Nano-ZnO-chitosan bio-composite beads were prepared for the sorption of $${\text{UO}}_{2}^{{2+}}$$ UO22+ from aqueous media. The resulting nano-ZnO/CTS bio-composite beads were characterized by TEM, XRD etc. The sorption of $${\text{UO}}_{2}^{{2+}}$$ UO22+ by bio-composite beads was optimized using RSM. The correlation between four variables was modelled and studied. According to RSM data, correlation coefficients (R2 = 0.99) and probability F-values (F = 2.24 × 10− 10) show that the model fits the experimental data well. Adsorption capacity for nano-ZnO/CTS bio-composite beads was obtained at 148.7 mg/g under optimum conditions. The results indicate that nano-ZnO/CTS bio-composite beads are appropriate for the adsorption of $${\text{UO}}_{2}^{{2+}}$$ UO22+ ions from aqueous media. Also, the suitability of adsorption values to adsorption isotherms was researched and thermodynamic data were calculated.