Removal of chromium from aqueous waste solution using liquid emulsion membrane.

This paper presents a comprehensive study in recovery of Cr (VI) from dilute HCl solution using liquid emulsion membrane (LEM). The liquid membrane is made up of Tri-octylphosphine oxide (TOPO) as a carrier, cyclohexane as an organic diluent, sodium hydroxide as a stripping solution and Span-80 (sorbitain monooleate) as an emulsifying agent. The selection of the extractant (TOPO) and the stripper (NaOH) was chosen on the basis of conventional liquid-liquid extraction studies. The important parameters affecting the permeation of Cr (VI) through the prepared membrane are hydrogen ion concentration in the external aqueous phase, stirring speed of mixing the two phases, type of diluents, carrier concentration, stripper concentration, membrane to feed ratio and volume fraction were systematically investigated. The effect of surfactant types and concentration on the stability of LEM were studied because of its important role in the permeation process.