Peroxymonosulfate Concentration Research Articles

CoFe2O4@Methylcelloluse as a New Magnetic Nano Biocomposite for Sonocatalytic Degradation of Reactive Blue 19

Reactive Blue 19 (RB19) removal from synthetic textile wastewater was investigated by using a CoFe2O4@methylcellulose (MC) activated with peroxymonosulfate (PMS) and the ultrasound process. CoFe2O4@MC as a new magnetic nano-biocomposite was prepared using a convenient and rapid microwave-assisted technique in presence of MC as a green biopolymer, and characterized by FESEM, EDS, Mapping, TEM, FTIR, XRD, TGA, VSM, and BET techniques. Then, the effective parameters including pH (4–10), reaction time (0–30 min), CoFe2O4@MC (0.2–1 g/L), and PMS concentration (0.5–10 mM) in the sonocatalytic degradation of RB19 were investigated. The maximum removal efficiency of RB19 was achieved as 97% for synthetic wastewater under the optimal conditions of pH 4, CoFe2O4@MC dosage (0.6 g/L), reaction time = 30 min, and PMS (5 mM) in the presence of ultrasonic waves (60 kHz) at the ambient room temperature of 22 °C. The CoFe2O4@MC catalyst was simply isolated using a magnet and recycled with no remarkable loss of catalytic activity following usage in four runs. The results showed that the CoFe2O4@MC sonocatalysis process is practical, and effective for degrading complex and resistant dyes such as RB19.

Degradation of Ciprofloxacin Using Ultrasound/ZnO/Oxone Process from Aqueous Solution-Lab-Scale Analysis and Optimization

Nowadays, the existence of antibiotic compounds in pharmaceutical wastewaters is one of the new problems that can be considered in environmental pollution. The removal of ciprofloxacin from aqueous solutions is examined in the present study by using peroxymonosulfate (Oxone=PMS) activated with hybridized ultrasonic waves and synthesized ZnO nanoparticles. Operational parameters like ZnO nanoparticles dosage, initial pH, and peroxymonosulfate concentration, and their effect on the removal of the antibiotic have been investigated. The results showed 98.3% antibiotics removal observed with an initial pH of 3, ZnO nanoparticles dosage of 1 g/L, and peroxymonosulfate concentration of 1 g/L. This process had a high removal efficiency and was suitable for the removal of ciprofloxacin from aquatic environments.

UV-A activation of peroxymonosulfate for the removal of micropollutants from secondary treated wastewater

The occurrence of micropollutants (MPs) in the aquatic environment poses a threat to the environment and to the human health. The application of sulfate radical-based advanced oxidation processes (SR-AOPs) to eliminate these contaminants has attracted attention in recent years. In this work, the simultaneous degradation of 20 multi-class MPs (classified into 5 main categories, namely antibiotics, beta-blockers, other pharmaceuticals, pesticides, and herbicides) was evaluated for the first time in secondary treated wastewater, by activating peroxymonosulfate (PMS) with UV-A radiation, without any pH adjustment or iron addition. The optimal PMS concentration to remove the spiked target MPs (100 μg L−1) from wastewater was 0.1 mM, leading to an average degradation of 80% after 60 min, with most of the elimination occurring during the first 5 min. Synergies between radiation and the oxidant were demonstrated and quantified, with an average extent of synergy of 69.1%. The optimized treatment was then tested using non-spiked wastewater, in which 12 out of the 20 target contaminants were detected. Among these, 7 were degraded at some extent, varying from 10.7% (acetamiprid) to 94.4% (ofloxacin), the lower removals being attributed to the quite inferior ratio of MPs to natural organic matter. Phytotoxicity tests carried out with the wastewater before and after photo-activated PMS oxidation revealed a decrease in the toxicity and that the plants were able to grow in the presence of the treated water. Therefore, despite the low degradation rates obtained for some MPs, the treatment effectively reduces the toxicity of the matrix, making the water safer for reuse.

