recovery of bi(iii) from hydrochloric acid solutions using a plasticized polymer inclusion membrane composed of cta and toa

Polymer inclusion membranes (pims) are a type of liquid membranes with excellent potentials for the separation-recovery of both metal ions and organic compounds [1]. they are considered as environmentally friendly technique because the toxic and expensive organic solvents required for the solvent extraction methods are practically eliminated in pims techniques [2]. pims incorporate small amounts of an extractant within a polymer matrix, and in some cases a plasticizer/modifier can be added to improve the mechanical or extraction characteristics [3]. the present study is devoted to the application of a polymer inclusion membrane composed of 40 wt% cellulose triacetate polymer (cta), 25 wt% trioctylamine (toa) as the carrier, and 35% tributyl phosphate (tbp) as the plasticizer/modifier, for the transport of bi(iii) from chloride solutions. to achieve the highest efficiency, the parameters affecting the transport process were investigated and optimized. these parameters were time, initial concentration of bi(iii), phases stirring rate, the type and the concentration of the stripping reagent. under optimized conditions, the membrane was capable to transport completely bi(iii) (initial concentration 20 mg/l) from the feed phase including 150 ml of 0.5 m hydrochloric acid solution into the receiving phase (150 ml of 2 m sodium carbonate solution) after 4 h. the selectivity of the investigated membrane toward bi(iii) was evaluated by performing competitive transport experiments of bi(iii) accompanied with copper(ii), nickel(ii), zinc(ii), cadmium(ii), iron(iii), lead(ii), cobalt(ii), molybdenum(vi), chromium(iii) and tungsten(ii) cations and nitrate and sulfate anions. the potential of the studied membrane for multiuse in bi(iii) transport process was appraised and the strategies for improving this ability were checked by saturating the feed and aqueous phases with the membrane constituents. the membrane was used for the recovery of bi(iii) from some real samples.