High separation sharpness of hydrocyclones has attracted much interest with its classification becoming increasingly popular. It is well known that the separation process in hydrocyclones is always accompanied by low sharpness. Therefore, the coarse particles escape by the overflow, and the fine particles are collected through the underflow. This paper presents a numerical study of the effects of the configurations of vortex finder on the separation sharpness of a hydrocyclone. A regression model for the effect of the configurations of vortex finder on the separation sharpness was developed by the application of central composite design. The results show that among the configurations of vortex finder, the effects of the parameters on the separation sharpness follow the order: the diameter (highest) > vortex finder length > the thickness (lowest). A high separation sharpness can be achieved by an appropriate range of the diameter and vortex finder length. According to the fitted regression model, the predicted results of separation sharpness is found to be in satisfactory agreement with the observed data, and an optimal configuration is proposed for the vortex finder to achieve a higher separation sharpness. Based on this result, titanium was recycled from acid leaching tailings using a hydrocyclone with a high sharpness during titanium dioxide production through the optimization of vortex finder. (C) 2014 Elsevier B.V. All rights reserved.