摘要 : The coagulation of colloidal MnO2 by several divalent cations, both in the absence and presence of a complexing ligand (L-histidine), has been studied. The efficiency as coagulating agents increases in the order Mg2+ < Ni2+ < Zn2+... 展开 The coagulation of colloidal MnO2 by several divalent cations, both in the absence and presence of a complexing ligand (L-histidine), has been studied. The efficiency as coagulating agents increases in the order Mg2+ < Ni2+ < Zn2+ < Cu2+ <Co2+ < Mn2+. For a given cation, the coagulating efficiency increases with increasing pH and with increasing temperature, and decreases with increasing concentration Of L-histidine. Apparent values for the equilibrium constants of complexation of divalent cations by L-histidine have been obtained. The apparent equilibrium constant of formation of the complex increases in the order Mg2+ < Mn2+ < Zn2+ <Cu2+ < Ni2+. The value corresponding to Co2+ could not be determined because L-histidine acted as a catalyst for the reduction of colloidal MnO2 by that cation. (C) 2003 Elsevier B.V. All rights reserved. [References: 26] 收起