PMS Concentration Research Articles

Degradation of surrogate and real naphthenic acids from simulated and real oil sands process water using electrochemically activated peroxymonosulfate (EO-PMS) process

The remediation of dissolved organics in oil sands process water (OSPW), specifically, naphthenic acids (NAs) is considered a major challenge facing the oil sands industry due to recalcitrant and persistent nature of this class of organics in the environment. Herein, the degradation of 5-Phenylvaleric Acid (PVA) as a NA surrogate compound and real NAs in a simulated OSPW and real OSPW was investigated by coupling electro-oxidation and electrochemically activated peroxymonosulfate (EO-PMS) process. The combined EO-PMS process showed high removal efficiency of PVA, in which EO was enhanced by the successful electrochemical activation of PMS at different electrode surfaces. The effects of different cathode and anode materials, initial PMS concentration, and applied current intensity on the PVA degradation were investigated. The PVA degradation efficiencies increased with the increase in the PMS concentration and applied current, however, decreased at higher levels. Carbon felt cathode and BDD anode showed the highest improvement during EO-PMS process. Both sulfate radicals (SO4•‾) and hydroxyl radicals (•OH) were found to be the primary reactive oxidants identified for the PVA degradation by both radical scavenger and spin-trapped techniques. A complete degradation of 50 mg/L PVA solution and significant reduction of the classical and oxidized NAs as well as aromatics in real OSPW were achieved by EO-PMS compared to EO alone. The results confirmed that the combination of electrochemical oxidation and electro-activated PMS process (EO-PMS) could be a promising and efficient technology for the treatment of recalcitrant NA compounds in OSPW.

Cu0 incorporated cobalt/nitrogen doped carbonaceous frameworks derived from ZIF-67 (Cu@Co[sbnd]N[sbnd]C) as PMS activator for efficient degradation of naproxen: Direct electron transfer and 1O2 dominated nonradical mechanisms

In this study, zero valent copper (Cu0) was incorporated into ZIF-67 to construct Cu0 and cobalt/nitrogen doped carbonaceous frameworks x-Cu@CoNCy. The obtained Cu@CoNC was employed to activate PMS to degrade naproxen (NPX) in aqueous phase. Influencing factors on NPX degradation were investigated, including mole ratio of Cu/Co, pyrolysis temperature, pH, catalyst dosage, PMS concentration, and coexisting inorganic anions. In the presence of 0.5 mM PMS and 25 mg/L 1:3-Cu@CoNC900, complete degradation of NPX (50 μM) could be achieved in 20 min within a wide pH range of 3 to 10. The superior catalytic activity of Cu@CoNC900 for PMS activation was related to the increased surface –OH groups, accelerated electron transfer rate induced by Cu0 with strong conductivity, formed surface PMS complexes with high oxidation activity, and synergistic effect between Cu and Co. EPR analysis, radical scavenging and probe tests excluded the participation of SO4− and OH in NPX degradation. Nonradical pathways of electron transfer from NPX to PMS and 1O2 oxidation contributed to the excellent degradation. The 1:3-Cu@CoNC900 demonstrated a decent degradation performance even after five consecutive recycles with low cobalt and copper ions leaching due to the encapsulation of Co and Cu on N-doped porous carbon. Further, the intermediates of NPX degradation were identified, and three possible degradation pathways were proposed. Overall, this work provides a feasible strategy to improve the stability and catalytic activity of ZIF-67 by the incorporation of Cu0.

Removal characteristics of ammonia nitrogen and refractory organic matter in waste leachate by Co2+/peroxymonosulfate process at high chloride ion concentration

