Environmentally Conscious Electrochemical Machining for Zero Discharge and Metal Recycling

This Phase I SBIR addresses the need for a manufacturing method for recovery and recycle of metal removed during electrochemical machining (ECM). Direct current (DC) ECM uses viscous solutions with additives such as fluoride resulting in difficult to control electrolytes, environmentally hazardous waste and low process yield. In contrast, FARADAYICSM ECM uses environmentally benign buffered salt solutions without additives, is robust and gives improved process control. The environmental benefit from implementation of the FARADAYICSM ECM process and the cost benefit from improved process control and higher process yield, have led to improved manufacturing competitiveness, and are critical to transitioning the technology from the bench to full scale manufacturing.However, a sludge byproduct forms during either ECM process, with a 300X volume increase relative to the metal removed. Sludge discard results in the loss of valuable “waste” metal as well as loss of electrolyte retained within the sludge, which must be filtered, dried and shipped for expensive landfilling and/or recycling. This practice is inconsistent with the EPA’s Resource Conservation and Recovery Act to “minimize the generation of hazardous waste and land disposal of hazardous waste by encouraging process substitution, materials recover, and properly conducted recycling and reuse, and treatment.” FARADAYICSM (R)ECM combines FARADAYICSM ECM with electrowinning to eliminate sludge and recover machine metal, while maintaining the electrolyte for immediate return to the process. FARADAYICSM (R)ECM employs electrolytes yielding soluble metals enabling 1) recycling to reclaim valuable metals, eliminating landfill 2) water conservation by elimination of sludge and 3) energy minimization by elimination of filtration, centrifugation and shipping of the sludge. Phase I will demonstrate the technical and economic feasibility of FARADAYICSM ECM of stainless steels in abuffered salt solution, coupled with recovery of the stainless steel components using FARADAYICSM Electrowinning process and cell. In Phase II, this technology would be scaled for implementation at commercial partners. The anticipated benefits are the ability to recover the value of the metals retained within the electrolyte and permit zero discharge use of the electrolyte, reducing environmental impact and lowering manufacturing costs. Applications for this technology include gas nozzles, heat sinks, turbine blades, castings, surgical devices of implants. Advances in manufacturing, and the use of more specialized materials are increasing the need for ECM, driving the growth of the ECM market, which was estimated to be on the order of $300M in 2010, with a compound annual growth rate of ~10%.