Effects of pH, adsorbate/adsorbent ratio, temperature and ionic strength on the adsorption of arsenate onto soil

In this study, the effects of pH, adsorbate/adsorbent ratio, temperature and ionic strength on the adsorption of arsenate, As(V) onto soil were investigated. Three soil samples, with negligible background levels of arsenic, were collected from the vicinity of the Jingok mine, an abandoned mine located in Bongwha, Korea. Results show that the adsorption of arsenate on soil strongly depends on pH, adsorbate/adsorbent ratio and temperature, but not on ionic strength; higher adsorption was found at lower pH, lower adsorbate/adsorbent ratio and/or higher temperature. It was observed that pH is a very strong factor in immobilization of arsenate onto soil by adsorption. Soil samples containing the highest concentrations of Fe and Al showed the greatest arsenate adsorption. Iron and aluminum (hydr) oxides are likely the main adsorbents, which are active under the natural conditions in the study area. The experimental data of isotherms at various pH values and temperatures from the three soil samples show good agreement with both Freundlich and Langmuir equations.