Landfill leachate contains high concentrations of refractory organic matter (ROM), ammonia nitrogen (NH4+), and chlorine ion (Cl–). With efficient ROM removal being the focus of advanced oxidation processes, there is an urgent need to clarify the role of high Cl– concentration on reactive species and preferential reactivity towards coexistent ROM and NH4+. This study investigated the removal characteristics of ROM and NH4+ using a Co2+/peroxymonosulfate (Co2+/PMS) process with high Cl– concentration. The results showed that the system produced large amount of hypochlorous acid (HOCl), with a maximum accumulated HOCl concentration reaching 2.78 mM at Co2+, PMS, and Cl– concentrations of 105 μM, 10 mM, and 17 mM, respectively. The differences in Cl–-to-PMS molar ratios altered HOCl formation pathway, and both Co3+ and SO4•− played important roles in HOCl generation. Although the initial concentrations of PMS, Co2+, and Cl– were proportional to the cumulative HOCl concentration, increasing pH significantly inhibited HOCl formation. The coexisting anions commonly found in waste leachate (i.e., CO32−, HCO3−, and NO3−) promoted HOCl production to some extent, but both NH4+ and dissolved organic matter (humic acid and amino acid complex) severely depleted the formed HOCl. Analysis of the removal characteristics of NH4+ and ROM in co-occurrence in actual waste leachate at high Cl– concentrations revealed that NH4+ and ROM competed for HOCl, and preferential removal of humic-like substances led to retention of fulvic-like substances. These results provide theoretical support for the design and optimization of methods for NH4+ and ROM removal from waste leachate containing high Cl– content.

Synthesis of porous carbon by composing Co-MOF as a precursor for degrading antibiotics in the water

Advanced oxidation process (AOPs) has been widely investigated by environmentalists for treating refractory pollutants in the water. Herein, a new composite Co/CoO/C was successfully synthesized via designing cobalt MOF precursor CUST-591 and carbonized under nitrogen condition. The cobalt based MOF precursor CUST-591 formulated as {[Co2(NTB)(DPE)0.5(H2O)2]}·4H2O·DMA, (NTB = 4,4ˊ,4ˊˊ-nitrilotrisbenzoic, DPE = 1, 2-di (4-pyridyl) ethane, DMA= N, N = dimethylacetamide) exhibits a three-dimensional net (3D) with 2-fold interpenetration. During carbonization, porous carbon obtained from MOF ligands embedded Co nanoparticles to form the porous carbon. The fabricated Co/CoO/C possess great property on degrading tetracycline, oxytetracycline with the activation for peroxymonosulfate (KHSO5, PMS) as a heterogeneous catalyst within 20 min under wide range of pH (3∼7). In addition, catalyst dosage, PMS concentration and pollutant amounts were further investigated to prove the advantages of the catalyst. Radical quenching experiments were conducted to discuss the possible mechanism. The experiment results proved that the reactive oxygen species (ROS) were SO4•- and •OH, especially SO4•− played an important role in the reaction. Meanwhile, the catalyst exhibited excellent stability, and can be easily separated from the water by magnet. This prepared material for PMS activation provided a new prospect to synthesize new compounds based on SR-AOPs.

Efficient degradation of Rhodamine B in water by CoFe2O4/H2O2 and CoFe2O4/PMS systems: A comparative study

In this work, a comparative study of efficient degradation of Rhodamine B (RhB) in CoFe2O4/H2O2 and CoFe2O4/PMS systems was performed. Batch experiments indicated that the RhB degradation rate of CoFe2O4/H2O2 system reached 95.5% at 90 min under the condition of 0.5 g L−1 of CoFe2O4 dosage, 10 mM of H2O2 concentration and 3.0 of initial pH. At certain conditions of initial pH = 7.0, 0.3 g L−1 of CoFe2O4 dosage, 7 mM of PMS concentration, CoFe2O4/PMS system could completely degrade RhB within 90 min. EPR and quenching experiments indicated that •OH was the main active species of CoFe2O4/H2O2 system, and •OH, SO4•-, •O2− and 1O2 participated in RhB degradation of CoFe2O4/PMS system. The circulate of Co(II)/Co(III) and Fe(II)/Fe(III) on the CoFe2O4 surface promoted the formation of free radical species in the two system. In CoFe2O4/PMS system, the formed •O2− and SO5•- realized the generation of non-free radical species (1O2). The LC-MS results indicated that N-de-ethylation, chromophore cleavage, opening rings and mineralization were the main steps for the RhB degradation of the two systems. After five cycles of degradation experiment, the CoFe2O4/H2O2 and CoFe2O4/PMS systems still maintained the high degradation rate (85.2% and 92.4%) and low mass loss (2.7% and 3.09%). In addition, CoFe2O4/PMS system had better potential value for the actual water and multi-pollutant degradation than CoFe2O4/H2O2 system. Finally, the toxicity analysis and cost assessment of the two oxidation systems were preliminarily evaluated.

Removal of Carbamazepine in Aqueous Solution by CoS2/Fe2+/PMS Process.

