A number of established techniques are available for the treatment of waste streams containing heavy and precious metals, including; precipitation, ion exchange, solvent extraction, adsorption, and cementation. All of these methods have the disadvantage of producing a secondary effluent consisting of a more concentrated metal-bearing solution or a mixed solid that requires further treatment.
C-Tech Innovation’s C-Flow 3D system uses electrochemical deposition to recover elemental metal directly from an aqueous solution, with no additional reagents. High value metals (e.g. Co, Ni) and precious metals (e.g. Pt, Ag) can be directly recycled, easily and at high purity.
Electrodeposition occurs at the cathode of an electrochemical cell, while oxygen is produced at the anode due to the oxidation of water, according to the following scheme (where M is the metal being deposited):
Cathode: M2+ + 2e– → M
Anode: H2O → ½ O2 + 2H+ + 2e–
Overall: M2+ + H2O → M + ½ O2 + 2H+
While conventional electrochemical cells relying on metal plate or mesh electrodes are limited in their performance by the low surface area, C-Flow 3D uses very high surface area carbon felt to maximise the deposition rate and to achieve much lower final solution concentrations.
C-Flow 3D is available as a self-contained laboratory scale unit, to study metal deposition from aqueous solutions. Students can study the effects of electrolyte, its flowrate, and the applied current on deposition rate, current efficiency, and cell voltage. Such parameters can be used in economic studies to minimise plant costs.
C-Flow 3D can process a range of metal-containing solutions typical in industrial applications, including copper, silver, and cadmium, and can reduce solution concentration down to ppb levels.