Heat-activated Persulfate Research Articles

Impacts of microplastic decomposition using heat-activated persulfate on antibiotic adsorption and environmental toxicity

The objective of this study was to determine microplastic-antibiotic interaction by examining how heat-activated persulfate decomposed polyamide adsorbed antibiotics and explored the environmental consequences of treated water. Sulfate radicals roughened the microplastic surfaces, significantly enhancing the adsorption capacity of polyamide. The kinetic and isotherm studies provided confirmation that electrostatic interactions were the primary mechanisms, with a minor contribution from H-bonding, highlighting that antibiotic adsorption was prone to occur, especially on the aged surface. Thermodynamic data indicated that the process was spontaneous and exothermic. The results showed significant negative effects of treated water on seed germination, copepod survival, and cell lines at only a higher concentration, due to a decrease in pH and the potential presence of polymer degradates. Our findings revealed the significant impact of decomposed polyamide on the antibiotic adsorption and offered insight into the potential harm that microplastic-treated water might cause to aquatic and marine ecosystems.

In situ chemical oxidation of tinidazole in aqueous media by heat-activated persulfate: kinetics, thermodynamic, and mineralization studies

This study investigated the use of heat-activated persulfate (HAP) as a chemical oxidation technique for removing tinidazole (TNZ) antibiotic from aqueous solutions. The impact of various operating parameters, including TNZ initial concentration (20 μM), persulfate (PS) initial dose (0.2–2 mM), solution pH (3–11), solution temperature (20–60 °C), and reaction time (10–120 min), was examined. The results indicated that sulfate radicals were the primary species responsible for TNZ degradation. Higher temperatures and PS concentrations improved the process, while higher pH values and TNZ initial concentrations slowed it down. Additionally, chloride and bicarbonate ions reduced reaction rates, with chloride ions having a more significant effect. Under optimal conditions (including [TNZ]0 = 20 μM, pH = 7, [PS]0 = 1 mM, temperature = 60 °C, and reaction time = 120 min), the removal efficiency achieved was 91.15%, with a mineralization rate of 85.8%. These results suggest that the process is relatively safe. The degradation of TNZ was best described by the pseudo-first-order model compared to other models. Additionally, the process was found to be exothermic and spontaneous, with a negative Gibbs free energy change indicating that it is thermodynamically feasible. The study found HAP to be an effective and cost-efficient technique for removing TNZ antibiotic due to its ease of operation and the absence of the need for additional chemicals or waste handling. Based on these findings, HAP can be considered an advanced oxidation technique for treating antibiotic-contaminated water.

Novel approach over template molecule elimination in molecularly imprinted polymers by using heat activated persulfate

This study proposes a new alternative for template removal from molecularly imprinted polymers by heat activated persulfate. It is known that trace amounts of template molecule remains in the polymer network after extraction by current methodologies leading to bleeding and incomplete removal of template which could compromise final determination of target analytes especially in trace analysis. A previously developed molecularly imprinted polymer specially designed for Coenzyme Q10 (CoQ10) extraction was employed as a model to test this template elimination approach. This polymer is based on methacrylic acid and ethylene glycol dimethylacrylate as monomers and Coenzyme Q0 as template. This coenzyme has the same quinone group as the CoQ10. Selectivity was analyzed comparing the recovery of CoQ10 and ubichromenol, a CoQ10 related substance. Chemical degradation using heat-activated persulfate allows the elimination of the template molecule with a high level of efficiency, being a simple and ecological methodology, yielding a polymer that exhibits comparable selectivity and imprinting effect with respect to traditional extraction methods.

Heat-activated persulfate for chemical cleaning of ceramic MBR

Irreversible membrane fouling is a major concern in the application of membrane bioreactors (MBRs), and periodic chemical cleaning is required to sustain MBR operation. However, conventional NaClO cleaning exhibited limited efficacy and caused secondary environmental risks (e.g. disinfection by-products). Therefore, it is necessary to develop safe and efficient chlorine-free cleaning methods. Here, we proposed a heat-activated persulfate (peroxymonosulfate PMS and peroxydisulfate PDS) process for efficient cleaning of fouled ceramic membrane in MBR. Results showed much higher chemical cleaning efficiency in heat-activated persulfate process (79–81%) than that in NaClO (34–52%). A medium solution temperature of 60 °C was enough to efficiently activate PMS and PDS, with the optimal persulfate concentration of 1 mM and solution pH of 7. Both SO4•− and •OH were identified as the main reactive oxygen species for membrane cleaning. Compared with PDS, PMS was easier to be activated, and thus more free radicals were generated in heat/PMS system. Further investigations demonstrated radicals degraded polymers and broke microbial cell structure, thereby effectively removing foulants from membrane. This work provides a new idea for developing safe and efficient chemical cleaning method for ceramic MBR.

