At present, there are two kinds of indium, indium primary and indium secondary. Primary indium is mainly extracted from raw ore and is the main source of smelting indium at present. Recycled indium is the smelting of waste metals, mainly as a by-product of the smelting process of ores such as lead, zinc, copper and tin, but the total amount of recycled indium is not large.
Primary indium mainly comes from mineral resources, and the total amount of primary indium is very large. No separate deposits of indium have been found, which are associated in trace amounts in minerals such as zinc and tin. When its content reaches 100,000, it has industrial production value. At present, it is mainly extracted from zinc blende. China's sphalerite is mainly distributed in yunnan province, where the proven reserves of high-speed railway sphalerite amount to 7 million metal tons.
Most of the indium currently produced is a by-product of the smelting process of ores such as lead, zinc, copper and tin. In the process of separating indium from volatile tin and copper, indium is mostly concentrated in flue ash and scum, while indium is enriched in furnace slag and filter slag when it is separated from volatile zinc and cadmium. In China, indium is mainly extracted from the by-products of lead and zinc smelting.
With the continuous improvement of the production technology of indium, the source of raw materials is also diversified. The soot, copper smelting slag and lead smelting slag of steel plant have all become the raw materials for the extraction of indium.
At present, the process of recovering indium from lead and zinc smelting byproducts has been mature. The proportion of recycled indium production is nearly half of total indium production (USGS 2012). Japan already consumes 60 per cent of the world's demand for indium and, despite a recovery rate of 70 per cent, 27 per cent has been abandoned, and less than 3 per cent has been used directly in circuits. Based on current usage, even if recycling rates are further improved and even if half of indium is consumed using alternative materials, pure indium resources will be exhausted by around 2018, at least in 2025. Therefore, first all of the problems we are facing is how to directly from lead and zinc ore containing indium, the extraction body metal metals such as lead, zinc and indium enrichment, the practical significance of comprehensive ore smelting process to achieve, rather than from a by-product of smelting recovery of indium, so can greatly reduce the production cost, improve the economic benefit.
