterojunction for efficient photocatalytic peroxymonosulfate activation to boost Co (IV)=O generation

Sustainable and rapid production of high-valent cobalt-oxo (Co(IV)=O) species for efficiently removing organic pollutants is challenging in permoxymonosulfate (PMS) based advanced-oxidation-processes (AOPs) due to the limitation of the high 3d-orbital electronic occupancy of Co and slow conversion from Co(III) to Co(II). Herein, S-scheme BiOCl-OV/CoAl-LDH heterojunction were constructed by ultrathin BiOCl with the oxygen-vacancy (OV) self-assembled with ultrathin CoAl-LDH. OV promoted the formation of charge transfer channel (Bi-O-Co bonds) at the interface of the heterojunction and reduced electron occupation of the Co 3d-orbital to facilitate the generation of Co(IV)=O in the BiOCl-OV/CoAl-LDH/PMS/Visible-light system. S-scheme heterojunction accelerated the photogenerated electrons to allow rapid conversion of Co(III) to Co(II), promoting the fast two-electron transfer from Co(II) to Co(IV)=O. Consequently, the developed BiOCl-OV/CoAl-LDH/PMS/Visible-light system showed excellent degradation efficiency for most of organic pollutions, and exhibited very high removal capability for the actual industrial wastewater. This study provides a new insight into the evolution of Co(IV)=O and the coordinative mechanism for photocatalysis and PMS activation.

Elucidating the performance of UV-based photochemical processes for the removal of trace organic contaminants: Degradation and toxicity evaluation

In this study, the performance of standalone ultraviolet (UV) photolysis and UV-based advanced oxidation processes (AOPs), namely, UV/hydrogen peroxide, UV/chlorine, UV/persulphate, and UV/permonosulphate, were investigated for the degradation of 31 trace organic contaminants (TrOCs). Under the tested conditions, standalone UV photolysis did not achieve effective removal of TrOCs. To improve the degradation efficiency of UV photolysis, four different oxidants were added individually to the test solution. The effect of these oxidants in the absence of UV irradiation was also explored and only chlorine showed promising degradation of some contaminants. During the chlorination of 31 investigated TrOCs, only six demonstrated greater than 50% degradation. The combined UV-based AOPs demonstrated much improved degradation (ranging from 65 to 100%) depending on TrOC-structure and oxidant concentration. The UV/hydrogen peroxide process showed similar degradation of TrOCs, irrespective of the functional groups (i.e., electron withdrawing groups, EWGs and electron donating groups, EDGs) present in their structures. Conversely, the UV/sulphate and UV/chlorine based processes achieved better degradation of the TrOCs with EDGs in their structures. TrOCs degradation improved up to 40% when oxidants concentrations were increased from 0.1 to 1 mM, and further increasing the concentration to 2 mM did not improve degradation. Toxicity evaluation using bioluminescence test (BLT assay) demonstrated that except for UV/hydrogen peroxide, all UV-based AOPs increased the toxicity of the treated effluent, indicating generation of toxic by-products. This study elucidates the performance of four different UV-based AOPs for the removal of commonly detected diverse TrOCs for the first time.

Engineered hydrochar from waste reed straw for peroxymonosulfate activation to degrade quinclorac and improve solanaceae plants growth

Hydrochar from agricultural wastes is regarded as a prospective and low-cost material to activate peroxymonosulfate (PMS) for degrading pollutants. Herein, a novel in-situ N-doped hydrochar composite (RHCM4) was synthesized using montmorillonite and waste reed straw rich in nitrogen as pyrolysis catalyst and carbon source, respectively. The fabricated RHCM4 possessed excellent PMS activation performance for decomposing quinclorac (QC), a refractory herbicide, with a high removal efficiency of 100.0% and mineralization efficiency of 75.1%. The quenching experiments and electron spin resonance (ESR) detection disclosed free radicals (•OH, •SO4-, and •O2-) and non-radicals (1O2) took part in the QC degradation process. Additionally, the catalytic mechanisms were analyzed in depth with the aid of various characterizations. Moreover, the QC degradation intermediates and pathways were clarified by density functional theory calculations and HPLC-MS. Importantly, phytotoxicity experiments showed that RHCM4/PMS could efficaciously mitigate the injury of QC to Solanaceae crops (pepper, tomato, and tobacco). These findings give a new idea for enhancing the catalytic activity of hydrochar from agricultural wastes and broaden its application in the field of agricultural environment.