Carbamazepine (CBZ), as a typical pharmaceutical and personal care product (PPCP), cannot be efficiently removed by the conventional drinking water and wastewater treatment process. In this work, the CoS2/Fe2+/PMS process was applied for efficient elimination of CBZ. The CBZ removal efficiency of CoS2/Fe2+/PMS was 2.5 times and 23 times higher than that of CoS2/PMS and Fe2+/PMS, respectively. The intensity of DMPO-HO• and DMPO- followed the order of Fe2+/PMS < CoS2/PMS < CoS2/Fe2+/PMS, also suggesting the CoS2/Fe2+/PMS process has the highest oxidation activity. The effects of reaction conditions (e.g., CoS2 dosage, Fe2+ concentration, PMS concentration, initial CBZ concentration, pH, temperature) and water quality parameters (e.g., , , , , , humic acid) on the degradation of CBZ were also studied. Response surface methodology analysis was carried out to obtain the best conditions for the removal of CBZ, which are: Fe2+ = 70 µmol/L, PMS = 240 µmol/L, CoS2 = 0.59 g/L. The sustainability test demonstrated that the repeated use of CoS2 for 8 successive cycles resulted in little function decrease (<10%). These findings suggest that CoS2/Fe2+/PMS may be a promising method for advanced treatment of tailwater from sewage treatment plant.

Photocatalytic activation of peroxymonosulfate using ilmenite (FeTiO3) for Enterococcus faecalis inactivation

In this work, a raw and low cost mineral, ilmenite (FeTiO3), has been tested for the first time as a photocatalyst paired with peroxymonosulfate (HSO5-; PMS) for the inactivation of Enterococcus faecalis as an alternative to conventional treatments to disinfect wastewater for reuse. The influence of some operational parameters such as reagent dosage, catalyst concentration, initial pH, or flow rate was also studied and optimized. After several tests, the scarce pure photoactivity under UV-A was remarked by ilmenite because of its high iron content, which favors photogenerated charge recombination. However, ilmenite activity was highly promoted when combined with low concentrations of PMS and UV-A light, reaching total inactivation of Enterococcus faecalis in 120 min. Quenching tests were performed using methanol, tert-butyl alcohol, furfuryl alcohol, and Cu(II) to assess the main reactive species involved in the disinfection process determining the critical role of both HO·and SO4·- radicals in the process. Finally, the influence of the water matrix was also evaluated by studying the effect of water hardness and the presence of nutrients on the system. Overall, the PMS/Ilmenite/UV-A system yielded promising results with a total removal of Enterococcus faecalis in 120 min. However, it also showed the need for further study and understanding of the disinfection mechanism to achieve the same level of performance in real wastewater.

Tailoring the Fenton-like mechanisms of surface functional groups by corrosive structural defects for superior pollutant degradation on platform carbon

The high abundance, low cost and no toxicity of solid catalyst play governing roles in Fenton-like catalysis via non-radical pathways. Reactive carbons exhibit low capacity for PMS activation and pollutant degradation, although they possess unique material properties. Herein, a simple and efficient two-step strategy of “chemical reduction + acidic corrosion” was proposed and validated to refine platform carbon for Fenton-like catalysis in environmental decontamination. Platform carbon treated by NaBH4 reduction and H2SO4 corrosion exhibited much superior reactivity and selectivity as well as stability for PMS activation to degrade phenolic pollutants in various water matrix. Effects of tailoring condition, catalyst dosage, pollutant concentration, pH range and PMS concentration were studied. Control tests with other catalysts, catalyst reusability and technical applicability were carried out. Reaction mechanisms were elucidated by ESR and radical quenching as well as electrochemical tests. Radical pathway was not a critical role, while catalysis was controlled by catalyst-oxidant surface interactions and non-radical pathways (1O2 and electron transfer), the latter played the dominant role mediated by surface CO group. Our findings provided a new chance to utilize platform carbon and other inert materials in selective Fenton-like catalysis for safe water purification.

