UPTAKES OF CU2+, PH2+ AND ZN2+ ON SYNTHETIC HYDROTALCITE IN AQUEOUS-SOLUTION

Uptakes of Cu2+, Pb2+ and Zn2+ on various synthetic hydrotalcite (HT-CO3, HT-SO4, HT-Cl and HT-NO3) were investigated in Cu(NO3)2, Pb(NO3)2, Pb(NO3)2 and Zn(NO3)2 aqueous solution (each conc.: 2000 mg.dm-3). Hudrotalcite has a pronounced activity for the uptakes of Cu2+, Pb2+ and Zn2+. Amounts of Cu2+, Pb2+ and Zn2+ removed by HT-CO3 are about 1.7 mmol Cu/g, 1.0 mmol Pb/g and 1.2 mmol Zn/g. In a mixed solution of Cu2+, Pb2+ and Zn2+ (the concentration of each ions : 20 mmol.dm-3), the order of activity for the uptakes of each ions on HT-CO3, HT-SO4, HT-Cl and HT-NO3 are Pb>Cu>Zn, Cu>Pb>Zn, Pb>Cu>Zn and Cu>Pb>Zn. When the HT-CO3 was immersed into the Pb(NO3)2 solution, a part of the Mg2+, OH- and CO3- of HT-CO3 (Mg6Al2(OH)16CO3.4 H2O) dissolve into the solution. The dissolved OH- and CO32- causes the Pb2+ to precipitate as Pb3(OH)2 (CO3)2 on the surface of the HT-CO3.