Study On Leaching Technology Of Indium From A Complex Converter Slag

In a domestic smelter, later-stage slag(mainly containing Pb, Cu, As, Zn, Sb and In) in reverberatory is produced from lead scum. The annual production of converter slag with 0.3-0.5% indium is 1000t. Converter slag is valuable because it consist of 3-5t indium,50-80t copper,200t lead,50t tin and antimony. there is no practicable technology for this slag recovery, especially for indium extraction. Grounded on this, the indium leaching with different leaching methods and its rules is studied in this paper, aiming at providing a base for the industrialization.Firstly, this thesis investigated the leaching process of converter slag with indium in sulfuric acid system. The effect of initial acid concentration, temperature, liquid to solid ratio, reaction time and stirring speed on leaching rate was studied. The results show that the highest leaching rate (50.32%) was obtained when following parameters were employed:liquid-solid ratio of Indium containing slag:5ml/g, initial acid concentration 6 mol/L, temperature: 90℃, stirring speed:280r/min. The chemistry analysis indicates the un-leaching indium is silicate or inclusions of indium silicate and SnO2.Secondly, the study explored methods of intensified leaching about converter slag, the experiment adopted the measures such as oxidation, concentrated sulfuric curing, sulfuric roasting, pressure applying, mechanical activation, ultrasonic activation and heat activation. The results show that high pressure acid leaching is the most effective method, indium leaching rate rise to 89.92% when the parameters set as follows:starting sulfuric concentration: 6mol/L,temperature:300℃, time:3h, stirring rate 200 r/min; concentrated sulfuric curing,sulfuric roasting-water leaching and heat activation sulfuric leaching rate is 78.22%,82.84% and 81.32%; the effect of mechanical activation and ultrasonic activation is not obviously, indium leaching rate is 63.2% and 56.66% under the optical condition, oxidizing acid leaching has no effect on this slag.The results show that indium leaching rate is high when treated by the processes such as concentrated sulfuric curing, sulfuric roasting-water leaching and heat activation sulfuric leaching. it has industrial prospect when high indium is contented in converter slag.