VOC REMOVAL - COMPARISON OF MCM-41 WITH HYDROPHOBIC ZEOLITES AND ACTIVATED CARBON

The recently discovered mesoporous molecular sieve MCM-41 was tested a s an adsorbent for VOC removal. Its adsorption/desorption properties w ere evaluated and compared with other hydrophobic zeolites (silicalite -1 and zeolite Y) and a commercial activated carbon, BPL. The adsorpti on isotherms of some typical VOCs (benzene, carbon tetrachloride, and n-hexane) on MCM-41 are of type IV according to the IUPAC classificati on, drastically different from the other microporous adsorbents, indic ating that VOCs, in the gas phase, have to be at high partial pressure s in order to make the most of the new mesoporous material as an adsor bent for VOC removal. However, a proper modification of the pore openi ngs of MCM-41 can change the isotherm types from type IV to type I wit hout remarkable loss of the accessible pare volumes and, therefore, si gnificantly enhance the adsorption performance at low partial pressure s. Adsorption isotherms of water on these adsorbents are all of type V , demonstrating that they possess a similar hydrophobicity. Desorption of VOCs from MCM-41 could be achieved at lower temperatures (50-60 de grees C), while this had to be conducted at higher temperatures (100-1 20 degrees C) for microporous adsorbents, zeolites, and activated carb ons.