Persulfate Dosage Research Articles

Degradation of benzothiazole by the UV/persulfate process: Degradation kinetics, mechanism and toxicity

Benzothiazole, a high-production chemical used in domestic and industrial applications, possesses a persistent nature and is ubiquitous in aquatic environments; this study aims to investigate benzothiazole degradation by utilizing a UV-activated persulfate process (UV/persulfate). The results demonstrated that the UV/persulfate process can efficiently degrade benzothiazole in deionized water (the pseudo-first-order degradation rate constant (kobs) was 0.0847 min−1 under the experimental conditions of [benzothiazole]0 = 10 mg/L, [persulfate]0 = 150 mg/L and initial solution pH = 7). kobs and persulfate dose (18.75 to 150 mg/L) exhibited a linearly proportional relationship (R2 = 0.9696). The optimal benzothiazole degradation rate occurred at pH 7 (kobs = 0.0847 min−1) compared with those at pH 3 (kobs = 0.0516 min−1) and 11 (kobs = 0.0450 min−1). The presence of common water constituents (HCO3–, Cl–, NO3– and dissolved organic matter) had an inhibitory effect on benzothiazole degradation. Radical scavenger experiments showed that both SO4•– and •OH were involved in benzothiazole degradation, with SO4•– playing a relatively predominant role. The second-order rate constant between SO4•– and benzothiazole was 2.1 × 109 M−1 s−1. Two transformation byproducts of benzothiazole degradation were detected, which were generated through the dihydroxylation and trihydroxylation reactions of benzothiazole. During the UV/persulfate process, the toxicity (Microtox®) increased and then declined within 60 min of reaction time. The results suggested that the UV/persulfate process is an efficient way to remove benzothiazole from water.

Magnetic amorphous carbon@manganese ferrite hybrid materials as a heterogeneous persulfate activator for catalytic oxidation of tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA), a typical brominated flame retardant in industry, has been recognized as a toxic chemical and an endocrine disruptor. Hence, it’s urgently required to remove it from aquatic environment. In this work, the magnetic amorphous carbon@manganese ferrite (C@MnFe2O4) hybrid materials have been fabricated by hydrothermal method with high temperature annealing method to serve as catalyst for the activation of persulfate (PS) to degrade the TBBPA. The structure characterization results manifest that the synthesized MnFe2O4 particles are evenly distributed on the surface of amorphous carbon in the C@MnFe2O4 hybrid. The factors to affect the catalytic degradation of TBBPA by C@MnFe2O4 hybrid/PS system including type of C@MnFe2O4 hybrid materials, PS dosage, concentration of C@MnFe2O4 and reaction time are investigated systematically. The results show that the highest removal ratio of TBBPA could reach 91.9% after treatment of 90 min by C@MnFe2O4 hybrid/PS system. Furthermore, the C@MnFe2O4 hybrid demonstrates a high stability and recyclability. The electron paramagnetic resonance (EPR) verifies that the introduction of C@MnFe2O4 hybrid into PS system could facilitate the generation of ⋅OH and SO4⋅- radicals for degradation of TBBPA. The degradation intermediates are detected and two possible degradation pathways are proposed. This work provides a new insight for the design and development of novel catalyst for the activation of PS to degrade organic pollutants.

Removal of bisphenol A and methylene blue through persulfate activation by calcinated α-MnO2 nanorods: effect of ultrasonic assistance and toxicity assessment.

