In order to apply grinding method for degradation of pentachlorophenol (PCP) to an industrial scale, the proportion of different materials [ CaO, SiO2 and CO(NH2)(2)] and the size of grinding balls were examined. For saving energy and increasing dechlorination efficiency, the rotation speed and grinding time were maintained at relatively low values. At a mass ratio of grinding balls to materials (40: 1), PCP was added into a big steel jar (300 ml) with other materials to grind at 300 r. min(-1) for 5 h. The results indicated that when PCP was mixed with CaO and SiO2 in a molar ratio of 1: 60: 60, the best dechlorination of 58.4% was achieved. CO(NH2) 2 could not be used as hydrogen donor in the dehalogenation by mechanochemical reaction, since it restrained the dechlorination process. The size of grinding balls has significant effect on the reaction. The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction, while steel balls of 10 and 15 mm could give better dechlorination reaction. It indicates that dechlorination depends on the mass of balls and fill rate. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.