Degrading arsanilic acid and adsorbing the released inorganic arsenic simultaneously in aqueous media with CuFe2O4 activating peroxymonosulfate system: Factors, performance, and mechanism

Arsanilic acid (ASA) is widely used as a feed additive in poultry production that tends to convert to highly toxic inorganic arsenic species in the natural environment. Herein, one-step process by CuFe2O4 activating peroxymonosulfate (PMS) was employed for ASA degradation and released inorganic arsenic absorption from aqueous media. The effect of some key parameters including catalyst dosage (0–0.5 g/L), PMS concentration (0–500 μM), initial pH (3.4–10.5) and water matrices (Cl-, HCO3-, NO3-, Fe2+, Fe3+, Mg2+, Ca2+, NH4+ and humic acid) on ASA degradation were investigated. More than 99% of ASA (26.72 μM, 2 mg-As/L) was converted to As(V), and 84.65% of it was adsorbed on CuFe2O4 simultaneously within 90 min at 0.3 g/L CuFe2O4, 200 μM PMS at initial pH 7. Specifically, the presence of humic acid significantly inhibited ASA degradation. Cl- had a dual effect, HCO3- and Fe2+ had a promoting effect and some common cations (Fe3+, Mg2+, Ca2+, and NH4+) had negligible effect on ASA conversion. FTIR and XPS analyses indicated the removal of inorganic arsenic followed the mechanism of inner-sphere complex. Radicals analyses showed that O2∙-, OH and SO4·- (free and surface-bound) accounted for arsenic species oxidation in the CuFe2O4/PMS system. Besides, ASA could also be oxidized to the nitrated product (nitarsone) through a non-radical pathway by PMS alone. The degradation products of ASA were identified by LC/MS/MS and the degradation pathways were proposed, and their toxicity was assessed using luminescent bacteria Vibrio fischeri. Moreover, the recovered catalyst exhibited high stability and reusability tested by SEM, TEM, XRD and leaching ions experiments.

Combustion synthesis of mesoporous CoAl2O4 for peroxymonosulfate activation to degrade organic pollutants

A mesoporous cobalt aluminate (CoAl2O4) spinel is synthesized through a combustion method and adopted for the activation of peroxymonosulfate (PMS) to degrade organic pollutants. Multiple characterization procedures are conducted to investigate the morphology and physicochemical properties of the CoAl2O4 spinel. Due to its mesoporous structure, large surface area, and high electrical conductivity, the obtained CoAl2O4 exhibits remarkable catalytic activity for Rhodamine B (RhB) degradation. Its RhB degradation rate is 89.0 and 10.5 times greater than those of Co3O4 and CoAl2O4 spinel prepared by a precipitation method, respectively. Moreover, the mesoporous CoAl2O4 spinel demonstrates a broad operating pH range and excellent recyclability. The influence of several parameters (catalyst amount, PMS concentration, initial pH, and coexisting inorganic anions) on the oxidation of RhB is evaluated. Through quenching tests and electron paramagnetic resonance experiments, sulfate radicals are identified as the predominant reactive species in RhB degradation. This paper provides new insights for the development of efficient, stable, and reusable cobalt-based heterogeneous catalysts and promotes the application of persulfate activation technology for the treatment of refractory organic wastewater.

Simultaneous Oxidation and Sequestration of Arsenic(III) from Aqueous Solution by Copper Aluminate with Peroxymonosulfate: A Fast and Efficient Heterogeneous Process.