Deciphering polymer degradation chemistry via integrating new database construction into suspect screening analysis.

Water-soluble synthetic polymers and their environmental degradation products are overlooked but important industrial pollutants in wastewater. However, the detection of degradation products is limited to bulk solution chemistry and molecular-level analysis remains unreachable. In this work, we assessed the feasibility of current suspect screening and nontarget workflow using liquid chromatography-high resolution mass spectrometry (LC-HRMS) to elucidate molecular level information about polyacrylamide (PAM) and its degraded products by free radicals. Radical chain scission of PAM (10 kDa) using heat-activated persulfate was conducted to simulate hydraulic fracturing conditions in the deep subsurface. We found that the current workflows in the commercial software generated predicted formulae with low accuracy, due to limited capability of peak picking and formula prediction for high mass and charge features. By modeling literature-reported degradation pathways, we constructed a degradation product database of over 463 000 unique formulae, which improved the accuracy of the predicted formula. For the matched features, the ratio of aldehyde/ketone terminating molecule abundance was found to increase over 24 h degradation time, suggesting increasing content of aldehydes by radical-induced oxidative chain scission of PAM. This is contradictory to previously proposed ratios of carbon-centered radical position on polymer backbone initiated by hydroxyl radicals. Using in silico fragmentation of MS1 features, we identified 11 structures with confidence levels 2b and 3 using their MS2 information. This is the first attempt to resolve complex polymer degradation chemistry using HRMS that can advance our ability to detect water-soluble polymer pollutants and their transformation products in environmental samples.

Poly- and per-fluoroalkyl substances in water: Occurrence, analytical methodologies, and remediations strategies: A comprehensive review

Abstract Poly- and perfluoroalkyl substances (PFASs) are fluoro-organic compounds comprising thousands of anthropogenically produced chemicals with various industrial and consumer applications. This review compiles recent information on the sources, occurrence, and health effects of PFAS in aquatic environments. Secondly, as a primary requirement for assessing the PFAS concentration in water, this review systematically summarised the analytical methodologies (sample preparation and analytical detection techniques) for PFAS. Furthermore, health risks associated with PFAS in water are outlined. Finally, researchers worldwide have investigated the strategies for the remediation and elimination of PFAS from water. Previous studies have shown that PFASs are present in various water bodies with the highest concentration detected in Germany (94–4,385 ng·L−1 in river and drinking waters). The findings of this review further revealed that solid-phase extraction techniques were the most preferred for sample preparation compared to liquid–liquid extraction techniques. Solid-phase extraction technique improved the limit of detection and the limit of quantification of many analytical techniques to 0.010–1.15 and 0.030–4.00 ng·L−1, respectively. For PFAS remediation, the adsorption method and chemical oxidation using heat-activated persulfate and photochemical oxidation were the most used techniques. The most studied water matrices were drinking, river, groundwater, wastewater, and modelled ultra-pure water. The most used detection technique was found to be liquid chromatograph-tandem mass spectrometer (LC-MS/MS).

Carbon and hydrogen isotopic evidence for atrazine degradation by electro-activated persulfate: Radical contributions and comparisons with heat-activated persulfate

