title: Oxidation of adsorbed ferrous iron: kinetics and influence of process conditions.
abstract: For the removal of iron from groundwater, aeration followed with rapid (sand) filtration is frequently applied. Iron removal in this process is achieved through oxidation of Fe(2 + ) in aqueous solution followed by floc formation as well as adsorption of Fe(2 + ) onto the filter media. The rate of oxidation of the adsorbed Fe(2 + ) on the filter media plays an important role in this removal process. This study focuses on investigating the effect of pH on the rate of oxidation of adsorbed Fe(2 + ). Fe(2 + ) has been adsorbed, under anoxic conditions, on iron oxide coated sand (IOCS) in a short filter column and subsequently oxidized by feeding the column with aerated water. Ferrous ions adsorbed at pH 5, 6, 7 and 8 demonstrated consumption of oxygen, when aerated water was fed into the column. The oxygen uptake at pH 7 and 8 was faster than at pH 5 and 6. However the difference was less pronounced than expected. The difference is attributed to the pH buffering effect of the IOCS. At feedwater pH 5, 6 and 7 the pH in the effluent was higher than in the influent, while a pH drop should occur because of oxidation of adsorbed Fe(2 + ). At pH 8, the pH dropped. These phenomena are attributed to the presence of calcium and /or ferrous carbonate in IOCS.
authors.affiliation: Department of Municipal Water and Infrastructure, UNESCO-IHE Institute for Water Education, P.O. Box 3015, 2601 DA, Delft, The Netherlands. r.buamah@unesco-ihe.org
authors.forename: R
authors.initials: R
authors.lastname: Buamah
authors.forename: B
authors.initials: B
authors.lastname: Petrusevski
authors.forename: J C
authors.initials: JC
authors.lastname: Schippers
mesh_terms: D000327:Adsorption; D005296:Ferrous Compounds / Q000737:chemistry*; D005374:Filtration; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013997:Time Factors
chemical_list: D005296:Ferrous Compounds; D010100:Oxygen