Degradation of oxytetracycline in aqueous solution by heat-activated peroxydisulfate and peroxymonosulfate oxidation

Degradation of methyl parathion in thermally activated peroxymonosulfate processes: Kinetics, reaction mechanism and toxicity evaluation

Methyl parathion, as widely utilized organophosphorus pesticide, was commonly detected in aquatic environments. Heat-activated peroxymonosulfate (PMS) represented an emerging advanced oxidation process. In this study, the degradation efficiency and reaction mechanism of methyl parathion by heat-activated PMS system were investigated by experimental and theoretical aspects. The findings indicated that the degradation efficacy of methyl parathion improved with the increase in temperature, PMS concentration and pH. The radical quenching experiments revealed that the primary reactive radical initiating methyl parathion degradation was ·OH. Moreover, we determined that the coexistence mechanism existed in the heat-activated PMS process involving both PMS direct oxidative and radical oxidative degradation of methyl parathion. Then, the possible reactions of methyl parathion with ·OH and SO4˙- in the water environment were calculated at SMD/M06-2X/6-311++G(3df,2p)//SMD/M06-2X/6-311+G(d,p) level to clarify the detailed reaction mechanism. It was found that two reactive radicals were more prone to react with methyl parathion via addition reaction at the P=S bond. The total reaction rate constants of methyl parathion with ·OH and SO4˙- slightly decreased as the temperature increased from 298 K to 333 K. Eventually, the toxicity evaluation by the QSAR-based toxicity prediction software demonstrated that the aquatic toxicity of most products was lower than methyl parathion, but still has positive mutagenicity and toxic developmental toxicity. This work offered novel insights into the reaction mechanism of methyl parathion with activated PMS and could also help to clarify the fate of methyl parathion in the water environment.

Activation of peroxymonosulfate by Fe,N co-doped walnut shell biochar for the degradation of sulfamethoxazole: Performance and mechanisms

Fe and N co-doped walnut shell biochar (Fe,N-BC) was prepared through a one-pot pyrolysis procedure by using walnut shells as feedstocks, melamine as the N source, and iron (III) chloride as the Fe source. Moreover, pristine biochar (BC), nitrogen-doped biochar (N-BC), and α-Fe2O3-BC were synthesized as controls. All the prepared materials were characterized by different techniques and were used for the activation of peroxymonosulfate (PMS) for the degradation of sulfamethoxazole (SMX). A very high degradation rate for SMX (10 mg/L) was achieved with Fe,N-BC/PMS (0.5 min-1), which was higher than those for BC/PMS (0.026 min-1), N-BC/PMS (0.038 min-1), and α-Fe2O3-BC/PMS (0.33 min-1) under the same conditions. This is mainly due to the formation of Fe3C and iron oxides, which are very reactive for the activation of PMS. In the next step, Fe,N-BC was employed for the formation of a composite membrane structure by a liquid-induced phase inversion process. The synthesized ultrafiltration membrane not only exhibited high separation performance for humic acid sodium salt (HA, 98%) but also exhibited improved self-cleaning properties when applied for rhodamine B (RhB) filtration combined with a PMS solution cleaning procedure. Scavenging experiments revealed that 1O2 was the predominant species responsible for the degradation of SMX. The transformation products of SMX and possible degradation pathways were also identified. Furthermore, the toxicity assessment revealed that the overall toxicity of the intermediate was lower than that of SMX.

