ABSTRACT
58Metal sulfide recovery in bioreactors highly depends on their purity and settling properties. In this study, the influence of macronutrients and biofilm on the Cu, Pb, Cd and Zn depletion kinetics and characteristics was evaluated in batch experiments with sulfide at different concentrations. The kinetic values from the plots of the metals followed the solubility product order of the metal sulfides. They also showed that at low sulfide concentrations, the metals with slower depletion rates are susceptible to other removal mechanisms as well, i.e. biosorption onto the biofilm and precipitation with the macronutrients. X-ray absorption spectroscopy showed that the main mechanism of Zn removal is its sorption onto apatite (Ca5(PO4)3 + (OH-), a compound formed due to the addition of macronutrients. The size of the precipitates was similar in all experiments regardless the sulfide concentration (8.1-10.0 µm).
