title: Electrochemical regeneration of Fe2+ in Fenton oxidation processes.
abstract: This study is to establish optimal conditions for the minimization of iron sludge produced in Fenton oxidation processes by electro-regenerating Fe(2+) with constant potential (CPM) or constant current mode (CCM). Results indicate that the optimal cathodic potential for Fe(2+) regeneration is -0.1 V vs. the saturated calomel electrode (SCE) in terms of current efficiency. Keeping the initial Fe(3+) concentration ([Fe(3+)](0)) constant, the average current density produced at -0.1 V vs. SCE (CPM) is approximately equal to the optimal current density applied in the CCM. The suitable pH range is below the pH value determined by Fe(3+) hydrolysis. As expected, increasing cathode surface area and solution temperature notably increases Fe(2+) regeneration rate. At the optimal potential, the average current density increases linearly with [Fe(3+)](0), exhibiting a slope of 8.48 x 10(-3)(A/m(2))(mg/L)(-1). The average current efficiency varies with [Fe(3+)](0), e.g., 75% and 96-98% at 100 and > or = 500 mg/L [Fe(3+)](0), respectively. Once reaching 75% of Fe(2+) regeneration capacity, further regeneration becomes difficult due to Fe(3+) mass transfer limitation. Fe(2+) can also be effectively regenerated by dissolving iron sludge at low pH (usually </=1). The unit energy consumption is 2.0-3.0 k Wh per kg Fe(2+) regenerated.
authors.affiliation: Department of Civil and Environmental Engineering, University of Delaware, 137, DuPont Hall, Newark, DE 19716-3120, USA.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Qiang
authors.forename: Jih-Hsing
authors.initials: JH
authors.lastname: Chang
authors.forename: Chin-Pao
authors.initials: CP
authors.lastname: Huang
mesh_terms: D004563:Electrochemistry; D004784:Environmental Monitoring; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006868:Hydrolysis; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: C045076:Fenton's reagent; D007220:Industrial Waste; D006861:Hydrogen Peroxide; D007501:Iron