Investigation of high-performance adsorption for benzene and toluene vapors by calix[4]arene based organosilica (CBOS)

Abstract

The immobilization of a calix[4]arene derivative bearing methyl ester moieties onto mesoporous silica was successfully achieved to obtain calix[4]arene based organosilica (CBOS). IR spectroscopy, X-Ray powder diffraction, energy-dispersive spectroscopy, and scanning electron microscopy analysis were carried out for the characterization of the CBOS. After that, the proposed mesoporous silica-supported adsorbent was studied for the adsorption of benzene and toluene vapors, which are essential VOCs. The effects of operating parameters on the adsorption of these vapors with the CBOS adsorbent were analyzed and optimized by applying response surface methodology (RSM)-central composite design (CCD). According to initial experimental results, CBOS exhibited excellent performance for these vapors. The adsorption capacities of calix-3, GBS, and CBOS adsorbents were determined to be 203, 357, and 606 mg g⁻¹ for benzene vapors, respectively, while they were found to be 258, 394 and 672 mg g⁻¹ for toluene vapors, respectively. Thus, the proposed CBOS adsorbent showed better adsorption performance when compared to its precursors. In addition to the distinctive adsorptive behavior, the CBOS adsorbent exhibited a high reproducibility adsorption/desorption capacity after five consecutive cycles. After the fifth adsorption/desorption cycle, the CBOS retained 94.2% and 95.1% of its initial adsorption capacities for benzene and toluene, respectively. Finally, adsorption phenomena of benzene and toluene vapors onto CBOS were evaluated in terms of isotherm and kinetic parameters.