Adsorption of Cu2+ ions onto silica surface from aqueous solutions containing organic substances

The influence of 2,2′-bipyridine and 2-picolinic acid on adsorption of copper ions onto a surface of highly dispersed silica has been investigated. The adsorption of copper ions is enhanced by 2,2′-bipyridine and attenuated by 2-picolinic acid as compared to noncomplex copper ions. These results are interpreted in terms of ternary surface complex formation. The intrinsic equilibrium reaction constants of binary and ternary complex formation have been calculated with the use of the constant capacitance model (CMC). According to one of the definitions of this model the adsorption of background electrolyte ions is assumed absent.