The major problem in arsenic (As(III)) removal using adsorbents is that the method is time-consuming and inefficient owing to the fact that most of the adsorbents are more effective for As(V). Herein, we report a new discovery regarding the significant simultaneous oxidation and sequestration of As(III) by a heterogeneous catalytic process of copper aluminate (CuAl2O4) coupled with peroxymonosulfate (PMS). Oxidation and adsorption promote each other. With the help of the active radicals, the As(III) removal efficiency can be increased from 59.4 to 99.2% in the presence of low concentrations of PMS (50 μM) and CuAl2O4 (300 mg/L) in solution. CuAl2O4/PMS can work effectively in a wide pH range (3.0–9.0). Other substances, such as nitrate, sulfate, chloride, carbonate, and humic acid, exert an insignificant effect on As(III) removal. Based on X-ray photoelectron spectroscopy (XPS) analysis, the exposed reductive copper active sites might drive the redox reaction of Cu(II)/Cu(I), which plays a key role in the decomposition of PMS and the oxidation of As(III). The exhausted CuAl2O4 could be refreshed for cycling runs with insignificant capacity loss by the combined regeneration strategy because of the stable spinel structure. According to all results, the CuAl2O4/PMS with favorable oxidation ability and stability could be employed as a promising candidate in real As(III)-contaminated groundwater treatment.

Peroxymonosulfate activation by tea residue biochar loaded with Fe3O4 for the degradation of tetracycline hydrochloride: performance and reaction mechanism.

The recycling of agricultural and food waste is an effective way to reduce resource waste and ameliorate the shortage of natural resources. The treatment of antibiotic wastewater is a current research hotspot. In this study, waste tea residue was used as a raw material to prepare biochar (T-BC) and loaded with Fe3O4 as a catalyst to activate peroxymonosulfate (PMS) for oxidative degradation of tetracycline hydrochloride (TCH). Analysis techniques such as BET, SEM, XRD, FT-IR, XPS and VSM indicated that the heterogeneous catalyst (Fe3O4@T-BC) with good surface properties and magnetic properties was successfully prepared. The results of batch-scale experiments illustrated that when the dose of the Fe3O4@T-BC catalyst was 1 g L−1, the concentration of PMS was 1 g L−1, and the initial pH was 7, the degradation rate of TCH with a concentration of 50 mg L−1 reached 97.89% after 60 minutes of reaction. When the initial pH was 11, the degradation rate of TCH reached 99.86%. After the catalyst was recycled four times using an external magnet, the degradation rate of TCH could still reach 71.32%. The data of removal of TCH could be best fitted by a pseudo-first-order model. The analysis of the degradation mechanism through a free radical quenching experiment and EPR analysis, as well as the exploration of TCH intermediate products and reaction paths through the LC-MS method, all confirmed that the Fe3O4@T-BC prepared by this method is expected to become a cost-effective and environmentally friendly heterogeneous catalyst for activating persulfate degradation of tetracycline antibiotics.

Synthesis of flower-like CoOOH with hierarchical micro/nano-structure as a catalyst for peroxymonosulfate activation

In this work, hierarchical flower-like CoOOH assembled from many nanoflakes with a thickness of 20 nm was fabricated by a simple chemical bath deposition (CBD) method, and its performance as a heterogenous catalyst to activate peroxymonosulfate (PMS) for degradation of methylene blue (MB) solution was explored. The results show that CoOOH/PMS is a high efficient system for MB removal, in which 91.95% degradation of MB can be realized within 25 min. Influences of process parameters, including dosage of PMS, addition of catalyst, and co-existed anions on MB degradation were also investigated. It is found that the degradation rate of MB increases with the increase of the amount of PMS from 0.15 mmol·L-1 to 0.45 mmol·L-1. In such PMS concentrations ranges, CoOOH catalyst amount of 0.03 g·L-1 is adequate for PMS activation in the reaction system. The presence of Cl-1and HCO3- anions has a negative effect on MB degradation, while SO42- has no significant influence. In addition, quenching experiments were conducted and SO4 ·- is confirmed as the main active specie during the MB degradation process. Moreover, cycling runs proven that CoOOH could be re-used to activate PMS for MB degradation without notable activity reduction. These results suggest that hierarchical CoOOH is a promising PMS activator for organic pollutant removal.

UV-enhanced nano-nickel ferrite-activated peroxymonosulfate for the degradation of chlortetracycline hydrochloride in aqueous solution.

