Triacetin Adsorption On Activated Carbon And Its Application To Tobacco

With the WHO Framework Convention on Tobacco Control (FCTC)implemented, how to reduce tar and hazardous materials in cigarette smoke was paidmore attention in the healthy, environment and cigarette fields. Activated carbon wasused for adsorbent in the cigarette filter because of its large internal surface area andhigh porosity. During filter rod manufacture of cellulose acetate based filters, aplasticizer such as triacetin (Glyceryl triacetate) was used to achieve desired filter rodcharacteristics such as hardness. If activated carbon was present in the filter, thiscarbon was ‘poisoned’ by the triacetin and thus loses some of its adsorptionperformance in cigarette smoke. Described in this paper was a method to exposecarbon to (and measure) triacetin vapour adsorption under different environmentalconditions. Activated Carbons had been selected based on their pore size, surface areaand surface chemistry. The aim of the work was to study the interactions between thedifferent carbons and triacetin and volatile organic compounds (VOCs) to allow thefuture design of carbons whereby the interactions with triacetin were minimized andthe interactions with VOCs were maximized.The triacetin adsorption on activated carbon was investigated using granularactivated carbon as standard adsorbent under different temperature and relativehumidity. The experimental rusults showed the triacetin adsorption mechanism wasphysisorption, triacetin adsorption isotherm on activated carbon was found to fitLangmuir model and the saturated adsorption amount was333mg·g-1. Triacetinadsorption amount increased as temperature increased (over the range30to80℃)and decreased as the relative humidity increased (over the range20%to90%).Modified activated carbon were prepared by ultrasound-immersion treatmentusing trimethyl chlorosilane, dimethicone and n-octadecyl mercaptan, respectively.The main findings summarized that the modified activated carbon reduced theefficiency of adsorption of benzene, toluene and acetone, and these VOCs adsorptionprocess were found to fit Freundlich model. Activated carbon modified by trimethylchlorosilane decreased the adsorption ability on triacetin, and also maintained a high adsorption ability to VOCs in the cigarette smoke, hence it should be a betteradsorbent of cigarette filter.Two kinds of activated carbon were prepared by chemical activation using zincchloride and calcium nitrate, respectively. The former mainly dontated microporesand the later mainly controrll mesopores in the activated carbon. The results showedthat triacetin adsorption maily depended microporous structure on activated carbon.When the pore area of activated carbon was greater than2.8times the smallestcross-sectional area of triacetin, adsorption amount of triactin increased on activatedcarbon, conversely reduced. In addition, mesopores appeared to be beneficial astransport pores in benzene, toluene and acetone adsorption.The VOCs in cigarette smoke could be selectively removed using activatedcarbon. Removal rate of toluene and styrene were more than50%, but removal rate ofphenol was less5%which showed smaller improvements. Film diffusion limitationsseem to be present at the very high space velocities encountered under the conditionsof a cigarette filter. Activated carbon with micropore size distribution (<0.85nm) andmesopore had less adsorption ability on triacetin and more adsorption ability onVOCs.