|dc.description.abstract||The feasibility of employing mesoporous silicate MCM-41 as a sorbent for enriching ambient polycyclic aromatic hydrocarbons (PAHs) was investigated. The properties of mesoporous silicates involving high thermal stability, uniform porosity, and adjustable pore size capability (2-50 nm), etc., have created their various applications in abatement of volatile pollutants, separation, large molecule catalytic reactions, photoelectric studies, etc. Based on our preliminary results, MCM-41 can quantitatively absorb volatile organic compounds (VOCs) larger than C6. Nevertheless, the technical difficulties in preparing low boiling gas mixtures and thermal desorption for gas chromatography analysis hindered the sorption test of MCM-41 extending to larger than C12 molecules. As a result, in this study motor vehicle exhaust was employed as the source of low boiling molecules, in which PAHs were the target compounds for the assessment of sorption ability of MCM-41, via comparing with the commercially available XAD-2 serving as a reference.
It was demonstrated that in the test of a 2-stroke motorcycle, lubricating oil in the exhaust contributed a serious matrix effect interfering with the PAH analysis. In testing the 4-stroke motorcycle, both MCM-41 and XAD-2 exhibited similar sorption ability and various target PAHs were found, e.g., naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene, and pyrene with concentration in the range of 15 ~ 2.8 x 105 ng/m3. In the test of diesel buses, 3 conditions of idle, 20 km/hr, and 40 km/hr, respectively, were tested on a dynamometer, and naphthalene, acenaphthylene, acenaphthene, fluorene, and phenanthrene were found with concentration in the range of 10 ~ 2.5 x 104 ng/m3. Other than naphthalene, whose recovery is 20~30% due to its volatility, the recovery for other PAHs are between 50 and 150%, demonstrating high applicability of MCM-41 as a potential sorbent for the enrichment of semi-VOCs.||en_US|