Silica gel based new adsorbent having enhanced VOC dynamic adsorption/desorption performance

Abstract

The diacid calix[4]arene tethered silica (DACTS) as an adsorbent was obtained by the tethering of calix[4]arene carboxylic acid derivative onto 3-glycidoxypropyl-bonded stationary phase (GBS). The characterizations were carried out by some analysis techniques such as FT-IR, XRD, EDS, SEM, and BET. The adsorption behavior of the prepared adsorbent was investigated towards the dynamic adsorption of volatile organic compounds (VOCs) such as xylene and toluene gases. For the optimization of process parameters, response surface methodology (RSM), and Box-Behnken design (BBD) were applied. The adsorption results were evaluated in terms of the kinetic and isothermal conditions. Hence, DACTS showed substantial adsorption performance towards xylene and toluene gases. It was observed that for xylene gas, the adsorption capacities of the precursor calixarene, GBS, and DACTS were 441.43, 542.98, and 882.94 mg/g, respectively. Additionally, their adsorption capacities towards toluene gas were found as 300.50, 398.14, and 660.87 mg/g, respectively. Hence, the tethering of calixarene units into GBS could considerably enhance the adsorption capacity of prepared adsorbent towards xylene and toluene gases. Additionally, as well as the excellent adsorption behavior towards xylene and toluene gases, DACTS adsorbent has a superior regeneration and repeatability performance towards VOCs. The possible adsorption mechanism can be explained by 7C-7C and, van der Waals interactions between the VOCs and the benzene rings on calixarene moiety. The findings of this study indicated that the successfully synthetized DACTS adsorbent has excellent adsorption capacity and repeatability for VOCs, which means that it will be useful adsorbent for many areas.