Selective leaching of chromium-containing slag by HCl

A batch of column experiments was carried out to investigate the change of Cr(VI) concentration leached out from chromium-containing slag with HCl as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr(VI) leaching. The optimal parameters were obtained for Cr(VI) leaching and a fitting model was established to describe the procedure of Cr(VI) leaching. The results show that Cr(VI) concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr(VI) leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr(VI) selective leaching are as follows: pH=3.0, 1.5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 degrees C of temperature. The procedure of Cr(VI) leaching fits well with the model: nu=1.87t(-0.54), indicating that the leaching rate of Cr(VI) declines in an exponential order of -0.54.