Adsorption of acetone, ethyl acetate and toluene by beta zeolite/diatomite composites: preparation, characterization and adsorbability.

Abstract

The hierarchical porous composites (Beta/Dt) were prepared by secondary growth method using natural diatomite and beta zeolite. Moreover, XRD, SEM, and BET characterize the composite's composition, surface structure, and pore structure. The adsorbability of Beta/Dt was evaluated by adsorption of three common volatile organic compounds (VOCs) of the printing industry: acetone, ethyl acetate, and toluene. The results show that under the optimum preparation condition, the adsorption capacities of the three VOCs on Beta/Dt were about 3.5 times those of pure beta zeolite and 4.7-35.3 times those of diatomite, respectively. It indicates the synergistic adsorption effect between beta zeolite and diatomite. The superior adsorption capacity of Beta/Dt can be attributed to the suitable micropore size, the increase of the diffusion channels, and the chemical adsorption on modification diatomite. The adsorption of acetone, ethyl acetate, and toluene on Beta/Dt conformed to the pseudo-second-order kinetic model. In contrast, adsorption isotherms conformed to the Langmuir model, meaning that both physical and chemical adsorption occurred simultaneously during the adsorption process, and the adsorption belonged to the monolayer adsorption. The chemical adsorption mechanism can be ascribed to the nucleophilic reaction between the three VOCs (acetone, ethyl acetate, and toluene) and Beta/Dt with positive charges resulting from the modification diatomite. Furthermore, the composite could still keep more than 90% of the adsorption capacity of the original adsorbent after five regeneration cycles.