Effect of different type of scavengers on the photocatalytic removal of copper and cyanide in the presence of TiO2@yeast hybrids

Abstract

Effect of different type of organic or inorganic additions (formic acid, AgNO3, NaCl) on the photocatalytic reduction of copper and photooxidation of cyanide with illuminated TiO2@yeast was studied in this work together with the impact of solution pH values and contact time. The results indicated that pH values exhibited a great effect on the adsorption and photocatalytic performance of cyanide and copper because the surface charge of the TiO2@yeast and the existence form of cyanide and copper are highly pH dependent. The optimal adsorption and photo-oxidation of cyanide was observed at pH 2.0 while the best adsorptive and photocatalytic efficiency for copper was achieved at pH 5.0 within the studied range. The addition of formic acid increased the photo-reduction rate of copper and inhibited the photo-oxidation of cyanide. AgNO3, as electron acceptor, restrained the Cu(II) reduction from 75.0 to 30.5 %, whereas accelerate the photo-oxidation of cyanide. Besides, the presence of chloride ions retarded the removal efficiency of both cyanide and copper. The first-order kinetic model well described the experimental data. One possible mechanism of the effect of additives on copper and cyanide degradation was discussed.