Study On The Removal Of Pollutants By Expanded Graphite

Expanded graphite is a kind of poriferous material. It has a wide range of pore diameter and a great pore volume. So it has a great potential in practical use for absorption. The main objective of this research is to study the absorping ability of expanded graphite against three main kinds of pollutant and optimize the reaction condition. Based on the data aquired in experiments, some mathematical analysis is conducted and some theories are given to explain the experiment results. Furthemore, the analysis method using by this article can also be used to predict the absorption ability of other materials and direct the development of special absorption materials.We have done a well-rounded study about the absorbing ability of expanded graphite. The main body of the research contains four aspects: first of all, the parameters about how to produce expanded graphite; secondly, absoption ability against oil; thirdly, absorption ability against Cr(Ⅵ); finally, absorption ability against nitrobenzene.First of all, in the production of expanded graphite, we find that at a temperature of 900℃, the graphite can get the greatest volume. And the process of expanding can be done in 35 seconds. Under this condition, the compounds inserted into natural graphite vaporize completely and the expanded graphite can get a good mechanical character.Expanded graphite can absorb oil very fast and the absorption ability is excellent. Another two absorption material, cotton and active carbon are used as a contrast. The result is that expanded graphite is much more excellent than the other two materials when used to oil absorption. We also have done some experiment about how the status of expanded graphite affects the absorption ability. The experiment shows that the worm-like physical shape is the most important reason of its high absorption ability. Through regeneration research, the regenerating rate of expanded graphite is high.When expanded graphite is used to absorb Cr(Ⅵ), After 120 minutes, the absorption amount reached the maximum amount. Absorption kinetics is used to describe the absorption characteristics. The rate of adsorption of Cr(Ⅵ)on expanded graphite followed second order kinetic model. When pH is 2,the absorption ability of expanded graphite is the highest. The process of absorption can be explained mainly as a kind of physical absorption. Absoption isotherm of Cr(Ⅵ) onto expanded graphite conforms with the langmuir equation. According to the parameters we can conclude that the process of absorption is single-layer absorption.When it comes to nitrobenzene, after 80 minutes, the absorption amount gets its maximum amount. The rate of adsorption of nitrobenzene on expanded graphite followed first order kinetic model。When pH is 6, the absorption reach es the maximum amount. Under 298K, Sorption isotherm of nitrobenzene onto expanded graphite conforms with the langmuir equation. The parameter R2 is 0.995, single-layer absorption amount Q is 30.67mg/g, which is near the experimental data. So we can infer that the process of absorption is a kind of single-layer absorption. According to the dynamic experiment of absorption, the dynamic absorping ability of expanded graphite is 22.47mg/g.