Ultraviolet light-activated peroxymonosulfate (UV/PMS) system for humic acid mineralization: Effects of ionic matrix and feasible application in seawater reverse osmosis desalination

The use of membrane-based technology has evolved into an important strategy for supplying freshwater from seawater and wastewater to overcome the problems of water scarcity around the world. However, the presence of natural organic matter (NOM), including humic substances affects the performance of the process. Here, we present a systematic report on the mineralization of humic acid (HA), as a model for NOM, in high concentration of salts using the ultraviolet light-activated peroxymonosulfate (UV/PMS) system as a potential alternative for HA elimination during membrane-based seawater desalination and water treatment processes. Effects of various parameters such as PMS concentration, solution type, pH, anions, and anion-cation matrix on HA mineralization were assessed. The results show that 100%, 78% and 58% of HA (2 mg/L TOC) were mineralized with rate constants of 0.085 min−1, 0.0073 min−1, and 0.0041 min−1 after 180 min reaction time at pH 7 when 0.5 mM PMS was used in deionized water, sodium chloride solution (35,000 ppm) and synthetic seawater, respectively. The reduced efficiency under saline conditions was attributed to the presence of anions in the system that acted as sulfate and hydroxyl radicals’ scavengers. Furthermore, the safety of the treated synthetic seawater was evaluated by analyzing the residual transformed products. Overall, pretreatment with the UV/PMS system mitigated fouling on the RO membrane.

Electrochemical activation of peroxymonosulfate with titanium suboxide anode for 4-chlorophenol degradation: Influencing factors, kinetics, and degradation mechanism

The unsuitable treatment of 4-chlor (4-CP) in industrial and municipal wastewater will bring a great risk to human health and eco-environment. Traditional adsorption methods for deeply degrading 4-CP suffer from intractable issues containing secondary pollution and resource waste. In this study, electrochemical oxidation coupled with PMS activation process (EO-PMS process) was used to degrade 4-CP via the generated reactive oxygen species (ROS). The increased PMS concentration and current density can effectively remove 4-CP within 20 min, and a high kinetic rate of 0.149 min−1 was obtained. It should be noted that SO4− and OH was dominant active species, and OH played a more important role in degrading 4-CP than SO4−. In addition, the EO-PMS process can remove multiple organic pollutants as well as effective as 4-CP. The EO-PMS process also kept good stability and tolerance with various pH values during continuous five-cycles operations. The analysis of degradation intermediates and DFT calculations confirmed two degradation pathways (Pathway I: P1 → P2 → P3 → P4 and Pathway II: P5 → P6 → P4) due to the attacking of ROS. The study provided a potential insight towards efficient and quick degradation of various organic pollutants through electrochemical advanced oxidation process.

Simulating micropollutant abatement during cobalt mediated peroxymonosulfate process by probe-based kinetic models

Prediction of micropollutant abatement during advanced oxidation processes by modelling can provide valuable information to optimize the process for efficient water treatment. In this study, a probe-based kinetic model was developed to simulate micropollutant abatement during water treatment by a cobalt-mediated peroxymonosulfate (Co(II)/PMS) process. Eight micropollutants (atrazine, primidone, sulfisoxazole, sulfamethoxypyridazine, gemfibrozil, chloramphenicol, p-chlorobenzoic acid, and perfluorooctanoic acid) were spiked in various water matrices (synthetic water and real surface water), which were then treated by the Co(II)/PMS process. By following the decay of PMS, atrazine, and primidone (as sulfate and hydroxyl radical (SO4·- and ·OH) probes) during the process, the exposures of PMS, SO4·- and ·OH were calculated using the model. Then, based on the determined exposures, the abatement efficiencies of the other micropollutants could be reasonably predicted with the model. The results indicate that by using a couple of probes to measure the SO4·- and ·OH exposures, the model can be used for the generalized prediction of the abatement of various micropollutants during water treatment by the Co(II)/PMS process. In addition, modelling results show that for a given water matrix, the ratios of SO4·- and ·OH concentrations to PMS concentrations (RSP and RHP) are almost constant during the Co(II)/PMS process. This finding allows the transient concentrations of SO4·- and ·OH to be quantified based on the constant RSP and RHP ratios and the PMS concentrations observed during the process. The results of this study suggest that the probe-based kinetic models can provide a useful tool to characterize the persulfate-based process and to predict the abatement efficiencies of various micropollutants during water treatment.

