A two-stage leaching process,namely,high-pressure acid leaching-atmospheric acid leaching,was used to treat laterite ores under mild conditions.The leaching ratio of Ni was low because of adsorption and incomplete leaching.In this work,surfactants were used as additives to boost the leaching ratio of Ni.The effect of surfactant type(cationic,anionic,and nonionic surfactants)on the leaching ratio of Ni was investigated.Leaching results showed that stearyl trimethyl ammonium chloride(STAC)apparently increased the leaching ratios of valuable metals.The variation in the physicochemical properties of the lixiviant and the residue improved the leaching ratio of Ni in the presence of STAC.Kinetics analysis indicated that the leaching process was controlled by chemical reaction.