* Corresponding author E-mail: mahmed@uowasit.edu.iq Received 7 /12/2019 Accepted 12/12/2019 DOI: 10.21608/ejchem.2019.17003.2042 ©2020 National Information and Documentation Center (NIDOC) The Removal Of Zinc Ions From Their Aqueous Solutions By Cr 2 o 3 Nanoparticles Synthesized Via The UV-irradiation Method Mahdi Ahmed Mohammed 1,* , Ahmed Mahdi Rheima 2 , Shaimaa Hamed Jaber 3 , Shahad Abbas Hameed 2 1 Wasit University, College of Science, Department of Physics. Iraq. 2 Wasit University, College of Science, Department of Chemistry. Iraq. 3 University of Mustansiriyah, College of Science, Department of Chemistry. Iraq. Egyptian Journal of Chemistry http://ejchem.journals.ekb.eg/ Egypt.J.Chem. Vol. 63, No.2, pp.425-431 (2020 36 Introduction The manipulation of particles into a nanoscale produces novel and improved physicochemical properties compared with the so-called bulk solid [1, 2]. These unique properties of nanoparticles are exhibit due to the high aspect ratio, shape, crystallinity and the shape of the surface edges [3-5]. Two stable chromium oxides can exist in the environment that are trivalent chromium (Cr III) and hexavalent chromium (Cr VI). Since its frst successful experiment in the chemistry of dyes by Augustus Schultz, It has remained the sole leather-tanning chemical [6]. Later, chromium oxides (Cr 2 O 3 ) have attracted great attention due to their contribution in many applications, such as coating for high temperature [7], the UV and microwave shielding [8], green pigments [9], solar energy collectors [10], photonic and electronic devices, heterogeneous catalysts [11, 12] and hydrogen storage [13]. Moreover, as many nanometal oxides, such as aluminum oxides [14], titanium oxides [15], cupper oxides [16], magnesium oxides [17], iron oxides [18, 19] and cerium oxides [20] have been shown an axcellent heavey metal adsoption from aqueous solutions, the spherical Cr 2 O 3 nanoparticles demonstrates a remarkable capacity in water treatment to extract azo-dye pollutant [21]. The Cr 2 O 3 nanospheries with excellent dye absorptions are therefore expected to be useful in alternative technologies for absorption. According to the advantage of the Cr 2 O 3 nanoparticles, they have been synthesised by several developing techniques inclouding the sol- gel process [22-24], mechanochemical process [25], precipitation-gelation [26, 27], sonochemical reactions [28], solid thermal decomposition [29, 30], bio method [31], nano casting method [32], laser irradiation method [33], gas condensation A modifcation of an UV-irradiation method is used to synthesis of Cr 2 O 3 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 o C. The adsorption process of zinc ions is endothermic (ΔH is 10.33 kJ/mol ) and its data ftted well with the Freundlich isotherm model (R 2 =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. Keywords. Cr 2 O 3 nanoparticles, chromium oxide, UV-irradiation, zinc ion, adsorption.