Characterization and Testing of Periodic Mesoporous Organosilicas as Potential Selective Benzene Adsorbents

• Published in: Langmuir Vol. 25; no. 21; pp. 12661 - 12669
• Main Authors: Borghard, W. G, Calabro, D. C, DiSanzo, F. P, Disko, M. M, Diehl, J. W, Fried, J. C, Markowitz, M. A, Zeinali, M, Melde, B. J, Riley, A. E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.11.2009
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Porous materials; Surface physical chemistry; Binary compound; Separation; Adsorption capacity; Alcohol; Potential; Surfactant; p-Xylene; Porous material; Silica; Powder; Template; Characterization; Cresol; Xylene; Adsorbent; Stationary phase; Hydrocarbon; Pore structure; Desorption; Nitrogen; X ray diffraction; Ethane; Mesoporosity; Sorption; Trapping; Adsorption; Benzene; Phenols; Benzenic compound; Surface area
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la901334z

The effects of surface imprinting on the adsorption and desorption properties of benzene- and diethylbenzene-bridged periodic mesoporous organosilicas (PMOs) acting as GC stationary-phase preconcentration sorbents for benzene and xylene were examined. Surface-imprinted and nonimprinted PMOs with diethylbenzene (DEB), benzene (BENZ), and ethane (BTSE) bridges and nonimprinted mesoporous silica (MCM-41) were prepared via well-established surfactant templating synthetic methods. The imprinted materials were synthesized using a surfactant demonstrated to produce trinitrotoluene (TNT) selective sorbents with increased adsorption capacity for cresol and 4-nitrophenol as well as TNT. Powder XRD and nitrogen sorption measurements revealed that all of the materials were mesoporous with the DEB materials having a random pore structure and lower surface area than the other materials which had ordered pore structures. Results for maximum uptake of benzene and p-xylene indicate a small but consistent positive effect on the adsorption of benzene and p-xylene due to surface imprinting. Comparing the surface area normalized uptakes (mg/m2) for materials having the same organic bridge with and without imprinting (DEB vs TDMI-DEB and BENZ vs TDMI-BENZ) shows that in seven of eight comparisons the imprinted analogue had a higher aromatic uptake. The imprinted samples showed higher weight normalized uptakes (mg/g) in five of eight cases. When used as a GC stationary phase, the organosilica materials yield more symmetrical chromatographic peaks and better separation than MCM-41, indicating superior trapping of BTX analytes, particularly at low concentrations. Additionally, these materials rapidly desorb the preconcentrated compounds.