Specific adsorption of nickel and zeta potential of silica at various solid-to-liquid ratios

The electrokinetic curves of silica obtained at given total concentrations of heavy metal cations depend on the solid-to-liquid ratio; namely, at low solid-to-liquid ratios the sign of the zeta potential of silica is reversed to positive at relatively low concentrations of heavy metal cations, while at higher solid-to-liquid ratios the electrokinetic curves are not substan tially influenced at much higher concentrations. The surface complexation m odel fails to properly reflect the Ni effect on the course of electrokineti c curves of silica. The course of electrokinetic curves [positions of the i soelectric point(s) and of the maxima in mobility] is correlated with a lin ear combination of the surface charge density in the absence of heavy metal cations at given ionic strength and the adsorption density of Ni. (C) 1999 Academic Press.