Evaluation of structural properties of novel activated composite membranescontaining organophosphorus extractants as carriers

This paper reports the results obtained by studying the structure of activa ted composite membranes (ACM) containing organophosphorus extractants as ca rriers. The porous structure of membrane samples containing different conce ntrations of di(2-ethylhexyl)phosphoric acid (DEHPA) and di(2-ethylhexyl)di thiophosphoric acid (DTPA) from 0 to 7 x 10(-3) mmol . cm(-2) was character ized by gas adsorption method (BET). The results obtained by the BET techni que indicate that both the total pore volume and the specific surface area of ACM samples decrease with the concentration of the carrier in the castin g solution. The carrier in the membrane is mainly located in pores having l arge and medium diameters. The chemical structure of the carriers studied d oes not influence their distribution in the ACM. These results correlate we ll with those obtained by using different spectroscopic techniques to evalu ate the properties of ACM samples. Thus, a quantitative correlation has bee n obtained between the carrier content; in the membrane and its initial con centration in the modifying solution for both organophosphorus extractants studied by using the ICP technique. Dependencies of this type can serve as a sort of calibration curve to prepare ACM samples with a desired carrier c ontent. X-ray microanalysis (EDS) was used as a nondestructive method for d etermination of carrier concentration in ACM. Both EDS and impedance spectr oscopy (IS) methods were applied to evaluate the changes of internal membra ne structure in the course of preparation of ACM samples with different car rier content.