ZNO-CATALYZED PHOTODEGRADATION OF KRAFT BLACK LIQUOR

Kraft black liquor was used as a model for effluent from the pulp and paper industry. Photochemical bleaching was attained when dilute samples were photolyzed with UV radiation using ZnO as catalyst. The photochemical mineralization of organic matter was first order and dependent on the oxygen pressure. A catalyst doped with Ag showed little effect on the discoloration or decrease in the chemical oxygen demand (COD) of black liquor. Platinum-impregnated ZnO yielded 100% discoloration after 60 min (190 kJ m-2) of UV radiation. Gel chromatography profiles and CO2 evolution measurements confirm the photomineralization of organic matter.