Zinc oxide photocatalyst was impregnated onto the activated carbon under mild hydrothermal conditions (T=150 degrees C, P = 20-30 bars) to form a ZnO:AC composite material. The ZnO:AC composite was characterized using powder X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), BET surface area measurements and scanning electron microscopy (SEM). As-prepared ZnO:AC composite exhibited higher photocatalytic activity when compared to the commercial ZnO and untreated activated carbon; this was testified by the degradation of acid violet dye using ZnO:AC and commercial ZnO. The effect of various parameters such as initial dye concentration, catalyst loading, pH of the medium, source and intensity of illumination on the photocatalytic degradation of acid violet using ZnO:AC were investigated. Real time textile effluents have also been considered for the degradation using ZnO:AC composites. The reduction in the chemical oxygen demand (COD) values of the treated effluents revealed a complete destruction of the organic molecules along with the color removal. (c) 2006 Springer Science + Business Media, Inc.