Initial Persulfate Concentration Research Articles

Tannic acid promotes the activation of persulfate with Fe(ii) for highly efficient trichloroethylene removal.

Trichloroethylene (TCE) is an Environmental Protection Agency (EPA) priority pollutant that is difficult to be removed by some remediation methods. For instance, TCE removal using persulfate (PS) activated by ferrous iron (Fe(ii)) has been tested but is limited by the unstable Fe(ii) concentration and the initial pH of contaminated water samples. Here we reported a new TCE removal system, in which tannic acid (TA) promoted the activation of PS with Fe(ii) (TA-Fe(ii)-PS system). The effect of initial pH, temperature, and concentrations of PS, Fe(ii), TA, inorganic anions and humic acid on TCE removal was investigated. We found that the TA-Fe(ii)-PS system with 80 mg L-1 of TA, 1.5 mM of Fe(ii) and 15 mM of PS yielded about 96.2-99.1% TCE removal in the pH range of 1.5-11.0. Radical quenching experiments were performed to identify active species. Results showed that SO4˙- and ˙OH were primarily responsible for TCE removal in the TA-Fe(ii)-PS system. In the presence of TA, the Fe-TA chelation and the reduction of TA could regulate Fe(ii) concentration and activate persulfate for continuously releasing reactive species under alkaline conditions. Based on the excellent removal performance for TCE, the TA-Fe(ii)-PS system becomes a promising candidate for controlling TCE in groundwater.

Exploring the scalability of solar-activated persulfate with iron-EDDS in raceway pond reactors for advanced wastewater treatment

In this study, the removal of microcontaminants (MCs) by the activation of persulfate (PS) with Fe(III)-EDDS under natural solar radiation in a low-cost raceway pond reactor (RPR) was investigated. The primary focus was to evaluate the effect of the Fe(III)-EDDS molar ratio, initial iron concentration, PS concentration, and initial pH on process performance while using sulfamethoxazole (SMX) and carbamazepine (CBZ) as model MCs. The investigation encompassed three different water matrices: natural water, synthetic municipal wastewater treatment plant (MWWTP) secondary effluent, and actual MWWTP secondary effluent. During experiments in natural water, it was found that 0.1 mM Fe(III) at a 1:2 molar ratio and 0.2 mM Fe(III) at a 1:1 molar ratio resulted in the most adequate operational conditions. Further experiments revealed a general decrease in process efficiency due to water matrix effects; however, this could be compensated by increasing the initial PS concentration and decreasing the initial operation pH. For example, the use of 0.2 mM Fe(III) at a 1:1 Fe(III):EDDS molar ratio, with 2 mM PS at pH 6, allowed for an 80% removal of the MCs sum in approximately 20 min, along with a significant decrease in chronic toxicity (Selenatrum Capricornutum) when working with actual waters. Nonetheless, the final experiment, focused on simultaneous MCs removal and wild bacteria inactivation in actual MWWTP secondary effluent, showed only a 1.6–1.8 log reduction of Escherichia coli, total coliforms, and Enterococcus faecalis. As such, further studies about the solar/Fe(III)-EDDS/PS process are needed to explore new strategies that improve its disinfection efficiency.

Hybrid water treatment flow plant using hydrogen peroxide-based electro-activated persulfate and photoelectro-Fenton processes: The combustion of Reactive Orange 16 dye

This paper implements an innovative hybrid water treatment process in a flow plant using hydrogen peroxide-based electro-activated persulfate (EPS-H2O2) combined with photoelectro-Fenton (PEF) method. The Reactive Orange 16 (RO16) azo dye was used as a persistent organic pollutant (POP) model. A filter-press reactor utilized a Ti|RuO2 plate and a gas diffusion electrode (GDE) as the anode and cathode. In EPS-H2O2, persulfate (PS) reacts with H2O2 yielding hydroxyl (•OH) and sulfate (SO4·-) radicals. In PEF, H2O2 reacts with Fe2+ producing more •OH, completing the TOC removal in the presence of UVA light. The influence of pH (3–9), initial PS concentration (0.5–1.5 mM), initial RO16 dye content (30–50 mg L-1 TOC), applied current density (j, 5–30 mA cm−2), and mean linear flow velocity (u, 7.3–29.1 cm s−1) on the EPS-H2O2 process efficiency was examined. The best trial for EPS-H2O2 achieved 37% TOC removal in 360 min electrolysis at j = 10 mA cm−1, u = 14.6 cm s−1, and PGDE = 3 psi. Subsequently, at t ≥ 360 min, the synergistic effect between the EPS-H2O2 and PEF processes was carried out by adding 0.5 mM Fe2+ and UVA light. The best hybrid (EPS-H2O2 + PEF) process test reached 98% mineralization with 30% current efficiency and 0.060 kWh (g TOC)-1 electrolytic energy consumption. Six carboxylic acids were determined as the main intermediaries, whereas ammonium was the main nitrogen compound throughout the EPS-H2O2 and PEF processes.

