Activated Persulfate Oxidation Process Research Articles

Recent Advancements in the Treatment of Emerging Contaminants Using Activated Persulfate Oxidation Process

Emerging contaminants (ECs) usually refer to pesticides, polycyclic aromatic hydrocarbons (PAHs), dioxins, personal care products, cosmetics, and medications. Due to the strong demand and quick growth of these businesses, the ECs have continuously been found in alarming amounts in groundwater, surface water, and wastewater. These ECs provide a significant non-esthetic threat to the ecosystem as a whole and can cause significant non-esthetic contamination when released into the aquatic environment. The conventional wastewater treatment techniques such as activated sludge, membrane filtration, coagulation, adsorption, and ozonation showed ECs removal performance to a certain extent. In turn, numerous emerging advanced oxidation processes (AOPs), especially activated persulfate oxidation, have garnered a huge amount attention due to their outstanding performance in the remediation of ECs. This article presents a systematic and critical review of electro, sono and thermal activation of persulfate for the treatment of ECs. The effect of key parameters such as electrode materials, solution pH, persulfate concentration, current density, and temperature on electro, sono- and thermal-activated degradation of ECs was discussed. The possible reaction mechanism of ECs degradation was also elucidated in detail. It was closed with a note on the situation now and the future course of electro, sono and thermal activation in ECs degradation applications. Experiments performed in recent studies show that with the aid of persulfate in electro activation, the removal efficiency of chemical oxygen demand can be achieved up to 72.8%. Persulfate activated by sono shows 100% removal efficiency of 1,1,1-trichloroethane and sulfamethoxazole. While for thermal activation of persulfate, 100% removal efficiency of carbamazepine, atrazine and sulfamethazine was achieved. All these vital shreds of evidence are substantial enough to picture the negative impact of ECs on the environment.

Treatment of arsenite contaminated water by electrochemically activated persulfate oxidation process

Arsenic pollution in the groundwater is a serious worldwide problem, where arsenite and arsenate are the most prevalent forms in groundwater. Most of the conventional methods are able to remove arsenate effectively as compared with arsenite. Hence, for complete elimination of arsenic, prior oxidation of arsenite to arsenate is needed. The present work assessed the possibility of electrochemically activated persulfate (PS) based advanced oxidation process (EAOP) for arsenite removal from the aqueous medium. EAOP using Pt/Ti as both anode and cathode, can completely oxidize arsenite with an initial concentration of 1 mg L-1 within 60 min of electrolysis at pH 3; ferrous ion concentration 250 mg L-1, persulfate concentration 500.

Treatment of old landfill leachate by persulfate enhanced electro-coagulation system: Improving organic matters removal and precipitates settling performance

Electro-coagulation process is an alternative method for the treatment of old landfill leachate. However, limited removal of chemical oxygen demand (COD) and long solid–liquid separation times are the key technical problems hindering its practical application. In this study, a persulfate-enhanced electro-coagulation system (PECS) was constructed to improve the removal of COD and shorten the settling time of the flocculation precipitates. Compared with the traditional electro-coagulation process, the PECS can improve the COD removal from 41.1% to 72.6% (60 min reaction and current density of 50 mA/cm2) using activated persulfate oxidation process. The PECS process involves the formation of sulfate and hydroxyl radicals as the main oxidants. The dissolved organic matter in the old landfill leachate mainly consisted of macromolecular humus-like substances. PECS can reduce the aromaticity and the complexity of organic matter, and generated small molecular-weight organic matter, which was helpful in further alleviating the pressure of subsequent treatment of the leachate. The evolution path of precipitates in PECS followed the process of α- FeOOH/Fe2O3·H2O → Fe3O4, which promoted the formation of Fe3O4, improved the precipitation performance, and reduced the volume of precipitates. PECS could improve the degree of degradation of organic matter, increase the removal of COD, and shorten the separation time of precipitates under similar treatment costs to conventional processes. The results of this study provide an important theoretical basis for improving the performance of existing electro-coagulation equipment in practical engineering applications.

