Preparation Of Activated Carbon And Its Application In Absorbing Volatile Organic Compounds

Activated carbon is a adsorbent with abundant pore structure. Its advantages are strong adsorption capacity and renewable use. The leaves is a kind of material that has a multiple source and easy to processing. Preparation of activated carbon with leaves can get high performance of activated carbon also can solve the problem of waste leaves. So it is an environmental and economic method for preparation of activated carbon.This study determined the best preparation condition of leave activated carbon by orthogonal test. The best preparation condition was at a H3PO4concentration of50%, an impregnation ratio of3:1, an impregnation time of12h, an activated temperature of400℃and an activated time of1h. The activated carbon prepared at the best preparation condition treated by BET analysis, Boehm titration and zero charge (PZC) titration method to get the physicochemical properties. The result showed that the BET special surface area of leave activated carbon was774.4m2/g with the micropore area148.2m2/g and the mesopore was the main structure of it. The acidic functional groups on the surface of the activated carbon activated by phosphoric acid had a significant advantage for basic functional groups. And its main constitute were hydroxide radical and phenolic hydroxyl group. And the PZC of the activated carbon was5.33.Volatile organic compounds (VOCs) is a kind of organic compound with low boiling point and volatile easily. These compounds can be absorbed through breathing and skin, and they are harmful to human body. This test studied the distribution characteristics in the air ambient by the method that collected by activated carbon tube, desorbed by CS2and detected by GC-MS. The result showed that the variation of concentration of VOCs in the air ambient at the point of crossing has a relationship with traffic flow,weather condition and light intensity. Increasing of traffic flow could make the concentration of VOCs be higher, but wind.rain and increasing of light intensity would decrease the concentration of VOCs. The main consist of VOCs in the air ambient is benzene series and alkane compounds. By source analysis, we got the conclusion that the concentration of VOCs at the point of crossing was significantly affected by motor vehicle exhaust, but at the points near to chemical laboratory and pharmaceutical laboratory, the concentration of VOCs was significantly affected by the solvent and pharmaceutical used in different laboratory.The test chose some kinds of compounds which had a relative high concentration to proceed activated carbon adsorption experiment. The result revealed that adsorption characteristics of toluene was slightly affected by the size of activated carbon and pH on the surface. The adsorption saturation concentration of difference substances on the surface of activated carbon was affected by their molecular size and the relationship was positive correlation. The adsorption saturation concentration of toluene, tetrachloromethane,1,2-dichloroethane,1,2,4-trimethylbenzene were228.4mg/g,275.2mg/g,253.4mg/g and176.6mg/g, respectively. Multicomponent adsorption at the same time would produce competition between the different components, resulting in the decrease of adsorption saturation concentration of each component. However, the sum of adsorption saturation concentration of all component was higher than one-component adsorption, which showed different component also had a synergistic effect.Proceeding a high temperature heating regeneration on the saturated adsorption activated carbon, which showed that the leave activated carbon can maintain a good adsorption performance. This phenomenon illustrated leave activated carbon had a good regenerability.