The Kinetic Simulation of Persulfate Activation by Nano-Ferrosoferric Oxide

Nano-ferrosoferric-oxide (nFe3O4)-activated persulfate (PS) technology was used to remove pollutant bisphenol A (BPA) in water. The effects of nFe3O4 concentration, PS concentration, BPA concentration, temperature, and pH were investigated in terms of the degradation effect of BPA. The results showed that more PS dosage and lower BPA concentration could improve the degradation rate of BPA. When other conditions were constant, the degradation rate of BPA increased with the increase of temperature. When pH was 5, the degradation rate of BPA was the highest. When the initial PS concentration and pH were changed, the degradation rate of BPA was consistent with the pseudo-secondary kinetic model. Under other conditions, the degradation rate of BPA was consistent with the pseudo-first-order kinetic model. Sulfate radical (SO4•−) produced by nFe3O4/PS system was mainly responsible for the degradation of BPA.

Peroxydisulfate activation by CuO pellets in a fixed-bed column, operating mode and assessments for antibiotics degradation and urban wastewater disinfection.

A fixed-bed column packed with copper oxide pellets (FBC-CuO) combined with peroxydisulfate (PDS) as a primary oxidant was assessed as an option for simultaneously wastewater decontamination (antibiotics) and disinfection (bacteria, viruses, and protozoa). Preliminary to these experiments, phenol was used as the target molecule to investigate the working mode of FBC-CuO under various operating conditions, such as varying flow rates, initial persulfate, and phenol concentrations. Then, the removal of a mix of five representative antibiotics (amoxicillin (AMX), cefalexin (CFX), ofloxacin (OFL), sulfamethoxazole (SMX), and clarithromycin (CLA)) in secondary treated urban wastewater (STWW) was evaluated. AMX, CFX, and OFL were effectively removed by simply flowing through the FBC-CuO, and the addition of PDS (500µM) systematically enhanced the degradation of all targeted antibiotics, which is also the necessary condition for the removal of SMX and CLA. Urban wastewater disinfection was evaluated by monitoring targeted pathogens originally in the STWW. A significant reduction of Escherichia coli, Enterococcus, F-specific RNA bacteriophages was observed after the treatment by FBC-CuO with 500µM PDS. X-ray diffraction measurement and scanning electron microscopy performed on CuO pellets before and after treatment confirmed that the structure of the catalyst was preserved without any phase segregation. Finally, quantification of Cu(II) at the outlet of FBC-CuO indicate a non-negligible but limited released. All these results underline the potential of the FBC-CuO combined with PDS at the field scale for the degradation of micropollutants and inactivation of pathogens in wastewater.

Study on cooperative treatment of natural gas pipeline cleaning wastewater and membrane module

Membrane module and pigging wastewater are common pollutants in natural gas transmission process. The treatment of these pollutants is difficult. In this paper, ultrasonic (US), persulfate (PS) and ultrasonic coupled persulfate were used to degrade organic matter in natural gas cleaning wastewater. The effects of pH, initial PS concentration, ultrasonic power, PS dosing batch and other factors on chemical oxygen demand (COD) degradation efficiency of pigging wastewater were investigated. The experimental results show that the optimal treatment effect can be obtained when the dosage of sodium PS is 80g/L, pH=4, the dosing number is 5, and the ultrasonic power is 840 W. After 6 h of reaction, the removal rate of COD can reach 80.08 %. Considering the synergistic treatment of the ultrasonic coupling PS on the solid-liquid pollutant, we adjust the ultrasonic power to 55W (frequency is 40kHz), pH=4.5, dosing twice (total dosage 150mg/L), and the final COD concentration below 100mg/L. However, when pre-ultrasonic activated persulfate in clear water, COD removal rate can reach 95.35 %, which can meet the effluent requirements.

Stability and Removal of Benzophenone-Type UV Filters from Water Matrices by Advanced Oxidation Processes.