Chemical oxygen demand and tannin/lignin removal from paper mill wastewater by electrocoagulation combined with peroxide and hypochlorite treatments

The present investigation sought to assess the practicality of utilizing a combined pre-treatment approach comprising electrocoagulation, peroxide, and hypochlorite treatments for the removal of chemical oxygen demand (COD) and tannin/lignin from paper mill wastewater. The study aimed to optimize the operating parameters with a view to maximizing the removal efficiencies while minimizing energy consumption. A pair of iron electrodes were used as anode and cathode in the study, and the main operating parameters were determined as initial pH, applied current, treatment time and oxidant dosage/COD ratio. Response surface methodology (RSM) was used to evaluate the effect of these parameters on COD and tannin/lignin removals. The primary findings of the investigation indicated that the integration of electrocoagulation with peroxide and hypochlorite treatments exhibited efficacy in removing COD, tannin/lignin, colour, phenol, and turbidity from paper mill wastewater. The optimized conditions resulted in COD removal efficiencies of 48.13 ± 2.2% and 29.53 ± 1.4% for EC with H2O2 and Ca(OCl)2, respectively. Tannin/lignin removal efficiencies were 92.59 ± 3.6% and 94.09 ± 1.8% for EC-H2O2 and EC-Ca(OCl)2, respectively. The specific energy consumption (SEC) values showed that EC-Ca(OCl)2 required 7 times more energy than EC-H2O2 for removing 1 kg COD. The principal deduction drawn from the study was that EC-H2O2 pre-treatment demonstrated superior COD removal efficiency and lower energy consumption, while EC-Ca(OCl)2 pre-treatment exhibited greater efficiency in removing toxic and recalcitrant pollutants. In future studies, it would be useful to conduct research to increase COD removal efficiency in addition to tannin/lignin removal in EC-Ca(OCl)2 process.

Antibiotic removal from synthetic and real aqueous matrices by peroxymonosulfate-based advanced oxidation processes. A review of recent development

The widespread use of antibiotics for the treatment of bacteriological diseases causes their accumulation at low concentrations in natural waters. This gives health risks to animals and humans since it can increase the damage of the beneficial bacteria, the control of infectious diseases, and the resistance to bacterial infection. Potent oxidation methods are required to remove these pollutants from water because of their inefficient abatement in municipal wastewater treatment plants. Over the last three years in the period 2021-September 2023, powerful peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have been developed to guaranty the effective removal of antibiotics in synthetic and real waters and wastewater. This review presents a comprehensive analysis of the different procedures proposed to activate PMS-producing strong oxidizing agents like sulfate radical (SO4•-), hydroxyl radical (•OH, radical superoxide ion (O2•-), and non-radical singlet oxygen (1O2) at different proportions depending on the experimental conditions. Iron, non-iron transition metals, biochar, and carbonaceous materials catalytic, UVC, photocatalytic, thermal, electrochemical, and other processes for PMS activation are summarized. The fundamentals and characteristics of these procedures are detailed remarking on their oxidation power to remove antibiotics, the influence of operating variables, the production and detection of radical and non-radical oxidizing agents, the effect of added inorganic anions, natural organic matter, and aqueous matrix, and the identification of by-products formed. Finally, the theoretical and experimental analysis of the change of solution toxicity during the PMS-based AOPs are described.

Degradation of tetracycline by heat/peroxymonosulfate and ultrasound/peroxymonosulfate systems: performance and kinetics

In recent decades, water pollution caused by emerging contaminants such as pharmaceuticals, has attracted much attention. Antibiotics are commonly used pharmaceuticals, and their residue in water may accelerate the development of antibiotic resistance genes, which can produce resistance to the treatment of diseases. In this study, two energy-based systems, heat/peroxymonosulfate (PMS) and ultrasound (US)/PMS were chosen to treat the typical antibiotic tetracycline (TC) in water. The influencing factors and kinetic equations of TC degradation by heat/PMS and US/PMS were investigated and the rates of TC degradation by the two systems were compared. The results showed that the optimal PMS concentration required for TC degradation in both systems was 0.3 mM, and neither system was affected by solution pH. The power of the US in the US/PMS system was as important as the temperature in the heat/PMS system because they provided activation energy. Both heat and US could activate PMS to degrade TC, and US was slightly superior with 80% TC removal under the conditions of [TC] = 20 mg/L, [PMS] = 0.3 mM, pH = 6.4, T = 20 °C, and US power = 550 W. US is considered to be more advantageous in activating PMS to degrade TC.

