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Study on the Competitive Adsorption Performent of Direct Deep Blue and Methyl Orange on Expanded Graphite Adsorbent

XY Pang, SX Ren, X Di, and SY Sun

Expanded graphite (EG) adsorbent was prepared with chemical oxidation method using H2SO4 as inserting reagent, KMnO4 as oxidizing agent and the intercalating product expanded at 900°C. The adsorption and competitive adsorption performance of methyl orange (MO) and direct deep blue (DDB) on the EG were assessed using a combination of the single and binary (MO and DDB) aqueous solution. Experimental results shown that: in single and binary aqueous solution, adsorption capacities of EG for these dyes increase with the increase of dye concentration, ionic strength and adsorbent specific surface area. In binary solution, the coexistence of DDB can obviously reduce MO adsorbance, and there are replacements of DDB for MO. It is worthwhile to note that there is a synergic effect of MO in the adsorption of DDB, the amount of DDB adsorbed on EG increases with the initial concentration of MO, and EG possess better adsorption performance for DDB than that for MO. The adsorption and competitive adsorption process of MO on EG follow the pseudo-second-order kinetic model, while the adsorption and competitive adsorption of DDB are affected by temperature. The kinetic data follow pseudo-first-order model at 5°C and 20°C, and pseudo-second-order model at 45°C, respectively.