Mechanistic understanding of the regulation of lead acetate on cyaniding behavior of chalcopyrite: NaCN consumption, ion dissolution and interfacial alteration

Abstract

Chalcopyrite dissolution during gold cyanidation consumes excessive NaCN and dissolved oxygen, generating byproducts that inhibit gold leaching. This study investigates the regulatory mechanism of lead acetate (C₄H₆O₄Pb·3H₂O) on the cyanidation behavior of chalcopyrite. Cyanide leaching tests with varying C₄H₆O₄Pb·3H₂O dosages were performed, and interfacial property changes were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results demonstrated that a 0.03 g·g⁻¹ dosage of C₄H₆O₄Pb·3H₂O reduced NaCN consumption from 0.60 to 0.28 g and decreased thiocyanate ion concentration from 1833.5 to 813.5 mg·L⁻¹ after 24 h of leaching. Dissolved oxygen remained above 5.9 mg·L⁻¹, indicating suppressed oxygen depletion. XPS and ToF-SIMS confirmed a ∼9 nm passivation layer composed of Pb(OH)₂, PbO, and PbS on the chalcopyrite surface, which inhibited the formation of CuCN, Fe(CN)₆⁴⁻, and SCN⁻ species. This passivation layer significantly reduced copper and iron dissolution, lowering their concentrations by 569.2 and 16.5 mg·L⁻¹, respectively. These findings indicate that C₄H₆O₄Pb·3H₂O effectively mitigates the detrimental impact of chalcopyrite on cyanide leaching and optimizes the chemical environment for gold leaching.

Keywords

cyanidation process / chalcopyrite / pulp chemistry / surface passivation / cyanide consumption

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