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| Enhancing Zinc Extraction Efficiency from Insoluble Zinc Cake through Citric Acid Leaching: A Hydrometallurgical Approach
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Sh.T. Khojiev, Sh.A. Rakhmataliev, M.S. Saidova, M.N. Suyarova, M.O. Esonova
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Abstract:
The present study employs the zinc cake leaching method as a means to enhance the extraction of zinc from insoluble tosoluble forms. Citric acid, identified as a water-soluble local reducing agent, facilitates this process, with a sulfuric acid solution serving as the solvent. Optimal results were obtained when the concentration ratio of sulfuric acid to citric acid was maintained at 28.7:4, resulting in an 86% dissolution rate of zinc cake. This technological advancement signifies a more efficient hydrometallurgical processing method for zinc cakes. Thermodynamic analysis elucidated that the limiting stage in the chemical reactions, involving zinc ferrite and a mixture of citric and sulfuric acids, is the mutual chemical interaction between zinc ferrite and citric acid. Complete reaction occurred at an optimal temperature of 338 K (65 °C). A kinetic study revealed that equilibrium constants for dissolving reactions of zinc and iron oxides in sulfuric acid exhibit high values, undergoing changes due to the recovery of zinc ferrite at the specified temperature. Quantitative analyses of the solution and secondary residual cake were conducted to ascertain the solubility of the zinc cake. To enhance the efficiency of hydrometallurgical processing at the optimal temperature, the impact of intensive mixing of the solution was investigated. Consequently, at 65 °C, the maximum average melting rate of zinc cake, reaching 90.3%, was achieved with a solution mixing speed of 55-65 times per minute. The proposed improvement method, if implemented on an industrial scale, holds the potential to significantly augment zinc production productivity.
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