In this study, nano-nickel ferrite (NiFe2O4) was successfully prepared by hydrothermal synthesis and applied to the oxidative removal of chlortetracycline hydrochloride (CTH) in the presence of ultraviolet radiation (UV) and peroxymonosulfate (PMS). Several characterization methods were used to reveal the morphology and surface properties of nano-NiFe2O4, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared absorption (FTIR) spectroscopy. The removal efficiency of CTH, the factors affecting the reaction process and the reaction mechanism of PMS activated by UV combined with nano-NiFe2O4 (UV + nano-NiFe2O4/PMS) in aqueous solution were systematically studied. The results showed that the UV + nano-NiFe2O4/PMS system led to a higher removal efficiency of CTH than other parallel systems. The results also showed that the CTH removal efficiency was enhanced under optimal conditions ([nano-NiFe2O4] = 1 g L−1, [PMS] = 1 g L−1, [UV wavelength] = 254 nm and [pH] = 11) and that a removal efficiency of 96.98% could be achieved after 60 min. In addition, the influence of the PMS concentration, CTH concentration, dosage of added nano-NiFe2O4 and pH on the PMS activation efficiency and CTH oxidative degradation effect was studied. Inorganic anions such as Cl−, HCO3−, CO32− and NO3− increased the removal efficiency of CTH by 21.29%, 27.17%, 25.32% and 5.96% respectively, while H2PO4− inhibited CTH removal, and the removal efficiency of CTH decreased 6.08% after 60 min. Free radical identification tests detected SO4−˙, OH˙ and 1O2 and showed that these species participated in the degradation reaction of CTH. The results of LC-MS and TOC analysis showed that CTH was degraded in the UV + nano-NiFe2O4/PMS system through hydroxylation, demethylation, deamination, and dehydration reaction and finally mineralized into CO2. These findings confirmed that nano-NiFe2O4 is a green and efficient heterogeneous catalyst for activation of PMS and demonstrates potential applicability in the treatment of antibiotic wastewater.

Enhanced removal of methylparaben mediated by cobalt/carbon nanotubes (Co/CNTs) activated peroxymonosulfate in chloride-containing water: Reaction kinetics, mechanisms and pathways

Chloride ion (Cl−) widely presents in natural water and wastewater, which can significantly affect the performance of sulfate radical-based advanced oxidation processes (SR-AOPs). However, few studies are available now on the generation of chlorinated by-products in the peroxymonosulfate (PMS) based systems. Here a novel catalyst (cobalt/carbon nanotubes, Co/CNTs) was synthesized and used as a PMS activator to remove methylparaben (MeP) with and without Cl−. The morphology and chemical composition of the fresh and used Co/CNTs were characterized by TEM, SEM, XRD, BET, and XPS. Results revealed that Co/CNTs exhibited significant catalytic activity toward MeP removal, and the removal efficiency increased with the augment of reaction temperature and concentrations of Co/CNTs and PMS. In the absence of Cl−, 83.2% of 10 μM MeP was degraded within 60 min by using 2 mg/L Co/CNTs and 100 μM PMS at 25 °C with pH 7.0. However, complete removal of MeP was achieved within 20 min in the presence of 100 mM Cl−, which enhanced the apparent rate constant by a factor of 4.3. Consequently, TOC removal was enhanced from 8.1% to 19.2% within 60 min. Through the quenching experiments, both SO4− and OH were found responsible for MeP degradation without Cl−, while Cl2− was the main reactive oxygen species (ROS) with 100 mM Cl−. Based on the intermediates identified via TOF-LC-MS, four potential reaction pathways were proposed, including hydrogen abstraction coupling reaction, hydroxylation, OH attack, and Cl2− attack. The intermediates also exhibited decreased toxicity compared to the parent compound based on the ecotoxicity evaluation. In addition, Co/CNTs + PMS system achieved over 60% MeP removal from real wastewater with elevated PMS concentration, indicating the process applicability. These findings provide valuable information of SR-AOPs to facilitate organic contaminants removal in Cl−-containing water.

