In the present investigation the photocatalytic activity of zinc sulphide has been enhanced using KCl in different molar ratios. The progress of the reaction was monitored spectrophotometrically. The effect of various parameters like pH, concentration of dye, amount of semiconductor, light intensity etc. upon the rate of photocatalytic bleaching of eosin Y has been observed. The molar ratio of KCl: ZnS = 0.25 was found to be a most efficient mixture for bleaching of eosin Y. A tentative mechanism for the photocatalytic bleaching of the dye has also been proposed.