title: Iron(VI) and iron(V) oxidation of thiocyanate.
abstract: Thiocyanate (SCN-) is used in many industrial processes and is commonly found in industrial and mining waste-waters. The removal of SCN- is required because of its toxic effects. The oxidation of thiocyanate (SCN-) by environmentally friendly oxidants, Fe(VI) and Fe(V), has been studied anaerobically using stopped-flow and premix pulse radiolysis techniques. The stoichiometry with Fe(VI) was determined to be 4HFeO(4-) + SCN(-) + 5H2O-->4Fe(OH)3 + SO4(2-) + CNO(-) + O2 + 2OH-. The rate law for the oxidation of SCN- by Fe(VI) was found to be -d[Fe(VI)]/dt = k11([H+]/([H+] + Ka,HFeO4)) [Fe(VI)][SCN-] where k11 = 2.04 +/- 0.04 x 10(3) M-1 s-1 and pKa,HFeO4 = 7.33. A mechanism is proposed that agrees with the observed reaction stoichiometry and rate law. The rate of oxidation of SCN- by Fe(V) was approximately 3 orders of magnitude faster than Fe(VI). The higher reactivity of Fe(V) with SCN- indicates that oxidations by Fe(VI) may be enhanced in the presence of appropriate one-electron-reducing agents. The results suggest that the effective removal of SCN- can be achieved by Fe(VI) and Fe(V).
authors.affiliation: Department of Chemistry, Florida Institute of Technology, 150 West University Boulevard, Melbourne, Florida 32901, USA. vsharma@fit.edu
authors.forename: Virender K
authors.initials: VK
authors.lastname: Sharma
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Burnett
authors.forename: Donald B
authors.initials: DB
authors.lastname: O'Connor
authors.forename: Diane
authors.initials: D
authors.lastname: Cabelli
mesh_terms: D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D008906:Mining; D010084:Oxidation-Reduction; D013861:Thiocyanates / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D007220:Industrial Waste; D013861:Thiocyanates; D007501:Iron; C031760:thiocyanate