Elaboration and characterization of new adsorbents based on conducting PANI/zeolite HY/TiO2 nanocomposite applied for chromate adsorption

The preparation of polyaniline/HY/TiO(2)p-n heterojunction/polymer is successfully performed by in situ chemical polymerization of aniline doped by 5 w% of HY zeolite (acid solid) using persulfate (NH4)(2)S2O8 as oxidant in aqueous solution containing 5 to 20 wt% of TiO2 with respect to aniline monomer quantity. The product is characterized by X-ray diffraction (XRD), FT-IR spectroscopy, SEM analysis, thermal gravimetry, UV-visible diffuse reflectance and electrical conductivity. The FT-IR spectra revealed the presence of TiO2 and PANI as a main matrix in nanocomposites while the XRD patterns show that the diameter of PANI/HY/TiO2 lies between 20 and 70 nm. In the second part, we investigate the effect of the physical parameters on the equilibrium adsorption of chromate Cr(VI) on PANI/HY/TiO2 nanocomposites. The adsorption characteristics of the composite toward Cr(VI) are followed by atomic absorption spectroscopy (AAS). The effect of contact time, sorbent size and Cr(VI) initial concentration (C-o) on the Cr(VI) uptake is also studied. It has been observed that the capacity of Cr(VI) adsorption on PANI/HY/TiO2 increases with increasing C-o while the PANI/HY/5TiO(2) has a larger uptake capacity. The isotherm data are well fitted with the Langmuir isotherm model with maximum adsorption capacity of 454.54 mg/g. The calculated thermodynamic parameters showed that the Cr(VI) adsorption onto PANI/HY/5TiO(2) is endothermic (Delta H degrees = 12.478 kJ/mol) and spontaneous (Delta G degrees(300 K) = - 11.186 kJ/mol).