Development of High-degree Separation Technique with Multiple-Solvent Extraction and its Practical Application

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The multiple-solvent extraction,simultaneous forward-,backward- solvent extraction has been proposed and studied theoretically and experimentally. Both the multiple-solvent extraction with crystallization and the countercurrent multistage solvent extraction with crystallization were proposed and studied theoretically and exprimentally. Results obtained from this study are summarized as follows;1. Equilibrium calculation method is proposed for the multiple-solvent extraction with and without crystallization. The multiple-solvent extraction with crystallization process is much superior to the conventional extraction processes, indicating that it makes a much lower equilibrium solute concentration in the raffinate phase, a much higher solute concentration in the final extraction phase and it makes a solute in a dilute solution recovered as high purity crystal in the crystallizer.2. The simultaneous forward-, backward-solvent extraction with crystallization was studied experimentally in case of a dilute copper solution. The copper ions are extracted into an organic phase (Lix64N in dispersol), then simultaneously stripped into a high concentrated sulfuric acid. The copper sulfate solution is concentrated upto supersaturation concentration, then simultaniously the high purity(99.998%) copper sulfate crystal can be recovered.3. The high degree separation of cobalt from nickel, copper from manganese, manganese from cobalt with the countercurrent multistage solvent extraction with crystallization are studied experimentally, both the high purity metal solution in the raffinate phase and the high purity metal sulfate crystals in the crystallization can be recovered respectively from a dilute cobalt and nickel-, copper and manganese- and manganese and cobaltsolution by respectively PC88A(M2EHPA), Lix64N and DP8R(D2EHPA) in kerosen.