选择吸附性活性炭颗粒的制备及性能

Simple preparation method and selective adsorption performance of novel activated carbon particles

根据非溶剂致相分离的原理,使用醋酸纤维素(cellulose acetate,CA)/丙酮/水3组分溶液于活性炭颗粒表面被覆多孔CA膜,并对改性后活性炭颗粒的吸附性能进行了研究。结果表明,这种多孔CA改性活性炭颗粒对气化状态和气溶胶状态的芘、肉桂腈、苯酚等有害物质的吸附量均高于活性炭原样,而对苯甲酸、麝香草酚等香味成分的吸附量均低于活性炭原样,表现出较好的选择吸附性。其中,对气化状态苯酚的吸附量相对于活性炭原样提高了17%,对苯甲酸的吸附量降低了60%;而对气溶胶状态苯酚的吸附量相对于活性炭原样提高了78%,对麝香草酚的吸附量降低了88%。

Summary Activated carbons （AC） are effective adsorbents for removal of a wide variety of organic pollutants in aqueous media or gaseous environments. Their high adsorption capacity largely depends on the well-developed internal pore structure, surface area and special surface reactivity. However, general AC have not selective adsorption ability, which are often required in many practical uses such as reducing certain harmful chemicals from mainstream cigarette smoke. Therefore, modification to endow AC with selective adsorptivity is important and attractive. Based on the findings of nonsolvent induced phase separation from a cellulose acetate （CA） ternary solution in a mixed solvent of acetone and water, we successfully covered a CA porous film on the surface of AC particles. Scanning electron microscopy （SEM） was used to observe the surface morphology of the CA films, and Brunner- Emmett-Teller （BET） measurement was used to characterize the surface area of the modified AC particles. The experimental results showed that the coverage rate of the porous CA film with an average pore size about 426 nm on the AC particles was over 80%, and the surface area of the modified AC particles （672 mZ/g） was lower than that of the original AC （834 m2/g） used. To investigate the selective adsorption property, ovrene, cinnamonitrile, benzene, phenol, benzoic acid,thymol and vanillin, which are the typical chemicals in the mainstream cigarette smoke, were selected as the model compounds in the simulating adsorption tests. For the gas adsorption experiments, the chemicals （each 0.1 g） were dissolved in chloroform （1.5 mL）. Sixty millilitres of the mixed solution was dropped to a ball of cotton fiber （0.1 g）, and put in a closed container after the chloroform had been volatilized. The control sample of the original AC and the modified one （each 0.2 g） were put in the closed container with the same distance （10 cm） to the cotton ball for 24 hours. For the aerosol adsorption experiments, the chemicals （each 0. 1 g） were dissolved in acetone （15 mL）. One point five millilitres of the mixed solution was uniformly sprayed to the tobacco （0.55 g） taken from a cigarette product, and burned in the closed container. Similar AC adsorption tests were carried out for 12 hours. These two tests were all repeated five times and the obtained samples were put together respectively. All adsorption quantities of the AC samples were analyzed by high performance liquid chromatography （HPLC） method. The adsorption results, both in gas and aerosol conditions, indicated that the modified AC particles could absorb more harmful substances, i. e. , pyrene, cinnamonitrile, phenol, but much fewer aroma components, i. e. , benzoic acid, thymol, than the original AC. Contrasted with the original AC in gas adsorption test, the adsorption capacity of the modified AC increased about 17% for phenol but reduced about 60% for benzoic acid. In aerosol condition, it increased about 78o/00 for phenol but decreased 88% for thymoh In conclusion, this study provides a novel surface modification method for AC by covering CA porous film on the surface of AC following the nonsolvent induced phase separation mechanism. It demonstrates that the modified AC have improved the selective adsorption property. One of the potential applications of the modified AC particles is the use as a cigarette filter additive to remove harmful chemicals with little loss on the flavor of the cigarette products.