Retention mechanism of phenol in mainstream cigarette smoke by cellulose acetate filters

To understand the retention mechanism of phenol in mainstream cigarette smoke by cellulose acetate(CA) filters, the phenol filtration efficiency, the phenol distribution in the gas phase and particulate phase during filtration and the retention characteristics of the filter for both the gas phase and particulate phenol species were investigated. The distribution of particulate bound phenol as a function of the particle size was examined. The ratio of phenol transferring from the particulate phase to the gas phase during smoke flowing through the CA filter were studied. Retention mechanisms for phenol in the gas phase as well as particulate phase phenol in the filter and the phase transition of phenol were proposed. Phenol filtration efficiency of the cigarette filter was calculated based on the proposed retention mechanisms and compared with available experimental data. The results showed that:1) Comparing with nicotine and the other particulate bound smoke constituents, CA filter exhibited a certain retention selectivity for phenol. 2) Although phenol was mainly bound to the particulate phase of the cigarette mainstream smoke, about 35% of gas phase phenol was found at the tobacco end of the filter, whilst this dropped to approximately 0 at the mouth end of the filter, mostly by selective chemical adsorption. 3) The weighted average smoke particle size and particulate phenol was 0.44 and 0.38 μm, respectively. The filtration efficiency of the filter to particulate phenol was near 40%. 4) About 19% of particulate bound phenol transferred to gas phase when smoke passing the filter, and was selectively adsorbed. 5) The overall filtration efficiency of the CA filter for phenol in mainstream cigarette smoke was 68.7%, with -7.7% variation compared with experimental data. The results demonstrated the phase transition of phenol during the filtration process and the selective retention with varying particle sizes. Our results showed that the application of CA filter in product designs reduces harmful constituents such as phenolic compounds in mainstream cigarette smoke.