Degradation of p-Nitrotoluene in aqueous environment by Fe(II)/Peroxymonosulfate using full factorial experimental design

ABSTRACT In this project, the removal of p-Nitrotoluene (PNT) in typical synthetic wastewater was investigated using Peroxymonosulfate (PMS) motivated by Ferrous Ion. The PNT was degraded by sulfate and hydroxyl radicals. The effect of various factors such as ferrous ion and PMS concentrations, and pH on the removal of PNT was studied. Three-level full Factorial design of experiments (FFD) was employed for experimental design and statistical analysis. It was revealed that the PMS and ferrous ion concentrations and quadratic terms were statistically significant while the factor interactions were insignificant model terms. Increasing the PMS and ferrous ion concentrations enhanced the PNT removal efficiency to some extent. The pH had two-contrast influence and the neutral pH was the best. The most significant term was the concentration of ferrous ion, which influenced greatly on PMS and considerably caused a change in the PNT removal efficiency. R-squared, as a measure of the amount of variation around the mean explained by the model was 0.9827. The maximum removal condition was obtained at pH of 7, ferrous ion concentration of 12 mM and PMS concentration of 25 mM. The maximum removal of PNT and COD was achieved as 96% and 67%, respectively.

Combination of hydrodynamic cavitation and SR-AOPs for simultaneous degradation of BTEX in water

• Hydrodynamic cavitation is effective in PS and PMS activation. • SO 4 •− and HO • radicals were predominant reactive species for BTEX degradation. • The inhibitory effect of inorganic anions on BTEX degradation ranked Cl − < SO 4 2− < CO 3 2– . • Surprising synergism of PMS and Cl − increased the degradation by formation of Cl-based radical species. • Degradation pathways of BTEX were proposed by intermediates identified by HPLC-DAD. Hydrodynamic cavitation (HC) is an emerging technology gaining interest in water treatment for use in elimination of a wide range of organic pollutants. The energy released during cavitation phenomenon has number of applications and, particularly, it can be utilized for activation of persulfate (PS) and peroxymonosulfate (PMS). In the present study, hybrid techniques: HC combined with persulfates – HC-PS and HC-PMS were tested for the degradation of BTEX in water. Studies on the effect of initial PS and PMS concentration showed that a molar ratio of the oxidant to BTEX equal to 5 is favorable for both cases. Thus, in 240 min HC-PS-5 process allowed to degrade 91.51%, 95.50%, 94.65%, 94.95% of benzene, toluene, ethylbenzene and o -xylene, respectively, while 90.85%, 94.50%, 94.36%, 93.07% of those compounds were degraded by HC-PMS-5. BTEX degradation pathway was proposed for HC-PS-5 and HC-PMS-5 processes relying on the identification of the main reaction intermediates using liquid chromatography coupled with UV diode array detector (HPLC-UV-DAD). Benzyl alcohol, phenol, benzoic acid, benzaldehyde and o -cresol were the main intermediates of BTEX degradation, which multistep pathway involved H-abstraction, OH addition and dealkylation in route to mineralization. At final time of treatment primary and secondary pollutants were effectively degraded. In terms of kinetics, BTEX degradation followed the pseudo-first-order reaction model and the degradation kinetics were faster in HC-PMS-5 system than in HC-PS-5. Surprisingly, the presence of chloride ions (Cl − ) in HC-PMS-5 improved the degradation efficiency of alkylated benzene derivatives indicating a synergistic effect of Cl − with SO 4 •− radicals.

Removal of 2,4-dichlorophenoxyacetic acid by the boron-nitrogen co-doped carbon nanotubes: Insights into peroxymonosulfate adsorption and activation

