Extraction of cerium(III) by polymer gels swollen with bidentate organophosphorus compounds.

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Abstract
The extraction of Ce(III) from aqueous solutions containing Al(NO3)3 was examined by using styrene-divinylbenzene copolymer (SDB) gels swollen with dihexyl-N,N-diethylearbamoylmethylphosphonate (CMP), octyl(phenyl)-N,N-diisobutylcarbanoylmethylphosphine oxide (CMEPO) and an equimolar mixture of CMP and CMPO. The extraction constants (Kex) for the gels with CMIP and CMPO were evaluated. The distribution ratio of Ce(III) for the gel with an equimolar mixture of CMP and CMFO was described as Kd = (KexCMP[CMP]3 +KexCMPO[CMPO] 3)[NO3–]3) by using these extraction constants. The extraction rate was found to be controlled by diffusion of Ce-complex [Ce(NO3)3(CMFO)3 or Ce(NO3)3(CMP)3] through the gel. The diffusion coefficient (Ds) was inversely proportional to the viscosity of extractant (η) and represented by an expression similar to the Stokes-Einstein equation, Dsη/T = constant. A decrease in the viscosity of extractant was effective for increasing the extraction rate.