A hollow fiber supported liquid membrane based on Aliquat 336 as a carrier for rhodium(III) transport and preconcentration

A hollow fiber supported liquid membrane system (HFSLM) for the transport of rhodium(III) from aqueous feed chloride solutions containing SCN− has been developed and characterized by using Aliquat 336 as a carrier. To dissolve the extractant, the aliphatic organic diluent dodecane modified with 4% dodecanol was chosen in order to avoid degradation of the polymeric support. The influence of the chemical composition of the system on the permeation rate was investigated. Among the options tested as a stripping solution, a mixture of NaHSO3/NaSCN at pH=5 was found to be the most effective to strip Rh(III) from the loaded organic phase. Under these chemical conditions different experiments have been run to obtain practical information concerning the lifetime of both the supported liquid membrane and the polypropylene hollow fiber. The results demonstrated the feasibility of the SLM system during six non-stop days’ operation, and also the resistance of the fibers used, which provided the same rate of rhodium(III) transport after 15 washes of the fiber with ethanol. The influence of the hydrodynamic conditions, as well as the mode of operation of the HFSLM system, have also been studied. Using the system described, some preconcentration experiments were done, obtaining a preconcentration factor of 24, that indicates that Rh(III) can be effectively concentrated by hollow fiber SLM containing Aliquat 336 as a carrier.