Benzophenone (BP) type UV filters are common environmental contaminants that are posing a growing health concern due to their increasing presence in water. Different studies have evidenced the presence of benzophenones (BP, BP-1, BP-2, BP-3, BP-4, BP-9, HPB) in several environmental matrices, indicating that conventional technologies of water treatment are not able to remove them. It has also been reported that these compounds could be associated with endocrine-disrupting activities, genotoxicity, and reproductive toxicity. This review focuses on the degradation kinetics and mechanisms of benzophenone-type UV filters and their degradation products (DPs) under UV and solar irradiation and in UV-based advanced oxidation processes (AOPs) such as UV/H2O2, UV/persulfate, and the Fenton process. The effects of various operating parameters, such as UV irradiation including initial concentrations of H2O2, persulfate, and Fe2+, on the degradation of tested benzophenones from aqueous matrices, and conditions that allow higher degradation rates to be achieved are presented. Application of nanoparticles such as TiO2, PbO/TiO2, and Sb2O3/TiO2 for the photocatalytic degradation of benzophenone-type UV filters was included in this review.

Degradation of hexacyanoferrate (III) ion by the coupling of the ultraviolet light and the activation of persulfate at basic pH

The ultraviolet light activation of persulfate (PS) under alkaline conditions was evaluated for treating hexacyanoferrate (III) ion ([Fe(CN)6]3-). The effect of the wavelength type (i.e., UVA and UVC), initial PS concentration (0.3, 0.6, and 0.9 g L−1), and pH value (11 and 13) on the degradation of 50 mg L−1 of [Fe(CN)6]3- were studied. Finally, the role of the main degrading agents (SO4•-, O2•-, or HO•) involved in the degradation process was determined using scavengers and a degradation pathway for [Fe(CN)6]3- was proposed. Results show that [Fe(CN)6]3- can be decomposed by UVC light, while UVA is not effective neither in [Fe(CN)6]3- photolysis nor in the activation of PS. Alkaline activation alone at pH 13 can also not degrade the cyanocomplex. However, the combination of UVC with PS (0.3 g L−1) at pH 13 showed high efficiency in the elimination of [Fe(CN)6]3-, achieving 93.3% of removal after 125 min of treatment. The highest CN- release and Fe dissolved removal also occurs at pH 13 and 0.3 g L−1 PS. Further increases in initial PS concentrations may lead to an excess of radicals in solution, resulting in detrimental recombination reactions that affect the efficiency of the process. Quenching tests showed that the importance of radicals involved in the degradation of [Fe(CN)6]3- follows the order: HO• > O2•- >>> 1O2 or SO4•-, and allowed to demonstrate that singlet oxygen could participate in the UVC photolysis of [Fe(CN)6]3-. All these results suggest the feasibility of this technology to treat this type of industrial wastewater efficiently.

Effect of the presence of inorganic ions and operational parameters on free cyanide degradation by ultraviolet C activation of persulfate in synthetic mining wastewater

This work studied the influence of several parameters on free cyanide (CN−) degradation (50 mg L−1) by the UVC-activated persulfate (PS) at alkaline conditions (UVC/PS). Firstly, photolysis and alkaline activation of PS were evaluated. Then, the effect of initial PS concentration (0.2, 0.4, and 0.6 g L−1) and dissolved oxygen in solution (absence/presence) were studied. Lastly, the influence of phosphate, carbonate, and nitrate presence at different concentrations (50, 150, 350, and 500 mg L−1) on CN− elimination was tested. Additionally, the electric energy per order (EEO), a measure of the energy consumption in the process was determined, and a mechanistic view of CN− degradation was proposed. The results show that photolysis and alkaline activation of PS degraded 8 and 11% of CN−, respectively, whereas their combination presented a synergistic effect on CN− pollutant elimination. While oxygen had a vital role in photolysis due to the formation of 1O2 to oxidize CN− to CNO−, HO• and SO4•− were primarily responsible for CN− degradation by UVC/PS. It was also found that cyanide removal followed a pseudo-first-order kinetics whose apparent reaction rate constant (k) increased from 0.0104 to 0.0297 min−1 as the initial concentration of PS increased from 0.2 to 0.6 g L−1, indicating a strong dependency of the removal efficiency on the PS amount. Remarkably, cyanide degradation by the combined UVC/PS showed a high CN− conversion and selectivity even in the presence of high concentrations of phosphate, carbonate, and nitrate ions (500 mg L−1), which resulted in CN− removals higher than 80% after 60 min of degradation treatment. Furthermore, the EEO values were similar in the presence and absence of phosphate or carbonate; however, they decreased slightly with nitrate presence. All these results suggest the feasibility of the combined UVC/PS process for the elimination of cyanide such as that found in mining wastewater.