Influence of water matrix components on the UV/chlorine process and its reactions mechanism

The UV/chlorine system has become an attractive alternative Advanced Oxidation Process (AOP) for the removal of recalcitrant pollutants in the last decade due to the simultaneous formation of chlorine and hydroxyl radicals. However, there is no consensus regarding the results and trends obtained in previous micropollutant removal studies by AOPs, highlighting the complexity of the UV/chlorine process and the need for further research. This study investigates the degradation of acetaminophen (ACTP) by UV/chlorine and the effects of the water matrix in the reaction kinetics. In particular, the effects of natural organic matter (NOM), alkalinity and mineral salts on the kinetics and reactive species were elucidated. The complexity of the system was revealed by the analysis of the radical generation and transformation in different water matrices, applying the kinetic modelling approach to complement the scavenger tests. The higher kinetic rates of ACTP at alkaline pH provided new insights into the chlorine reactions under UV radiation, where secondary and tertiary reactive oxygen species including ozone were proven to play the major role in degradation. On the contrary, at acidic pH, reaction kinetic modelling demonstrated that ClO^• radical occurs at high concentrations in the order of 10^-10 M, being therefore the main oxidant, followed by other chlorine radicals. It is noteworthy that at alkaline pH the presence of typical inorganic ions such as carbonate had little impact on ACTP degradation, contrary to the observed reduction of degradation rates at acidic pH. The expected detrimental effect of the NOM in AOPs was also evidenced, although the use of chlorine as radical source reduces the relevance of the inner filter effect in comparison to UV/H₂O₂.

Comparison of ribavirin degradation in the UV/H2O2 and UV/PDS systems: Reaction mechanism, operational parameter and toxicity evaluation

Residues in surface water of ribavirin, which used extensively during the COVID-19 pandemic, have become an emerging issue due to its adverse impact on the environment and human health. UV/H2O2 and UV/peroxydisulfate (PDS) have different degradation effects on ribavirin, and the same operational parameter have different effects on the two processes. In this study, the reaction mechanism and degradation efficiency for ribavirin were studied to compare the differences under UV/H2O2 and UV/PDS processes. We calculated the total rate constants of ribavirin with HO• and SO4 •- in the liquid phase as 2.73 × 108 and 9.39 × 105 M-1s-1. The density functional theory (DFT) calculation results showed that HO• and SO4 •- react more readily with ribavirin via H-abstraction (HAA). The nitrogen-containing heterocyclic ring is difficult to undergo ring-opening degradation. The UV/PDS process was more stable and performed better than the UV/H2O2 for the ribavirin degradation when the same molar oxidant dosage was applied. HO• plays an extremely important role in the degradation of ribavirin by UV/PDS. The reason for this phenomenon is the combination of the higher yield of HO• produced in the UV/PDS process and the faster reaction rate of ribavirin with HO•. The UV/H2O2 process is more sensitive to pH than UV/PDS. Alkaline condition can significantly inhibit the ribavirin degradation. The effects of natural organic matter (NOM) and ribavirin concentration were also compared. Eventually, the toxicity prediction of the product showed that the opening-ring products were more toxic than the parent compound.

