Studies on recovery of hexavalent chromium from plating wastewater by supported liquid membrane using tri-n-butyl phosphate as carrier

The transport of chromium(VI) ions from an aqueous feed solution through a flat type supported liquid membrane (SLM) containing tri-n-butyl phosphate (TBP) as carrier was studied. The influence of pH on the source phase, effect of concentration of receiving phase, stirring speed, effect of initial Cr(VI) concentration, feed to strip ratio and the influence of support characteristics was studied. Polytetrafluoroethylene (PTFE) with 1.0 μm pore size was found to have more flux permeability than 0.50 μm. The results indicated that the aqueous feed solution at pH 1 ± 0.1 to have high permeability. The initial feed phase Cr(VI) concentration of 9.6 × 10− 4 M can be completely extracted and stripped with 0.50 M sodium hydroxide as stripping solution within 8 h. Stirring of aqueous solutions at 500 rpm with a magnetic stirrer showed high transport rate. After ten transport studies with one impregnation of carrier, the TBP carrier showed no significant loss in its permeability and retained the same transport ability. Under the optimum conditions chromium(VI) recovery from real plating wastewater was tested and found to be satisfactory with a flux value of 1.4 × 10− 3 mol/m2/s.