This work investigates the efficacy of α-MnO2 nanorods for persulfate-mediated degradation of bisphenol A (BPA) and methylene blue (MB), in silent and ultrasonic-assisted systems. The conversion of α-MnO2 nanoparticle flakes to nanorods occurs upon calcination at a temperature of 400°C for 3h under the ramping conditions. The comparative characterization of nanomaterials pre- and post-calcination reveals better physical, chemical, and thermal properties of α-MnO2 nanorods. The impact of various operational parameters such as pH, dosage of nanorods, persulfate dose, selected contaminant concentration, ultrasound frequency and power, scavengers, and landfill leachate medium on the degradation of pollutants is also assessed. The ultrasonic assistance yields higher removal for both BPA and MB than the silent system. This may be attributed to the generation of more radicals as ultrasound activates persulfate. This can be due to acoustic cavitation, which leads to better solute dissociation and excited state. The results obtained through scavenger tests reveal that both OH• and SO4•- can contribute to degradation, but the role of SO4•- is found dominant. Significant removal of BPA and MB ((BPA)silent, 87.12%; (MB)silent, 96.54%; (BPA)ultrasonic, 88.75%; (MB)ultrasonic, 93.86%)) is observed in landfill leachate medium. The degradation pathway for pollutants is also proposed. The toxicity of pollutants and their degradation intermediates are evaluated using Ecological Structure Activity Relationships (ECOSAR) program. The results indicate reduced toxicity of BPA intermediates, while most MB degradation intermediates show higher toxicity. Therefore, it can be affirmed that removing pollutants does not ensure a completely non-toxic process. However, the study proposes a comprehensive toxicity evaluation and eliminating toxic intermediates for completely harmless wastewater treatment.

Mesoporous Ultrathin g‐C3N4 with Surface Defects Activates Peroxodisulfate for Tetracycline Removal under Visible Light: Synergy and Mechanism

AbstractMetal‐free catalysts combined with a persulfate‐based advanced oxidation process (PS‐AOP) are considered to be a promising purification technology. In this study, porous thin layers of g‐C3N4 with nitrogen defects are synthesized by a simple method. Multiple characterization methods demonstrate the porous thin layer structure and the N defects of P‐CNx‐1. Photoelectrochemistry tests show that the combination of morphological modulation and defect engineering produces an excellent photocurrent response. The P‐CNx‐1/PS/Vis system shows the best tetracycline (TC) removal efficiency degrading 74.2% of TC within 90 min, and the degradation kinetics are significantly improved. Optimal degradation conditions such as catalyst dosage, persulfate (PS) dosage, initial TC concentration, and initial pH are investigated. Cyclic and anionic experiments demonstrate the excellent stability of P‐CNx‐1 and its ability to treat complex aqueous bases. Mechanistic experiments show that ˙OH/SO4˙−/˙O2−/h+/1O2 are all involved in the degradation of TC. Liquid chromatography‐mass spectrometry (LC‐MS) suggests possible degradation pathways for TC. This work aims to provide new ideas for the application of metal‐free g‐C3N4 in PS activation.

Dexamethasone degradation in aqueous medium by a thermally activated persulfate system: Kinetics and transformation products

Dexamethasone (DEX) is a synthetic steroid hormone that, owing to its endocrine disruptive effects, has the potential to be detrimental. DEX must be successfully removed during drinking water treatment to preserve human and aquatic animals' health. This study investigates the thermally activated persulfate (TAP) process for the efficient decomposition of DEX. The effectiveness of several variables such as pH, persulfate dose, DEX concentration, reaction temperature, and water matrices was studied. Removal of 500 μg/L DEX reached 100 % by using 100 mg/L of persulfate in ultrapure water (pH = 7) at 50 °C, within 45 min of reaction time. DEX removal usually followed exponential decay. The removal efficiency of DEX in the TAP process was pH-dependent, as 61 % of DEX was removed at a pH value of 9. In contrast, complete degradation was achieved under acidic and near neutral conditions.Moreover, environmentally relevant degradation experiments showed that, in principle, the presence of bicarbonate ions and humic acid had a negative effect on DEX decomposition by reducing the percentage removal of the target compound by >50 %. Six transformation products derived from DEX oxidation were identified using high-resolution LC-MS. TAP system could be proposed as a promising application for removing steroid hormones n real water matrices after process optimization in real conditions.

