RECYCLING OF CdTe PHOTOVOLTAIC MODULES: RECOVERY OF CADMIUM AND TELLURIUM

Research on recycling of CdTe PV modules and manufacturing waste aims in optimizing the separations and recovery of glass, cadmium and tellurium while minimizing life-cycle emissions and energy use, under the constraint of low cost (e.g. a few cents per watt). The major tasks of our research are: a) Cleaning of glass from the metals and recycling of glass; b) separation of Te from Cd and other metals and recovery of Te for its value; c) recovery of Cd for re-use or effective sequestration. The modules were crushed in fragments and were subjected to hydrometallurgical processing involving leaching, ion exchange separation, precipitation and electrowinning. Low concentration sulfuric acid solutions were effective in totally leaching cadmium and tellurium out of the glass matrix. We used ion exchange columns in series to separate copper and tellurium from cadmium in solution. Subsequently, we recovered Cd and Te from the corresponding solutions with electrowinning and reactive precipitation respectively. Electrowinning produced cadmium sheets of 99.5% wt purity in sizes of 2 by 4 cm and 11 by 11 cm at an estimated cost of only 0.1 cents/Wp. Precipitation of Te in metallic form was obtained by various reduction agents. Ongoing studies aim in improving the purity of the recovered cadmium metal and optimizing the recovery of tellurium.