Sorption of selenium(IV) onto magnetite in the presence of silicic acid

Sorption of selenium(IV) and silicic acid onto magnetite (Fe3O4) was investigated in binary systems, with concentrations of silicic acid under the solubility limit of amorphous silica. Using the double diffuse layer model (DDLM), surface complexation constants of selenium(IV) and H4SiO4 onto magnetite were extracted using Fiteql 4.0. Then, prediction curves of the sorption of selenium(IV) in the presence of silicic acid onto magnetite were obtained, using the calculated surface complexation constants.Finally, laboratory experiments were performed and showed a competition between selenium(IV) and silicic acid for the surface sites of magnetite. Experimental results matched the model predictions, confirming its ability to model qualitatively and quantitatively the ternary system.

This figure represents experimental sorption edges of selenium(IV) onto magnetite in the presence of silicic acid, as well as calculations done with double diffuse layer model to account for the experimental observations.Figure optionsDownload as PowerPoint slide