Kinetics of extraction of aluminum and beryllium by mixture of bis(2-ethylhexyl)phosphoric acid and dinonylnaphthalene sulfonic acid

The kinetic behavior of the extraction of aluminum and beryllium with dinon ylnaphthalene sulfonic acid (DNNSA), bis(2-ethylhexyl)phosphoric acid (D2EH PA) and their mixture was studied using a stirred transfer cell. The extrac tion rate obtained with DNNSA is 5-50 times larger than that obtained with D2EHPA, The rate-determining step in the extraction with D2EHPA is the reac tion between metal ion and dimeric D2EHPA. The diffusion steps for the DNNS A reverse micelles in the organic phase and for the metal ions in the aqueo us phase, however, govern the overall rate of extraction with DNNSA, The ex traction rate obtained with the DNNSA-D2EHPA mixed micelles is greater than the sum of those obtained with each extractant, This increased rate is als o expressed satisfactorily by the diffusion steps as in the case of DNNSA m icelles, The synergistic effect on the extraction rate for beryllium is exp lained by an increase in the distribution ratio of the metal caused by incl usion of D2EHPA molecules into DNNSA micelles, A larger acceleration effect is observed for aluminum, suggesting reactive extraction by D2EHPA at the micro interface of reverse micelles in addition to the bulk interface.