Adsorption of malachite green from aqueous solution by carboxylate group functionalized multi-walled carbon nanotubes: Determination of equilibrium and kinetics parameters

•MWCNTs-COOH was used as adsorbent for removal of malachite green.•The optimized contact time and pH was found to be 10 min and 9, respectively.•Adsorption capacity increases with increase in pH.•Adsorption capacity increases with increase in temperature.•Adsorption capacity increases with increase in time but reach equilibrium after 10 min.

MWCNTs functionalized with the carboxylate group are used as efficient adsorbent for the rapid removal and fast adsorption of malachite green from the aqueous solutions. The optimized contact time and pH were 10 min and 9, respectively. The effect of temperature revealed that the adsorption capacity of malachite green (MG) dye increased with increasing contact time, temperature and pH of the working solution. The adsorption equilibrium and kinetic data was well fitted and found to be in good agreement with the Langmuir isotherm model and pseudo second order kinetic model respectively with high correlation coefficient.

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