Reactive Green 19 degradation using O3/S2 O8(2-) process: Intermediates and Proposed Degradation Pathway

ABSTRACT The massive drawbacks of conventional wastewater treatment have led to a demand investigation about new advanced wastewater treatment technology. The issue can be addressed via advanced oxidation processes (AOPs) as witnessed recently. Therefore, the objective of this study was to investigate the performance of ozone/persulfate () process to assess its use as potential degradation of diazo dye which is Reactive Green 19 (RG19). In this work, efficiency, color, and COD removal were investigated over a range of initial pH, persulfate concentration and initial concentration of RG19. The amount of sodium persulfate () was varied at different levels (20–100 mM) relative to precursor radical to assess the optimum usage of persulfate concentration for RG19 degradation. Evidence that RG19 could degrade efficiently had occurred at 100 mg/L, initial pH 9, 60 mM persulfate concentration was identified by FTIR and GC/MS analysis. The results revealed that RG19 could achieve complete decolorization easily as compared to mineralization. In addition, RG19 degradation pathway gave the best representation of level degradation. The GC/MS and FTIR results exhibited the proposed RG19 degradation pathway that involved the characteristic of sulfonic group, accompanied with became as an indicator of their structure broken down one by one. The degradation products such as oxalic acid, formic acids and others were analyzed and finally converted to carbon dioxide and water. The diazo dye structure itself aided with has its superior characteristic as an aid for the efficient degradation process.

Construction of ternary CuO/CuFe2O4/g-C3N4 composite and its enhanced photocatalytic degradation of tetracycline hydrochloride with persulfate under simulated sunlight

In this study, a graphitic carbon nitride (g-C3N4) based ternary catalyst CuO/CuFe2O4/g-C3N4 (CCCN) is successfully prepared thorough calcination method. After confirming the structure and composition of CCCN, the as-synthesized composites are utilized to activate persulfate (PS) for the degradation of organic contaminant. While using tetracycline hydrochloride (TC) as pollutant surrogate, the effects of initial pH, PS and catalyst concentration on the degradation rate are systematically studied. Under the optimized reaction condition, CCCN/PS is able to give 99% degradation extent and 74% chemical oxygen demand removal in assistance of simulated solar light, both of which are apparently greater than that of either CuO/CuFe2O4 and pristine g-C3N4. The great improvement in degradation can be assignable to the effective separation of photoinduced carriers thanks to the integration between CuO/CuFe2O4 and g-C3N4, as well as the increased reaction sites given by the g-C3N4 substrate. Moreover, the scavenging trials imply that the major oxidative matters involved in the decomposition are hydroxyl radicals (•OH), superoxide radicals (•O2−) and photo-induced holes (h+).

Surfactant-assisted removal of 2,4-dichlorophenol from soil by zero-valent Fe/Cu activated persulfate

The organic compounds contaminated soil substantially threatens the growth of plants and food safety. In this study, we synthesis zero-valent bimetallic Fe/Cu catalysts for the degradation of 2,4-dichlorophenol (DCP) in soils with persulfate (PS) in combination of organic surfactants and exploring the main environmental impact factors. The kinetic experiments show that the 5% (mass) dosage of Fe/Cu exhibits a higher degradation efficiency (86%) of DCP in soils, and the degradation efficiency of DCP increases with the increase of the initial PS concentration. Acidic conditions are favorable for the DCP degradation in soils. More importantly, the addition of Tween-80, and Triton-100 can obviously desorb DCP from the soil surface, which enhances the degradation efficiency of DCP in soils by Fe/Cu and PS reaction system. Furthermore, the Quenching experiments demonstrate that S O 4 - · and OH are the predominant radicals for the degradation of DCP during the Fe/Cu and PS reaction system as well as non-radical also exist. The findings of this work provide an effective method for remediating DCP from soils.

