Abstract: The structure and characteristics of synthetic G-COOH were studied using the FTIR technique. The adsorption of four ionic dyes, methyl violet, neutral red, brilliant yellow and alizarin red, onto G-COOH in aqueous solution was studied in a batch system with respect to adsorbent dose, contact time, initial dye concentration and solution pH. Also, the desorption properties of methyl violet dye was investigated. The desorption data show that the removal percent of dye methyl violet from G-COOH is 88.2% by using NaOH/EtOH eluting reagent, and the desorbed G-COOH can be reused to adsorb the dye. The Langmuir and Freundlich adsorption models have been applied to describe the equilibrium isotherms and the isotherm constants are determined. The Langmuir model agrees very well with the experimental data of cation dyes(methyl violet and neutral red), while the adsorption behavior of anion dyes(brilliant yellow and alizarin red) are fitted to Freundlich isotherms. The calculated absorption parameters indicate that absorption process of dyes on G-COOH is easy to take place. Batch kinetic data from experimental investigations on the removal of four ionic dyes from aqueous solutions fit well with the pseudo-secondorder kinetic model. The results in this study indicate that G-COOH is an attractive candidate for removing dyes from dye wastewater.

Key words: carboxylated graphene, ionic dyes, adsorption, desorption, thermodynamics, kinetic