Separation and purification of carrier-free I-131 by the wet-distillation method from thermal neutron irradiated tellurium dioxide targets along with their Al wrappers in 8N H2SO4, HNO3 and HCl acid solutions containing H2O2 and refluxing for 3 h is investigated. The distilled off I-131 is absorbed in a mixture solution of NaOH + Na2S2O3 after passing through 0.5N H2SO4 acid filter. The corresponding I-131 separation factor, recovery yield and percentage trapped in the acid filter and radionuclidic, radiochemical and chemical purity indices and discussions favour the use of H2SO4 acid as the distillation medium. The corresponding separation and purification indices of I-131 are investigated as a function of chemical composition of the distillation medium (e.g., concentration of H2SO4, kind and concentration of the oxidant, the sequence of addition of H2SO4/H2O2, chemical impurities and catalyst), chemical composition of the acid filter (e.g., concentration of H2SO4 and additives such as H2O2 and oxalic acid) and radioiodine carrier-gas (e.g., air and nitrogen). By applying the recommended separation and purification procedure, I-131 product solution of high separation, recovery and purity indices is obtained. (C) 2009 Elsevier B.V. All rights reserved.