Experimental Study of the Co-Adsorption of Cadmium and Citrate Ions onto a TiO 2 (Anatase)/Electrolyte Solution Interface

A study of the co-adsorption of cadmium and citrate ions onto the mono-dispersed TiO 2 (anatase)/NaClO 4 aqueous solution interface is presented. The influence of ionic strength and pH on the adsorption of cadmium and citrate ions in this system was investigated. The surface charge density, the ζ-potential and adsorption-edge (or envelope) parameters such as pH 50% and ΔpH 10–90% were also determined for different concentrations of adsorbed ions. The presence of citrate anions increased the adsorption of Cd(II) ions at low pH values but led to a corresponding decrease at high pH values. The influence of pH on the shapes of the corresponding adsorption isotherms for citrate anions was characteristic of that for anion adsorption onto metal oxides; this is referred to as the “adsorption envelope”.