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    Preparation and characterization of novel polysulfone-red mud composite capsules for the removal of fluoride from aqueous solutions
    (ROYAL SOC CHEMISTRY, 2016) Kazak, Omer; Tor, Ali; Akin, Ilker; Arslan, Gulsin
    This study is the first investigation on the encapsulation of red mud by a polysulfone matrix through a phase inversion process to obtain composite capsules for the removal of fluoride from aqueous solutions. This approach facilitates the use of red mud in batch and column sorption techniques because the polysulfone matrix renders efficient aqueous diffusivity. The produced polysulfone-red mud composite capsules (red mud@ PSF capsules) were characterized by using FT-IR, TGA, SEM and BET. The batch sorption experiments showed that the red mud@ PSF capsules prepared with a mass ratio of red mud to polysulfone (1 : 1, g : g) provided maximum removal at equilibrium pH between 3.2 and 4.7. The batch equilibrium was attained within 30 minutes and sorption behavior was governed by pseudo-second-order kinetics together with intra-particle diffusion. Isotherm analyses showed that the Freundlich and Redlich-Peterson isotherm models better represented the sorption data, which was confirmed by the Chi-square (chi(2)) statistical test. The capsules could be reused for at least two sorption-desorption cycles without significant change in their sorption efficiency. Batch and column experiments on a real mineral water sample fortified with fluoride (final concentration 10 mg L-1) showed that the red mud@ PSF capsules could be applied to real water samples to reduce the fluoride concentration below the limit value (1.5 mg L-1) recommended by the World Health Organization (WHO) for drinking water.
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    Preparation of new polysulfone capsules containing Cyanex 272 and their properties for Co(II) removal from aqueous solution
    (ELSEVIER SCI LTD, 2015) Kazak, Omer; Tor, Ali; Akin, Ilker; Arslan, Gulsin
    In this study, new polysulfone capsules containing Cyanex 272 (Cyanex 272@PSF capsules) were prepared by phase inversion technique for the sorption of Co(II) from aqueous solution. The characterization of the Cyanex 272@PSF capsules which were performed by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermal gravimetric analysis (TGA) indicated that Cyanex 272 was successfully encapsulated by polysulfone. For the Cyanex 272@PSF capsules having the highest sorption efficiency, the encapsulation efficiency was determined as 7.2%. The batch sorption experiments showed that removal of Co(II) from aqueous solutions occurred through the cation-exchange and chelation mechanisms and maximum removal was achieved at an initial pH of 8.0 (final pH of 5.9). The Cyanex 272@PSF capsules produced with dispersed phase containing 2.0% of Cyanex 272 (by wt.) provided the highest Co(II) removal. The sorption equilibrium time was attained within 120 min. By confirming the non-linear Chi-square (x(2)) statistical test, Langmuir isotherm model was the best fit model. Langmuir sorption capacity (Q(o)) and sorption constant (b) were 2.014 mg/g and 0.281 L/mg, respectively. The regenerated capsules could be used three times with no change in their sorption capacities. Based on the experiments performed at initial pH of 8.0 for other metal ions, including Ni(II), Pb(II) and Cd(II), sorption ability of Cyanex 272@PSF capsules was in the order: Co(II) approximate to Ni(II)>Cd(II)>Pb( II). Consequently, Cyanex 272@PSF capsules have potential for removing Co(II) from aqueous solutions. (C) 2015 Elsevier Ltd. All rights reserved.