In multi-mineral indium associated non-ferrous metal sulphide minerals, particularly zinc sulfide ore, followed galena oxide, lead, tin ore, copper sulfide and antimony sulfide mineral ore. Although indium is initially enriched in some non-ferrous metal concentrates, due to the low indium grade, it is generally not directly used as an indium raw material. And said non-ferrous metal smelting crude zinc concentrate passes, crude lead, slag, leaching residue, solution, soot, alloys, or anode mud obtained after the blast furnace ironmaking Indium and the like are the main raw material.

The extraction process of indium is mainly based on extraction-electrolysis, which is also the mainstream process technology of indium production in the world today. The principle process is: indium containing raw materials → enrichment → chemical dissolution → purification → extraction → back extraction → zinc ( aluminum ) replacement → sponge indium → electrolytic refining → refined indium.

Indium is mostly symbiotic with zinc, lead, copper and tin which are similar in nature. It has been found that natural indium, sulfur indium iron ore (FeIn 2 S 4 ), sulfur indium copper ore (CuInS 2 ), sulfur copper zinc indium ore [ Five kinds of indium-containing minerals such as Cu, Zn, Fe) 3 (In, Sn)S 4 ] and indium oxychloride [In(OH) 3 ]. Indium is the highest content in sulfide ore. Sphalerite is the main industrial source. Copper, galena, yellow tin and cassiterite also contain high indium, but because of the small amount of production, it is very dispersed and cannot be directly produced. The raw material of indium is generally recovered from by-products of heavy metal smelting such as zinc, lead and tin. Due to the many similarities in the chemical properties of rare metal ions, the separation, enrichment, and recovery are difficult. In recent years, as the demand for indium has increased, many studies have been conducted on the enrichment and recovery of indium.

Ninety percent of the world's indium production comes from by-products of lead and zinc smelters. The smelting and recovery method of indium is mainly recovered from the smelting slag, slag and anode mud of copper, lead and zinc by enrichment. According to the source of the recovered raw materials and the difference in the amount of indium, different extraction processes are applied to achieve the best configuration and maximum benefit. Commonly used process technologies include oxidative slag formation, metal replacement, electrolytic enrichment, acid leaching extraction, extraction electrolysis, ion exchange, and electrolytic refining. Currently widely used is solvent extraction, which is a highly efficient separation and extraction process. The ion exchange method for the recovery of indium has not been reported in industrialization. In the process of separating indium from less volatile tin and copper, indium is mostly concentrated in the flue ash and scum. When separated from volatile zinc and cadmium , indium is enriched in the slag and the filter residue. Although there are many methods for producing indium, according to relevant data, the most common and effective methods for industrial production development are as follows:

1. Recovery of indium from zinc smelting by-products

Japan Tonghe Mining Company uses the liquid residue generated in zinc smelting as raw material, first separates and leaches, removes copper and removes aluminum, removes heavy metals similar in nature to gallium and indium, and then adds hydrochloric acid to the solution enriched in gallium and indium. After mixing and adjusting the acidity, indium is extracted with ether to separate it from gallium and other metals. Finally, indium is stripped back out with water, replaced, melted and electrolyzed. In each electrolysis, the current density and the acidity of the electrolyte are adjusted to remove a trace amount of cadmium, tin, and aluminum to produce a metal indium of 4 N or more. In addition, the selective separation method of indium is to use a trace amount of indium soot, anode sludge and other residues and electrolytic effluent generated in the lead and zinc smelting process as a raw material, and an extracting agent containing phosphonic acid di(2-ethylhexyl) is used. The organic solvent of the ester is extracted by a sulfuric acid solution containing indium and other metals at a pH of less than 1.0, and then stripped with hydrochloric acid at 30-700 C to selectively separate indium. Its efficiency of extracting indium can be as high as 98% or more.

Second, hard zinc vacuum distillation to extract zinc and enrich in indium silver

"Hard to distillation in vacuo zinc and zinc indium silver enriched Ge" project is materials science, metallurgy field research. Hard zinc is an intermediate product produced in the rectification process of crude zinc fire. It is composed of high-boiling substances in crude zinc. It is mainly a multi-alloy alloy mainly composed of zinc, lead, iron and arsenic and containing elements such as antimony indium and silver. . The yield of hard zinc accounts for about 4% of the crude zinc treatment. The “hard zinc vacuum distillation zinc extraction and enrichment of indium silver” project, which was conducted by Dai Yongnian, an academician of the Chinese Academy of Engineering of Kunming University of Science and Technology, won the second prize of the 2003 National Technology Invention Award.