Efficient degradation of cellulosic ethanol wastewater by perovskite activation of Sr element A-site doped lanthanide copper chalcogenide materials

The degradation of cellulosic ethanol wastewater by peroxymonosulfate (PMS) is one of the important methods to solve the environmental problems caused by it. In order to improve the degradation efficiency of cellulosic ethanol wastewater, the design of more catalytically active and stable chalcogenide catalysts has become a problem that needs to be solved nowadays. The application of foreign cations to replace the A- or B-site to increase the oxygen vacancy of the chalcocite catalyst to improve the efficiency of chalcocite catalytic degradation of wastewater has received much attention. In this work, the perovskite material LaCuO3 was synthesized using a citric acid-sol-gel method, and the novel material La1-xSrxCuO3 was prepared by doping of Sr element at the A position. In order to prepare catalytic materials with better performance, this study carried out performance-optimized degradation experiments on the prepared materials and determined that the catalytic efficiency of La0.5Sr0.5CuO3 prepared under the conditions of the complexing agent dosage of 1:2, the gel temperature of 80 °C, and the calcination temperature of 700 °C was better than that of the catalytic materials prepared under other conditions. The prepared material has good recycling function; after four times recycling, the removal rate of pollutant COD is still more than 85%. This work provides a new synthesis method of perovskite material with good recycling function and high catalytic efficiency for the degradation technology of cellulosic ethanol wastewater.

Microbe combined with Fe2+-heat activated persulfate to decompose phenanthrene in red soil: comparison of acid-resistant degrading microflora and indigenous bacteria

This work is designed to counteract the deficiency of targeted research on the PAHs polluted specific soil, especially when the chemicals extremely denatured it. Phenanthrene-contaminated red soil was treated through two-stage process: persulfate oxidation (on dosages of 3.48%, 5.21%, and 6.94%, combined with Fe2+ and β-cyclodextrin, then heated) followed by biodegradation (indigenous bacteria vs. acid-resistant PAHs-degrading microflora (named ADM)) for 90 days. The dosage of oxidant greatly affected the removal efficiencies, which ranged from 46.78 to 85.34% under different treatment. After undergoing oxidation, the soil pH dropped below 3.0 synchronously and retained relatively strong oxidation state. The indigenous bacteria in red soil showed considerable degradation potential that will not vanish upon the sudden change of soil properties, whose average combined removal reached 95.43%, even higher than subgroups of bioaugmentation, but the population structure showed extremely simplex (Proteobacteria as superior occupied proportion of 91.77% after 90-day rehabilitation). The ADM screened from the coking wastewater was dominated by Klebsiella (75.4%) and Pseudomonas (23.6%), whose cooperation with 6.94% persulfate made the residual PHE reduced to less than 50 mg·kg-1 in about 28 days. High-throughput sequencing analysis showed that the microbial community composition of the ADM applied-group was more abundant in the later stage of remediation. ADM inoculation has the advantages of shortening the restoration period and having a positive impact on the soil micro-ecology.

Enhanced conversion of superoxide radical to singlet oxygen in peroxymonosulfate activation by metal-organic frameworks derived heteroatoms dual-doped porous carbon catalyst

The activation of persulfate technology using carbon-based materials doped with heteroatoms has been extensively researched for the elimination of refractory pollutants in wastewater. In this study, metal-organic frameworks were utilized as precursors to synthesize P, N dual-doped carbon material (PNC), which was employed to activate peroxymonosulfate (PMS) for the degradation of tetracycline hydrochloride (TCH). The results demonstrated a 90.2% removal efficiency of total organic carbon within 60 min. The significant increase of surface defects on the nitrogen self-doped porous carbon materials anchored with phosphorus promoted the conversion of superoxide radical to singlet oxygen during PMS activation, which was identified as the key active species of PNC/PMS system. Additionally, the enhanced direct electron transfer also facilitated the degradation of TCH. Consequently, TCH was successfully degraded into nontoxic and harmless inorganic small molecules. The findings of this research provide valuable insights into improving the performance of heteroatom-doped carbon materials for pollutant degradation by activating PMS and transforming the non-radical pathway. The results highlight the potential of metal-organic frameworks derived heteroatoms dual-doped porous carbon catalysts for the development of advanced treatment technologies in wastewater treatment.