Chloride-Enhanced Removal of Ammonia Nitrogen and Organic Matter from Landfill Leachate by a Microwave/Peroxymonosulfate System

Landfill leachate contains not only high concentrations of refractory organic matter and ammonia nitrogen, but also high concentrations of chloride ions (Cl−). The modification of reactive species of the peroxymonosulfate (PMS) oxidation system by Cl− and its priority sequence for the removal of NH4+-N and organic matter from landfill leachate remain unclear. This study investigated the removal characteristics of NH4+-N and organic matter in the microwave (MW)/PMS system with high Cl− content. The results show that increasing Cl− concentration significantly improves the production of hypochlorous acid (HOCl) in the MW/PMS system under acidic conditions, and that the thermal and non-thermal effects of MW irradiation have an important influence on the HOCl produced by PMS activation. The maximum cumulative concentration of HOCl was 748.24 μM after a reaction time of 2 min. The formation paths of HOCl are (i) SO4•− formed by the MW/PMS system interacting with Cl− and HO•, and (ii) the nucleophilic addition reaction of PMS and Cl−. Moreover, the high concentration of HOCl produced by the system can not only remove NH4+-N in situ, but also interact with PMS to continuously generate Cl• as an oxidant to participate in the reaction with pollutants (e.g., NH4+-N and organic matter). Common aqueous substances (e.g., CO32−, HCO3−, NO3−, and humic acid) in landfill leachate will compete with NH4+-N for reactive species in the system, and will thereby inhibit its removal to a certain extent. It was found that when NH4+-N and leachate DOM co-exist in landfill leachates, they would compete for reactive species, and that humic acid-like matter was preferentially removed, leading to the retention of fulvic acid-like matter. It is hoped that this study will provide theoretical support for the design and optimization of methods for removing NH4+-N and organic matter from landfill leachate with high chloride ion content.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects

The presence of 1,4-dioxane in various water streams poses a threat to the health of human beings. In this study, the oxidative combination of ozone with peroxymonosulfate (PMS) was for the first time used to remove 1,4-dioxane from water. Near complete abatement of 1,4-dioxane was achieved by ozone-PMS after reaction of only 15 min and the degradation kinetics was found to be positively correlated with doses of PMS and ozone. Ozone-PMS oxidation had the optimum performance at slight base pH values. Both sulfate radicals and hydroxyl radicals were generated in ozone-PMS oxidation and these radicals resulted in the degradation of 1,4-dioxane. The effects of common water constituents and real water matrices were investigated. It was found that bicarbonate ions with a concentration up to 10 mM had a slight promoting effect, while either chloride ions or natural organic matter inhibited only slightly the degradation. Meanwhile, no obvious difference in the degradation of 1,4-dioxane was found among the real water matrices and deionized water, which demonstrates that ozone-PMS oxidation has high tolerance and stability. The results from this study demonstrate that ozone-PMS may be a promising technology for the removal of 1,4-dioxane from various water matrices.

Magnetically separable Fe-base deposited on different carbon sources for ultrasound/persulfate-like heterogeneous activation: Optimized synthesis and field driving process

The eco-friendly composite materials, micro-nano Fe-base/glucose-derived hydro-chars (Fe_b/HCs), were prepared, whose magnetic separation can be achieved in both preparation and water treatment stages. The performances of Fe_b/HCs after N₂ heat-treatment to activate persulfate, chlorite, hydrogen peroxide, etc., in ultrasound field, obtained great improvement by extracting "O". For comparison, other different sized and magnetic iron-carbon based composites based on different carbon sources of activated carbons, cornstalk-derived bio-chars, and glucose-derived pyrolytic carbons were prepared and applied to systematically compare the performance of activation. The Fe_b/HCs with optimizing preparation were utilized as activators to well treat different structures (triphenylmethane-, azo-, and xanthene-) contaminants. The detected p-Benzoquinone and 2-chloro-p-Benzoquinone could be considered as transitional and characteristic intermediates from carbocyclic compounds to chain compounds. The degradation mechanisms were evoked by pH and absorption to trigger via free/non-free radicals processes: high valence iron-oxo species, sulfate radicals, hydroxyl radicals, Cl-based substances, etc. The findings contrastively provided the potential applications of magnetically separable iron-carbon based composites for heterogeneous activation in environmental remediation.

