Determination And Pollution Control Of Benzene Series Compounds In Air

Benzene Series Compounds, including benzene, toluene, ethylbenzene, and xylene(BTEX), are some of the most common air pollutants that need to be controlledaccording to increasing stringent environmental regulations. Atmospheric emissions ofthese volatile organic compounds from industrial facilities and motor vehicles exhaustcause serious environmental problems and financial losses. They are toxic andcarcinogenic to human health. There are many of separation processes to address thisproblem: adsorption, condensation and membrane fractionation and so on. The mostcommom treatment method is adsorption using materials with a big specific surfacearea. Furthermore the absorbents can be reused. Therefore, increased attention has beenpaid to the treatment of indoor and outdoor air pollution in recent years.In this study, indoor air was investigated, and the home-made activated carbon wasemployed to adsorb BTEX from air, with comparison of that of commecial activatedcarbon are showed as follows:(1) Monitoring of the indoor air pollutionThe average concentrations of five BTEX compounds including benzene, toluene,ethylbenzene, m, p-xylenes and o-xylene in indoor and outdoor air were monitored bythermal desorption and gas chromatography (TD-GC), and samples were collected froma university campus. Results showed that the concentrations of all the compound ofBTEX met the indoor air quality standard of China. The average concentrations oftoluene accounted for the largest percentage（27.9%~32.0%）of the6compounddetermined．The indoor concentrations of BTEX were a little higher than their outdoorcounterparts. The BTEX indoor air pollution can be reduced by ventilation.(2) In this work, activated carbon was prepared by the waste raw yeast to adsorbthe BTEX. The optimized parameterswere obtained as follows:the temperature from650℃to720℃. The characteristics and adsorption capacity for the methylene blueadsorption value of the activated carbon as follows: the surface area of900—l000m2/g,the pore volume of0.80—0.95mL/g, the average pore size of3.70—3.80nm，X-raydiffraction (XRD)and scanning electron microscopy (SEM)were employed toobserve the microstructures. The results showed that AC was mainly amorphous.Functional groups including carbonyl, amide, carboxyl and hydroxyl groups werepresent on the surface of the activated carbons. N2adsorption isotherm of activatedcarbon analysis showed that material with narrowpores. The pores were mainly between 1.5to4nm, the pore structure of AC with micropore is mainly, also contains a certainamount of large pores.(3) the AC with the particle size of100mesh shows the best absorption of BEXT,at the condition: temperature:30℃, gas rate:40m~3/h. the adsorption isotherm andadsorption breakthrough curve were determined. The adsorption experimental data wereprocessed by Langmuir，Freundlieh，pseudo first order and pseudo second order.The experimental study result indicated that，taken the brewers yeast based AC asthe absorbent adsorption BTEX, its craft is feasible, should serve as upholstery for thebrewing yeast based AC in the air purification domain.