New insights on the role of NaCl electrolyte for degradation of organic pollutants in the system of electrocatalysis coupled with advanced oxidation processes

The role of sodium chloride (NaCl) in pollutant degradation in electrocatalysis coupled with advanced oxidation processes (EAOPs) system remains debatable and the formation of toxic chlorine-substituted byproducts during this process has raised growing concern. Herein, the role of NaCl electrolyte for the degradation of p-nitrophenol (4-NP) in the EAOPs (Co3O4/PMS/NaCl) system was identified. Different from the effect of mass transfer, the presence of NaCl electrolyte improved the 4-NP degradation efficiency and the degradation products were affected by the concentrations of peroxymonosulfate (0.01–8 mM) and Cl- (10–100 mM). Besides, different active species (SO4•−, HOCl, or Cl•/ClO•) with different amounts can be produced in the EAOPs systems with three typical PMS concentrations (0.01, 0.032 and 4 mM). Moreover, the formation of chlorine-substituted byproducts can be effectively avoided via adjusting the concentrations of PMS and NaCl to inhibit the formation of Cl•/ClO•. Finally, this EAOPs system was used to degrade the kimchi processing wastewater and 34% of COD and 99% of TN were removed, revealing it has a good practical application. This study illuminates a new role of NaCl as the electrolyte for the degradation of organic pollutants in the EAOPs system for the first time.

Marine Air Pollution in Israel: Extent, Proposed Mitigation Targets, Benefits and Feasibility

Marine air pollution is a major contributor to seaports and coastal air pollution, and Israel has yet to seriously confront this issue. This study aimed to update previous marine air pollution estimations in Israel’s two major ports: Haifa and Ashdod. The objectives were to examine technical and regulatory measures to address the problem, to propose mitigation targets and to estimate their potential benefits. Based on a model of emission-calculations that relies on an updated ship-inventory data as well as real-time ships’ location and movement tools, the combined marine NOx, SOx and PM2.5 annual emissions in these ports were found to be 18,415, 15,128 and 1453 tons, respectively. These values are considerably higher than previous estimates, are comparable to the constant pollution emitted at ground level from a 1000-MW coal powered city power plant and are 3–20 times higher than the industrial and land transportation sectors in these cities. Relatively high nickel concentration in PM was found in Israel only relatively adjacent to the Haifa and Ashdod ports. Since high nickel concentration in PM is today mainly associated with marine air pollution, this finding supports the hypothesis that marine air pollution worsens the air quality in these cities. SOx and PM2.5 emissions can be reduced by 78% and 27%, respectively, if Israel enforces the revised International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI regulations in its territorial waters. While the latter step can achieve external benefits of NIS 518.4 million/year (EUR 132 million/year), additional mitigation actions and local regulations are suggested, focusing on NOx emissions but also on other pollutant criteria. Such actions can achieve further benefits of NIS 274.3 million/year (EUR 70 million/year). Achieving the suggested targets is challenging yet attainable, and their potential benefits will probably outweigh their costs.

Synthesis of bimetallic NbCo-piperazine catalyst and study on its advanced redox treatment of pharmaceuticals and personal care products by activation of permonosulfate

Here, a nano disc-shaped bimetallic organic framework (NbCo-piperazine) was prepared by the solvothermal method for the activation of PMS for the degradation of contaminants. The effects of Nb/Co ratio, synthesis time and temperature on the morphology, structure and performance of the NbCo-piperazine catalyst were characterized by XRD, FT-IR, SEM-EDS and TEM. The optimum conditions for NbCo-PZ to activate PMS degradation of tetracycline were investigated by adjusting the dosage of catalyst, tetracycline concentration, pH and PMS concentration. The catalytic performance of NbCo-PZ in the presence of co-existing anions (Cl−, NO3–, HCO32–, H2PO4−) was also evaluated. XPS explained that cyclic changes in the valence states of Nb4+/Nb5+ and Co2+/Co3+ accelerated the activation of the PMS degradation process. EPR results showed the presence of free radicals (SO4·−, ·OH and O2·−) and non-free radicals (1O2) in the degradation process, with free radicals playing a major role in the degradation process. The degradation rate of tetracycline after three cycles was 92.2%. In addition, NbCo-piperazine showed good catalytic performance for other organic pollutants such as methyl blue, tylosin tartrate and tetracycline with the degradation rate of 97.8%, 95.2% and 95.5%, respectively. Moreover, it also has good catalytic properties in various water systems such as river water and sea water.