Oxidative Degradation of Pharmaceutical Waste, Theophylline, from Natural Environment

The elimination of organic contaminants from natural resources is extremely important to ensure their (re-)usability. In this report, the degradation of a model pharmaceutical compound, theophylline, is compared between natural and laboratory-controlled environments. While the concentration of H2O2 variably affected the degradation efficiency (approximately from 8 to 20 min for complete degradation) in the photo-irradiation experiments, the inorganic compounds (NaNO3, KH2PO4 and ZnSO4) present in the medium seemed to affect the degradation by scavenging hydroxyl radicals (•OH). The end-product studies using high-resolution mass spectrometry (HRMS) ruled out the involvement of secondary radicals in the degradation mechanism. The quantitative calculation with the help of authentic standards pointed out the predominant role of hydroxylation pathways, especially in the initial stages. Although a noticeable decline in the degradation efficiency was observed in river water samples (complete degradation after 25 min with an approximately 20% total organic carbon (TOC) removal), appreciable TOC removal (70%) was eventually achieved after prolonged irradiation (1 h) and in the presence of additional H2O2 (5 times), revealing the potential of our technique. The results furnished in this report could be considered as a preliminary step for the construction of •OH-based wastewater treatment methodologies for the remediation of toxic pollutants from the real environment.

Synergistic effect of ultrasonication and sulfate radical on recovering cobalt and lithium from the spent lithium-ion battery

Ultrasonication has been mechanically applied widely in the recycling of spent lithium-ion (SLI) batteries while its influence on chemical pathways has barely been reported. In this study, ultrasonication and sulfate radicals were used in a coupling system to obtain efficient recoveries of Co and Li from SLI batteries. The synergistic effect of ultrasonication and sulfate radicals on recycling was quantitatively analysed by significance analysis and surface responses in a central composite design. The employment of persulfate significantly affected the whole recycling process during the sonication. Factors including acoustic time, operating powers, and temperature all had a significant effect on the recoveries of Co and Li. The maximum recovery efficiencies of Co and Li of 97.33% and 99.25%, respectively, and the minimum loss rate of Al of 4.13% were simultaneously obtained by the fitting predictor. The optimal combination of factors for the sonication system included an acoustic time (min) of 5.5, an operating power (W) of 168, a temperature (°C) of 86, and a ratio of cathode foil to S-solution (mg/mL) of 1:60. A moiety of cathode active material was directly separated from the aluminium collector by sulfate radical-related reactions. Co and Li cations dissolved from LiCoO₂ by carbon dioxide radicals were reprecipitated by excess oxalate. The research demonstrated the positively synergistic influence caused by ultrasonication and sulfate radicals on achieving efficient recoveries of Co and Li from SLI batteries, explicitly expanding the technical choices for the recycling procedure.

Removal of recalcitrant organics in reverse osmosis concentrate from coal chemical industry by UV/H2O2 and UV/PDS: Efficiency and kinetic modeling

The lack of stability in catalytic ozonation treatment of reverse osmosis (RO) concentrate from coal chemical industry calls for new advanced oxidation processes. Herein, UV/H₂O₂ and UV/PDS were employed to remove the bulk recalcitrant organics in the RO concentrate with a focus on the process efficiency and kinetic modeling. Results show that UV/H₂O₂ overmatched UV/PDS in reducing the COD and DOC of the wastewater and the advantage became more evident in aspects of biodegradability improvement and energy cost. Specifically, the COD and DOC were removed by 62.0% and 55.5% with UV/H₂O₂ (6 mM) while the BOD₅/COD was elevated to 0.54 at a specific energy consumption of 0.83 kWh g^-1 (lab-scale). The UV/H₂O₂ process also exhibited a good adaptability to the fluctuation of wastewater quality. Afterwards, the reaction rate constants of the bulk organics upon UV photolysis and HO^• oxidation were calculated based on pseudo-first-order kinetics and radical steady-state approximation of DOC removal in the bench-scale UV/H₂O₂ reactor. A computational fluid dynamics model was then developed for the analysis of distributions of flow, radiation and chemicals in flow-through reactors which facilitated the practical process efficiency assessment. This work demonstrates the applicability of UV/H₂O₂ in removing recalcitrant organics in the RO concentrate and presents an approach from bench-scale experiments to flow-through system evaluation.

