A study on the sorption of strontium (Sr2+) and uranium (UO22+) onto zirconium-antimony oxide/PAN (Zr-Sb oxide/PAN) composite was conducted. The zirconium-antimony oxide was synthesized and was then turned into composite spheres by mixing it with polyacrylonitrile (PAN). The single and combined effects of independent variables such as initial pH, temperature, initial ion concentration and contact time on the sorption of Sr2+ and UO22+ were separately analyzed using response surface methodology (RSM). Central composite design (CCD) was separately employed for Sr2+ and UO22+ sorption. Analysis of variance (ANOVA) revealed that all of the single effects found statistically significant on the sorption of Sr2+ and UO22+. Probability F-values (F=2.45 x 10(-08) and F=9.63 x 10(-12) for Sr2+ and UO22+, respectively) and correlation coefficients (R-2 = 0.96 for Sr-2+ and R-2 =0.98 for UO22+) indicate that both models fit the experimental data well. At optimum sorption conditions Sr2+ and UO22+ sorption capacities of the composite were found as 39.78 and 60.66 mg/g, respectively. Sorption isotherm data pointed out that Langmuir model is more suitable for the Sr2+ sorption, whereas the sorption of UO22+ was correlated well with the Langmuir and Freundlich models. Thermodynamic parameters such as Delta H, Delta S and Delta G indicate that Sr2+ and UO22+ sorption processes are endothermic and spontaneous. (c) 2014 Elsevier B.V. All rights reserved.