Modeling As(III) and As(V) Removal by an Iron Oxide Impregnated Activated Carbon in a Binary Adsorbate System

Abstract

The adsorption behavior of As(III) as a function of pH on an iron oxide impregnated activated carbon (FeAC) at different adsorbate/adsorbent concentrations was modeled using the surface complexation modeling approach (SCM). The surface complexation constants developed from single sorbate experiments successfully predicted competition between As(V) and As(III) and the SCM predictions were verified experimentally. The monoprotic surface site representation described the experimental data better than the diprotic representation. Based on surface complexation modeling simulations, the effect of As(V) on As(III) removal was greater than As(III) on As(V) removal. As(III) → (As(V) was observed for the FeAC and the virgin carbon beginning at pH = 8.

Keywords:

• As(III) and As(V)
• competitive adsorption
• surface complexation modeling

ACKNOWLEDGEMENTS

The authors are grateful to Dr. Seokjoon Kwoon and Dr. Anjuman Ira Islam for their help with the IC-ICP.

Notes

^a Pore diameter > 50 nm.

^b Pore diameter between 2 nm and 50 nm.

^c Pore diameter < 2 nm.

^a Species in parentheses indicate an outer-sphere complex.

^b X = general diprotic surface site, P = monoprotic surface site carrying a positive charge, N = monoprotic surface site carrying a negative charge, k = an index to differentiate between different positively and negatively charged sites.

^a C₁ and C₂ in F/m².

^b Total number of surface sites (N_s), total number of positive surface sites (), and total number of negative surface sites () in mM.

Equations (18) and (19) were used in two-monoprotic modeling schemes.