title: Modeling silica sorption to iron hydroxide.
abstract: Experiments were conducted to investigate the fundamentals of silica sorption onto preformed ferric hydroxide at pH 5.0-9.5 and silica concentrations of 0-200 mg/L as SiO2. At all pHs studied, sorption densities exceeding monolayer sorption were observed at silica levels typical of natural waters. Under some circumstances, sorption equaled or exceeded a monolayer while the particle zeta potential remained positive, a phenomenon that is completely inconsistent with available surface complexation models. To address this deficiency, an extended surface complexation model was formulated in which soluble dimeric silica (i.e., Si2O2(OH)5-) sorbs directly to iron surface sites. This new model fit sorption density data up to 0.40 mol SiO2/mol Fe and accurately predicted trends in zeta potential and observed H+ release during silica sorption to ferric hydroxide.
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg 24061-0246, USA.
authors.forename: Christina C
authors.initials: CC
authors.lastname: Davis
authors.forename: Hsiao-Wen
authors.initials: HW
authors.lastname: Chen
authors.forename: Marc
authors.initials: M
authors.lastname: Edwards
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry*; D005544:Forecasting; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D012822:Silicon Dioxide / Q000737:chemistry*; D014873:Water Pollutants
chemical_list: D005290:Ferric Compounds; D014873:Water Pollutants; C021024:ferric hydroxide; D012822:Silicon Dioxide