 ISSN 0235-7216 ISSN 2424-4538 (online) |
2009 m. Nr. 4 Formation of Cu(I) compounds in the Cu|Cu(II) – maleic acid system
Electrochemical quartz crystal microgravimetry was applied to study the interactions between copper electrode and Cu(II) solutions containing maleic acid (LH2). The electrode mass was found to decrease under open-circuit conditions in sufficiently acidic solutions (pH ≤ 5) due to the heterogeneous reaction Cu + Cu2+ ↔ 2 Cu. Its rate falls into the region from 0.4 to 0.8 nmol cm–2 s–1 depending on pH. Conditions favorable for Cu2O formation emerge in less acidic media (5.5 < pH < 6.0); the rate of this process accounts for some nmol cm–2 s–1. Simulations based on the material balance equations show that deep chemical changes are possible in the system with a 90% transformation of Cu(II) into Cu(I). Formation of Cu2O at the electrode surface enhances this process. Spectrophotometric investigations were carried out with solutions subjected to preelectrolysis. Actually, complete saturation with intermediate Cu(I) compounds can be achieved, if a sufficiently large charge passes through the solution. According to the simulated data, a neutral CuLH complex should predominate in the final state. Keywords: copper, maleic acid, complexes, quartz crystal microgravimetry, spectrophotometry |
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