Combination of hydrodynamic cavitation with oxidants for efficient treatment of synthetic and real textile wastewater

In this study, the degradation of direct red 89 (DR89) dye from synthetic wastewater was assessed by lab-scaled hydrodynamic cavitation (HC) combined with different oxidants such as periodate (PI), persulfate (PS), and oxalic acid (OA). The degradation tests were carried out by combining the three oxidants in the absence of HC, and using HC with only one of the oxidants (HC/OA, HC/PS, and HC/PI) or with all combined (HC/PS/OA/PI). In all processes, the degradation constants followed first-order reaction kinetics, being the highest one that of the HC/PS/OA/PI process, equal to 2.01 × 10−1 min−1. The degradation of DR89 was affected by pH, initial dye concentration, and reaction time. The degradation efficiency increased when pH decreased obtaining the best results at pH 3.0 due to favorable conditions for the generation and persistence of radical species. The degradation of the dye improved with increasing dose of OA, PS and PI. The best results were achieved using dosages of OA, PS, and PI of 100.0, 125.0, and 150.0 mg L−1, respectively. The quenching experiments revealed the presence of OH, SO4−, IO3, O2–, and 1O2 in the HC/PS/OA/PI process, while OH, SO4− and IO3 were the dominant responsible radicals. The rate constants of the individual processes were used to calculate the value of the synergetic coefficient of HC/PS/OA/PI process. At the optimum conditions, the calculated synergetic coefficient was 15.39. The effectiveness of the HC/PS/OA/PI process in the removal of color and COD from real textile wastewater was also investigated and exhibited the 96.23 ± 1.92 % and 93.84 ± 0.94 % reduction of color and COD after 70 min reaction time, respectively. The results showed that the combined process can be a useful technology for the treatment of textile wastewater.

Degradation of chloramphenicol in soil with catechin-enhanced ferric iron/persulfate system

Chloramphenicol (CAP) is a broad-spectrum antibiotic that has been commonly used in the world for the past few decades because of its high antibacterial activity. Although CAP has been banned, high concentration is still detected in the soil environment because of its low self-degradation. In the present research, the polluted soil was treated in situ in a sulfate radical (SO4•−) based process. CAP was degraded by persulfate (PS) activated with Fe(III) and catechin (CAT). Fe(II) could be produced efficiently via complexation and reduction through Fe(III) and CAT reaction to enhance the PS activation efficiency. The optimal dosages of PS, CAT and Fe(III) were investigated. The degradation rate of CAP could reach 94.3% after 120 min of reaction. The contribution of free radicals on CAP degradation was also detected, and the results showed that SO4•− and HO• resulted in pollutant removal of 83.8% and 16.2%, respectively. The reaction between CAT and Fe(III) mainly occurred on the surface of soil particles because of the strong adsorption of CAT. However, the oxidation process between radicals and CAP mainly occurred in the liquid phase. Moreover, the biological toxicity of the reaction system and the total organic carbon of organic matter were also significantly reduced.

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.

Experimental Study on the Treatment of Landfill Leachate by Electro-Assisted ZVI/UV Synergistic Activated Persulfate System

To solve the problem of the poor treatment of high concentration landfill leachate, an electro-assisted ultraviolet (UV)/zero-valent iron (ZVI) synergic activated persulfate (PS) system was used to treat landfill leachate. The effects of PS and ZVI dosage, initial pH value, and current density on the removal efficiency of COD and NH3-N in landfill leachate were investigated. The treatment effects of single PS, single electrochemical, UV/PS, electro-assisted ZVI activated PS, and electro-assisted ZVI/UV co-activated PS were compared. At the same time, UV-visible and three-dimensional fluorescence spectroscopy were performed on the landfill leachate before and after treatment. The results show that under the optimal conditions of initial pH = 3, the dosage of PS/12COD = 1, ZVI = 1.5 g/L, current density 62.5 mA/cm2, and t = 6 h, most of the macromolecular organic substances such as humic acid and fulvic acid were removed. Removal efficiencies of COD, NH3-N, and Chroma reached 81.99%, 89.90%, and 99.75%, respectively. The BOD5/COD value increased from 0.23 to 0.46. In addition, the radical identification results showed that the degradation of COD was due to the combined action of sulfate radicals (SO4•−) and hydroxyl radicals (•OH) and that SO4•− was dominant. The combined means of synergistic activation of PS for landfill leachate treatment was significantly better than that of single means of PS activation, confirming that electrically assisted ZVI/UV synergistic activation of PS is a promising method for landfill leachate treatment.

