Effect of 2,2′-bipyridine on the adsorption of Zn2+ ions onto silica surface

The influence of 2,2 ' -bipyridine (bipy) on adsorption of zink ions onto a highly dispersed silica surface has been studied. The enhanced adsorption of zink ions onto silica surface from the solution containing 2,2 ' -bipyridine is explained by ternary surface complex formation, {equivalent to SiOH_Zn-m(bipy)(n)((2-m)+)}. The adsorbed Zn2+ and bipy concentrations were measured at the adsorption from solutions with different ratios of Zn:bipy. The equilibrium reaction constants of binary and ternary complexes have been calculated using the constant capacitance model. The potentiometric titration data were used in order to determine the H+/Zn2+ exchange stoichiometry. The composition of formed surface complexes has been confirmed with their UV absorption spectra. (C) 2001 Academic Press.