Comparison of Arsenic Adsorption on Lignite, Bentonite, Shale, and Iron Sand from Indonesia

Arsenic (As) is a toxic element found in both natural and anthropogenic sources. High concentration of this element was recently uncovered in the groundwater of Sumbawa Island, Indonesia. This contamination seems to be caused by the operation of gold mining in the island. To mitigate this problem, As adsorption potential of natural geological materials like lignite, bentonite, shale, and iron sand obtained in Indonesia were evaluated by batch experiments. These materials were selected because of thei r low cost and availability. The results showed that among these natural materials tested, lignite was the most effective adsorbent of As(V) followed by bentonite, shale and then iron sand, and that the amounts of As(III) adsorbed onto all adsorbents were lower than those of As(V).This indicates that As(III) is more mobile in comparison to As(V). The adsorption isotherms of As(III) and As(V) conformed to nonlinear types, either Langmuir or Freundlich. Solution pH also affected the amount of As adsorbed.