Removal of Arsenate from Contaminated Water via Combined Addition of Magnesium-Based and Calcium-Based Adsorbents

The effects of the combined addition of Mg- and Ca-based adsorbents (MgO, Mg(OH)(2), MgCO3, CaO, Ca(OH)(2), and CaCO3) were systematically tested for improving arsenic-removal performance and inhibiting the leaching of base material components from the adsorbent. Arsenic-removal tests were conducted with each single type or combination of two types of adsorbents. Results obtained after the combined-addition tests were compared with those obtained from the single-addition test with each adsorbent. The arsenic-removal performance improved in most combined additions but decreased in certain combined additions of MgO or Mg(OH)(2) with Ca-based adsorbents. The arsenic-removal performance of the combined addition of MgCO3 and Ca(OH)(2) was the highest. The combination of Mg-based adsorbents with CaO or Ca(OH)(2) inhibited Mg-leaching, whereas that of CaO or Ca(OH)(2) with MgCO3 inhibited Ca-leaching. Improvement in arsenic-removal performance for the combination of MgCO3 with CaO or Ca(OH)(2) was caused by the incorporation and co-precipitation with arsenic when Mg(OH)(2) and CaCO3 were produced. MgCO3-Ca(OH)(2) and MgCO3-CaO are recommended for both arsenic removal and environmental adsorbent stability that can be effectively applied over a wide range of arsenic concentrations.