Photocatalysis-PMS oxidation system based on CQDs-doped carbon nitride nanosheets for degradation of residual drugs in water

Graphite-like carbon nitride (g-C3N4) is favored for its excellent physicochemical properties. However, the high complexation rate of photogenerated carriers greatly limits its practical applications. Based on this, a novel CQDs-doped carbon nitride nanosheets composite (CNS/CQDs) was prepared and applied to the visible light-induced activation of peroxymonosulfate (PMS) for meloxicam (Mel) and tetracycline (TC) degradation. The photocatalytic degradation of Mel and TC were remarkably promoted in the CNS/CQDs+PMS+vis system. Mel photodegradation of 99.90% was achieved over 30 min with 20 mg CNS/CQDs and 20 mg PMS at pH11. And TC photodegradation of 95.97% was achieved over 45 min with 20 mg CNS/CQDs and 20 mg PMS at nature pH6.5. The TOC mineralization rates of Mel and TC were 75.49% and 52.00%, respectively. The transient photocurrent response and electrochemical impedance measurements (EIS) results indicated that the doping of CQDs could improve the charge transfer efficiency of pure g-C3N4, and CNS/CQDs had a low charge transfer resistance. Capture experiments and EPR tests explored the effective actives in the CNS/CQDs+PMS+vis system. Possible degradation pathways of Mel were also analyzed. This study provides valid residual drugs degradation under the dual conditions of visible light catalytic oxidation and persulfate oxidation, which will be a novel perspective for advanced oxidation technology to effectively remove organic pollutants from water.

Piezoelectric-channels in MoS2-embedded polyvinylidene fluoride membrane to activate peroxymonosulfate in membrane filtration for wastewater reuse

The conjugation of membrane filtration (MF) with advanced oxidation process (AOPs) is being considered as an alternative advanced treatment process for the potable reuse of wastewater. Beyond conventional MF/AOPs conjugation, a new downstream MF process with piezoelectric-channels induced piezo-activated peroxymonosulfate (PMS) is herein constructed to deal with antiepileptic carbamazepine (CBZ) pollutants through polyvinylidene fluoride (PVDF) membrane (PVDF-M10). Through a MF process, ca. 93.8% CBZ pollutants can be removed under an ultrasonic-assisted piezo-activation PMS, whereas only 18.3% and 60.2% CBZ can be removed by using pure PVDF membrane under the same condition and PVDF-M10 membrane without ultrasonic-assisted piezo-activation. Even after 9-cycles, CBZ removal efficiency was maintained at 56.4% under this MF process. These superior performances are attributed to the piezoelectric exfoliated-MoS2 nanosheets (E-MoS2) embedded PVDF nanofibers in PVDF-M10 membrane, which lead to rich piezoelectric-channels in the membrane. These piezoelectric-channels not only produced more charges to activate PMS to boost the yield of reactive oxide species (ROS) but also provided an ideal platform for the rapid reaction between CBZ and ROS during MF process. This investigation develops a new MF technique to conjugate piezo-activation of PMS-AOPs for the efficient removal of emerging pollutants for the potable reuse of wastewater.