Removal of antibiotic resistant microbes by Fe(II)-activated persulfate oxidation

Sewage in WWTPs is one of main way to spread antibiotic resistant microbes (ARMs), and beach bay water is in direct contact with human skin. It is necessary to pay attention to remove the ARMs in WWTP sewage and bay water. Our results showed that ARMs and total microbes (TMs) can be effectively removed by S2O82-/Fe2+ in the effluent stage of WWTPs and bay water. Quenching experiments using tert-butyl alcohol, dimethyl sulfoxide and Al2O3 as scavengers confirmed that the primary reactive oxidants responsible for microbes removal during the Fe(II)-activated persulfate oxidation process might be SO4•- and Fe(IV), rather than •OH. The bacterial community shifted and the alpha diversity significantly reduced after treatment. In WWTP group, relative abundance of Firmicutes increased to 8.56%, and potential pathogens such as genus Vibrio decreased to 0.03% in bay water after treatment. The ecological toxicity to the environment of S2O82-/Fe2+ further illustrated that the mortality of indicator species Oryzias latipes did not increase after treatment, and the dosage of 60/30 μM can be potentially ideal dosage of S2O82-/Fe2+. This study revealed Fe(II)-activated persulfate oxidation as an eco-friendly and economical method could reduce TMs and ARMs in WWTP sewage and bay water.

Transformation of iodide and formation of iodinated by-products in heat activated persulfate oxidation process

Formation of halogenated disinfection by-products (DBPs) in sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable concerns recently. Previous studies have focused on the formation of chlorinated and brominated DBPs. This research examined the transformation of I− in heat activated PS oxidation process. Phenol was employed as a model compound to mimic the reactivity of dissolved natural organic matter (NOM) toward halogenation. It was found that I− was transformed to free iodine which attacked phenol subsequently leading to iodinated DBPs such as iodoform and iodoacetic acids. Iodophenols were detected as the intermediates during the formation of the iodoform and triiodoacetic acid (TIAA). However, diiodoacetic acid (DIAA) was formed almost concomitantly with iodophenols. In addition, the yield of DIAA was significantly higher than that of TIAA, which is distinct from conventional halogenation process. Both the facts suggest that different pathway might be involved during DIAA formation in SR-AOPs. Temperature and persulfate dose were the key factors governing the transformation process. The iodinated by-products can be further degraded by excessive SO4− and transformed to iodate. This study elucidated the transformation pathway of I− in SR-AOPs, which should be taken into consideration when persulfate was applied in environmental matrices containing iodine.

Denitration and renitration processes in sulfate radical-mediated degradation of nitrobenzene

Nitrobenzene (NB) is a recalcitrant organic compound caused great environmental concerns. Sulfate radical-based advanced oxidation processes (SR-AOPs) are promising environmental remediation and wastewater treatment technologies. In this contribution, we observed that degradation of NB by thermally activated persulfate oxidation process resulted in the formation of a suite of intermediates including 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), 2,6-dinitrophenol (2,6-DNP), and 2,4,6-trinitrophenol (2,4,6-TNP) as well as coupling products. The formation of the nitrophenols was suggested to follow the sequence of mononitrophenols→dinitrophenols→trinitrophenol. Time-dependent evolutions of mononitrophenols and dinitrophenols were illustrated and their formation mechanisms were proposed. The evolution patterns of mononitrophenols were fitted by sequential reaction kinetic model. The formation of polynitrated phenolic compounds suggests that both denitration and nitration processes occurred during SO4−-based oxidation of NB. Nitration agent (i.e., NO2) arising from the conversion of nitro group upon SO4−/HO attack is proposed to play an important role in the formation of polynitrated compounds. TOC measurement revealed that mineralization was less efficient as compared with NB degradation. The presence of NO2− was found to inhibit the degradation of NB but promote the formation of 2,4-DNP. Temperature played an important role in both the degradation of NB and the distribution of products. Since polynitrated aromatics are more persistent and mutagenic, the results of this contribution suggest that particular attention should be paid to their formation during SO4−-based oxidation processes.