A microwave irradiation-persulfate-formate system for achieving the detoxification and alkali-activated composite geopolymerization of the chromate-contaminated soil

A microwave (MA) irradiation-persulfate-formate system was constructed to detoxify Cr contamination and solidify the geopolymerization of the alkali-activated composite material. Three series of experiments were correspondingly conducted to evaluate the treatment for the chromate-contaminated soil. The changes in the molar ratios of formate to persulfate and the mass rates of fortifier to soil led to a significantly greater reduction of Cr^VI in the detoxification experiments. The increase of blast furnace slag from 50% to 80% in the composite cementitious materials (CCM) intensified the immobilization efficiencies of chromate and the compressive strengths of geopolymer blocks. MA irradiation potentially enhanced the binding of Ca cations to the aluminosilicate compounds. The degree of reaction in the phenomenological kinetics model mathematically verified the geopolymerization process. Ettringite was formed within the structure of the geopolymer in the coupling system. Sulfate radicals released from persulfate not only contributed to the detoxification process but also strengthened the immobilization process.

Solar photon-Fenton process eliminates free plasmid DNA harboring antimicrobial resistance genes from wastewater

This work aimed to assess the elimination and inactivation of resistance-conferring plasmids (RCPs) present in suspension in secondary wastewater by solar photo-Fenton as these are important vectors for the dissemination of antimicrobial resistance. Experiments were performed in synthetic secondary wastewater (SWW) and municipal wastewater treatment plant effluent (MWWTPE). Solar photo-Fenton (50 mg L-1 of H2O2 and 30 mg L-1 of Fe2+) was carried out for 60 min at neutral pH by applying the intermittent iron addition strategy. The removal of RCPs was assessed by Real-Time Polymerase Chain Reaction (qPCR). The transformation of competent non-resistant E. coli was used to evaluate the inactivation of target RCPs harboring antibiotic resistance genes (ARGs) to ampicillin (pSB1A2) or kanamycin (pSB1K3) after treatment and controls. Solar photo-Fenton completely removed RCPs initially present in both matrixes (SWW and MWWTPE), showing enhanced performance compared to the dark Fenton process. Both RCPs were inactivated after 30 min of solar photo-Fenton treatment, while 60 min were necessary to achieve the same effect for the dark Fenton reaction under similar conditions. These results indicate the potential of solar photo-Fenton to improve wastewater quality and reduce the spread of antimicrobial resistance in the environment by hampering the discharge of cell-free RCPs present in suspension in MWWTP onto environmental waters.

Synergistic mechanism and degradation kinetics for atenolol elimination via integrated UV/ozone/peroxymonosulfate process

