Study On The Competitive Adsorption Capacities Of Expanded Graphite For Dye And Polyethylene Glycol

Expanded graphite EG is a type of new carbon adsorption material with loose porousstructure. The graphite intercalation compound with some atomes and radicles is preparedthrough electrochemical oxidation methods or chemical oxidation methods using naturalleprose graphite as raw materials. EG is obtained through the instant expand of the graphiteintercalation compound.EG were prepared with H₂SO₄as inserting reagent and KMnO4as oxidizing agent.Adsorbates’（Poly ethylene glycol （PEG） and two kinds of dye） adsorption and competitiveadsorption kinetics and thermodynamics on EG were investigated.The research showed adsorption, competitive adsorption capacities of two kinds ofcompetition system （PEG with a molecular weight of10000and Acid brilliant red3B （ABR,M=675） with azo-structure, PEG with a molecular weight of10000and Auramine lake yellowO （ALYO, M=318） with diphenyl methane structure） on expanded graphite （EG）.The resultsare:（1） EG has adsorption capacity for ABR, PEG and ALYO. In the adsorption andcompetitive adsorption of coexistence systems on EG, the adsorption isotherms are all type I.（2） In the competitive adsorption of dual component system, whether ABR and PEG orALYO and PEG, the existence of the other component would decrease the adsorbance of EGfor ABR, ALYO or PEG, which might be caused by the competitive adsorption of PEG withABR or PEG with ALYO for the same adsorbing site on EG.While, the total adsorbances incompetitive adsorption are higher than that of single component.（3） Adsorption of PEG,ABR,ALYO on EG are all spontaneous, and the increase of ionic strength, temperature andspecific surface area of EG would cause the increase of adsorbates adsorbance.（4） No matterthe adsorption of single component system, or the competitive adsorption of dual componentsystem, the kinetic models can all be described with pseudo second-order kinetic model.Adsorption rate increases with the increase in temperature. Physical adsorption is the mainaction between EG with adsorbates.The research for adsorption, competitive adsorption capacities of EG for Methyl Orange（MO） with azo-structure and Fuchsin basic（FB）with tritane structure were investigated. Theresults are:（1） EG has adsorption capacity for both MO and FB. In the adsorption andcompetitive adsorption of MO and FB on EG, the adsorption isotherms are all type I.（2） Inthe competitive adsorption of dual component system, the existence of the other component MO or FB would decrease the adsorbance of EG for FB or MO, which might be caused by thecompetitive adsorption of MO and FB for the same adsorbing site on EG.（3） The totaladsorbances in competitive adsorption are higher than the adsorbance of MO or FB in singlesystem, these adsorbates can also be adsorbed on different adsorbing site.（4） Adsorption ofMO or FB on EG is spontaneous, and the increase of ionic strength, temperature and specificsurface area of EG would cause the increase of adsorbates adsorbance.（5） No matter theadsorption of single component system, or the competitive adsorption of dual componentsystem, the kinetic models can all be described with pseudo second-order kinetic model.Adsorption rate increases with the increase in temperature. Physical adsorption is the mainaction between EG with adsorbates.In dual component system, the existence of the other adsorbate would cause the decreaseof single component’s adsorbance, but it can increase the total capacities of EG, and increasethe using rate of EG surface.