B, N co-doped CNTs were synthesized by a simple one-step thermal process and the advanced oxidation processes (AOPs) of 2,4-dichlorophenoxyacetic acid (2,4-D) over the catalyst involved peroxymonosulfate (PMS) activation was investigated. The co-doped catalysts showed higher isoelectric points (IEPs) than those of CNTs and single doped CNTs, facilitating the adsorption of PMS anion (HSO5−) on the catalyst surface, and the AOPs of 2,4-D depended on PMS concentration could be illustrated by the Langmuir-Hinshelwood model. The removal efficiency of 2,4-D over CNTs, CB450, CN450 and CBN450-2 was 20%, 23%, 34% and 68%, respectively. The enhancement of catalytic activity was due to the synergistic effect between B and N dopants and both the pyrrolic N and B-N complex played roles in the catalytic reaction. The quenching test and electron paramagnetic resonance (EPR) results showed that 1O2 contributed most to the oxidation of 2,4-D and the reaction experienced both the free radical and non-radical pathways. Additionally, the DFT calculation results showed that the adsorption energy of PMS on the surface N dopants decreased by B co-doping, implying that a moderate adsorption energy may facilitate the release of active species generated by PMS activation.

Cobalt ferrite nanoparticles and peroxymonosulfate system for the removal of ampicillin from aqueous solution

Emerging contaminants (EC) are classified as major leading issues in treating wastewater, especially drugs and pharmaceuticals in the urban regions, and the detection and degradation of these pollutants have become an arduous task. Ampicillin is one such portentous β- lactam antibiotic compound used extensively in the medical field for their antimicrobial and growth-enhancing properties in humans as well in veterinary sectors. Due to continuous exposure, the microbes in due course developed a shield towards the implication of antibiotics. The degradation of Ampicillin has also been succeeded by mixed metal oxides nanoparticles generally specified as AxB2-xO4, which has been a fundamental catalyst in the Advanced Oxidation Process (AOPs). Magnetic nanoparticles, Cobalt Ferrite nanoparticles (CoFe2O4) were synthesized by the coprecipitation method further; it has employed in the activation of oxidizing agent Peroxymonosulfate (PMS) in the Ampicillin degradation. The material and chemical characterization of synthesized nanoparticles using XRD, TEM, SEM-EDX, and FTIR analysis were done. From the investigation, the nanoparticles were found to exhibit a cubic spinel configuration with a crystallite size of 10.10 nm. The impact of working parameters, such as the presence/absence of catalyst, pH, PMS concentration, and the time required for ampicillin degradation, were investigated. At neutral pH with 0.1 g/L of catalyst measure, 0.2 mM of PMS, 90 ± 1.94 % Ampicillin degraded over 25 min of contact time. The degraded intermediate products of Ampicillin were identified using LC–MS analysis.

Activation of peroxymonosulfate by WTRs-based iron-carbon composites for atrazine removal: Performance evaluation, mechanism insight and byproduct analysis

Water treatment residuals (WTRs), inevitable waste generated from drinking water production, are potential iron resource and can be used for pollution control. In this study, iron-rich WTRs bonded with powder activated carbon (PAC) were calcinated to synthesize iron‑carbon (Fe C) composites, which were then applied to activate peroxymonosulfate (PMS) for the elimination of herbicide atrazine (ATZ). Characterization results showed that Fe 0 and Fe 3 C coexisted in these Fe C composites, among which Fe-15%C exhibited the highest degradation efficiency (91.6%) in 120 min under the condition of 0.25 mM PMS, 0.06 g L −1 Fe-15%C and initial pH 3.58. The effects of Fe-15%C dose, PMS concentration, initial pH and humic acid were systematically investigated. In addition to sulfate radical (SO 4 − ) and hydroxyl radical ( OH), singlet oxygen ( 1 O 2 ) and superoxide radical (O 2 − ) were also involved in the Fe-15%C/PMS system. The iron species and carbon structure jointly contributed to PMS activation, and the conversion of Fe(III) to Fe(II) was enhanced by the addition of p -benzoquinone (BQ). LC-MS technique was used to detect the degradation intermediates of ATZ, which were mainly generated through dechlorination-hydroxylation and dealkylation processes. Cl − had a dual effect (inhibitory and accelerating effect) on the degradation of ATZ, and could influence the yield of chlorinated byproducts desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA), i.e., DEA was hardly affected, but DIA was increased to varying degrees. Ultimately, Fe-15%C had potential to be a viable activator for the removal of ATZ as well as protein- and humic-like substances in natural water. • Fe C composites derived from bonded WTRs and PAC were applied in PMS activation. • SO 4 − , OH, 1 O 2 and O 2 − simultaneously existed in the Fe-15%C/PMS system. • Activation mechanism was proposed and degradation intermediates were identified. • Cl − showed a dual effect on ATZ removal while influencing chlorinated byproducts. • The conversion of Fe(III) to Fe(II) was accelerated by the addition of BQ.