The technology uses the new process and new process of “zinc extraction and enrichment of indium and silver in vacuum distillation”, and successfully developed the production equipment matched with the process, breaking through the conventional technical transformation in the existing production technology. The traditional approach has been successful. Relevant experts commented that the invention process is the first in China, safe and reliable, easy to operate, no “three wastes” pollution, and belongs to the “green metallurgy” new technology, in line with the sustainable development strategy of comprehensive utilization of resources advocated by the state, with novelty. , creative and practical.

Third, the recovery of metal indium from slag

The recovery of metal indium from bismuth and zinc slag is generally carried out by acidification leaching-extraction. In other slags, such as iron slag, copper slag, etc., also contain rare metal indium. The indium content of the copper slag obtained by the bronzing smelting converter is 0.6%-0.95%, which has a large recovery value. The enrichment and recovery of indium from the iron slag can be carried out by a new process of reducing volatilization and extracting indium. The iron slag is reduced with carbon at a high temperature, and an additive is added to volatilize the indium from the slag to form an indium-rich material. Then, by leaching-extraction-electrowinning, high-purity indium with a purity of 99.99% can be obtained, and the indium recovery rate is more than 80%, and the problem of contamination of the iron slag is solved.

Fourth, the recovery of metal indium from soot

The smelting soot mainly contains metals such as zinc, lead, copper and iron, and contains a small amount of indium. Indium is mainly present in the smelting soot as phases such as In2O3, In2S3 and In2(SO4)3. The recovery of indium from smelting soot is mainly carried out by acid leaching-solvent extraction. Zhuzhou Smelting Group uses the direct leaching-extraction method of sulfuric acid to extract indium from the lead scum reverberatory furnace dust, leaching in 200g?L-1 sulfuric acid solution, the leaching rate of indium is 90%, using P204 as extractant, the solution under appropriate conditions The extraction rate of indium is up to 85%. With HCl as the stripping agent, the stripping rate is above 95%. The addition of NaCl during the acid leaching process is beneficial to further increase the leaching rate of indium. Acidizing roasting of lead soot - water immersion, indium leaching rate increased to more than 88%. In the extraction process using P204 horizontal tank extraction method, the extraction rate of indium increased from 90% to 95%.

V. Recovery of metal indium from wastewater

(1) Extraction method

Extraction is an important method in the enrichment and recovery of indium. The extractant includes bis(2-ethylhexyl)phosphonic acid (HDEHP, P204), P5708, P507D, P350, PV?HQPF, Cyanex923, TR-PO, TBP and petroleum sulfoxide, etc.

(2) Ion exchange method

The leaching resin has the advantages of less extractant flow rate, high column loading capacity and good mass transfer performance, and is widely used in separation engineering.

(3) Liquid film method

The liquid membrane separation method is a high-efficiency, rapid and energy-saving high-tech separation technology. To P291 as carrier, L113A is a surfactant, a film enhancer liquid paraffin, kerosene solvent into a film, an aqueous solution of sulfuric acid and hydrazine sulfate as the phase reagent, separation and enrichment using indium for the emulsion liquid membrane system.

6. Recovery of metal indium from the alloy

A multi-component alloy and a metal compound mainly composed of lead, tin, etc., containing valuable metals such as indium and antimony, and which are capable of recovering valuable metals such as indium and antimony by alkali fusion or acid leaching. For example, the lead at the bottom of the electric furnace is a multi-component alloy and a metal compound mainly composed of lead, tin, etc., and NaOH is added to the lead at the bottom of the electric furnace to perform alkali fusion and alkali boiling, and the fine leaching residue is acid leached, and the total leaching rate of the two-stage acid leached indium is as follows. Up to 99%, the direct yield of indium is 84.3%.

The extraction process of indium in China achieved breakthroughs in the early 1990s. In the context of the rapid development of the non-ferrous metal industry, the extraction process of indium has been very popular. Especially after the high price of indium, the comprehensive recovery of indium has been widely valued by enterprises. Domestic research institutes and production companies have made great progress in indium-doping processes for various indium-containing materials, so China's indium production has grown rapidly. The main manufacturer's process is characterized by different preliminary enrichment methods and dissolution techniques for different indium-containing raw materials, and then selecting suitable extractants according to the medium. For example, Huaxi Group and Liuzhou Indium Technology Co., Ltd. provide indium raw materials for zinc-concrete iron- vanadium slag containing about 0.2% of indium; Huludao Zinc Plant, Shaoguan Huali Company, Shaoguan Smelter is from indium 2%~ 3% of the hard zinc block is extracted indium; Zhuzhou smelter uses the replacement slag (indium 2% to 3%) as the raw material for indium extraction; Liuzhou Zinc Products Company extracts the leaching residue (containing 0.2% of indium) from the production of Liede powder.

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