Tetracycline hydrochloride degradation by activation of peroxymonosulfate with lanthanum copper Ruddlesden-Popper perovskite oxide: Performance and mechanism

ABO₃-type perovskite oxides have been regarded as a kind of potential catalyst for peroxymonosulfate (PMS) activation. But some limitations such as specific pH conditions and coexisting ion interference restrict its practical application. Herein, a lanthanum copper Ruddlesden-Popper perovskite oxide (La₂CuO₄) was successfully synthesized through the sol-gel process and applied in the activation of PMS. And for the first time the La₂CuO₄/PMS system was used for tetracycline hydrochloride (TC-HCl) degradation. Results showed that La₂CuO₄ was a potential PMS activation catalyst in the removal of antibiotics. At optimized condition (0.2 g/L catalysts, 1 mM PMS, pH₀ 6.9), 96.05% of TC-HCl was removed in 30 min. In experiments of debugging control conditions, over a wide pH range of 3-11, more than 90% of TC-HCl can be removed. In the natural water treatment process, TC-HCl removal rates of about 84.2% and 70.3% were obtained in tap water and River water, respectively. According to the reusability and stability tests and the results of FTIR and XPS analysis, La₂CuO₄ had high structural and chemical stability. Electron paramagnetic resonance (EPR) suggested that the active species including ·OH, SO₄^-· and ¹O₂ were detected in degradation reaction. Finally, reasonable reaction mechanisms and possible degradation pathways of TC-HCl were proposed. These results indicate that La₂CuO₄ can act as a potential catalyst for PMS activation to degrade TC-HCl in water.

Porous boron nitride intercalated zero-valent iron particles for highly efficient elimination of organic contaminants and Cr (VI)

Developing novel bifunctional materials to high efficiently degrade organic pollutants and eliminate hexavalent chromium (Cr (VI)) is significantly desired in the wastewater treatment field. The porous boron nitride (p-BN) was fabricated by a two-stage calcination strategy and was innovatively employed to support zero-valent iron (ZVI), achieving the bifunctional material (p-BN@ZVI) to degrade carbamazepine (CBZ) and eliminate Cr (VI). p-BN@ZVI could degrade more than 98% CBZ in 6 min with the high apparent first-order constant (k_obs) of 0.536 min^-1, almost 5 times higher than that of the ZVI/PMS system and outperformed most previous reported ZVI supported catalysts, which was mainly ascribed to the fact that the introduction of p-BN with high surface area (793.97 m²/g) improved the dispersion of ZVI and exposed more active sites. Quenching tests coupled with electron paramagnetic resonance (EPR) suggested that •OH was the major reactive oxygen species with a contribution of 71.6%. Notably, the p-BN@ZVI/PMS system expressed low activation energy of 8.23 kJ/mol and reached a 65.69% TOC degradation in 20 min even at 0 °C. p-BN@ZVI possessed remarkable storage stability and could still degrade 92.3% CBZ despite three-month storage. More interestingly, p-BN@ZVI was capable to eliminate 98.1% of 50 mg/L Cr (VI) within 5 min through adsorption and reduction, where nearly 80% Cr (VI) was transformed to Cr (III), and exhibited the maximum Cr (VI) elimination capacity of 349 mg/g. This study provides new insights into the efficient organic contaminants degradation and Cr (VI) elimination in the treatment of wastewater.

Sodium tetraborate simultaneously enhances the degradation of acetaminophen and reduces the formation potential of chlorinated by-products with heat-activated peroxymonosulfate oxidation