Transformation of acetaminophen in solution containing both peroxymonosulfate and chlorine: Performance, mechanism, and disinfection by-product formation

With the fast development of peroxymonosulfate (PMS)-dominating processes in drinking water and wastewater treatment, residual PMS is easy to come across chlorine as these processes are usually followed by secondary chlorine disinfection. The synergistic effect of PMS and chlorine on the degradation of micro-organic pollutants is investigated by selecting acetaminophen (ACT) as a reference compound for the first time in this study. Unlike conventional PMS or chlorine activation which generates reactive species such as hydroxyl radical (HO•), sulfate radical (SO4•−), chlorine radical (Cl•), and singlet oxygen (1O2), the efficient ACT removal is attributed to the direct catalytic chlorination by PMS due to the significantly enhanced consumption of chlorine along with negligible change of PMS concentration at neutral condition, and the same reaction pathways in both PMS/chlorine and chlorine processes. The kinetic study demonstrates that ACT oxidation by PMS/chlorine follows second order reaction, and the degradation efficiency can be promoted at alkaline conditions with peak rate constants at pH 9.0−10.0. The presence of chloride can enhance the removal of ACT, while ammonium and humic acid significantly retard ACT degradation. Higher formation of selected disinfection by-products (DBPs) is observed in the PMS/chlorine process than in the sole chlorination. This study highlights the important role of PMS in organic pollutants degradation and DBPs formation during the chlorination process.

Aqueous degradation of artificial sweeteners saccharin and neotame by metal organic framework material

The artificial sweeteners (ASs) saccharin (SAC) and neotame (NEO) are widely used across the globe and are considered as emerging contaminants in surface, ground, and drinking waters. To degrade SAC and NEO, the metal organic framework material Co-based bio-MOF-11 was prepared by hydrothermal reaction and used with peroxymonosulfate (PMS) activator. The effects of the initial concentration of SAC and NEO, bio-MOF-11-Co dosage, PMS concentration, initial pH, temperature, and competitive anions were determined. The results revealed that bio-MOF-11-Co effectively catalyzed the degradation of SAC and NEO and possessed good stability and recycling efficiency. The degradation reaction was effective from pH 3.6–9.8 and followed quasi-first-order kinetics with degradation rate constants of 0.001–0.013 min−1 for SAC and 0.03–0.52 min−1 for NEO. Increased temperature was conducive to the degradation of both artificial sweeteners. The presence of Cl− inhibited the degradation of SAC and NEO, while the presence of CO32− promoted their degradation. Electron paramagnetic resonance (EPR) and free radical quenching demonstrated that the primary free radicals were sulfate radicals (SO4−·) and hydroxyl radicals (HO). The change of cobalt oxidation state and electron transfer in bio-MOF-11-Co mainly induces the production of SO4−·. A plausible mechanism for degradation is SO4−· and HO attack on CS bonds, NS bonds, and benzene rings.

Degradation of petroleum hydrocarbons in soil via advanced oxidation process using peroxymonosulfate activated by nanoscale zero-valent iron

