Unraveling the adsorption and diffusion properties of hexamethyldisiloxane on zeolites by static gravimetric analysis

Utilization of biogas from wastewater treatment plants (WWTPs) as a kind of renewable energy can effectively alleviate the escalating energy crisis. However, volatile methylsiloxanes (VMS) exist in biogas as impurities and hinder its efficient use. Adsorption is the main technology to achieve high-efficiency purification of VMS currently, yet studies on the adsorption processes and mechanisms are quite insufficient. Here, we use the static vapor adsorption method to investigate the adsorption performances and mechanisms of four typical zeolite adsorbents (Hbeta, SBA-15, MOR and MCM-41) towards hexamethyldisiloxane (L2), which is a representative of VMS. Results suggest the adsorption interaction of L2 and zeolite is closely related to the pore size of zeolite and follows the order of Hbeta > MCM-41 > SBA-15 > MOR. The adsorption rate constants of L2 on MCM-41 are larger than the others in the most relative pressure ranges. Besides, cyclic adsorption/desorption performances of L2 on MCM-41, SBA-15 and Hbeta show their super recycling properties. These studies would provide important information on designing an effective zeolite-L2 adsorption system, and are helpful to understand the deeper adsorption mechanisms of VMS on zeolites.