Facile diazonium modification of pomegranate peel biochar: A stupendous derived relationship between thermal and Raman analyses

Abstract

There is an ever growing interest worldwide in the development of biochar from a large variety of agrowastes. This work contributes to the domain by tackling an agrowaste represented in pomegranate peels powder. The latter was activated by acid treatment and then pyrolyzed to generate low cost biochar. To enrich the surface of the resulting biochar, it was arylated with various in-situ generated diazonium salts of 4-aminobenzoic acid (H2N-C6H4-COOH), sulfanilic acid (H2N-C6H4-SO3H) and Azure A dye. The effect of diazonium nature and concentration on the arylation process was monitored essentially using thermal gravimetric analysis (TGA), and Raman spectroscopy. These techniques showed gradual changes in the arylation of biochar at low concentrations of 10-5, 10-4 and 10-3 M of 4-aminobenzoic acid. Interestingly, Azure A diazonium salt induces lower extent of surface modification, likely due to steric hindrance. One key feature of this work is the correlation between D/G Raman peak intensity ratio and the mass loading of the aryl groups. To the very best of our knowledge this is the first report ever on diazonium modification of agrowaste-derived biochar and opens new avenues for such carbon allotrope, i.e. surface arylation and applications.

Surface Treatment of Biochar: Methods, Surface Analysis and Potential Applications. A Comprehensive Review

“…Relative deformations may arise in this structure expressing a weak D band with a directly proportional intensity to the extent of disorders in this structure. Khalil et al 65 investigated fundamental variations in the D/G peak intensity ratio on going from the pristine biochar derived from pomegranate peels when compared to different arylated biochar samples; namely Biochar-COOH, biochar-SO3H and biochar-Azure A. The results expressed that D/G peak ratio grows with arylation without depending on the kind of the diazonium compound.…”

“…Indeed, chemical grafting reactions no longer affect the carbon allotrope support, but the organic layer, previously attached. Reprinted from 65 with the permission of Springer Nature.…”