Precipitation stripping of Nd(III) carbonate from Nd(III)-loaded D2EHPA with NH3-(NH4)(2)CO3 solution

Precipitation stripping of Nd(III) carbonate from Nd(III)-loaded D2EHPA was investigated using a mixture of NH, and (NH4)(2)CO3 as a stripping solutio n. Precipitation stripping of Nd(III) was achieved with appropriate NH3 and (N H4)(2)CO3 concentrations, however, it is necessary to make the concentratio n of NH3 greater than that of D2EHPA, and to keep the (NH4)(2)CO3 concentra tion above 0.3 kmol m(-3). Increase in NH3 and (NH4)(2)CO3, over a concentration range suitable to rec over Nd(III) carbonate, results in an increase in soluble Nd(III) in the aq ueous phase, and thus a decrease in percent stripping. The precipitates produced in the aqueous phase were identified as Nd-2(CO3) (3) . 8H(2)O from the Nd(III) content, IR spectra, X-ray diffraction patter n, and thermal analyses. By calcining the precipitates at 873 and 973 K, cu bic Nd2O3 and a mixture of cubic and hexagonal Nd2O3, respectively, was pro duced. The distribution of D2EHPA in an aqueous phase of high alkalinity was extre mely limited. The ammonium salt of D2EHPA was formed by contact of D2EHPA i n the organic phase with the aqueous phase of high alkalinity, resulting in a shift in the distribution equilibrium of Nd(III). Thus, Nd(III) is strip ped into the aqueous phase and reacts with (NH4)(2)CO3 in stripping solutio n to form Nd(III) carbonate. (C) 2000 Elsevier Science B.V. All rights rese rved.