Hexamethyldisiloxane Removal from Biogas Using a Fe(3)O(4)–Urea-Modified Three-Dimensional Graphene Aerogel

Volatile methyl siloxanes (VMS), which are considered to be the most troublesome impurities in current biogas-cleaning technologies, need to be removed. In this study, we fabricated a series of Fe(3)O(4)–urea-modified reduced graphene-oxide aerogels (Fe(3)O(4)–urea–rGOAs) by using industrial-grade graphene oxide as the raw material. A fixed-bed dynamic adsorption setup was built, and the adsorption properties of the Fe(3)O(4)–urea–rGOAs for hexamethyldisiloxane (L2, as a VMS model pollutant) were studied. The properties of the as-prepared samples were investigated by employing various characterization techniques (SEM, TEM, FTIR, XRD, Raman spectroscopy, and N(2) adsorption/desorption techniques). The results showed that the Fe(3)O(4)–urea–rGOA–0.4 had a high specific surface area (188 m(2) g(−1)), large porous texture (0.77 cm(3) g(−1)), and the theoretical maximum adsorption capacity for L2 (146.5 mg g(−1)). The adsorption capacity considerably increased with a decrease in the bed temperature of the adsorbents, as well as with an increase in the inlet concentration of L2. More importantly, the spent Fe(3)O(4)–urea–rGOA adsorbent could be readily regenerated and showed an excellent adsorption performance. Thus, the proposed Fe(3)O(4)–urea–rGOAs are promising adsorbents for removing the VMS in biogas.