title: Kinetics and efficiency of H2O2 activation by iron-containing minerals and aquifer materials.
abstract: To gain insight into factors that control H(2)O(2) persistence and ·OH yield in H(2)O(2)-based in situ chemical oxidation systems, the decomposition of H(2)O(2) and transformation of phenol were investigated in the presence of iron-containing minerals and aquifer materials. Under conditions expected during remediation of soil and groundwater, the stoichiometric efficiency, defined as the amount of phenol transformed per mole of H(2)O(2) decomposed, varied from 0.005 to 0.28%. Among the iron-containing minerals, iron oxides were 2-10 times less efficient in transforming phenol than iron-containing clays and synthetic iron-containing catalysts. In both iron-containing mineral and aquifer materials systems, the stoichiometric efficiency was inversely correlated with the rate of H(2)O(2) decomposition. In aquifer materials systems, the stoichiometric efficiency was also inversely correlated with the Mn content, consistent with the fact that the decomposition of H(2)O(2) on manganese oxides does not produce ·OH. Removal of iron and manganese oxide coatings from the surface of aquifer materials by extraction with citrate-bicarbonate-dithionite slowed the rate of H(2)O(2) decomposition on aquifer materials and increased the stoichiometric efficiency. In addition, the presence of 2 mM of dissolved SiO(2) slowed the rate of H(2)O(2) decomposition on aquifer materials by over 80% without affecting the stoichiometric efficiency.
authors.affiliation: Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720-1710, USA.
authors.forename: Anh Le-Tuan
authors.initials: AL
authors.lastname: Pham
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Doyle
authors.forename: David L
authors.initials: DL
authors.lastname: Sedlak
mesh_terms: D052918:Environmental Restoration and Remediation / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry; D008903:Minerals / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D019800:Phenol / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry; D014481:United States; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D017895:Manganese Compounds; D008903:Minerals; D010087:Oxides; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D017665:Hydroxyl Radical; D019800:Phenol; C027424:manganese oxide; D012822:Silicon Dioxide; D006861:Hydrogen Peroxide; D007501:Iron