Fabrication of Epigallocatechin-3-gallate (EGCG) functionalized Mn3O4 for enhanced degradation of carbamazepine with peroxymonosulfate activation

Peroxymonosulfate activation via heterogeneous catalyst was broadly applied for the treatment of PPCPs. In this work, a novel material of Epigallocatechin-3-gallate (EGCG) fuctionalized Mn3O4 nano-octahedra (E@MO) was synthesized and utilized for the degradation of carbamazepine. Various technologies such as X-ray diffraction, Fourier transform-infrared spectroscopy, Scanning electron microscope, Transmission electron microscope, Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy were employed for the characterization of the as-synthesized catalyst. The results depicted that under the conditions of CBZ concentration 5 mg/L, PMS concentration 1 mM, catalyst dosage 0.2 g/L, initial pH 5.8 and 25 °C, the targeted pollutant could be totally degraded in 60 min with a rate constant of 0.0622 min−1. When temperature raised to 45 °C, CBZ was removed completely in 20 min and the rate constant (0.1668 min−1) was 2.59 times than that of 25 °C, implying the degradation process was an endothermic reaction. Scavenging experiments and EPR analysis confirmed the main reactive oxygen species generated in the reaction were sulfate radical (SO4•) and hydroxyl radical (•OH), while SO4• serviced as the leading role. Due to the reduction property of EGCG, compared with bare Mn3O4, the CBZ degradation was markably enhanced and the degradation reaction were accurately matched with the pseudo first-order kinetics equation. The possible twelve intermediates produced in the decomposition of CBZ were identified by HPLC-MS/MS, their ecotoxicity were evaluated and compared by ECOSAR model. Together with the consequences, the degradation mechanism of CBZ in the E@MO/PMS system was propounded.

Has COVID-19 Lockdown Affected on Air Quality?—Different Time Scale Case Study in Wrocław, Poland

Due to the COVID-19 pandemic, there are series of negative economic consequences, however, in limiting mobility and reducing the number of vehicles, positive effects can also be observed, i.e., improvement of air quality. The paper presents an analysis of air quality measured by concentrations of NO2, NOx and PM2.5 during the most restrictive lockdown from 10 March to 31 May 2020 on the case of Wrocław. The results were compared with the reference period—2016–2019. A significant reduction in traffic volume was identified, on average by 26.3%. The greatest reduction in the concentration of NO2 and NOx was recorded at the station farthest from the city center, characterized by the lowest concentrations: 20.1% and 22.4%. Lower reduction in the average concentrations of NO2 and NOx was recorded at the municipal station (7.9% and 7.7%) and the communication station (6.7% and 10.2%). Concentrations of PMs in 2020 were on average 15% and 13.4% lower than in the reference period for the traffic station and the background station. The long-term impact of the lockdown on air quality was also examined. The analysis of the concentrations of the pollutants throughout 2020, and in the analyzed period of 2021, indicated that the reduction of concentrations and the improvement in air quality caused by the restrictions should be considered as a temporary anomaly, without affecting long-term changes and trends.

Electrochemically activated persulfate and peroxymonosulfate for furfural removal: optimization using Box–Behnken design

ABSTRACT Furfural removal by electrochemically activated peroxydisulfate (E-PS) and peroxymonosulfate (E-PMS) was investigated. The effect of different anodes was investigated for the electrochemical activation of oxidants. Box Behnken Design was applied to determine optimum operating conditions, which were determined as follows; PS concentration: 2.3 mM, applied current: 1.15 A, pH: 3.5, and reaction time: 118.3 min for E-PS process; PMS concentration: 1.8 mM, applied current: 1.05 A, pH: 3.3, and reaction time: 107.8 min for E-PMS process. The results of the study showed that the E-PMS process is more advantageous in terms of the chemical and electricity costs to be used.

Mechanistic insights into the potential applicability of a sulfate-based advanced oxidation process for the control of transparent exopolymer particles in membrane-based desalination

Transparent exopolymer particles (TEPs), often massively produced from algal blooms, are considered one of the most difficult foulants in membrane-based desalination processes and contribute significantly to membrane biofouling. This study explored the potential application of a UV-activated peroxymonosulfate (UV/PMS) system for the mineralization of TEP using alginate as a model. The effects of salinity in the form of chloride ions on the removal of organics were investigated, and the reaction mechanisms were postulated. In addition, the scavenging effect of the co-presence of cations and anions with chloride ions was examined. The results indicated that 100% TEP mineralization could be achieved in freshwater when a PMS concentration above 0.25 mM was added. However, the presence of chloride retarded the removal efficiency by approximately 25%, with more severe retardation observed in the presence of chloride with bromide. This was ascribed to the generation of less reactive and more selective halogen species. Furthermore, approximately 44% organic mineralization was observed when this system was applied to seawater, implying its feasibility as a pretreatment unit in membrane-based desalination.

