Pulp and paper mill wastewater is characterized by very high chemical oxygen demand (COD) values that inhibit the activity of microorganisms during biological oxidations. The electrochemical degradation of pulp and paper mill wastewater catalyzed by molybdenum and phosphate (Mo-P) modified kaolin with graphite as anode and cathode was investigated. The catalyst was characterized by XRD, XPS and SEM spectra and the effects of pH, metal ion and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found out that the modified kaolin loaded with Fe 3' had higher electrochemical catalytic activity in the electrochemical degradation of paper mill wastewater at pH 4. A 96% COD removal efficiency was obtained in 40 min of electrochemical treatment of the wastewater at current density 30 mA cm(-2). A possible mechanism for degradation of the mill wastewater constituents was also proposed. (c) 2006 Elsevier B.V. All rights reserved.