Recently, the use of nanoscale zero-valent iron (nZVI) for removal of organic contaminants from aqueous and soil system has increased. In this study, we employ nZVI to activate peroxymonosulfate (PMS) for the degradation of total petroleum hydrocarbons (TPHs) in aged diesel-contaminated soil. Upon PMS activation by nZVI, PMS produces more highly reactive oxygen species (ROS) in both aqueous solution and soil compared to other compounds (PMS/Co(II)), as determined by electron paramagnetic resonance spectroscopy. Thus, nZVI is an effective catalyst for PMS activation, leading to the efficient degradation of diesel oil in soil compared to other catalysts and oxidants. The optimal concentrations of PMS and nZVI were found to be 3 and 0.2%, respectively, showing the best degradation efficiency (61.2% in 2 h). The observed TPH degradation was retarded (up to 19.1–37% efficiency) in the presence of radical scavengers, such as tert-butyl alcohol, nitrobenzene, ethyl alcohol, and isopropyl alcohol. These results also demonstrate that ROS (hydroxyl and sulfate free radicals) are generated via PMS activation by nZVI. Moreover, more than 96% of TPH can be degraded by sequential applications of PMS/nZVI. Factors affecting TPH degradation, namely PMS/nZVI concentration, soil:solution ratio, soil pH, activators, and oxidants, are also analyzed. The results demonstrate that TPH is degraded to below the residential soil quality limit using PMS/nZVI based on the advanced oxidation process (AOP), which is therefore an effective option for chemical remediation of diesel-contaminated soils over a wide range of pH.

Effect of borate buffer on organics degradation with unactivated peroxymonosulfate: Influencing factors and mechanisms

Considering that borate buffer is frequently used to maintain the pH in the peroxymonosulfate (PMS)-based advanced oxidation process and several oxygenated anions (OH−, PO43−, and CO32−) can stimulate PMS, the efficient degradation of organic pollutants through a PMS/borate system was systematically reported in this work. The presence of borate significantly enhanced the degradation of acid orange 7 (AO7) by PMS at all PMS concentrations, but not by persulfate or hydrogen peroxide. Additionally, concentrations of borate from 0.04 to 0.6 M accelerated the degradation of AO7 by PMS, while the corresponding kobs values increased and then decreased, reaching a maximum of 0.0284 min−1 at 0.1 M borate. The decline at higher borate concentrations resulted from the generation of unreactive intermediate peroxoboric acid (HOOB(OH)2) between HSO5− and H3BO3, which consumed a portion of PMS. The removal of AO7 was stimulated by the presence of borate at lower pH = 7.0–9.0 but was suppressed at a higher of pH 9.5 and 10.0. Based on scavenging experiments and electron paramagnetic resonance tests, it can be inferred that 1O2 together with SO4− and OH were responsible for AO7 removal in the PMS/borate system. TOC removal was also enhanced by PMS/borate system compared to PMS alone. PMS/borate system was also effective in the degradation of other organic contaminants and preferentially oxidized the electron-rich moieties. Consequently, more attention should be paid to the use of borate buffer in the studies of PMS-based advanced oxidation processes, and this work can provide a reference for future research.

Efficient degradation of organic dye using Ni-MOF derived NiCo-LDH as peroxymonosulfate activator

Nickel-based metal-organic framework (Ni-MOF) was employed as a sacrificial template for the preparation of nickel-cobalt layered double hydroxide (NiCo-LDH) under different hydrolysis time. The template etching rate varied at different hydrolysis time, resulting in variations of the structural and morphology of NiCo-LDHs. The NiCo-LDH/10 sample showed a large specific surface area and the well-oriented larger dimension of thinner sheets due to the sufficient in-situ etching of the Ni-MOF template. The NiCo-LDH/10 was an excellent heterogeneous catalyst to activate peroxymonosulfate (PMS) for highly efficient Reactive Red-120 dye degradation. The results exhibited that the degradation efficiency of the NiCo-LDH/10-PMS catalyst was 89% for RR-120 dye within 10 min in the presence of the PMS system, which is higher than other NiCo-LDHs. Moreover, the other influencing factors such as PMS concentration, catalyst dosage, initial pH were also investigated towards degradation. The radical quenching measurement proved that the sulfate (SO4•−) and hydroxyl (OH•) had been indicated as the primary radicals. Besides, the NiCo-LDH/10-PMS catalyst showed excellent reusability even after five consecutive cycles (83.6% of the degradation efficiency). This work offer insight study on the construction of controlled morphology NiCo-LDH heterogeneous structure for high-efficiency PMS activation.