Leaching of Copper from Cuprous Oxide in Aerated Sulfuric Acid

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The leaching behavior of copper from Cu₂O in H₂SO₄ solution was investigated to establish the leaching process for cathode powders produced by the recycling of waste printed circuit boards. When air was not introduced in sulfuric acid solution, the dissolution of copper from Cu₂O was inhibited by the formation of elemental copper (Cu⁰). The dissociated cuprous ions (Cu⁺) transformed into elemental copper (Cu⁰) or cupric ions (Cu²⁺) owing to the instability of Cu⁺ in H₂SO₄. Cu⁺ can be reduced to elemental copper (Cu⁰) by accepting an electron generated from the oxidation of another Cu⁺ to Cu²⁺, which is known as a “disproportionation reaction.” The introduction of air enhanced the leaching efficiency of copper due to the role of oxygen in the air as oxidant by accepting the electron generated from the oxidation of Cu⁺ to Cu²⁺. In the leaching test using Cu₂O reagent, the leaching efficiencies of copper increased with increasing air flow rate, temperature and agitation speed, but decreased with increasing pulp density. Copper leaching efficiency increased to up to 99% within 60 min in the aerated sulfuric acid solution at 30℃, 400 rpm, and pulp density of 2%.