title: Selective oxidative degradation of toluene for the recovery of surfactant by an electro/Fe²⁺/persulfate process.
abstract: An electro/Fe(2+)/persulfate process has been conducted for toluene removal from surfactant (SDS) flushing solution, and the pseudo-second-order reaction rate constant (k2 value) of toluene removal has been optimized by a response surface methodology (RSM). The results indicated that in this process, the reaction between persulfate and externally added Fe(2+) generates sulfate-free radicals, and at the same time, Fe(2+) is electro-regenerated at the cathode by the reduction of Fe(3+). RSM based on Box-Behnken design (BBD) has been applied to analyze the experimental variables, of which the concentrations of persulfate and Fe(2+) showed a positive effect on the rate constant of toluene removal, whereas the concentration of SDS showed a negative effect. The interactions between pairs of variables proved to be significant, such as between SDS, persulfate, and Fe(2+) concentrations. ANOVA results confirmed that the proposed models were accurate and reliable for analysis of the variables of the electro/Fe(2+)/persulfate process. The shapes of the 3D response surfaces and contour plots showed that the SDS, persulfate, and Fe(2+) concentrations substantially affected the k2 value of toluene removal. The results indicated that increasing persulfate or Fe(2+) concentration increased the k2 value, whereas increasing SDS concentration decreased the k2 value. The reaction intermediates have been identified by GC-MS, and a plausible degradation pathway for toluene degradation is proposed.
authors.affiliation: Department of Environmental Engineering, Wuhan University, Wuhan, 430079, China.
authors.forename: Anhua
authors.initials: A
authors.lastname: Long
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
mesh_terms: D055664:Electrochemical Techniques; D052918:Environmental Restoration and Remediation; D007501:Iron / Q000737:chemistry; D010084:Oxidation-Reduction; D012989:Soil Pollutants / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D014050:Toluene / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D012989:Soil Pollutants; D013431:Sulfates; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D014050:Toluene; D007501:Iron
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