Modeling As(V) removal by a iron oxide impregnated activated carbon using the surface complexation approach

Abstract

The objective of this research was to model As(V) removal onto a iron oxide impregnated activated carbon (FeAC) using the surface complexation model (SCM) approach. As(V) removal by FeAC was due to the impregnated Fe oxide, not the base carbon material and was a strong function of pH. The two-monoprotic site-triple layer model adequately described As(V) removal using 2 fitting parameters compared with the 3 parameters needed for the diprotic site model. This, along with a better representation of the recognized As(V) removal mechanism (ligand exchange with -OH) as well as the acid-base behavior makes the two-monoprotic approach the better model for As(V) removal by the impregnated iron oxide although the diprotic model was able to describe the pH dependent removal of As(V). Both models were also able to predict As(V) removal at different adsorbent/adsorbate ratios using K(As) determined from a single FeAC adsorption experiment. Thus, fewer adsorption experiments are required in order to model As(V) removal in equilibrium and column systems. The results described in this work will be used as a foundation in developing a dynamic model to predict As(V) adsorption in a fixed-bed adsorber.