A supported liquid membrane method was developed using chlorinated cobalt dicarbollide (CCD) in phenyltrifluoromethyl sulphone (FTMS) as the carrier, impregnated in PTFE flat sheet membranes for the selective separation of Cs(I) from nitric acid feed solution. Solvent extraction studies were carried out for optimizing the feed as well as strip conditions. >95% Facilitated transport of Cs(I) was observed in about 3 h when 1 M HNO3 and 8 M HNO3 were used as the feed and strip solutions, respectively while 0.025 M CCD in PTMS was used as the carrier extractant. Selectivity studies, carried out using a mixture of radiotracers viz. Cr-51, Fe-59, Mo-99, Tc-99m, Ru-106, Cs-137, Eu-152 and Am-241, indicated selective transport of Cs(I) with OF values >100. Though reproducibility of the transport data was excellent when carried out in two successive transport experiments with freshly loaded carrier solvent, the stability of the membrane was poor which restricts its long term use. (C) 2010 Elsevier B.V. All rights reserved.