Degradation of HCHs by thermally activated persulfate in soil system: Effect of temperature and oxidant concentration

Soils contaminated with hexachlorocyclohexanes (HCHs) are a legacy of the heavy use of lindane during the 20th century. This pesticide production generated large amounts of residues of other HCH isomers, which were habitually mismanaged. The sediments treated in this work (coming from an old lindane landfill) are an example of this environmental problem of global dimensions. The efficient remediation of these sediments, mainly contaminated with β-HCH (99 mg kg−1) and α-HCH (254 mg kg−1) isomers, is still a challenge. The thermal activation of persulfate (PS) required excessive reaction times, which could be reduced by optimizing the variables of the process. This study aims to explore the effect of using higher reaction temperatures (35, 45, and 55 ºC) and initial oxidant concentrations (10, 20, 40, 60, and 80 g L−1). Batch experiments (liquid/soil = 2/1, 100 rpm) were performed to evaluate the influence of these two variables in HCHs abatement, dechlorination degree, generation of intermediate compounds, and oxidant consumption. An increase in the reaction temperature accelerates the pollutant oxidation and dechlorination rate and decreases the concentration of chlorinated byproducts. The initial PS concentration also plays a crucial role in HCHs degradation. At selected operating conditions (55 ºC, PS = 80 g L−1), a conversion of HCHs around 83% was achieved, without chlorinated byproducts (chlorine balance ≈ 100%) at only 9 days of treatment. A plausible pathway for the degradation of HCHs-polluted soils by thermally activated PS has been proposed from the identified species, involving a scheme of series-parallel reactions.

Degradation of benzothiazole pollutant by sulfate radical-based advanced oxidation process

ABSTRACT Benzothiazole (BTH) is an aromatic heterocyclic compound with wide industrial applications. In view of its toxicity and wide environmental presence, previous efforts have been made to decompose BTH via different degradation pathways. However, due to its recalcitrant nature, conventional biological treatment methods cannot completely degrade BTH in the wastewater. In this study, sulfate radical-based advanced oxidation process (AOP) technique has been adopted to degrade BTH in aqueous phase. Persulfate (PS) was employed as radical promotor to generate sulfate radical via heat activation. Degradation of BTH by thermally activated persulfate via AOP has been experimentally evaluated in a systematic manner. Laboratory efforts have been made to examine the impact of a number of physiochemical parameters including the type of oxidants, reaction temperature, initial concentrations of PS and BTH, solution pH, and the presence of anionic species. It shows that a higher BTH degradation rate can be achieved by lowering BTH initial concentration or increasing PS concentration. Increasing solution pH or the presence of 10 mM of Cl−, Br−, , or species can decrease BTH degradation rate. Furthermore, the primary radical(s) responsible for BTH degradation have been identified as sulfate radical at an acidic aqueous condition, and hydroxyl radical and sulfate radical combined at a basic condition. This study provides the necessary theoretical and technical foundations for BTH degradation via sulfate radical-based AOP technique. The conclusions from this study can substantially promote the field application of AOP, especially sulfate radical-based AOP technique, for BTH degradation in wastewater treatment process.

Evaluate the effectiveness of the UV/ persulfate process to remove catechol from solution aqueous

<p>Catechol is used as an antioxidant, fungicide, and polymerization inhibitors in a variety of industries such as petrochemical. Catechol must be removed from effluents before it enters to environment. This study aimed to investigate combined UV radiation and persulfate process in removal of catechol from aqueous solutions. All experiments were performed in a batch reactor. Data analysis were done with Design of Experiment (DoE) software. The effects of various variables such as pH, initial persulfate concentration, and initial Catechol concentration were investigated. The findings indicated with increases in persulfate concentration and decrease in catechol concentrations, the removal efficiency increased. Acidic pH and UV radiation were the leading factors in removal of catechol. The optimum pH, persulfate concentration, and catechol concentration were obtained 7, 0.04 M, and 100 mg l-1, respectively. More removes of catechol was achieved in optimum conditions within contact time of 60 min. The synergic effects of UV and persulfate radical were about 88%. Approximately 60% of catechol was mineralized within contact time of 60 min. Persulfate radicals resulting from UV/S2O82- were the main effective oxidants in removal and mineralization of catechol. Owing to high removal efficiency of persulfate compounds which are, also, abundant and inexpensive, these can be applied in removal of persistent organic pollutants from aqueous solutions.</p>

Study of Fe3O4/PS System in Degrading BPA in Aqueous Solution

The degradation of bisphenol A (BPA) by Fe3O4/persulfate system was investigated in aqueous solution. The influences of the initial concentrations of Fe3O4, persulfate (PS) and BPA, pH value, and initial reaction temperature on BPA removal were studied. The radical species was investigated by adding excessive dose of scavenger (methanol (MeOH) and tert-butanol (TBA)) into Fe3O4/PS system for the purpose of radical scavenging. The degradation products of BPA were detected by gas chromatography-mass spectrometry (GC-MS). The recyclability of Fe3O4 was also evaluated. The BPA removal rate of 80.7% was achieved under the following conditions: [BPA]0 = 1 mg L-1, [PS]0 = 0.2 mM, [Fe3O4]0 = 0.1 g L-1, T0 = 20 ± 1 ºC, pH0 = 6.8 ± 0.2. The results confirmed that the main free radicals in the reaction process were sulfate radicals, followed by hydroxyl radicals. Some intermediate products of BPA degradation, such as phenols, benzoquinones and benzoic acid were identified by GC-MS.