Efficient Separation and Recovery of Petroleum Hydrocarbon from Oily Sludge by a Combination of Adsorption and Demulsification.

The treatment of oily sludge (OS) can not only effectively solve environmental pollution but also contribute to the efficient use of energy. In this study, the separation effect of OS was analyzed through sodium lignosulfonate (SL)-assisted sodium persulfate (S/D) treatment. The effects of SL concentration, pH, temperature, solid–liquid ratio, revolving speed, and time on SL adsorption solubilization were analyzed. The effects of sodium persulfate dosage, demulsification temperature, and demulsification time on sodium persulfate oxidative demulsification were analyzed. The oil removal efficiency was as high as 91.28%. The results showed that the sediment was uniformly and finely distributed in the S/D-treated OS. The contact angle of the sediment surface was 40°, and the initial apparent viscosity of the OS was 56 Pa·s. First, the saturated hydrocarbons and aromatic hydrocarbons on the sediment surface were adsorbed by the monolayer adsorption on SL. Stubborn, cohesive oil agglomerates were dissociated. Sulfate radical anion (SO4−·) with a high oxidation potential, was formed from sodium persulfate. The oxidation reaction occurred between SO4−· and polycyclic aromatic hydrocarbons. A good three-phase separation effect was attained. The oil recovery reached 89.65%. This provides theoretical support for the efficient clean separation of oily sludge.

Persulfate contribution to photolytic and pulsed corona discharge oxidation of metformin and tramadol in water

Degradation and mineralization of antidiabetic metformin (MTF) and opioid tramadol (TMD) in water were studied in UV photolytic oxidation and pulsed corona discharge (PCD) combined with extrinsic persulfate (PS) as UV/PS and PCD/PS systems. The effect of PS dose variation on the oxidation rate and efficiency was assessed. The UV/PS combination showed considerable effect in MTF and TMD removal, enhancing the removal of TOC up to 60–65% at maximum applied PS dose, thus providing the highest cost efficiency. As for the PCD/PS oxidation, the synergy was noticed for MTF, moderately increasing the oxidation rate and mineralization at somewhat increased expense. The PS addition to PCD treatment, however, demonstrated no effect on TMD oxidation. The highest energy efficiency in MTF and TMD degradation was thus showed by non-assisted PCD treatment with an energy yield at 90% conversion of the target compound of 5.6 and 13 g kW-1 h-1, respectively, confirming its practical applicability. The effective mineralization of the target compounds in persulfate photolysis makes it promising for use in advanced water purification. To assess the environmental safety of the studied oxidation processes, the acute toxicity of the treated MTF and TMD solutions to luminous bacteria (Vibrio fischeri) was examined.