Simultaneous removal of bisphenol A and phosphate in zero-valent iron activated persulfate oxidation process

In this study, the removal of bisphenol A (BPA) and phosphate in zero-valent iron activated persulfate (ZVI/PS) oxidation process was investigated. Activation of PS by ZVI mainly produces strong oxidizing sulfate radicals (SO4−) which can efficiently degrade organic contaminants. ZVI is ultimately transformed to ferric iron (Fe3+) which works as a coagulant to remove phosphate. It was demonstrated that BPA and phosphate could be simultaneously removed in this system. The oxidation of BPA in ZVI/PS process followed pseudo-first-order kinetics. The reaction rate increased with increased PS and ZVI dosage. Eight transformation products were identified using gas chromatography–mass spectrometry (GC–MS) technique. SO4−-induced oxidative transformation of BPA included electron transfer and hydrogen abstraction mechanisms. Carbonate exhibited no obvious influence on the removal both of phosphate and BPA. Natural organic matter (NOM) showed inhibitory effect on BPA degradation but had no appreciable negative effect on phosphate removal. Simultaneous removal of BPA and phosphate was also observed in wastewater treatment plant effluent with relatively high efficiency. The results of this work indicate that ZVI/PS process could serve as a novel treatment technique for removal of trance organic contaminants and phosphate simultaneously.

Advanced treatment of effluents from an industrial park wastewater treatment plant by ferrous ion activated persulfate oxidation process.

The advanced oxidation technology, ferrous ion (Fe(II)) activated persulfate (PS) producing sulfate radicals, was used for the advanced treatment of effluent from an integrated wastewater treatment plant in a papermaking industrial park. Separate and interactive effects of PS dosage, Fe(II)/PS ratio and initial pH on chemical oxygen demand (COD) removal were analyzed by the response surface methodology (RSM). The results showed that Fe(II)-PS system was effective in COD removal from the secondary effluent. PS dosage was the most dominant factor with positive influence on COD removal, followed by initial pH value. The optimum conditions with COD removal of 54.4% were obtained at PS/COD of 2.2, initial pH of 6.47 and Fe(II)/PS of 1.89. UV-visible spectrum analysis showed that after RSM optimization, Fe(II)-PS system effectively degraded large organic molecules into small ones, and decreased humification degree of the effluent. Three-dimensional fluorescence analysis demonstrated that aromatic protein and fulvic substances were fully decomposed by the Fe(II)-PS treatment.

Degradation of tetrabromobisphenol A in heat activated persulfate oxidation process

Sulfate radicals (SO4˙−) generated by heat activated persulfate were employed to degrade brominated flame retardant tetrabromobisphenol A (TBBPA).

Transformation of bromide in thermo activated persulfate oxidation processes

Sulfate radicals (SO4−·) are applied to degrade various organic pollutants. Due to its high oxidative potential, SO4−· is presumed to be able to transform bromide to reactive bromine species that can react with natural organic matter subsequently to form brominated products including brominated disinfection by-products (Br-DBPs). This research was designed to investigate the transformation of bromide in thermo activated persulfate oxidation process in the presence of humic acid (HA). Significant formation of bromoform and bromoacetic acids was verified. Their formation was attributed to the reactions of HA and reactive bromine species including Br·, Br2−· HOBr−, and free bromine resulted from the oxidation of bromide by SO4−·. Yields of Br-DBPs increased monotonically at persulfate concentration of 1.0 mM and working temperature of 70 °C. However, the time-depended formation exhibited an increasing and the decreasing profile when persulfate was 5.0 mM, suggesting further degradation of organic bromine. HPLC/ICP-MS analysis demonstrated that the organic bromine was eventually transformed to bromate at this condition. Thus, a transformation scheme was proposed in which the bromine could be recycled multiple times between inorganic bromide and organic bromine before being finally transformed to bromate. This is the first study that reveals the comprehensive transformation map of bromine in SO4−· based reaction systems, which should be taken into consideration when such technologies are used to eliminate contamination in real practice.

