Separation of chromium and nickel from aqueous solitions by bupported liquid membranes

Keywords: Supported liquid membranes; chromium-nickel separation; tri-octylamine (TOA); TBP; solvent extractionThe extensive use of chromium in leather tanning, metallurgy, electroplating and other industries has resulted in the release of aqueous chromium to the subsurface at numerous sites. Cr (VI) has received considerable attention owing to its extensive industrial applications and has long been recognised as a toxic substance due to its strong oxidising potential and the ease with which it can cross the biological membranes.In this work the selective separation of chromium from acidic media, containing the mixtures of chromium and nickel by SLM was investigated using TOA (tri-octylamine) as carrier. The liquid membrane was consisted of the desired concentration of an extractant (TOA), a modifier (TBP), and a diluent (chloroform, kerosene, cyclohexane). The membrane support was microporous hydrophobic polypropylene Celgard 2500. Such parameters as, the solvent type, feed solution pH, extractant (TOA) concentration, modifier (TBP) concentration and temperature were experimentally studied and the optimum conditions were determined. The permeation coefficients (P) and the initial fluxes of chromium (Jo) were calculated. Separation factors of chromium over nickel was calculated from the experimental measurements.Competitive transport of the equimolar and non-equimolar mixtures of Cr and Ni ions across the SLM from the aqueous solutions was studied using a two-compartment permeation cell, made from a pyrex glass, with flat-sheet membranes of 12.56 cm2 area (A).In all experiments the supports used for the liquid membranes were microporous hydrophobic polypropylene Celgard 2500, 25?m thick, 0.209 ?m x 0.054 ?m pore size and 55 % porosity.