Feasibility of UVC laser-activated persulfate with concentrated beam for micropollutant degradation in water

A novel UV light, UVC laser, was used to activate persulfate (PS) for degrading bisphenol A (BPA) in this study. This new light source can emit concentrated beam, and achieve 74.5% of BPA removal within only 60 s when activating PS. Sulfate radicals (SO4−) and hydroxyl radicals (OH) were identified in the UVC laser/PS system. In the case of the same total irradiance energy, the concentrated beam performed a better removal efficiency of BPA than the diffused beam. Compared with the diffused beam, the steady-state concentrations of SO4− and OH under concentrated beam increased by 26.21% and 361.25%, respectively. In addition, the depth-to-diameter ratio (h/D) of the reaction vessels also had a significant effect on the removal efficiency of BPA and the highest degradation rate obtained at h/D = 0.65. High UVC laser intensity, high PS dosage, and circumneutral pH conditions could promote BPA degradation, whereas the presence of water matrix (including chloride, bromide, bicarbonate, and natural organic matter) exhibited opposite effects. The BPA degradation intermediates in the UVC laser/PS system were identified by LCMS and the BPA degradation pathways were proposed accordingly. This study is the first one illustrating the influence of laser beam types, h/D ratio of the reactor vessel, and water matrix on UVC laser/PS application in water treatment process, which can provide essential knowledge for removing micropollutants in water using the novel UVC laser/PS AOP.

Perspective on Fe0-PS synergetic effect and reaction mechanism in the thallium(I) contaminated water treatment

Due to extreme toxicity of the element of thallium (Tl), increasing aqueous Tl pollution incidents have aroused growing concerns. As the prevalent and stable form, i.e., monovalent Tl, the highly efficient removal methodologies of Tl(I) from (waste)water remains limited and challenging. In this study, an advanced oxidation method, the feasibility of using zero valent iron (Fe0) coupled with persulfate (PS) to treat Tl(I)-containing synthetic wastewater was investigated. Its influence parameters, including reaction time, initial Tl concentration, dosages of PS and Fe0, initial and coagulation pH, temperature, coexisting ions and organic matter (NO3−, SO42−, Cl− and HA) were examined. The results revealed that the system can be applied to a wide range of pH and temperature and the reaction equilibrium can be reached in about 30 min. Favorable Tl(I) removal rate (>98%) was observed in the synthetic wastewater with medium and relatively high Tl(I) concentration (≤0.250 mM). The analyses of characterization results including electron spin resonance spectrometer and X-ray photoelectron spectroscopy indicated that ·OH played a vital role in the removal of Tl(I), which was oxidized and removed by co-precipitation. Fe0 can be served as a stable source of Fe2+ to efficiently catalyze PS. The remaining Fe0 can be easily separated because of its magnetism, assuring the promising reusability of the reactant. The study aims to provide references for treatment of real Tl polluted wastewater.

Efficient degradation of imidacloprid in soil by thermally activated persulfate process: Performance, kinetics, and mechanisms

Imidacloprid (IMI) as a first-generation commercial neonicotinoid has been frequently detected in the environment in recent years. In this study, the efficient degradation of IMI in soil by a thermally activated persulfate (PS) process was investigated. The degradation efficiencies of IMI were in the range of 82–97% with the PS dosage of 10 mM, when the initial concentrations of IMI were 5–50 mg/kg in the soil. Degradation of the IMI was fitted with a pseudo-first-order kinetic model under different reaction temperatures. Inhibition effects of the common inorganic anions on the IMI degradation in the system followed the order Cl- > HCO3- > H2PO4- > NO3-. Soil pH and soil organic matter were also main factors affecting the degradation of IMI. The degradation efficiencies (64–97%) of three other typical neonicotinoids (acetamiprid, clothianidin, and dinotefuran) indicated that the thermally activated persulfate process could be used for remediation of neonicotinoid-contaminated soil. Quenching experiments indicated that the major reactive species in IMI degradation were SO4•-, O2•-, and •OH. Six degradation intermediates of IMI were inferred in the soil, and degradation pathways of IMI included hydroxylation, denitrification, C-N bond break and further oxidation.

