Recovery of metals from silicon based solar cells

摘要

An electrochemical method was developed to recover silver from discarded solar cells. The method used a solution of cerium sulfate in diluted sulfuric acid to dissolve the silver. During the dissolution of silver cerium is reduced from Ce(Ⅳ) to Ce(Ⅲ). The corresponding change in color - from yellow to colorless - can be used to monitor the concentration of Ce(Ⅳ) by continues spectrophotometric measurements at 450 nm. Solutions with varying concentrations of silver were used for electroplating of silver on to a cathode. While depositing silver on the cathode, Ce(Ⅲ) is oxidized back to Ce(Ⅳ) at the anode - thus enabling dissolution of silver from more solar cells. Measurements of dissolution rate and current efficiency for both silver deposition and cerium oxidation were used to find a balance between dissolution of sliver from the solar cells (which will also depend on the submerged area) and deposition of silver on the cathode. Using on-line spectrophotometric determination of the concentration of Ce(Ⅳ), it would be possible to monitor and control the process to run for a very long time without any waste or other environmental issues (only consumption of electricity).