Villasenor, J. Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.Photocatalysis using ZnO-Fe2O3 coupled catalyst removed partially the organic matter dissolved in kraft black liquor obtained from pinus wood cooking. The photo-assisted oxidation using different ZnO/Fe2O3 ratios was studied following the CO2 evolution during the course of the reaction. A synergy of the composite improves the mineralization observed. The optimal ZnO to Fe2O3 ratio varied from 0.5 to 0.7 which allowed the highest mineralization rates.