After 1 h soil washing at 200 rpm, the washed soils were rinsed twice with
deionized water. The washing and rinsing solutions can be treated either by neutralization and precipitation or by sorption on to adsorbents such as granular ferric oxide (Choi et al., 2007;Cheong and Kang, 2012; Yang et al., 2013). Also, As in the solutions can be removed by adding oxidants (e.g., hydrogen peroxide) and coagulants (Kim et al., 2012)