Photo-oxidative dissolution of CdS(s): the effect of complexing agents

The photo-oxidative dissolution of cadmium sulfide has been investigated in the presence of several complexing organic and inorganic compounds under oxygen-saturated conditions. At pH 4 and 7, aromatic organic ligands enhance the cadmium dissolution rate by a factor of 5–6 over that without the organic present; EDTA, NTA, and citric and oxalic acids have little effect. Sulfite and hydrogen sulfide/bisulfide slightly enhance the dissolution. Conversely, at pH 10, EDTA and NTA produce a significant increase in dissolved cadmium (factor of approximately 18) while the other compounds exert little effect. These phenomena are explained by ligand surface complexation, and both surface and homogeneous ligand-enhanced dissolution.