The present research systematically investigates the atenolol (ATL) degradation in integrated UV/Ozone (O₃)/peroxymonosulfate (PMS) process focusing on the synergistic mechanism, reaction kinetics, pollutant degradation pathway and antibacterial activity. The results manifested that the integrated UV/O₃/PMS process showed the noteworthy superiority to ATL degradation compared with UV/PMS, UV/O₃ and O₃/PMS systems. Simultaneously, the impacts of operating parameters like PMS dosage, initial ATL concentration, solution pH and water matrix were comprehensively explored. The ATL elimination efficiency increased linearly with PMS dose and significantly enhanced in alkaline conditions. The ^•OH and SO₄^•- were the primary reactive radicals for ATL oxidation in UV/O₃/PMS system based on the radical scavenging experiments and electron paramagnetic resonance characterization. Besides, a simplified kinetic model on the basis of the dominant reactions and the steady-state assumption was established to foretell the relative contributions of reactive oxidants for ATL elimination in UV/O₃/PMS process. Main transformation products were determined via UPLC-QTOF-MS to infer the possible degradation pathways of ATL. Furthermore, the UV/O₃/PMS process could distinctly mitigate the antibacterial activity of ATL and its intermediates to E. coli and B. subtilis. Our findings may have critical implications for the development of novel oxidation processes for recalcitrant contaminants mitigation in water purification.

Degradation of aqueous atrazine using persulfate activated by electrochemical plasma coupling with microbubbles: removal mechanisms and potential applications

Persulfate (PS) activated by dielectric barrier discharge (DBD) integrated with microbubbles (MBs) was designed to decompose atrazine (ATZ) from aqueous solutions. The degradation efficiency reached 89% at a discharge power of 85W, a PS concentration of 1mM, and a air flow rate of 30mL/min after 75min treatment. Heat caused by DBD favoured ATZ removal. Besides, the effect of PS dosage, discharge power and initial pH values on ATZ removal was evaluated. The calculated energy yield revealed that it was economical and promising to treat 1L of ATZ-wastewaters. The existence of SO₄^2-, Cl^-, CO₃^2- and HCO₃^- lead to negative effects, while positive effect was observed when the presence of MBs and humic acid. The identification results of radicals and degradation intermediates suggested that multiple synergistic effects (such as heat, e_aq^- and H•) activated PS, and ¹O₂/reactive nitrogen species, •OH and SO₄^-• with contributions of 18%, 26%, and 29%, were main species attacking ATZ. ATZ degradation pathways including olefination, alkylic-oxidation, dealkylation, and dechlorination were proposed. An environment-friendly and a novel method for enhancing the PS-activation and ATZ-decomposition was provided, which fully utilised the electric-chemical conversion of DBD and high mass transfer efficiency of MBs.

Efficient removal of bisphenol A with activation of peroxydisulfate via electrochemically assisted Fe(III)-nitrilotriacetic acid system under neutral condition

In this work, an innovative electrochemically assisted Fe(III)-nitrilotriacetic acid system for the activation of peroxydisulfate (electro/Fe(III)-NTA/PDS) was proposed for the removal of bisphenol A (BPA) at neutral pH with commercial graphite electrodes. The efficient BPA decay was mainly originated from the continuous activation of PDS by Fe(II) reduced from Fe(III)-NTA complexes at the cathode. Scavenger experiments and electron paramagnetic resonance (EPR) measurements confirmed that the removal of BPA occurred through graphite adsorption, direct electron transfer (DET) and radical oxidation. Sulfate and hydroxyl radicals were primarily responsible for the oxidation of BPA while graphite adsorption and DET played a minor role in BPA removal. The influence of Fe(III) concentration, PDS dosage, input current, NTA to Fe(III) molar ratio as well as coexisting inorganic anions (Cl^-, NO₃^-, H₂PO₄^- and HCO₃^-) on BPA elimination was explored. The BPA removal efficiency reached 93.5 % after 60 min reaction in the electro/Fe(III)-NTA/PDS system under the conditions of initial pH 7.0, 0.30 mM Fe(III), 0.15 mM NTA, 5 mM PDS and 5 mA constant current. Overall, this research provided a novel perspective and potential for remediation of organic wastewater using NTA in combination with electrochemistry in the homogeneous Fe(III)/persulfate system.