The activation ways of persulfate (PS) were dominate for pollutant degradation and energy consumption. For the first time, this research compared electro-activated PS and heat-activated PS from the perspective of isotope fractionation, in order to “fingerprinted” and precisely interpretate reaction contributions and degradation pathways. As results, PS can be electrochemically activated with atrazine (ATZ) removal rates of 84.8% and 88.8% at pH 4 and 7. The two-dimensional isotope plots (ɅC/H) values were 6.20 at pH 4 and 7.46 at pH 7, rather different from that of SO4·― -dominated process with ɅC/H value of −4.80 at pH 4 and -23.0 at pH 7, suggesting the weak contribution of SO4·―. ATZ degradation by electro-activated PS was controlled by direct electron transfer (DET) and ·OH radical, and ·OHPS (derived from PS activation) played the crucial role with contributing rate of 63.2%–69.1%, while DET and ·OHBDD (derived from electrolysis of H2O) contributed to 4.5–7.9% and 23.0%–30.8%, respectively. This was different from heat activation of PS, of which the latter was dominated by SO4·― with contributions of 83.9%–100%. The discrepant dominating reactive oxygen species should be responsible for their different degradation capabilities and pathways. This research provided isotopic interpretations for differences of PS activation mode, and further efforts can be made to realize the selective degradation by enhancing the specific reaction process.

Insight into the application of micro-nano bubbles combined with heat-activated persulfate oxidation for removing dissolved organic matter from printing and dying wastewater

The effluent quality of printing and dyeing wastewater after secondary treatment does not meet industry discharge standards, which poses serious environmental risks. In this work, micro-nano bubbles and a heat-activated persulfate advanced oxidation process were innovatively combined to thoroughly treat industrial printing and dyeing wastewater. Under the optimal reaction conditions (a reaction time of 60 min, persulfate concentration of 20 mM, and temperature of 40 °C), the effluent quality met the discharge standards. Furthermore, the degradation and transformation mechanisms of dissolved organic matter during the wastewater treatment process were investigated by three-dimensional fluorescence spectroscopy and Fourier ion transform spin resonance mass spectrometry. The results showed that organic compounds in the wastewater were clearly degraded by the treatment process, and this was accompanied by a significant increase in molecular diversity. In summary, this work provides insight into the practical application of micro-nano bubbles in the advanced oxidation treatment of industrial wastewater as well as the degradation mechanism responsible for removing pollutants from this wastewater.

Sulfate radical-based advanced oxidation process effects on tire wear particles aging and ecotoxicity

Tire wear particles (TWPs) are widely distributed in natural water and pose as major pollutants in aquatic environments. In this study, heat-activated persulfate (HPT) and ultraviolet-activated persulfate treatments (UPT) were employed to investigate the influence of sulfate radical (SO4−•)-based advanced oxidation process (SAOPs) on TWP physicochemical properties and to clarify their ecotoxic effects in laboratory-level studies. Results showed that the specific surface areas of TWPs increased after UPT but decreased after HPT. In terms of chemical properties, the increase of oxygen-containing functional groups on the surfaces of TWPs was more evident in UPT than that in HPT. The atrazine (ATZ) adsorption capacity of TWPs after HPT and UPT was increased compared with the untreated TWPs. Atrazine adsorbed by TWPs was easily resolved and released in artificial intestinal fluid (1.89–2.08 mg/g) and artificial gastric fluid (1.60–2.04 mg/g) conditions. Acute toxicity experiments of Photobacterium phosphoreum and SEM-EDS detection results suggested that various heavy metals (e.g., Zn2+, Cu2+) in the TWPs would be released into the water system in SAOPs. ATZ released from TWPs that adsorbed ATZ herbicide, rather than TWPs themselves, had a negative effect on aquatic plant growth (e.g., C. vulgaris). The leaching solution of oxidized TWPs (after HPT and UPT) showed a more significant inhibition effect on the zebrafish survival compared with that of untreated TWPs, which was possibly caused by the generation of oxidation byproducts such as N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone.

Elucidating sulfate radical-induced oxidizing mechanisms of solid-phase pharmaceuticals: Comparison with liquid-phase reactions

