Photo-reduction of Chromium from water by TiO 2 nanoparticles
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.313
Photo-reduction of Chromium from water by TiO2 nanoparticles M. Ali Ahmed1, A. Taj Elsir2, F. Mohammed2, H. A. Elbushra3, S. Tawer3, N. Eassa3 1
Department of Basic Sciences, National Ribat University, Box 55, Khartoum, Sudan
2
Department of Chemistry, Industrial Research and Consultancy Center IRCC, P. O. Box 268, Khartoum Sudan
3
Department of Physics, Al Neelain University, P. O. Box 12702, Khartoum, Sudan
Abstract This work aims to develop simple and cost-effective methods in reduction of Cr(VI) from water to less toxic and easy separated Cr(III) using Titanium dioxide (TiO2). TiO2 nanoparticles are prepared by a sol-gel method using titanium tetra-chloride and characterized using X-Ray Diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray Fluorescence spectrometer (EDX) and UV-visible spectroscopy. XRD shows Anatase structure of TiO2 after annealing at 600oC for four hours. The particles size is estimated to be 70 nm using SEM.UV-Visible spectroscopy indicated that TiO2 nanoparticles played important role in decreasing the concentration of Cr (VI) in water samples for different pH range of 1 to 4. The decrease in Cr(VI) concentration after the treatment is ascribed to the reduction caused by the photocatalyst effect that resulted from the presence of TiO2 nanoparticle in water samples under direct exposure to direct sunlight.
E-mail: [email protected] (corresponding author)
1. Introduction Chromium is one of the toxic heavy metals that may be considered as a major source of pollution for the environment because of its non-biodegradability and tendency to accumulate in an organism [1,2]. Chromium occurs in two forms trivalent and hexavalent chromium, the latter is carcinogenic and extremely toxic than Cr(III), because it can penetrate to the cell membrane and cause harmful effects to its content, and it is found in industrial processes such as leather tanning, metallurgy, and electroplating[3]. Seven forms of Cr(VI) exist including chromate CrO4−2, dichromate Cr2O7−2, hydrogen chromate HCrO-4, dihydrogen
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chromate H2CrO4, hydrogen dichromate HCr2O-7, tetrachromate Cr4O13−2 , trichromate Cr3O10−2 . Presence of these forms is dependent on the pH of the medium [4, 5]. Titanium dioxide (TiO2) has three polymorphs; Anatase, Rutile, and Brookite, all are easily prepared in laboratories.TiO2 nanoparticles are non-toxic and widely investigated due to high photocatalytic reactions, and other desirable properties such as surface area, the particle size in a crystalline phase, low cost, thermal and chemical stability [2]. Reduction of Cr(VI) to Cr(III) can be achieved by using TiO 2 nanoparticles as photocatalytic material under direct exposure to sunlight which is potential
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