Peroxymonosulfate/solar radiation process for the removal of aqueous microcontaminants. Kinetic modeling, influence of variables and matrix constituents

New technologies to address the presence of pharmaceutical and personal care products (PPCPs) in wastewater are needed, especially in those cases in which water will be reused. In this work, the activation of peroxymonosulfate (PMS) with simulated solar radiation has been applied to the oxidation of a mixture of six PPCPs, i.e. caffeine, primidone, N,N-diethyl-3-methylbenzamide (DEET), methylparaben, clofibric acid and ibuprofen. The sole application of solar radiation, i.e. solar photolysis, only led to the oxidation of clofibric acid (complete degradation in 90 min). The combination of PMS and solar radiation resulted in the degradation of all target micropollutants. The complete degradation of this mixture at initial 100 ppb was achieved with 0.5 mM of initial PMS after 90 min. A kinetic study that acceptably simulates the experimental data under different conditions has been proposed. The effects of initial PPCP concentration (1 mg L^-1-100 μg L^-1), PMS dose (0.1-5 mM), and pH (3-9) were tested and kinetically simulated. Finally, the PPCPs removal study was carried out in two real water matrices (river and a secondary effluent of an urban wastewater treatment plant). A higher dose of PMS, ten times higher, was required to achieve complete degradation of the micropollutants if compared to ultrapure water.

Efficient degradation of bisphenol A in water by heterogeneous activation of peroxymonosulfate using highly active cobalt ferrite nanoparticles

Cobalt ferrite CoFe₂O₄ catalyst was fabricated and systematically investigated as an efficient peroxymonosulfate (PMS, HSO₅^-) activator for the degradation of recalcitrant organic contaminants (ROCs) in water treatment. Both SO₄^- and OH on the surface of catalyst were unveiled to be primarily responsible for bisphenol A (BPA) degradation by a comprehensive study using electron paramagnetic resonance (EPR), radical scavengers and quantification of SO₄^-, and the negligible contribution of singlet oxygen (¹O₂) was also observed. BPA degradation was accelerated in the presence of humic acid, and it increased first but then decreased with the further addition of fulvic acid. Moreover, the presence of chloride and bicarbonate ions can enhance both BPA and TOC removal. The toxicity of the target aqueous solution ascended slowly at the early stage but then declined dramatically and almost vanished as the reaction proceeded. The removal efficiencies of other typical ROCs (clofibric acid, 2,4-dichlorophenol, etc.) and the decontamination of natural surface water spiked with BPA were also evaluated. This CoFe₂O₄/PMS process could be well applied as a safe, efficient, and sustainable approach for ROCs remediation in complex wastewater matrix.

Characterization of wastewater effluent organic matter with different solid phase extraction sorbents

Effluent organic matter (EfOM) from municipal wastewater treatment plants (WWTPs) has received increasing attention due to its impacts on natural and engineered aquatic systems. A comprehensive understanding of molecular compositions of EfOM is crucial for controlling its negative effects and effective removal of it. Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS) is a powerful method to characterize molecular compositions of EfOM. However, application of this powerful technique is very depending on the sample preparation procedures (i.e. solid phase extraction, SPE) for enrichment and desalting. In this study, a systematic comparison of the difference in molecular compositions of the EfOM extracted using eighteen different SPE sorbents (Envicarb, PPL, ENV, HLB, C18, C18OH, C8, PH, CH, WAX, WCX, MAX, MCX, CBA, C2, CN-E, NH2, and SI) was investigated. Molecular characterization using FTICR MS showed that non-polar sorbents (Envicarb, PPL, ENV, HLB, C18, C18OH) and mixed mode sorbents (WAX, WCX, MAX, MCX) prefer to extract more aromatic and unsaturated molecules, while strongly-polar (SI), mid-polar (CBA, NH2), and weakly non-polar (C2, CN-E) sorbents prefer to extract more aliphatic components. In addition, it is found that combining extracts of CBA, ENV, and EnviCarb sorbents might be a practical way to provide a comprehensive information of molecular composition of EfOM. The results reported in this study provide valuable information on molecular compositions of EfOM and the selectivity of EfOM by different SPE sorbents.