Effect of activated persulfate on the properties of contaminated soil and degradation behavior of PAHs

Sulfate radical-based advanced oxidation processes have been applied in the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil, during which sulfate can be activated in different ways. In this work, effects of four different ways (FeSO4, NaOH, H2O2, and Heat) activated sodium persulfate (PS) on PAHs removal and soil physicochemical properties (pH, organic matter, functional groups, surface morphology, and partial heavy metal elements) were compared, and the influencing factors and mechanism of soil PAHs removal by thermally activated PS were also studied. The results showed that at the dosage of 3% of persulfate, the removal efficiency of PAHs followed the sequences of Heat (91.4%) > FeSO4 (86.6%) > H2O2 (86.2%) > NaOH (72.9%). However, thermal activation decreased the soil pH and organic matter content more significantly than other treatments. The reaction tended to reach equilibrium at 6 h when the dosage of persulfate was 3% and the activation temperature was 60 °C, and the reaction obeyed pseudo-first-order kinetics. Through quenching experiments, it was found that the free radicals playing a dominant role in the oxidation process were sulfate radicals. Compared with pH, liquid to soil (L/S ratio) and the temperature had more significant impacts on the degradation efficiency of PAHs.

Tetracycline degradation by persulfate activated with novel magnetic composite ferrocene/chitosan@Fe3O4

AbstractBACKGROUNDFerrocene (Fc) is a chemically stable, safe and non‐toxic substance with excellent redox performance and is often used to activate various oxidants. However, Fc is a nanoscale non‐magnetic material, which needs a suitable carrier such as chitosan (CS) to be fixed and being compounded with magnetic material for recycling.RESULTSA new magnetic catalyst, Fc/CS@Fe3O4, was prepared for activating persulfate (PS) to degrade tetracycline (TC) in water. The catalyst prepared was characterized by X‐ray powder diffraction, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and vibrating sample magnetometry, and the effects of the dosage of PS and catalyst, pH, temperature, coexisting anions and fulvic acid on TC degradation were investigated. The results showed that the removal of TC could be promoted by increasing the temperature, and acidic conditions are more beneficial to TC degradation than alkaline conditions. Cl−, CO32−, HCO3− and fulvic acid could all inhibit the degradation of TC. Light and catalyst had a synergistic activation effect on PS. Under conditions of PS and catalyst dosage all 400 mg L−1, temperature 25° C, TC concentration 30 mg L−1 and initial pH 5, TC could be completely degraded within 60 min. Both SO4−• and HO• contributed to TC degradation, and SO4−• was the main active species in the degradation system.CONCLUSIONThe results indicate that Fc/CS@Fe3O4 has good catalytic activity and stability, and has potential application in the treatment of antibiotics in water. © 2022 Society of Chemical Industry (SCI).

Heterogeneous catalytic oxidation of tetracycline hydrochloride based on persulfate activated by Fe3O4/MC composite

In this study, a novel magnetic mesoporous carbon composite (Fe3O4/MC) was prepared by manganese carbonate (MnCO3) as the template to activate persulfate (PS) for tetracycline hydrochloride (TC) degradation. The characterization results showed that Fe3O4 nanoparticles were evenly distributed on the surface of MC, and Fe3O4/MC had the large surface area of 433.88 m2∙g−1. When the initial TC concentration was 50 mg·L−1, Fe3O4/MC dosage was 0.0336 g, PS dosage was 0.0476 g and the reaction temperature was 30 °C, Fe3O4/MC + PS system could degrade 92.9% of TC within 90 min. TC degradation efficiency increased with the increase of Fe3O4/MC dosage and temperature, but decreased with the increase of TC initial concentration and pH value. The increase of PS concentration first improved TC degradation efficiency, and then was not conducive to its degradation. The quenching experiments indicated that the sulfate radical (SO4•−), superoxide radical (•O2–) and singlet oxygen (1O2) in Fe3O4/MC + PS system contributed to TC degradation. Meanwhile, the toxicity evaluation of the degradation products confirmed that the toxicity of TC in Fe3O4/MC + PS system was greatly reduced. Totally, this study systematically investigated the performance of the Fe3O4/MC + PS system for TC removal, laying a theoretical and practical foundation for treatment of potential antibiotic wastewater (ppm range) in the future.

