A modification of an UV-irradiation method is used to synthesis of Cr2O3 nanoparticles. It is a simple and easy way to produce small particles of chromium oxide at a range of 2 – 30 nm according to the transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations. In this study, the synthesized nanoparticles are used as an adsorbent for zinc ions from their aqueous solutions under effect of different temperatures 15, 25, 35, 45 and 55 oC. The adsorption process of zinc ions is endothermic (ΔH is 10.33 kJ/mol ) and its data fitted well with the Freundlich isotherm model (R2=0.9601). The data of adsorption show non-spontaneously in nature when the thermodynamic parameter ΔG is positive (1.515 kJ/mol). However, the ΔG changes to a negative value with the temperature rising and the process begins spontaneously because the adsorption capacity increases with increase in temperature.