The transport of metal ions of indium, gallium and thallium from source solution to receiving phase through the chromatographic fiber supported solid membrane in the acetylacetone (HAA) containing mixed solvent system has been explored. The fibers supported solid membranes were prepared with chemical synthesis from cellulose fibers and citric acid with the carboxylic acid ion exchange groups introduced. The experimental variables, such as concentration of metal ions (10(-2) to 10(-4) mol.L(-1)) in the source solution, mixed solvent composition [for example, acetylacetone, (2,4-pentanedione), (HAA) 20% (by volume), 1,4-dioxane 10% to 60% and HCl 0.25 to 2 mol.L(-1)] in the receiving phase and stirring speed (50-130 r.min(-1)) of the bulk source and receiving phase, were explored. The efficiency of mixed solvents for the transport of metal ions from the source to receiving phase through the fiber supported solid membrane was evaluated. The combined ion exchange solvent extraction (CIESE) was observed effective for the selective transport of thallium, indium and gallium metal ions through fiber supported solid membrane in mixed solvents. The oxonium salt formation in the receiving phase enhances thallium, indium and gallium metal ion transport through solid membrane phase. The selective transport of thallium metal ions from source phase was observed from indium and gallium metal ions in the presence of hydrochloric acid in organic solvents in receiving phase. The separation of thallium metal ions from the binary mixtures of Be(II), Ti(IV), Al(III), Ca(II), Mg(II), K (I), La(III) and Y(III) was carried out in the mixed solvent system using cellulose fiber supported solid membrane.