As(V) and PO4 Removal by an Iron-Impregnated Activated Carbon in a Single and Binary Adsorbate System: Experimental and Surface Complexation Modeling Results

Abstract

The objective of this study was to predict As(V) removal by an iron-oxide impregnated carbon (L-Act, 9% Fe(III) amorphous iron-oxide) over a range of environmental conditions using the surface complexation modeling (SCM) approach. The L-Act surface sites and electric double layer were modeled using the two monoprotic site-diffuse layer model (2MDLM). As(V) and PO4 surface complexes were modeled as bidentate complexes at low hydrogen ion concentration (pH) and monodentate complexes at high pH. L-Act-As/PO4 surface complexation constants were determined from a single pH-adsorbent edge, and these were used to effectively predict pH-dependent removal of As(V) and PO4 across a range of adsorbent/adsorbate ratios in single and binary adsorbate systems and from a National Sanitation Foundation challenge water. The 2MDLM also successfully predicted As(V) removal by three literature-based iron-based adsorbents: two iron-impregnated ion exchange resins (PWX5, 16% Fe; PWX3, 10% Fe) and a hydrous ferric oxide that was incorporated into a porous diatomite.