Copper Refining
The industrial process of purifying mined copper into high-grade metal, typically via electrorefining; also the source of most of the world's byproduct tellurium, gold and silver, recovered from anode slime.
Covered in 1 MetalsCost.com News Intelligence article, most recently on August 25, 2026.
Overview
Copper refining is the step after smelting: impure "blister" copper (about 98-99% pure) is cast into anodes and dissolved electrolytically in a copper sulfate/sulfuric acid bath, with pure copper (99.99%) plating out onto cathodes. Global refined output reached an estimated 28.7 million tonnes in 2025. The impurities that don't dissolve or redeposit sink to the bottom of the cell as anode slime, typically 2 to 20 kg of it per tonne of cathode copper produced.
Metals It Depends On
Anode slime is where copper refining earns its keep beyond copper itself: it's the concentrated source of nearly all the gold, silver, tellurium and platinum-group metals that arrived, in trace amounts, in the original ore. Roughly 90% of the world's tellurium is recovered this way, and in China — which dominates global refining capacity — anode slime is reported to supply around half the country's gold and silver output.
Sources
- ~90% of world tellurium recovered from copper anode slime — A comprehensive review on tellurium extraction and recycling technologies from copper anode slime (2025)
- Global refined copper output ~28.7 million tonnes in 2025 — THE WORLD COPPER FACTBOOK 2025 (2025)