Insights into Elemental Composition and Sources of Fine and Coarse Particulate Matter in Dense Traffic Areas in Toronto and Vancouver, Canada.

Traffic is a significant pollution source in cities and has caused various health and environmental concerns worldwide. Therefore, an improved understanding of traffic impacts on particle concentrations and their components could help mitigate air pollution. In this study, the characteristics and sources of trace elements in PM2.5 (fine), and PM10-2.5 (coarse), were investigated in dense traffic areas in Toronto and Vancouver, Canada, from 2015–2017. At nearby urban background sites, 24-h integrated PM samples were also concurrently collected. The PM2.5 and PM10-2.5 masses, and a number of elements (i.e., Fe, Ba, Cu, Sb, Zn, Cr), showed clear increases at each near-road site, related to the traffic emissions resulting from resuspension and/or abrasion sources. The trace elements showed a clear partitioning trend between PM2.5 and PM10-2.5, thus reflecting the origin of some of these elements. The application of positive matrix factorization (PMF) to the combined fine and coarse metal data (86 total), with 24 observations at each site, was used to determine the contribution of different sources to the total metal concentrations in fine and coarse PM. Four major sources were identified by the PMF model, including two traffic non-exhaust (crustal/road dust, brake/tire wear) sources, along with regional and local industrial sources. Source apportionment indicated that the resuspended crustal/road dust factor was the dominant contributor to the total coarse-bound trace element (i.e., Fe, Ti, Ba, Cu, Zn, Sb, Cr) concentrations produced by vehicular exhaust and non-exhaust traffic-related processes that have been deposited onto the surface. The second non-exhaust factor related to brake/tire wear abrasion accounted for a considerable portion of the fine and coarse elemental (i.e., Ba, Fe, Cu, Zn, Sb) mass at both near-road sites. Regional and local industry contributed mostly to the fine elemental (i.e., S, As, Se, Cd, Pb) concentrations. Overall, the results show that non-exhaust traffic-related processes were major contributors to the various redox-active metal species (i.e., Fe, Cu) in both PM fractions. In addition, a substantial proportion of these metals in PM2.5 was water-soluble, which is an important contributor to the formation of reactive oxygen species and, thus, may lead to oxidative damage to cells in the human body. It appears that controlling traffic non-exhaust-related metals emissions, in the absence of significant point sources in the area, could have a pronounced effect on the redox activity of PM, with broad implications for the protection of public health.

Enhanced atrazine degradation in the Fe(III)/peroxymonosulfate system via accelerating Fe(II) regeneration by benzoquinone

Fe(II)-involved advanced oxidation processes could effectively degrade refractory contaminants, but the slow transformation of Fe(III) to Fe(II) limits their wide application. Herein we reported that p-benzoquinone (BQ) could accelerate Fe(III)/Fe(II) cycle and promote atrazine (ATZ) degradation in the Fe(III)/peroxymonosulfate (Fe(III)/PMS) system through reconstructing active Fe(II)/PMS system. Under the identical experimental conditions, ATZ degradation efficiency in the BQ/Fe(III)/PMS system (99.8%) was superior to that in the Fe(III)/PMS system (23.2%), suggesting the indispensable role of BQ in Fe(II) regeneration and PMS activation. Reactive species sulfate radical (SO4•−), hydroxyl radical (•OH) and ferryl ion (Fe(IV)) were involved in the BQ/Fe(III)/PMS system based on alcohol quenching experiments, ESR tests and the selective transformation from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2). ATZ degradation mechanism was proposed based on LC-MS detection, among which dealkylation and dechlorination-hydroxylation were the dominant transformation pathways. The BQ/Fe(III)/PMS system showed satisfactory catalytic performance at pH 2.5–7.0 and low Fe(III) concentration, which expanded the pH range and avoided the addition of a large amount of Fe. More importantly, the increase of PMS concentration not only enhanced the oxidative degradation of ATZ and its two main chlorinated byproducts (atrazine-desethyl (DEA) and atrazine-desisopropyl (DIA)), but also facilitated the removal of toxic BQ. Cl− inhibited the degradation of ATZ and caused the accumulation of DEA and DIA, and the higher Cl−, the more obvious this effect. This study provided a new approach to improve the Fe(III)/PMS system by boosting Fe(III)/Fe(II) cycle with quinons.