Application of full factorial design for methylene blue dye removal using heat-activated persulfate oxidation

In this study, a thermally activated persulfate oxidation process was investigated to treat aqueous methylene blue (MB) dye. Effects of temperature (55–80°C), initial pH (2.3–9.3), and potassium persulfate concentration (500–2000 (mg/L)) on MB color removal were examined. Results showed that acidic and neutral pH values were more favorable for MB oxidation than basic pH values. Based on experimental results, increasing the temperature from 55 to 80 (°C), and oxidant dose from 500 to 2000 (mg/L) enhanced the color removal efficiency (CR%) from 36% to 99.5% and from 55% to 98%, respectively. Kinetic study indicated that MB dye removal was a pseudo first-order reaction with respect to the various concentrations of MB and persulfate. Activation energy for the hot persulfate oxidation of MB was obtained as 112.3 (kJ/mol). To analyze the experimental data, an experimental design was applied by considering four operating parameters, including initial dye concentration, oxidant dosage, temperature and reaction time as input variables. A model was proposed for the statistical analysis of color removal prediction. Model predictions were found to be in good agreement (R2=0.96, adjusted R2=95.6%) with experimental data.

Degradation of carbamazepine and toxicity evaluation using the UV/persulfate process in aqueous solution

AbstractBACKGROUNDUsing persulfate in an advanced oxidation process to degrade organic pollutants has gained more attention in recent years. In this study, an ultraviolet activated persulfate oxidation process used to degrade carbamazepine (CBZ) in aqueous solution was investigated. The effect of persulfate dosage, pH, inorganic anions and humic acid on the degradation of CBZ was determined. In addition, the transformation intermediates produced during the process were identified using gas chromatograph–mass spectrometry (GC‐MS). Photobacteria were used to evaluate the toxicity of the transformation products.RESULTSThe results showed that the degradation efficiency increased with increasing persulfate dosage but decreased with the addition of Cl− and NO3−. Acidic conditions were more suitable for the treatment. Sulfate radical was identified to be the predominant radical in the oxidation process when the solution pH was not adjusted. Several compounds including 10, 11‐epoxycarbamazepine, acridine‐9‐carbaldehyde, acridine and other low molecular compounds were identified. A possible degradation pathway was also proposed. Acute toxicity tests indicated that the inhibition ratio decreased from 100% to 65% in 60 min, illustrating that the toxicity significantly decreased with the degradation of CBZ.CONCLUSIONConsidering all of the factors, UV/persulfate may be a promising option for CBZ treatment. © 2014 Society of Chemical Industry

Degradation of Toluene by a Selective Ferrous Ion Activated Persulfate Oxidation Process

The Fe2+-activated persulfate (PS) oxidation of toluene was evaluated using single-factor tests and response surface methodology (RSM). The results indicated the degradation efficiency increased as the PS and Fe2+ concentrations increased, while excessive dosages inhibited the degradation efficiency. The pH had an insignificant effect on the degradation of toluene. Based on the RSM optimization approach, the degradation efficiency reached a maximum of 84.4%. The main intermediates were also separated and identified by GC–MS, and a plausible degradation pathway of toluene was proposed. Further studies of surfactant recovery from flushing effluents mixed with toluene and surfactant were explored. Compared with the Fe2+/H2O2 process, a great enhancement of the toluene degradation efficiency and lower sodium dodecyl sulfate (SDS) degradation efficiency were obtained by the Fe2+/PS process. The results demonstrated that the Fe2+/PS selective oxidation process could be used for SDS recovery and for the degradat...

Bisphenol A treatment by the hot persulfate process: Oxidation products and acute toxicity

In this study, a thermally activated persulfate oxidation process was investigated to treat aqueous Bisphenol A (BPA) solution. The effect of temperature (40–50–60–70°C), initial pH (pH=3.0, 6.5, 9.0 and 11.0) and persulfate concentration (0–20mM) on bisphenol A (BPA) and TOC removals was examined. The activation energy for hot persulfate oxidation of BPA was calculated as 184±12kJ/mol. Acidic and neutral pH values were more favorable for BPA oxidation than basic pH values. TOC removals did not exhibit a specific pattern with varying initial pHs. Gas chromatography/mass spectrometry was employed to identify oxidation products. Several aromatic and a few aliphatic compounds could be detected including benzaldehyde, p-isopropenyl phenol, 2,3-dimethyl benzoic acid, 3-hydroxy-4-methyl-benzoic acid, ethylene glycol monoformate and succinic acid. Acute toxicity tests conducted with Vibrio fischeri indicated that the inhibitory effect of 88μM BPA solution originally being 58%, increased to 84% after 30min and decreased to 22% after 90min hot persulfate treatment that could be attributed to the formation and subsequent disappearance of oxidation products.