Composite Carbon Anode for Selective Metals Removal from Aqueous Waste Streams

Selective removal of metals from a variety of waste streams is often difficult due to the complexity of dissolved contaminants and the need to change bulk solution properties to enable precipitation or plating. Typically, pH adjustments and coagulants are used to precipitate species from solution, resulting in a sludge by-product that must be handled and disposed of through hazardous waste mechanisms. To avoid sludge generation and instead provide highly specific solution conditions, electrochemical cells can be employed that offer not only customizable electrode-electrolyte interfaces, modulated through localized pH regions and voltages, but also containment of the metal of choice inside of a disposable and possibly reusable filter. The pH and voltage needed to immobilize a metal either through oxidation/precipitation or plating can be determined through Pourbaix diagrams constructed for a metal given a proposed aqueous environment. PowerTech Water has shown the ability of lead (Pb) to be selectively removed from aqueous streams given the proper combination of carbon materials, applied voltage, and induced localized pH environments. In this project, a new electrochemical cell will be constructed and validated for the selective removal of copper (Cu) from complex aqueous industrial waste streams. To accomplish this selective Cu removal, a dense, high surface area, composite carbon anode with a charged polymer binder will be combined with a lower surface area, highly porous carbon cathode to create an electrochemical cell capable of >90% Cu removal with residence times of <60 seconds. A dense polymer- carbon composite anode will direct most of the flow through the porous cathode, where a local reduction potential will selectively plate Cu from solution. The charged polymer binder will enable quick charging of the dense carbon anode, enabling faster start-up and lower residence times. The combination of these performance parameters with readily available feedstocks will enable an economically viable separation process, capable of competing with chemical additive-based removal processes while offering much higher operational simplicity. The ability of this process to be highly specific for Cu removal can then 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.