Adsorptive removal of humic acid on activated carbon prepared from almond shell: approach for the treatment of industrial phosphoric acid solution

ABSTRACT

Almond shell was used as a precursor to prepare activated carbon, using carbon dioxide as a physical activation agent. Its ability to remove the humic acid was evaluated. The surface area of almond shell activated carbon was found to be 1,310 m²/g. The effects of experimental parameters such as pH, initial humic acid concentration, contact time, adsorbent dosage, and solution temperature on the adsorption were investigated. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. Pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated for predicting the nature of adsorption. For an approach to an industrial application, activated carbon prepared from almond shell seems to be an effective, low-cost, and good adsorbent precursor for the removal of humic acid from commercial phosphoric acid solution.

Keywords:

• Adsorption
• Activated carbon
• Humic acid
• Isotherm
• Kinetic

Acknowledgments

The authors gratefully acknowledge financial support from the Tunisian Chemical Group. They also wish to express their gratitude to Mr. A. Charfi, Mr. L. Fourati, K. Foued, and Mme F. Bennour Mrad for their help and support. Thanks are due to Mr. Z. Fakhfakh from Faculty of Science of Sfax for the assistance in MEB. Also, I thank Mme. L. Mahfoudhi for this linguistic assistance in this manuscript.