DOI: 10.1007/s10967-008-7378-1 Journal of Radioanalytical and Nuclear Chemistry, Vol. 279, No.3 (2009) 811–816 0236–5731/USD 20.00 Akadémiai Kiadó, Budapest © 2009 Akadémiai Kiadó, Budapest Springer, Dordrecht Contribution to the external surface of a titanium-rich sand (Abou-Khashaba, Egypt) in the uranium uptake processes R. Tykva, 1 Khaled Salahel Din, 1,2 C. C. Pavel, 3 A. Cecal, 3 K. Popa 3 * 1 Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo 2, 166 10 Prague 6, Czech Republic 2 Faculty of Science, Physics Department, South Valley University, 83523, Qena, Egypt 3 “Al.I. Cuza” University, Department of Chemistry, 11 - Carol I Blvd., 700506 - Iaşi, Romania (Received October 14, 2008) The present study reports the U(VI) uptake from solution on a Ti-rich Egyptian black sand, showing that the crystal surfaces exhibit a marginal influence to the total process of U(VI) uptake onto Ti-containing micro- and mesoporous silicate materials. The results were evaluated using Lagergren first order equation and the apparent thermodynamic parameters of uranium uptake onto the considered materials were calculated. Introduction Uranium is a natural and commonly occurring radioactive element having typical concentrations in most materials a few parts per million (ppm). Natural uranium is a mixture of three isotopes: 234 U (0.01%), 235 U (0.72%), and 238 U (99.27%). Exposure to natural uranium is unlikely to be a significant health risk to the population and may have no measurable effect. However, exposure to enriched uranium, used as fuel in nuclear energy production, may present a radiological health hazard. The toxicity of uranium varies according to its chemical form and the route of exposure. Generally, hexavalent uranium, which tends to form soluble compounds, is more likely to be a systemic toxicant than tetravalent uranium, which forms insoluble compounds. 1,2 As an effort to reduce the uranium level in waste water, drinking water or water for the agriculture to the maximum permissible concentration (10 –4 g/L), selective removal processes (e.g., ion-exchange, adsorption, precipitation, membrane separation, and biosorption) are currently employed. 3–6 A group of microporous materials which was found to possess a high potential for these technologies is constituted by crystalline microporous titanosilicates, e.g., the Engelhard Titanium Silicates ETS-4, ETS-10, and the crystalline silicotitanate CST. 7 AL ATTAR et al. 8,9 reported the uranium uptake onto ETS-4 and ETS- 10. We had improved the uranium uptake capacity on ETS-10 by mesopores generation. 10 The kinetic and thermodynamic aspects of the uranium uptake on as- made and mesopores-containing ETS-10 were extensively studied and recently reported. 11 The present study is aimed to determine the contribution of the external surface to the uranium uptake process by titanium-rich materials. The sands * E-mail: kpopa@uaic.ro do not present any internal porosity, but they have quite similar average chemical formulas as the synthetic counterparts. This could help us to distinguish between the physical and chemical sorption processes in the case of micro- and mesoporous titanosilicates. Experimental Sand characterization Metal-rich sand is generally found on beaches as sea waves concentrate the heavy minerals that are not easily removed back to the sea. They are economically important because of high concentrations of Ti, Fe, 232 Th, and 238 U are in their structures. It is normally concentrated in the form of thin streaks alternating with the beach sand layers. Black sand contains overall an order of magnitude less 40 K and two orders of magnitude more 238 U and 232 Th when compared with normal sand. 12 In Egypt, the occurrences of black sand deposits are known at the Nile mouth near Damietta and Rosetta and have been worked for their magnetite, ilmenite, zircon and monazite content since the Second World War. Normally, the grain size fraction of black sand was found to be below 0.2 mm. 13 The Mediterranean coast of Egypt is spotted with black sand in many places. Rosetta promontory is the area with the highest black sand places in Egypt. Three samples were collected from the Egyptian black beach sand of the Abou-Khashaba area near Rosetta north of Egypt. Figure 1 shows a map of Egypt and the location of Rosetta area. The samples were ground, sieved to 200 mesh and the powder samples (10 g in each case) were put in thin-walled plastic bags and prepared for analysis. The sample with the highest content of Ti was chosen for further experiments.