precious metals (precious metals)

Precious metals in e-waste refers to the group of high-unit-value metallic elements present in printed circuit boards, connectors, and integrated circuits — primarily gold, silver, palladium, platinum, and rhodium. They are the single largest revenue driver per kilogram of feed material in formal e-waste recycling, even though they form less than 0.1% of total e-waste mass.

Typical concentrations and where they sit: Mobile-phone main PCBs contain 200-350 grams of gold, 1,500-2,500 grams of silver, and 80-130 grams of palladium per tonne of clean PCB. Server motherboards reach 250-400 grams of gold per tonne. RAM modules and CPUs are even richer because of dense gold bonding wires (see entries for IC, CPU, and RAM). By comparison, the richest natural gold ore in the world contains roughly 5-8 grams of gold per tonne — so e-waste PCBs concentrate gold 40-50 times above primary mining ore, and silver 100-300 times above silver ore.

Recovery routes: Two industrial pathways exist. Pyrometallurgical recovery (used at large integrated smelters such as Umicore in Belgium and Boliden in Sweden) melts shredded PCBs into a copper-anode bath, then refines the bottom slime electrochemically. Hydrometallurgical recovery (the dominant Indian route) dissolves shredded boards in aqua regia, thiourea, cyanide, or chloride leach chemistry, then selectively precipitates each metal using reducing agents and ion-exchange resins. Both routes recover 92-97% of contained precious metals at industrial scale; informal acid bath operators typically recover 40-60% with severe environmental damage.

Economic trade-offs and Indian context: The economics of precious-metal recovery depend on three variables: spot metal prices, feed grade, and labour and reagent cost. At recent gold prices of Rs 60,000+ per 10 g and palladium at Rs 30,000+ per 10 g, a single tonne of high-grade smartphone PCB yields Rs 12-18 lakh INR in gross precious-metal value before processing cost. The challenge for Indian recyclers is securing enough volume to justify a hydromet plant — typical break-even is 50-100 tonnes of PCB feed per month, which requires aggregation across multiple bulk consumers under the EPR framework.