Remediation of persistent organic pollutants in aqueous systems by electrochemical activation of persulfates: A review

Electro-Persulfate Processes for the Treatment of Complex Wastewater Matrices: Present and Future

“…Electro-persulfate processes consist in the electrochemical activation of persulfate (peroxymonosulfate-PMS, HSO 5 − , E° = 1.82 V; or peroxydisulfate—PDS, S 2 O 8 2− , E° = 2.01 V) to generate the highly reactive sulfate radical, which presents a redox potential of 2.5–3.1 V) [ 4 ]. Both PMS and PDS contain a peroxide bond (−O−O−) that can be electrochemically cleaved by the reaction with an electron to form SO 4 •− (Equations (1) and (2), respectively) [ 5 , 6 ]. For this purpose, persulfate (PS) can be externally added to the system or it can be electrochemically produced, in sulfate-containing solutions, from the oxidation of SO 4 2− and HSO 4 − ions, through the reactions described by the Equations (3) and (4), respectively [ 7 ].…”

“…Electrochemically produced or externally added, when activated, PS originates the strong and highly oxidizing sulfate radical (Equations (1) and (2)), which presents higher redox potential than that of a hydroxyl radical, promoting the nonselective oxidation and efficient removal of a wide range of organic compounds [ 4 , 5 ]. Moreover, the half-life time of SO 4 •− is usually referred as being longer than that of HO • , enabling better mass transfer performance and contact with the organic compounds in solution, promoting their complete or partial mineralization [ 5 ]. This high efficiency in pollutants removal is further enhanced by secondary radicals, generated from a sulfate radical reaction with water, for instance, to give hydroxyl radical (Equation (8)).…”

“…This high efficiency in pollutants removal is further enhanced by secondary radicals, generated from a sulfate radical reaction with water, for instance, to give hydroxyl radical (Equation (8)). In fact, SO 4 •− readily reacts with water at a wide range of pH values [ 5 ]. According to the literature, hydroxyl radicals are the primary reactive species under alkaline pH conditions [ 10 ].…”

“…Among the different SO 4 •− generation processes, the electrochemical ones, usually designated as electro-persulfate processes, were extensively investigated and considered the most efficient for the formation of sulfate radicals [ 5 ]. There are several studies reporting the application of electro-persulfate processes in the treatment of wastewaters with recalcitrant properties, with very promising results, making this technology a possible solution for the remediation of complex wastewater matrices.…”

Photo-assisted electrochemical advanced oxidation processes for the disinfection of aqueous solutions: A review

“…In the last decade, (SO 4 •- ) based treatment processes have gained attention due not only to the high oxidation power of sulphate radicals (E° = 2.5–3.1 V vs. SHE), but also to their nonselective reactivity ( Zhi et al., 2020 ). The SO 4 •- radical species is therefore a powerful oxidant that rapidly attacks a variety of organic compounds, as well as pathogen membrane structures; following reaction pathways that are similar to those that characterize • OH chemistry, ( Tan et al., 2021 ).…”