Extraction kinetics of zinc by new extractant in ammoniacal system

Abstract

The controlling step and the extraction reaction rate equation of zinc extraction from Zn(II)-NH₃ solution by using a newly synthesized organic compound, 2-acetyl-3-oxo-dithiobutyric acid-myristyl ester as the zinc extractant, were clarified. The effects of agitation speed, specific interfacial area, temperature, extractant concentration and Zn ion concentration on the extraction rate are studied in constant interfacial area cell. The results show that the extraction rate depends on interfacial chemical reaction and diffusion by using this new extractant to extract zinc, and the apparent activation energy of this extraction reaction is measured as 28.2 kJ/mol, which demonstrates that the extraction reaction is controlled by the mixed-controlled reaction rate. The apparent reaction orders a and b are measured as 1 and 0.38, and the constant k ₀ is 138.70. So, when extraction conditions are controlled as [HR]=20%–50%, T=0–30 °C, N=120–177 r/min and S=72.6–127.5 m⁻¹, the solvent extraction reaction rate can be depicted as ${v \mathord{\left/ {\vphantom {v {\left( {mol \cdot m^{ - 2} \cdot s^{ - 1} } \right) = 138.7 \cdot \exp \left( { - \frac{{28 206}} {{8.314 T}}} \right) \cdot \left[ {Zn^{2 + } } \right]_T \cdot \left[ {HR} \right]_o^{0.38} }}} \right. \kern-\nulldelimiterspace} {\left( {mol \cdot m^{ - 2} \cdot s^{ - 1} } \right) = 138.7 \cdot \exp \left( { - \frac{{28 206}} {{8.314 T}}} \right) \cdot \left[ {Zn^{2 + } } \right]_T \cdot \left[ {HR} \right]_o^{0.38} }}$.