From waste liquid to pure indium: An analysis of the technology for efficient indium recovery using ion exchange resins

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I. Introduction: Why are new technologies needed for indium recycling? Indium (In), as a typical representative of rare metals, is gaining an increasingly important strategic role in modern industry. From ITO targets for liquid crystal displays and semiconductor compounds to copper indium gallium selenide (CIGS) thin films in photovoltaic cells, indium is used across nearly the entire electronic information industry chain. However, indium is only present at 0.1 ppm in the Earth’s crust, and it rarely forms independent deposits; it mainly occurs as an impurity in the processing of zinc, lead, tin, and other metals. This contradiction between scarcity and demand makes the efficient recovery of indium from smelting waste liquids and leachates from electronic waste an important issue in resource recycling. Traditional indium recovery processes mainly rely on chemical precipitation and solvent extraction methods. The precipitation method is simple to operate, but it requires large amounts of reagents and generates a lot of slag; moreover, the separation selectivity for indium is poor, as it often precipitates together with impurities such as iron and aluminum, resulting in high costs for subsequent purification. Although solvent extraction methods (such as P204 and P507 systems) can achieve good separation, issues such as the volatilization loss of the organic phase, emulsification problems, and the stringent requirements of the extractants on the operating environment deter many companies from using them due to environmental concerns. As an ion exchange resin engineer with extensive experience in hydrometallurgy, I believe that the ion exchange resin method offers unique advantages in the field of indium recovery: it features a friendly operating environment, high selectivity, good process continuity, and is suitable for handling low-concentration indium-containing solutions