title: Removal of Persistent Organic Contaminants by Electrochemically Activated Sulfate.
abstract: Solutions of sulfate have often been used as background electrolytes in the electrochemical degradation of contaminants and have been generally considered inert even when high-oxidation-power anodes such as boron-doped diamond (BDD) were employed. This study examines the role of sulfate by comparing electro-oxidation rates for seven persistent organic contaminants at BDD anodes in sulfate and inert nitrate anolytes. Sulfate yielded electro-oxidation rates 10-15 times higher for all target contaminants compared to the rates of nitrate anolyte. This electrochemical activation of sulfate was also observed at concentrations as low as 1.6 mM, which is relevant for many wastewaters. Electrolysis of diatrizoate in the presence of specific radical quenchers (tert-butanol and methanol) had a similar effect on electro-oxidation rates, illustrating a possible role of the hydroxyl radical ((•)OH) in the anodic formation of sulfate radical (SO4(•-)) species. The addition of 0.55 mM persulfate increased the electro-oxidation rate of diatrizoate in nitrate from 0.94 to 9.97 h(-1), suggesting a nonradical activation of persulfate. Overall findings indicate the formation of strong sulfate-derived oxidant species at BDD anodes when polarized at high potentials. This may have positive implications in the electro-oxidation of wastewaters containing sulfate. For example, the energy required for the 10-fold removal of diatrizoate was decreased from 45.6 to 2.44 kWh m(-3) by switching from nitrate to sulfate anolyte.
authors.affiliation: Advanced Water Management Centre, The University of Queensland , Brisbane, Queensland 4072, Australia.
authors.forename: Ali
authors.initials: A
authors.lastname: Farhat
authors.affiliation: Advanced Water Management Centre, The University of Queensland , Brisbane, Queensland 4072, Australia.
authors.forename: Jurg
authors.initials: J
authors.lastname: Keller
authors.affiliation: Advanced Water Management Centre, The University of Queensland , Brisbane, Queensland 4072, Australia.
authors.forename: Stephan
authors.initials: S
authors.lastname: Tait
authors.affiliation: Advanced Water Management Centre, The University of Queensland , Brisbane, Queensland 4072, Australia.|Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona , 17003 Girona, Spain.
authors.forename: Jelena
authors.initials: J
authors.lastname: Radjenovic
mesh_terms: D001895:Boron; D018130:Diamond; D003973:Diatrizoate / Q000737:chemistry; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004572:Electrolysis; D017665:Hydroxyl Radical; D007700:Kinetics; D009566:Nitrates; D009578:Nitrobenzenes / Q000737:chemistry; D009930:Organic Chemicals / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D013461:Sulfur Oxides; D062065:Wastewater; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D020002:tert-Butyl Alcohol
chemical_list: D001895:Boron; D018130:Diamond; D003973:Diatrizoate; D017665:Hydroxyl Radical; D009566:Nitrates; D009578:Nitrobenzenes; D009930:Organic Chemicals; D013431:Sulfates; D013461:Sulfur Oxides; D062065:Wastewater; D014874:Water Pollutants, Chemical; D020002:tert-Butyl Alcohol; C069025:sulfate radical; C036077:nitrobenzene