As a class of organic micropollutants of global concern, pharmaceuticals have prevalent distributions in the aqueous environment (e.g., groundwater and surface water) and solid matrices (e.g., soil, sediments, and dried sludge). Their contamination levels have been further aggravated by the annually increased production of expired drugs as emerging harmful wastes worldwide. Sulfate radicals (SO4•−)-based oxidation has attracted increasing attention for abating pharmaceuticals in the environment, whereas the transformation mechanisms of solid-phase pharmaceuticals remain unknown thus far. This investigation presented for the first time that SO4•−, individually produced by mechanical force-activated and heat-activated persulfate treatments, could effectively oxidize three model pharmaceuticals (i.e., methotrexate, sitagliptin, and salbutamol) in both solid and liquid phases. The high-resolution mass spectrometric analysis suggested their distinct transformation products formed by different phases of SO4•− oxidation. Accordingly, the SO4•−-mediated mechanistic differences between the solid-phase and liquid-phase pharmaceuticals were proposed. It is noteworthy that the products from both systems were predicted with the remaining persistence, bioaccumulation, and multi-endpoint toxicity. Therefore, some post-treatment strategies need to be considered during practical applications of SO4•−-based technologies in remediating different phases of micropollutants. This work has environmental implications for understanding the comparative transformation mechanisms of pharmaceuticals by SO4•− oxidation in remediating the contaminated solid and aqueous matrices.

Enhanced treatment of azo dyes in wastewater using heat-activated persulfate with micro-nano bubble aeration

Azo dyes-containing wastewater can lead to environmental issues and pose threats to public health. The efficient degradation of azo dyes with novel and potent techniques, remains a challenge. This study presented an innovative utilization of micro-nano bubble aeration technology to improve the treatment of Rhodamine B through heat-activated persulfate oxidation. Through single factor experiments, the impacts of persulfate concentration, temperature, initial Rhodamine B concentration, and pH values were systematically explored on the degradation of Rhodamine B in heat-activated persulfate oxidation. The removal rate of Rhodamine B was 94.53% optimized by Response surface optimization method. The reaction rate was in the range of 0.0109–0.0528 min−1, governed by pseudo-first-order kinetics. By applying the Arrhenius equation, the activation energy was determined to be 14.06 KJmol−1. Furthermore, properties of micro-nano bubbles and their synergistic coefficient were investigated in heat-activated persulfate oxidation. Quenching tests revealed the predominance of sulfate radicals, and full wavelength scanning facilitated an in-depth investigation of the reaction mechanism. Additionally, a proposed electron shell structure elucidated the decomposition process of Rhodamine B. Therefore, the implementation of micro-nano bubble aeration technology based on heat-activated persulfate oxidation, held the promise as an efficient and effective approach for the treatment of printing and dyeing wastewater.

Enhanced reduction of uranium (VI) in groundwater via regulation of heat-activated persulfate: The role of formate and its mechanisms

Hexavalent uranium (U(VI)) in groundwater may cause human health problems. Therefore, the effectively removal of U(VI) from groundwater has become a urgent issue. Advanced reduction processes based on persulfate (PS) have been used to reduce pollutants. However, low efficiency limited its application. In this study, the U(VI) reduction in groundwater by heat-activated persulfate was systematically examined in the presence of formate (FA). The results indicated that FA enhanced U(VI) reduction compared to heat-persulfate system. The U(VI) reduction efficiency reached 86% in the presence of 5 mg·L−1, 0.5 M persulfate and 0.3 M formate at acidic pH (4.6) and 70 °C within 60 min. Coexisting HCO3-, acetic acid and oxalic acid influenced U(VI) reduction, while NO3- and Cl- had no effect on U(VI) reduction by heat-persulfate-formate (H-PS-FA) process. According to the electron spin resonance experiment (ESR) results, CO2·- was verified to be largely responsible for U(VI) reduction in H-PS-FA system, meanwhile, S2O8·- and O2·- radicals also play a non-negligible role in reduction. More importantly, the test of U(VI) reduction in real groundwater validated that H-PS-FA system has significant potential and can be applied for reduction of U(VI) contaminated groundwater in uranium mining areas.

Can Heat-Activated Peroxymonosulfate Be Used as a Pretreatment to Mitigate Fouling for Membrane Distillation: Performance of Individual Organics?

Heat-activated persulfate preoxidation was recently proposed as a potential approach to mitigate membrane fouling in membrane distillation (MD) for treating actual water. However, the possible mitigation mechanism involved has not yet been elucidated. In this study, we explored the relationship between membrane fouling and the pretreatment of natural organic matter (NOM) solutions with peroxymonosulfate (PMS). Individual humic acid (HA), bovine serum albumin (BSA), and sodium alginate (SA) contaminants were chosen as model NOM samples. The degradation efficiency of heat-activated PMS preoxidation was investigated. The removal rates of organic contaminants improved as the PMS dose and activation temperature of the feed increased. Specific flux (J/J0) measurements coupled with multiple characterizations were performed to assess the fouling behavior. The fouling data showed that when pretreatment was conducted without PMS, pure HA caused the most severe fouling, followed by pure BSA, whereas pure SA caused almost no membrane fouling. After PMS preoxidation, the oxidation products of the NOM unexpectedly caused more fouling, despite the reduction in the amount of the NOM. Further work is needed to evaluate fouling mitigation when working with complex streams.

