indium (indium)

Indium (In, atomic number 49) is a soft, malleable post-transition metal with low melting point (157°C), produced almost exclusively as a by-product of zinc smelting from sphalerite ores. Its global primary production is roughly 800-900 tonnes per year — minuscule compared to copper (25 million tonnes) or aluminium (70 million tonnes) — and the EU's Critical Raw Materials list, the US Geological Survey's Critical Minerals list and India's 2023 Critical Mineral List all designate indium as supply-chain-strategic.

The dominant end-use is Indium Tin Oxide (ITO), a transparent conducting oxide coating applied to flat-panel LCD, OLED and touchscreen displays at film thicknesses of 100-200 nm. ITO uses roughly 75-80% of global indium consumption; the remainder goes to indium-based solders (low-temperature electronics joining), thermal interface materials, indium-gallium-arsenide (InGaAs) infrared semiconductors, and indium-phosphide for high-speed photonics. A 65-inch LCD TV contains roughly 0.5-1.5 g of indium in its ITO layer; a smartphone has 50-150 mg.

Recovery from end-of-life displays is technically demanding. The screen lamination is bonded with adhesive and back-light units; mechanical separation of the ITO-bearing glass from polariser films, back-light reflectors and driver electronics requires precise cutting (laser delamination, wet chemical debonding) without contaminating the indium fraction. The recovered ITO glass is leached in dilute hydrochloric or sulphuric acid; indium reports to the leach solution along with tin. Selective indium precipitation by pH adjustment (indium hydroxide precipitates around pH 3.5-4.5) separates it from tin and impurity metals. Electrowinning produces 99.99% indium metal cathodes.

For Indian e-waste recyclers, indium recovery is rare at present. The recovered ITO content from a tonne of mixed display scrap is typically 50-200 g of indium — at Rs 25,000-40,000 per kg of indium metal (mid-2025), Rs 1,000-8,000 per tonne of feed. Capex for selective indium recovery (lamination separation, acid leach, electrowinning) is Rs 15-40 crore, and the throughput justification requires concentration of national display flows that no single recycler currently commands. The pragmatic path is for display fractions to be aggregated at specialised pre-treatment hubs and exported as ITO-glass concentrate to global refiners (in Belgium, Japan, South Korea) until domestic capacity scales. The trade-off worth noting is supply security: 75% of global indium production comes from China, which has imposed export controls; India's domestic recovery infrastructure is strategically valuable but not yet commercially mature.