Application of MCM-48 with large specific surface area for VOCs elimination: synthesis and hydrophobic functionalization for highly efficient adsorption.

Abstract

MCM-48 molecular sieve with a large specific area (1470.87 m2/g) was hydrothermally synthesized for VOCs elimination by the adsorption method. The dynamic adsorption behaviors of toluene on this material were evaluated via breakthrough curves under both dry and wet conditions. A high toluene adsorption capacity of 171.13mg/g was observed under dry conditions; however, in the presence of water vapor (20% RH), the adsorption capacity greatly decreased to 58.88mg/g due to the competitive occupation of adsorption sites between water molecules and toluene molecules. To improve the affinity to toluene, functionalized MCM-48 materials were obtained by the co-condensation method and grafting method, respectively. It was found that co-M48(1:5)-100/48 sample by co-condensation method presents the highest dynamic adsorption capacity at both dry condition (194.62mg/g) and 20% RH (122.42mg/g), which has a significant advantage in the same type of adsorbent. This could be ascribed to the conjugated π-electrons effect between aromatic rings of phenyl groups uniformly distributed in MCM-48 skeleton and toluene molecules, which was qualitatively confirmed by FTIR. Moreover, cycle tests confirmed that this adsorbent possesses superior stability. The Yoon-Nelson model was successfully employed to describe the dynamic adsorption behavior of toluene over the organofunctionalized MCM-48 adsorbents, and the adsorption force of toluene was explained. Finally, a diagram describing the effect of different functionalization methods on the hydrophobicity and organophilicity of MCM-48 was given for a better understanding.