Functionalization of SBA-15 mesoporous materials with 2-acetylthiophene for adsorption of Cr(III) ions

Abstract

Abstract SBA-15 mesoporous materials functionalized with 2-acetylthiophene-derived Schiff's base denoted as A-SBA-15, were synthesized for removal of Cr(III) ions from aqueous solution. The adsorbent materials were characterized by means of XRD, SEM, TEM, N2 adsorption-desorption, TGA, EDXS, FTIR, 13C CP-MAS NMR and XPS. Tests were then performed to investigate the adsorption of Cr(III) ions onto A-SBA-15 in batch systems. The maximum adsorption capacity of A-SBA-15 (114.2 mg/g) for Cr(III) ions was much higher than that of the pure SBA-15 (15.6 mg/g). The kinetics analysis revealed that the adsorption process was well described by pseudo-second-order kinetic model. In addition, the Langmuir isotherm model was better fitted with the adsorption data for Cr(III) compared to the Freundlich isotherm model. Furthermore, the Cr(III) adsorption onto A-SBA-15 was found to be spontaneous, endothermic, and mainly chemical adsorption as shown by the investigate of various thermodynamic parameters, such as, ΔG°, ΔH°, and ΔS°. The characterization of A-SBA-15 materials before and after adsorption of Cr(III) ions showed that the chemical combination of the organic groups on A-SBA-15 and Cr(III) ions through coordination bond. The as-prepared A-SBA-15 materials could be reused in five successive recycles without significantly decreasing its adsorption capacity. Moreover, four batches of A-SBA-15 prepared at different synthesis times have the similar adsorption capacity. Besides, the adsorbent showed good selective separation of Cr(III) ion in the presence of Cu(II), Zn(II) and Ni(II) ions. The good reproductivity, reusability and selectivity suggest that A-SBA-15 material can be used as a promising adsorbent for efficient removal of heavy metals from aqueous solution.