The extraction kinetics of lanthanum (III) from a chloride medium by bis(2-ethylhexyl) phosphate(HDEHP) and dimethylheptyl methyl phosphate(P350) in the presence of sulfonated kerosene are investigated using a Lewis cell. The effects of the stirring rate, temperature, and specific interfacial area on the extraction rate are investigated. The results show that the extraction process is controlled by diffusion and chemical reactions in the interfacial area rather than in the bulk phase. The apparent activation energy and the changes in the enthalpy, entropy, and Gibbs free energy of the extraction reaction are calculated using the Arrhenius equation and transition state theory. The rate equation derived from the experimental results is similar to that of the interface reaction model. A mass transfer model with a rate-control step is proposed. This study provides guidance and data support for an HDEHP-P350 system in industrial production applications.
The present work used solvent extraction method to extract lithium from hydrochloric acid leaching solution of high-alumina coal fly ash. In extraction stage, the optimum conditions were explored, at 20 ℃ and O/A = 1:4, using 70%(Vol.) tributyl phosphate-30%(Vol.) sulfonated kerosene-0.36 mol/L Fe 3+ as extractant, extraction of lithium could reach 99% by two-stage extraction. In scrubbing stage, 95% of Al 3+ in loaded organic phase was scrubbed with 6 mol/L HCl at O/A = 40:1, then 97% of Ca 2+ in the loaded organic phase was scrubbed by three-stage countercurrent scrubbing with 5.5 mol/L LiCl + 0.5 mol/L HCl at O/A = 30:1. In stripping stage, 99% of Li + in scrubbed organic phase was stripped by five-stage countercurrent stripping with 6 mol/L HCl at O/A = 10:1. In regeneration stage, 2 mol/L NaOH was used as regenerant to remove free acid and exchange H + of extractive compound. There were no third phase, emulsification and solid deposition during the whole experiment. The structure of extractive compound was determined by slope method, and extracted complex ratio of Li + , Fe 3+ , and TBP was 1:1:1. The extraction process was found to be exothermic and spontaneous by thermodynamic study. Therefore, it’s a promising method to recover lithium from hydrochloric acid leaching solution of high-alumina coal fly ash by TBP-FeCl 3 -sulfonated kerosene extraction system.
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