Removal of N-methyldiethanolamine in wastewater by using electro-activated persulfate: Mechanisms and applicability

In this study, the feasibility of N-methyldiethanolamine (MDEA) degradation by electrochemical activation of persulfate (PS) was evaluated. Effects of PS dosing, voltage and initial pH on the removal rate of MDEA were investigated. The removal rate of COD and TOC were more than 80% and 60% respectively when PS dosage was 0.84 mM, pH = 7 and voltage (U) was 50 V. Due to the synergistic effect between SO4-· and three-dimensional (3D) electrochemical system, the removal rate was increased by 23–61% compared to the system acting alone. Kinetic analysis showed that the degradation process followed a pseudo-first-order model reaction and that the apparent reaction rate constant (kobs) increased with increasing voltage over a range of values, but was greater at PS dosing levels of 0.84 mM and at neutral pH. Two possible pathways for the degradation of MDEA were proposed by Gas Chromatography-Mass Spectrometry (GC-MS) detection of the degradation products. The theoretical sulfate radical content of 1.653 × 10−5 mol/L was also calculated by dynamic model when the dosage of PS was 0.84 mM and the initial pH was 5.

Persulfate activation of CuS@Ti3C2-based MXene with Bi-active centers toward Orange II removal under visible light

The Ti3C2-based MXene with unique lamellar nanostructure and high conductivity is expected to effectively improve photocatalytic ability of composites as a cocatalyst. Herein, two dimensional Ti3C2-based MXene nanosheets decorated with copper sulfide particles (CuS@MXene) were synthesized by hydrothermal treatment to boost catalytic persulfate (PS) activation under light, exhibiting remarkable reactivity and stability for the rapid removal of Orange II. The phase composition of CuS@MXene was detected by X-ray diffraction (XRD), the morphology of CuS@MXene was characterized by scanning electron microscope (SEM), and the results of X-ray photoelectron spectroscopy (XPS) proved the elemental composition and valence state of elements in the CuS@MXene. The dosage of PS and initial pH of solution were the main factors affecting the removal rate of Orange II, and the quenching experiment showed that 1O2 was the primary reactive species for the removal of Orange II in CuS@MXene -PS system. In addition, this study showed that CuS@MXene provided bi-active centers for PS activation, which was mainly attributed to the rapid charge transfer between dual electron-rich active centers of Cu and Ti. This system may be applicable to the degradation of other challenging organic pollutants.

Aerobic and anaerobic regulation induced different degradation behaviors of parachloronitrobenzene in soil by microwave activated persulfate oxidation

Persulfate (PS) oxidation is a promising soil remediation technology. Information regarding pollutant degradation in soil by PS-based technique under different oxidizing atmospheres is still lacking. In this study, p-chloronitrobenzene (p-CNB) degradation in soil in a microwave (MW) activated persulfate (MW/PS) system was evaluated under aerobic and anaerobic conditions. The experimental results demonstrated that anaerobic condition was more conducive to p-CNB degradation. Only 46% of p-CNB was degarded within 60 min treatment under aerobic conditions, but it increased to more than 80% under anaerobic conditions. The increase of PS dosage and MW temperature both promoted p-CNB degradation. SO4•− and •OH played important roles in p-CNB degradation under aerobic conditions, and p-CNB was mainly converted to hydroxylated byproducts including 4-nitrophenol and hydroquinone. The reductive radical S2O8•- was responsible for p-CNB degradation under anaerobic conditions, and aminated byproducts were generated. The residual toxicities of these byproducts were predicted to be decreased, compared with those of p-CNB. Furthermore, by regulating the aerobic and/or anaerobic conditions, other pollutants including pyrene and ethion were also effectively removed in the MW/PS system. Overall, this study highlighted new insights into degradation behaviors of pollutants by MW/PS treatment via aerobic and anaerobic regulation.