Natural red earth as a possible low cost substrate for arsenic removal in water—comparison of laboratory controlled and uncontrolled conditions

摘要

The dominant process used in arsenic (As) removal is adsorption onto earth materials (Anderson et al., 1976; Manning&Goldberg, 1996;Thirunavukkarasu & Viraraghavan, 2003; Weerasooriya et al., 2003; Genc-Fuhrman et al., 2004; Vithanage et al., 2007). However, most of these studies were carried out in the laboratory controlled conditions where pH kept as desired and background electrolyte was added to activate surface sites of the solid material. In that case, adsorption could be different when the adsorbent is applied in household filters in natural conditions. Therefore, this study was carried out to see the effect of laboratory controlled and uncontrolled conditions on adsorption to identify the possibility of using Natural Red Earth as a low cost adsorbent for As removal from water. Subsequently, the effect of competing ions such as nitrate and phosphate for both As(Ⅲ) and As(V) adsorption was also examined. NRE was selected for this experiment because it is well known As adsorption ability (Vithanage et al., 2006, 2007) and was characterized with >FeOH and >AlOH reactive sites, with variable surface charge.