PREPARATION AND CHARACTERIZATION OF SELECTED METAL-HUMATE COMPLEXES

Soil humic acid complexes with Ca2+, Co2+, Cu2+, Th4+, and UO22+ ions were prepared using humic acid (HA) and the metal ion in aqueous solution. The solid complexes were isolated and studied by elemental analysis, solubility, infrared spectroscopy, and X-ray powder diffraction. The isolated complexes have the following empirical formulae: Ca3HA(H2O)2, CoHA (H2O), Cu2HA(H2O)3, Th4HA(H2O)2.5, and UO2HA(H2O)7. Infrared spectroscopy showed the participation of OH and COOH groups in binding to the metal ions. Also that Th4+ formed a more ionic bond with humic acid than did UO22+, which was more than Ca≈2+ Co≈s2+ Cu2+. X-ray diffraction suggested that Th4+ disturbed the humic acid structure more than UG22+, which was more than Ca2+. But, for Ca2+, Co2+, and Cu2+, Co2+, caused more disturbance than Cu2+, which was more than Ca2+, indicating that the stronger the bonding the greater the disturbance. © 1990 Williams and Wilkins.