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.

Synergistically enhanced heterogeneous activation of persulfate for aqueous carbamazepine degradation using Fe3O4@SBA-15

The exploration of low-cost, high-performance and stable catalytic materials for sulfate radical-based advanced oxidation processes (SR-AOPs) is of great importance. This study presents Fe3O4-wrapped SBA-15 mesoporous silica catalyst (Fe3O4@SBA-15) for persulfate (PS) activation. The Fe3O4@SBA-15 with an Fe3O4 to SBA-15 weight ratio of 3:1 exhibited an impressive carbamazepine (CBZ) removal efficiency of ~100% after 30 min of SR-AOP at an initial pH of 3.0, a temperature of 25 °C, an initial PS concentration of 300 mg L−1 and a catalyst concentration of 0.50 g L−1. The primary oxidizing species produced in the system were identified as SO4− and HO by electron paramagnetic resonance spectra and radical quenching experiments. Benefiting from the synergetic effects of improved Fe3O4 dispersion and enhanced adsorption of CBZ and PS by SBA-15, the as-obtained heterogeneous Fe3O4@SBA-15 catalysts offer large numbers of active sites for free radical generation and high surface concentrations of CBZ and PS for SR-AOPs, as verified by physicochemical characterization and Langmuir−Hinshelwood model analysis. In addition, the activity of Fe3O4@SBA-15 was maintained throughout six successive cycling tests. Various inorganic anions, including Cl−, NO3−, HCO3−, and CO32−, as well as organic material in natural water, exert a negative impact on the Fe3O4@SBA-15 catalyzed SR-AOPs and deserve special attention.

Degradation of aniline by ferrous ions activated persulfate: Impacts, mechanisms, and by-products

Wastewater contains a large number of anions and organics which can scavenge reactive radicals and limit the application of sulfate radical-based advanced oxidation processes (SR-AOPs) in practical engineering. Here, we studied the removal rate and mechanism of aniline by SR-AOPs in different influencing factors, such as sodium persulfate dosage, ferrous ions dosage, solution pH, Cl-, HCO3-, NO3-, and other organic matter. By recognizing and analyzing free radicals, we concluded that SO4•- plays a major role in aniline degradation. The aniline removal rate increased with the initial concentrations of persulfate and ferrous ions, but aniline degradation was inhibited by excessive dosage. The aniline removal rate by ferrous-ions-catalyzed persulfate was higher under acidic conditions and could be improved under alkaline conditions if no ferrous ions were added. The addition of bicarbonate ions inhibited aniline removal, and the addition of nitrate ions barely caused the effect. While the addition of chloride ions promoted aniline degradation, which was confirmed that HClO generated from the reacting of Cl- and persulfate played a key role. However, TOC indicated that aniline was not completely mineralized in the process. Further analysis of the products from GC-MS demonstrated that chloride-ion additions produced some harmful halogenated by-products. Our results can act as a basis for developing processes for the aniline degradation in wastewater.

Heterogeneous activation of persulfate by activated carbon supported iron for efficient amoxicillin degradation

Activated carbon supported iron (Fe-AC) was prepared as an efficient catalyst for activating persulfate (PS) to degrade amoxicillin (AMO). The complete degradation of AMO in Fe-AC/PS system was attained within 10 min. The AMO degradation efficiency increased as the initial catalyst dosage and PS concentration increased but was not affected by the initial pH. AMO degradation fitted the pseudo-first-order kinetic model, and the apparent activation energy was calculated to be 28.11 kJ⋅mol−1 using the Arrhenius Equation. Both hydroxyl radical and sulfate radical were identified during AMO degradation by electron paramagnetic resonance spectroscopy and radical scavenger tests. The surface-adsorbed hydroxyl radicals played significant roles in AMO degradation. In addition, tests using ADP1_recA_lux bioreporter were performed to assess the degrees to which the solutions containing degraded AMO were toxic. The Fe-AC/PS system markedly decreased microorganism growth inhibition and genotoxicity caused by the solution containing degraded AMO, providing important information for applying Fe-AC/PS technology to application.