The kinetics of Eu(III) sorption onto and desorption from sorbents containing XAD-7 impregnated with both dicarbollide and DBDECMP

Abstract

The kinetics (1–1000 minutes shaking) of 5·10⁻⁴M Eu sorption from 0.1M HNO₃ onto the support XAD-7 impregnated with approximately equimolecular mixture of DBDECMP and dicarbollide depends appreciably on the technique of the preparation of the impregnated support. The highest distribution factors are obtained if DBDECMP is only used to impregnate the support and dicarbollide is added directly to the aqueous phase. The rate of sorption increases slightly with adding 1·10⁻⁵M surfactants but the effect is too weak for practical use. The best stripping agent found is an equimolecular mixture of DCTA and citric acid at pH 7. This work is a continuation of the investigation^1–3 of the synergic effect occurring in the sorption of low concentrations of europium due to the simultaneous presence of H⁺[(C₂B₉H₈Cl₃)₂Co]⁻ (abbreviated as dicarbollic acid, HB) and di-butyl-N-di-ethyl-carbamoylmethyl phosphonate (DBDECMP) on a suitable support. The system is promising for the separation of small amounts of tervalent transuranium and lanthanoid elements from radioactive waste. In the previous paper we have investigated quasi-equilibrium sorption of various Eu concentrations (24 hour shaking). In the present paper kinetic data of sorption and quasi-equilibrium data on desorption are studied. Preliminary kinetic studies of similar systems^2,3 have shown that the rate of both the sorption and desorption processes in this type of system is one of the decisive factors in the practical application of this separation method. Whereas in the previous paper¹ both DBDECMP and CMPO (octyl-phenyl-N,N-diisobutyl carbamoylmethyl phosphineoxide) combined with dicarbollide were studied, for reasons given previously¹ (mainly a higher synergic effect) herein DBDECMP was only investigated.