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Electrochemical measurements have been made on the system Cu2+‐adipic acid‐HNO3 (which models the effluent from adipic acid plants) to investigate the reasons for the observed low current efficiency for copper deposition from such solutions. The most probable cause is a cathodic shift in the deposition potential of copper making the reduction of NO3− the preferred process. Depletion experiments have been carried out on real effluent in two three‐dimensional cells, a bipolar trickle tower and a porous reticulated carbon bed. Each performs reasonably well and, while the current efficiencies are low (c 20%), the deposition is essentially mass‐transfer controlled.