SELECTIVE SEPARATION AND CONCENTRATION OF VANADIUM(V) BY A CHEMICAL PUMPING HOLLOW-FIBER SUPPORTED LIQUID MEMBRANE

A hollow fiber supported liquid membrane (HFSLM) system far the separa tion and concentration of vanadium (V) has been developed and characte rized by using tricaprylylmethylammonium chloride (Aliquat 336(R)) dis solved in dodecane as carrier. The transport of vanadium through the l iquid membrane is based on a pH gradient between feed and stripping so lutions to provide an appropriate change on the chemical species of aq ueous vanadate, i.e., aqueous metavanadate, VO2(OH)(2)(-) (4.0<pH<7.0) is extracted by Aliquat 336 and VO3OH2-(pH>8.0) is not extracted. Sel ective separation and concentration experiments were carried out at lo w vanadium(V) concentration (mg l(-1) level). The study of the HFSLM i ncludes the influence of hydrodynamic, physical and chemical condition s, i.e., flow rate of feed solution through the fibers, number and len gth of fibers, lifetime of the system, initial vanadium concentration in the feed solution, and pH of aqueous phases. Transport of V(V) incr eases with the flow rate of the feed solution through the fibers until a 'plateau' is reached (>0.2 ml min(-1) in a single fiber). It has be en shown that in a HFSLM module, the membrane area increases with the number of fibers but also there is an increase of the sterical hindran ce between the fibers which reduces the expected increase of vanadium transport. On the other hand, the length of the fibers has a scarce in fluence on the transport process. The effect of the acidity of the fee d solution on the vanadium transport shows a similar behavior to that obtained previously for liquid-liquid distribution and laminar SLM stu dies. The results obtained indicate that vanadium(V) can be effectivel y concentrated and selectively separated by hollow fiber SLM containin g Aliquat 336(R) as carrier.