Remediation of atrazine contaminated soil by microwave activated persulfate system: Performance, mechanism and DFT calculation

Effective remediation of pesticide-contaminated sites is challenging due to high concentrations of pollutants with complete habitat destruction. Herein, microwave (MW)-activated persulfate (PS) system was proposed for remediation of organochlorine pesticide contaminated soil with atrazine (ATZ) as representation. The results revealed that the MW/PS system could achieve 97.9% of ATZ (50 mg/kg) degradation after treatment of 60 min, superior to that by conventional heat-activated PS. And more excellent degradation performance was identified in relatively higher microwave temperature (80 °C) with appropriate PS concentration (24 mmol/L), MW power (400 W) and water-soil ratio (1:1). Moreover, the MW/PS system possessed high tolerance to co-existing substances including Cl−, HCO3− and H2PO4−, and appropriate organic substance content favored ATZ degradation in soil. Reactive oxygen species consisting of SO4•−, OH•, O2•− and 1O2 contributed to ATZ decomposition, among which O2∙− played a principal role. The ATZ degradation pathway was then elucidated by combination of HPLC/MS spectra and DFT calculations, and ATZ overall toxicity was effectively alleviated in MW/PS system in term of toxicity assessment. Additionally, the MW/PS system presented high-performance degradation on such organochlorine pesticides as trichloro ethylene, tetrachloride, hexachlorobenzene and chlordane, suggesting great potentials of this system for remediation of organochlorine pesticides contaminated sites.

Using heat-activated persulfate to accelerate short-chain fatty acids production from waste activated sludge fermentation triggered by sulfate-reducing microbial consortium

Persulfate has been applied extensively for waste activated sludge (WAS) decomposition due to the strong oxidizing sulfate radical generated as a product. However, the efficiency is not improved without activation to produce free radicals. In this study, a novel coupling strategy of heat-activated persulfate (Heat_PS) pretreatment and sulfate-reducing bacteria (SRB) triggering was explored to enhance short-chain fatty acids (SCFAs) produced by WAS fermentation. The remaining sulfate acts as an essential acceptor of electrons for the metabolism of synergistic SRB, thereby boosting WAS acidification by energetic cooperation with anaerobic fermenters. The results showed that SCFAs yield in the Heat_PS + SRB group peaked at 431.89 mg COD/gVSS, with the proportion of acetate reaching 57.8 %. This was 6.33 and 1.75 times higher than that in raw and single Heat_PS treated WAS, respectively. Carbon balance revealed a conversion rate of 26.1 % of carbon content in WAS to SCFAs, with 4.5 % lower CO2 equivalents emitted than that in raw WAS fermentation by the assessments of environmental impacts. This was partially attributed to the strong decomposition of WAS by SO4•− and •OH oxidation from heat-activated PS and the SRB trigger. In addition, the synergistic relationship among acidogenic/fermentative bacteria and SRB consortia was further verified by the positive correlation among Desulfovibrio, the hydrolytic Escherichia-Shigella, Morganella and the fermetative Macellibacteroides and Bacteroides, as revealed by molecular ecological networks (MENs) analysis. The results of this study may highlight the cooperation of the synergistic micribial consortia as an additional perspective for the recovery of value-added biological metabolites from complex biotransformation.

