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In this study, we fabricated a new hybrid adsorbent, titania-silica binary oxide (TiO 2 -SiO 2 )-polyacrylonitrile (PAN), by loading nanosized sol-gel-derived TiO 2 -SiO 2 onto a porous PAN polymer for enhanced arsenite [As(III)] and arsenate [As(V)] species removal from aqueous media. The resulting sorbent was characterized by thermogravimetric analysis, scanning electron microscopy, X-ray powder diffraction, IR spectroscopy, and porosity measurements. The sorption process for the removal of As(V) and As(III) was assessed with various parameters, including the effects of the pH, contact time, temperature, and existence of foreign competing ions. We found that the adsorption of As(III) and As(V) species onto TiO 2 -SiO 2 -PAN was dependent on the pH of solution, and it could be well represented by the Langmuir and Dubinin-Radushkevich isotherm models. The prepared hybrid adsorbent exhibited highly selective arsenic retention from water in the presence of Cl2À , and SO 3 2À anions at much greater levels than those toxic metals examined. The values of the standard free energy, enthalpy, and entropy proved that the sorption of As(V) and As(III) species onto the hybrid adsorbent TiO 2 -SiO 2 -PAN was an endothermic and spontaneous process. All of the results validated the feasibility of TiO 2 -SiO 2 -PAN for the highly effective removal of As(V) and As(III) from contaminated waters.

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A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85-95 %.

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