Although the hydrometallurgical zinc smelting process occupies a dominant position in global zinc production, it faces severe challenges in processing high-iron zinc roasted sand. The stable spinel structure of zinc ferrite leads to a significant negative correlation between the leaching efficiency of zinc and indium in the traditional high-acid leaching system. This contradictory phenomenon is due to the similar coordination chemical properties of trivalent iron and indium, as well as the lattice wrapping effect of zinc ferrite on indium.
In response to the above technical bottlenecks, Zhengzhou Tiei Extraction Technology Co., Ltd. conducted a large number of experiments, selected the CWL-M series centrifugal extractor for repeated verification, and researched and developed a new gradient recovery process of "acidic medium regulation-sulfate phase change-centrifugal kinetic separation".
In the primary acid leaching stage, by precisely controlling the pH range and introducing a sulfate concentration gradient, selective dissolution of zinc and directional enrichment of indium were successfully achieved. The key innovation lies in the subsequent sulfation roasting process: using a fluidized reactor with composite additives, under optimized conditions of a certain temperature, not only the decomposition rate of zinc ferrite meets the requirements, but also the sulfate conversion rate of indium is increased to the standard requirements.
The selection of zinc and indium extraction equipment is very important. In order to achieve efficient separation of indium from zinc and iron, in the traditional solvent extraction process, the distribution ratio of indium and iron in the two phases is similar, which makes it difficult to effectively separate the two. The centrifugal extractor technology uses the strong centrifugal force field generated by high-speed rotation to enhance the mass transfer efficiency of the two phases. At the same time, combined with the difference in mass transfer rates of different metal ions in the organic phase and the aqueous phase, effective separation of indium from zinc and iron can be achieved. By selecting a suitable extractant (such as P204, P507, etc.), selective extraction of indium can be completed in a short time, while zinc and iron are mainly retained in the aqueous phase, thereby achieving the goal of efficient metal separation. After stripping and subsequent purification, a high-purity indium product can be obtained.
The CWL-M series centrifugal extractor launched by Zhengzhou Tiei Extraction is developed to address the shortcomings of traditional centrifugal extractor. The power consumption is only 10% to 30% of that of traditional annular gap extractor. At the same time, the centrifugal extractor has short stage retention time, rapid phase separation, high extraction efficiency, and save investment costs and solvent recovery and regeneration costs.
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