Understanding the membrane fouling control process at molecular level in the heated persulfate activation- membrane distillation hybrid system

Sulfate radical (SO4●−) based advanced oxidation is considered as a promising pretreatment strategy to degrade organic pollutants and thereby mitigate the membrane fouling in the membrane process. In this study, heat-activated persulfate (PS) activation was integrated with the membrane distillation (MD) process for the alleviation of membrane fouling in treatment of wastewater treatment plant (WWTP) secondary effluent and surface water. In-depth understanding of the molecular fate during membrane fouling control process was performed by using a non-targeted screening method of two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC−TOF−MS) coupling with multiple characterizations. It was found that the heat-activated PS activation pretreatment could effectively degrade the dissolved organic matter (DOM) and change its molecular conformation, wherein the relative abundance of oxygen-containing substances was remarkably increased through oxygenation reactions. Moreover, the refractory organics with higher molecular weight (MW) and unsaturation degree were more inclined to be destroyed, following by partial mineralization during pretreatment process. It was also identified that oxygen-deficient compounds and the molecular formulas featuring higher double bond equivalent (DBE) values and lower MW tended to be deposited on the membrane surface to cause the membrane fouling. In particular, the aliphatic substances were the predominant components irrespective of membrane foulant samples from secondary effluent or surface water. Meanwhile, the complexation between organic compounds and high valence cations as well as the precipitation of inorganics were restrained owing to the reduction of DOM concentration and the transformation of molecular structure, consequently leading to reduced membrane fouling. This study is believed to further provide new insight into the membrane fouling control mechanism at molecular level.

Insights into atrazine degradation by thermally activated persulfate: Evidence from dual C–H isotope analysis and DFT simulations

SO4– -assisted oxidation was of great concern and the accurate interpretation of reaction pathway was crucial. Innovatively, this study introduced compound-specific isotope fractionation analysis (CSIA) into atrazine (ATZ) degradation by heat-activated persulfate (PS), in order to provide “in-situ” and “fingerprinted” analysis of reaction contribution and bond cleavage process based on isotope fractionation. As results, radical oxidants including SO4- and OH were generated through thermal activation of PS, and proved to play dominate roles in ATZ degradation. Inconceivably, the isotope fractionation by single SO4-dominated reaction showed weak and positive C isotope fractionation, with εC of 1.58 ‰ at pH 4 and 0.65 ‰ at pH 7, respectively. Reactions by single SO4- and OH can be distinguished resulting from their significantly different ε and ɅC/H values. Changes of δ13C and δ2H values during ATZ degradation by heat-activated PS followed Rayleigh equation well, with the εC, εH and ɅC/H values of −1.5 ‰, −21.1 ‰, 6.60 at pH 4 and −2.7 ‰, −36.6 ‰, 10.02 at pH 7 respectively. The relative contribution of SO4- radical to ATZ degradation was ca.100 % at pH 4 and 83.9 % at pH 7. The isotope fractionation study and DFT calculations suggested that single electron transfer with the cleavage of C-Cl bond was dominated and displayed inverse C isotope fractionation for SO4- oxidation, which was different from that of OH oxidation and more selective to dehalogenate reaction. This research emphasized the promising technology of CSIA, which can achieve accurate identification of reaction contribution and pathways in advanced oxidation process.

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.

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.

Heat-activated persulfate oxidative degradation of ofloxacin: Kinetics, mechanisms, and toxicity assessment

• The mechanism of ofloxacin degradation by heat-activated persulfate were investigated. • Ofloxacin degradation in the system fitted well with the pseudo-first-order reaction model. • The four degradation pathways of ofloxacin were proposed. • The toxicity of ofloxacin and its intermediates was predicted. The widespread occurrence of fluoroquinolone antibiotics, such as ofloxacin (OFX), in natural water and soil has received increasing attention in terms of their potentially dangerous impacts on public health and ecosystems. In this study, the kinetics and mechanisms of OFX degradation by heat-activated persulfate (HAP) was investigated. Results showed that OFX degradation could be achieved effectively and fitted well with the pseudo-first-order reaction model in the HAP system. The OFX degradation efficiency was dramatically enhanced with increased temperature and initial persulfate dosage and inhibited in the presence of the common coexisting water matrices (e.g., bicarbonate, chloride, and humic acid). Quenching tests and electron paramagnetic resonance studies demonstrated the simultaneous contribution of both radicals with sulfate radicals having a slightly higher effect than hydroxyl radicals in the degradation process of OFX. Various intermediates of OFX degradation were characterized using High-performance liquid chromatography-Mass spectrometry (HPLC-MS), and detailed degradation pathways of OFX were proposed. And the toxicity of OFX and its intermediate products was predicted using the Ecological Structure-Activity Relationships (ECOSAR) and Toxicity Estimation Software Tools (TEST).