Study on the competitive adsorption thermodynamic and kinetic performance of methyl orange and fuchsin basic on expanded graphite adsorbent

Author(s): Xiu-Yan Pang, Zhi-Xiao Zhai, Li-Li Zhang, Sheng-Sheng Nie, Bing-Jie Gong

In this study, expanded graphite (EG) is prepared through chemical oxidation method with graphite as rawmaterials, potassiumpermanganate as oxidant, vitriol as intercalation compound and expanded at 900 °C. Methyl Orange (MO) with azo-structure and Fuchsin basic (FB) with tritane structure are selected as organic adsorbates, and theirs adsorption and competitive adsorption thermodynamic, kinetic characteristics on EG are investigated. The results are: In the adsorption and competitive adsorption of MO and FB on EG, the adsorption isotherms are all type I, and the existence of the other component MO or FB would decrease the adsorbance of EG for FB and MO due to the competitive adsorption of MO and FB for the same adsorbing site. But the total adsorbances in competitive adsorption are higher than adsorbance of MO or FB in single system because these adsorbates can also be adsorbed on different adsorbing site. Adsorption of MO or FB on EG is spontaneous, and the increase of ionic strength, temperature and specific surface area of EG would cause the increase of adsorbates adsorbance. No matter the adsorption of single component system, or the competitive adsorption of bi-component system, 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 main action between EG with adsorbates.

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