Characterization of the carbonaceous materials obtained from different agro-industrial wastes

Abstract

This paper reports the preparation and characterization of carbonaceous materials obtained from three types of vegetable wastes provided by agricultural industries. Soft carbonization (280°C) and H₃PO₄-activation procedures were used to convert the agricultural wastes to carbon powders with high adsorbent capacities. This process is excellent for eliminating and exploiting the huge masses (many tons) of vegetable residues remaining after each harvest every year in several Colombian agro-industries. The powders were characterized by X-ray diffraction (XRD), IR spectroscopy, scanning electron microscopy (SEM), and N₂-adsorption isotherms. XRD and IR verified the formation of carbons, and SEM showed small particles (20–500 µm) with characteristic morphology for each type of residue used and abundant cavities of different sizes. The N₂-adsorption analyses showed that the carbons had high adsorption capacities with important surface area values and large pore volumes. The use of the activated carbonaceous materials as adsorbent of azo dyes (allura red and sunset yellow) from aqueous solutions was evaluated. The results showed a good adsorption capacity indicating the potentiality of these materials as pollutant adsorbents in food industry wastewaters. These results indicate that these powders can be used as potential adsorbents for different gaseous or liquid pollutants.

GRAPHICAL ABSTRACT

Keywords:

• carbon
• agricultural waste
• coconut shell
• corn cob
• rice husk

Acknowledgments

The authors gratefully acknowledge the Universidad Nacional de Colombia (UNAL-Bogotá) and the Universidad de Córdoba (Montería-Colombia) for supplying the resources for this scientific investigation. A portion of this work was developed at the 125-Lab (Lab-DRES: Laboratorio de Diseño y Reactividad de Estructuras Sólidas) of the UNAL-Bogotá.