Composite Carbon Anode for Selective Metals Removal from Aqueous Waste Streams

Specific removal of metals such as copper from water streams often involves the use of iron-based coagulants to meet regulated discharge compliance standards. While effective, these coagulants require large chemical and operator demands and produce large amounts of waste that must be properly disposed of, often as hazardous waste. The recovery and recycle of copper from these coagulants is not straightforward and expensive. Instead of using a coagulant, an electrochemical cell using composite carbon-polymer electrodes is employed here, which can provide the selective removal of copper down to discharge compliance levels. Using this method, copper can be concentrated into a separate stream, enabling recycling of copper and providing a valuable resource as opposed to a waste stream. In Phase I, the development and validation of a new composite carbon anode was first carried out, combining an advanced polymer with conventional carbon materials (activated carbon and carbon black) to promote a capacitive charging and carbon oxidation. A proof-of-concept device demonstrated the use of this dense carbon anode paired with a porous carbon cathode. Separation testing was conducted that examined copper removal from feed streams containing 0.05 ppm to 100 ppm copper. In Phase II, electrode formulations were modified, and lifetime of the composite carbon anode were determined with activated carbon mass having the largest impact. Copper recovery was demonstrated through a newly designed electrowinning unit, and construction and automation of a pilot system was completed. In Phase IIB, work with a project partner will be completed to scale-up designed composite carbon anodes while continuing to increase the activated carbon mass and decrease the resistivity to prolong separation lifetimes. Validation of Cu separations for additional product markets, specifically for the mining sector, will take place. Finally, in situ analytics will be added to the process system to determine end-of-life for the carbon anode in real time. The ability of this process to be highly specific for copper removal can eventually be adapted to other metals and environments. This process enables metals-specific removal, removing the need for chemical coagulant based processes and the large amount of waste associated with them.