Adsorption of Copper on Modified Galvanic Sludge

The possibility of extracting Cu compounds through adsorption using galvanic sludge modified with solutions of humic acids was investigated. The chemical and structural composition of rigid galvanic sludge from printed circuit board production was examined. The primary phase-forming element is Fe compounds in the form of β-FeOOH, constituting up to 45% of the sludge mass. X-ray phase analysis of the sludge revealed the presence of two main phases: akaganeite (β-FeOOH) and an atacamite-like crystalline phase of copper hydroxychloride (Cu(OH)₃Cl) in quantities exceeding 10%. The conditions for leaching Cu compounds from the sludge and the effect of thermal treatment on the sludge adsorption capacity were determined. Copper was leached from galvanic sludge using an H₂SO₄ solution within the pH range of the equilibrium solution of 3–5.5. This allowed for the leaching of up to 97% of copper, with minimal dissolution of Fe compounds. The Cu concentration in the leaching solution reached 10–15 g/dm³, while the concentration of Fe ions did not exceed 1 mg/dm³, enabling the subsequent utilization of these solutions for Cu electroextraction. The modification of the sludge with humic acid solutions increases its adsorption capacity for copper ions by more than threefold.