PowerTech Water, Inc. — Department of Energy SBIR Phase II: C56-15b

Description

"Statement of the Problem: Decommissioned solar panels will account for up to 10 million tons of waste in the USA by 2050. PV recycling has seen little development in reclaiming valuable materials present in low concentrations. Copper and silver account for 1% and 0.1%, respectively, of the total waste mass, but represent 7% and 42% of the waste value. To make mass PV recycling economically viable, keep these metals out of the environment, and support future PV manufacture, this value must be captured. General Statement of how this problem is being addressed: Chemical extractions are costly, multistep processes. Electrochemical methods offer a simpler way to extract metals. By dissolving the metal-bearing PV components in acid, a silver and copper-rich feed can be generated. Electrowinning systems use a potential difference to “plate out” metals onto their electrodes for recovery, consuming only electricity. Limited by their electrode design to operating at high concentrations, they display prohibitively long reaction times to obtain high yields at the expected levels of silver in PV waste. ElectraMet™ systems utilize porous, high surface area electrodes to overcome processing speed limitations and efficiently capture metals. Our copper recovery units are used in battery recycling, wastewater treatment, and metal finishing. Installed units removed copper present in the ppb range with a 5 second residence time. However, a bulk metals solution for both silver and copper is needed. We propose to develop a new electrochemical cell capable of selective, rapid silver and copper recovery in the dilute regime typical of silver in PV-leachate. What is to be done in this work: To enable selective, bulk removal, a novel cathode will be developed and deployed in an electrochemical cell capable of removing 99+% of the silver and over 90% of the copper in a PV-leachate solution as metal solids. Flow will be directed through the cathodes. A dense anode supplies electrons for the reaction, while the high cathode surface area allows for rapid metal reduction. The cell design allows for the facile collection of produced metal. The result is a scalable metal recovery system with a novel cathode and electrochemical cell integrated with automated controls and telemetry. Commercial Applications and Other Benefits: By 2050, estimates suggest that silver and copper will account for 10,000 and 100,000 tons, respectively, of all PV waste in America. Assuming 50% recovery with current techniques, $3,450,000,000 and $450,000,000 is still lost at current prices. The proposed system allows recyclers to recover this value and reduce metal waste."