SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

Abstract

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m² g⁻¹) and the highest iodine adsorption (1511 mg g⁻¹) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m² g⁻¹ and 1076 mg g⁻¹). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L⁻¹). It was found that a Langmuir isotherm gave a better fit (R ² = 0.999) to the observed adsorptions than a Freundlich isotherm (R ² = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R ² > 0.998, Δq _e  = 3.7%) than a pseudo-first-order model (R ² ≈ 0.95, Δq _e  = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.

Keywords:

• Activated carbon
• Iodine
• Jatropha seed coat
• Kinetics
• Methylene blue

Acknowledgements

The authors would like to sincerely thank C. Gigantic Carbon Co., Ltd. for the provision of the commercial activated carbon and Assoc. Prof. Siriporn Daopiset for her cooperation on SEM measurements.

Notes

VM = volatile matter, FC = fixed carbon, C = carbon, H = hydrogen, O = oxygen, S = sulfur, A _BET  = BET surface area, V _T  = total pore volume, V _Mi  = micropore volume, V _Non-Mi =non-micropore volume, JSC = jatropha seed coat.

^a Dry basis.

^b By difference.

^a Dry basis.

^b By difference.