Adsorption and Desorption Characteristics of Nanozeolites as Adsorbent for Dimethyl Methylphosphonate

Abstract

The selective adsorption of dimethyl methylphosphonate (DMMP) onto zeolites is described in this paper. Three types of zeolite, silicalite-1, ZSM (Zeolite Socony Mobil)-5, and Cu-ZSM-5, were synthesized and assembled onto the surface of a quartz crystal microbalance (QCM) covered with a Au film. The QCM was adopted as an effective tool to analyze the adsorption and desorption characteristics. The optimum desorption conditions were determined experimentally as a desorption temperature of 523 K and a desorption time of 30 min. Good repeatability could be obtained under these optimal desorption conditions. Adsorption capacity was determined by comparing the different zeolites as selective adsorbents for DMMP. Cu-ZSM-5 had the highest adsorption capacity and the best selectivity for the three zeolites. The effect of copper ions on the adsorption of DMMP was tested by synthesizing five Cu-ZSM-5 zeolites with different copper ion contents. Adsorption sensitivity increased in proportion to copper content before saturation. The sensitivity and detection limit of a QCM coated with Cu-ZSM-5 reached about 8.8 Hz/ppm and 0.3 ppm, respectively, confirming that Cu-ZSM-5 zeolite is a promising adsorbent for DMMP detection.