Value-added utilization of silicon and iron in copper smelting slag

Abstract

ABSTRACT The methodology enhanced by synergic catalyzation with sodium nitrate and ultrasonic irradiation under alkaline leaching condition at atmospheric pressure was proposed, for separating silicon and iron in acid leaching residue of copper smelting slag. And the preparation of white carbon black from the alkaline leachate obtained was conducted for utilizing the silicon in the copper smelting slag, as well as the alkaline leaching residue can be used as raw materials with high quality for iron making. The effects of leaching temperature, sodium hydroxide concentration, ultrasonic power, stirring speed, liquid-solid ratio, leaching time and additional amount of sodium nitrate on silica leaching rate were studied. The leaching kinetics of SiO2 from the acid leaching residue of copper smelting slag was also studied. The results showed that under the optimal leaching conditions of temperature 130°C, sodium hydroxide concentration 20 wt.%, ultrasonic power 315 W, stirring rate 500 rpm, liquid-solid ratio 6 mL/g, leaching time 60 min and sodium nitrate addition 2.5 g, the leaching rate of SiO2 reached 94.5 wt.%. Among 90 ~ 130°C, the leaching process was controlled by diffusion and consistent with Johnson Mehl Avrami. The quality of white carbon black prepared was of meeting grade A in Chinese national standard.