Removal of phosphorus from solution using biogenic iron oxides

Phosphorus removal by biogenic iron oxides was investigated, providing an initial characterization of a potentially regenerable iron-rich sorbent. The biogenic iron oxides were collected from a wetland ecosystem and were dominated by the sheaths of Leptothrix ochracea. Sorption kinetics followed a pseudo-1st order model (R(2)=0.998) with a rate constant of 0.154+/-0.013h(-1). The Langmuir isotherm adequately described sorption for all samples (R(2)=0.923-0.981); the Freundlich model was a better fit for only one of four samples. Maximum phosphorus sorption estimated using the Langmuir parameter ranged from 46.9+/-2.9 to 165.0+/-21.2mgP/gFe and was similar to other iron-rich substrates. Maximum sorption normalized to total solids ranged from 10.8+/-0.7 to 39.9+/-3.2mgP/g, which represented the highest published values for iron-rich substrates. The high sorption capacity with respect to both iron and solids warrants further evaluation of biogenic iron oxides as a substrate for phosphorus removal.