Extraction and separation of Pd(II) by N, N'-diethyl-N, N'-dicyclohexylmalonamide in a nitric acid system

Abstract

This study indicated the extraction and separation of Pd(II) by N, N'-diethyl-N, N' -dicyclohexylmalonamide (DEDCHMA) from the aqueous nitric acid solution. The effects of extraction time, nitric acid concentration, diluent, extraction temperature, and extractant concentration on extraction distribution ratio were investigated. The extraction mechanism and the composition of the complex were further discussed based on FT-IR and slope analysis. Compared with N, N, N', N'-tetraoctyl diglycolamide (TODGA) and N, N, N', N'-tetracyclohexylmalonamide (TCHMA), the DEDCHMA showed higher extraction capacity for Pd(II), which is 46 and 15 times higher than that of TCHMA and TODGA, respectively. The stripping extraction ratio obtained in Pd(II)-loaded organic phase using thiourea or oxalic acid reached 99%. The extraction selectivity to Pd(II) and noble metals such as Ru(III), Rh(III), and some common base metals, such as Al(III), Fe(III), Ni(II), Cu(II), Zn(II), Ca(II), Mg(II), Pb(II), Sr(II), Cr(III) and CO(II), was also investigated. The results demonstrate that DEDCHMA can be used to treat and recover Pd(II) from nitrate-based wastes containing associated precious metals, such as Pd(II), Ru(III), Rh(III), and common base metal, as well as from the spent fuel reprocessing.