The use of cement kiln dust for the removal of heavy metal ions from aqueous solutions

Abstract

The possibility of removal and utilisation of heavy metal (HM) ions from aqueous solutions by cement kiln dust (CKD) has been studied. The experiments have shown that CKD may be used for industrial wastewater decontamination. They revealed that CKD may be used for neutralisation of acidic wastewaters (alkalinity 12–16 meq g−1) and for removal of HM ions such as Cu(II), Ni(II), Pb(II), Cd(II) and Co(II). CKD acts as an alkaline agent and sorbent. The main crystalline components of CKD are: calcite, CaCO3 (80% by mass), 10–15% SiO2 and the remainder is basic calcium silicate, Ca5(SiO4)2(OH)2. The maximal capacity of CKD to remove Cu(II) is 0·29 g g−1 CKD (9·1 meq g−1); Ni(II), 0·14 g g−1 CKD (4·7 meq g−1); Pb(II), 2·0 g g−1 CKD (19 meq g−1); Cd(II), 0·42 g g−1 CKD (7·4 meq g−1); and Co(II), 0·20 g g−1 CKD (6·8 meq g−1). Interaction of CKD with Cu(II) ions produces devillite Cu4(CaSO4)2(OH)6·3H2O, with Pb(II) – basic carbonate Pb3(CO3)2(OH)2 and with Cd(II) ions – Cd(OH)Cl. The products of interaction of CKD with Ni(II) and Co(II) ions are amorphous: apparently hydrated Ni(OH)2 and Co(OH)2.