Optimization of adsorption parameters of activated carbon modified with the oxidizing agent on adsorptive removal of toluene using response surface methodology (RSM)

Abstract

Commercial activated carbon of coconut shell has been oxidized with nitric acid, and their oxygen surface complexes have been characterized by classical titration following Boehm’s method and by FTIR. The surface areas of both the original and oxidized activated carbon were obtained 814 m² g⁻¹ and 626 m² g⁻¹ with an average micropore volume of 1.67 and 1.79 cm³ g⁻¹, respectively. A comparative study on the toluene adsorption revealed that the oxidized activated carbon showed better toluene adsorption. The adsorption capacity of toluene was enhanced dramatically by oxidation of the activated carbon. The highest adsorption and breakthrough times of the functionalized (FAC) and nonfunctionalized activated carbon (NFAC) were 110.39 mg g⁻¹, 67.18 min, and 65.38 mg g⁻¹, 32.29 min, respectively. An adsorbent mass of 60 mg, the flow rate of 90 mL min⁻¹, toluene concentration of 500 ppm, the humidity of 30%, and temperature of 26 °C was found to be the optimum conditions for the maximum adsorption capacity of toluene of 112.11 mg g⁻¹ by the FAC in a dynamic adsorption system. The FAC obtains an adsorption capacity of 71.28 mg g⁻¹ in the third cycle, which is about 65% of the preliminary values. Due to the high adsorption capacity of the FAC in the adsorption of toluene and proper reusability and stability, it can be used as a suitable and economical adsorbent.

GRAPHICAL ABSTRACT

Keywords:

• Toluene adsorption
• response surface methodology (RSM)
• process optimization
• activated carbon
• oxygen functional groups

Additional information

Funding

This project was funded (grant no. 97025376) by the INSF, Iran National Science Foundation. This study was supported by the Tehran University of Medical Sciences under the Ph.D. thesis scheme (no.: 9421138001).