What are the main methods for enriching indium?

(1) Hydrolysis method The main elements such as copper , zinc , cadmium and indium are separated by adjusting different pH values ​​during hydrolysis of various elements, and indium hydroxide can be completely precipitated at pH=4.67 to 4.85.

(2) Selective Dissolution and Precipitation Method The indium-containing precipitate is dissolved in sulfuric acid, so that most of the lead is precipitated as a poorly soluble sulfate and separated from the indium. The hydroxide precipitate is treated with a caustic soda solution to cause aluminum , zinc and lead to enter the human solution, while indium remains in the precipitate to achieve separation from indium. The indium-containing solution is treated with ammonia to cause indium and iron , aluminum to co-precipitate, and copper, cadmium and zinc to form an ammonia salt in the solution. The phosphorus acid salts from a weak acid solution (pH = 3.2) to precipitate indium, and indium can lead, zinc, iron and cadmium separation.

(3) selective displacement method using a metal deposition potential different selective accumulation of indium, zinc powder can be replaced with the copper in the first solution, after the addition of copper, indium and cadmium zinc can be replaced with various other elements separated. The zinc oxide roasting leaching of Zhuzhou Torch Metal Company adopts neutral and acidic two-stage leaching process, and then the indium enrichment is replaced by zinc powder. By adopting a series of improvements in the process, the recovery rate of zinc indium oxide is about 40%. Increased to over 55% now. The main chemical reactions are as follows:

(4) Extraction method Indium P204 is an acidic phosphate extractant, usually in the form of a bimolecular form, which can form a compound with a trivalent element. This compound does not contain a hydrophilic group, so it is hardly soluble in water, and is easily soluble in an organic solvent and can react with the same series of metal ions. Its extraction rate for various ions is a function of the pH of the solution, so controlling the different pH values, the efficiency of extraction of each metal ion is also different. The indium special effect extractant has not been found in China, and the indium extraction mechanism of the acidic phosphorus extractant has been studied. The order of the indium extraction ability of the phosphorus extractant is as follows: P204>P5708>P507>P5709, anti-extraction ability On the contrary, they are arranged in the order of P5709>P507>P5708>P204. Industrial commonly used extractants have the advantages of stable performance, low price and easy operation. The P 204 extractant has good selection performance for indium, and indium is extracted from the indium-containing solution to make the indium enter the organic phase, and is separated from the copper, zinc, cadmium and arsenic and the ferrous iron which are difficult to extract in the aqueous phase. The indium entering the organic phase is back extracted by a high concentration of hydrochloric acid, and the indium enters the aqueous phase to obtain an aqueous solution of indium containing hydrochloric acid.