Abstract
The precious metal has a long history of usage not only as jewelry but as the industrial materials such as catalysis, parts of electrical products and dental filling. The precious metal is extremely expensive because of the small amount of the deposit. The supply of the precious metal from recycling is more desirable than that from the ore deposit. As the method of recovery of the precious metal, precipitation-crystallization has been employed, but a lot of process steps are needed to obtain the recovery with high purity and high yield. In stead of the method mentioned above, solvent extraction with 2-ethylhexanal oxime (EHO), which is known as the selective extractant for Cu(II), Ni(II) and Pd(II), was investigated to separate Pd(II) from other metals.
It was clarified that almost perfect recovery of Pd(II) can be attained by the multistage-countercurrent solvent extraction with EHO, when Pd(II) concentration is approximately 0.005 mol / dm3 in the aqueous phase. The reaction stoichiometry is like Pd(II) : EHO : Cl- = 1 : 2 : 2. It is impossible to strip the extracted Pd(II) with EHO by using water, but the aqueous phase containing thiourea enables the perfect stripping of Pd(II). Palladium (II)with high purity can be obtained by the scrubbing process with water to remove small amounts of other metals present as an impurity in the organic phase.
