A solid polymer electrolyte reactor is designed for the electrochemical hydrodehalogenation (HDH) of 2,4-dichlorophenol (DCP) in paraffin oil. The reactor has been evaluated at 0.05, 0.1, 0.2, 1 and 2 dm(3) scales in terms of cathode materials and structure and ratio of the cathode surface area to the solution volume. A cathode of titanium mini mesh with a palladium electrocatalyst produced by electrodeposition was particularly effective. Current efficiencies of up to 80%, percentage of DCP removal of up to 50%, space-time yields of up to 5.0 kg DCP m(-3) h(-1) and energy consumption as low as 1.5 kW h (kg DCP)(-1), were achieved. The reactor showed stable operation for periods of up to 170 h. (C) 2003 Elsevier B.V. All rights reserved.