In this study, sodium tetraborate (Na₂B₄O₇) was introduced to enhance the degradation of acetaminophen (ACT) in heat-activated peroxymonosulfate (PMS) process. The elimination of ACT in Na₂B₄O₇/heat/PMS process followed the pseudo-first order kinetics. The corresponding k_obs value with 10 mM Na₂B₄O₇ was 33.1 times higher than that in heat/PMS process. ¹O₂ and HO· were identified as primary reactive species via quenching experiments and electron paramagnetic resonance technology. B(OH)₄^-, the hydrolysis product of Na₂B₄O₇, reacted with PMS to generate HOOB(OH)₃^-. ¹O₂ was generated by the self-decomposition of PMS using B(OH)₄^- as catalyst, while HO· was produced via the breakage of peroxide bond of PMS and HOOB(OH)₃^-under high temperature. ACT was degraded by reactive species via the pathways of -NH- bond breakage, -OH replacement, -NH₂ oxidation and benzene ring cleavage. Nine transformation intermediates were detected by LC/Q-TOF/MS, and the toxicity of reaction solution decreased significantly with the elimination of ACT. Increasing Na₂B₄O₇ dosage, PMS concentration, initial pH and reaction temperature were conducive to ACT elimination. Humic acid, Cl^- and CO₃^2- inhibited the degradation of ACT heavily, while SO₄^2- and NO₃^- had the negligible effects. Moreover, B(OH)₄^- could react with free chlorine to the inert B(OH)₃OCl^- and further significantly suppress the formation of chlorinated by-products for the treatment of Cl^--containing water in Na₂B₄O₇/heat/PMS process. This study provided an effective way to enhance the oxidation capacity of heat/PMS process and suppress the formation of chlorinated by-products in chloride-containing water, and the findings had important implications for using borate buffer in the studies of PMS-based advanced oxidation processes.

Enhanced Degradation of Rhodamine B through Peroxymonosulfate Activated by a Metal Oxide/Carbon Nitride Composite

The development of high catalytic performance heterogeneous catalysts such as peroxymonosulfate (PMS) activators is important for the practical remediation of organic pollution caused by Rhodamine B (RhB). An economical and facile synthesized composite of copper–magnesium oxide and carbon nitride (CM/g-C3N4) was prepared by the sol-gel/high-temperature pyrolysis method to activate PMS for RhB degradation. CM/g-C3N4 exhibited a splendid structure for PMS activation, and the aggregation of copper–magnesium oxide was decreased when it was combined with carbon nitride. The introduction of magnesium oxide and carbon nitride increased the specific surface area and pore volume of CM/g-C3N4, providing more reaction sites. The low usage of CM/g-C3N4 (0.3 g/L) and PMS (1.0 mM) could rapidly degrade 99.88% of 10 mg/L RhB, and the RhB removal efficiency maintained 99.30% after five cycles, showing the superior catalytic performance and reusability of CM/g-C3N4. The synergistic effect of copper and g-C3N4 improved the PMS activation. According to the analyses of EPR and quenching experiments, SO4•−, •OH and O2•− radicals and 1O2 were generated in the activation of PMS, of which SO4•− and 1O2 were important for RhB removal. The toxicity of RhB was alleviated after being degraded by the CM/g-C3N4/PMS system. This study provides an efficient and promising strategy for removing dyes in water due to the hybrid reaction pathways in the CM/g-C3N4/PMS system.

Mechanism of Oxytetracycline Removal by Coconut Shell Biochar Loaded with Nano-Zero-Valent Iron

In this paper, coconut shell biochar (BC), pickling biochar (HBC), and nano-zero-valent iron-loaded biochar (nZVI-HBC) were prepared; these were used to remove oxytetracycline (OTC), and the removal mechanism and degradation product were analyzed. These biochars were characterized using SEM, XRD, FTIR, and XPS. The effects of biochar addition amount, pH, ion type, and ion concentration on OTC adsorption were studied by a batch adsorption experiment. Under the optimal conditions, the equilibrium adsorption capacity of nZVI-HBC to OTC was 196.70 mg·g-1. The adsorption process can be described by Langmuir isothermal adsorption equations, conforming to the pseudo-second-order dynamics model, indicating that adsorption is dominated by single-molecule chemical adsorption, and a spontaneous process of increasing heat absorption entropy. Mass spectrometry showed that the OTC removal process of nZVI-HBC included not only adsorption but also degradation. These results provide a practical and potentially valuable material for the removal of OTC.