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 carbon oxidation reaction. Then, 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. A specially designed pH cell was used to thermodynamically validate local conditions at the electrode surfaces for copper plating to be accomplished. Scale-up and performance conditions were identified to allow for wider use of this technology. In Phase II, electrode formulation conditions, including a binary polymer binder, will be modified as well as electrode thicknesses to increase the current density and lifetime possible from the composite carbon anode. Scale-up of these electrodes will take place to evaluate performance in a pilot unit. Coding and operation of a pilot unit will be carried out to not only validate copper removal but also examine concentrating copper into a separate stream that can be used to produce recyclable copper solids. The ability of this process to be highly specific for copper removal can eventually be adapted to other metals and environments. This process will enable metals-specific removal, removing the need for chemical coagulant-based processes and the large amount of waste associated with them.