There is an ever growing interest in the development of biochar from a large variety of agrowastes. Herein, the main objective is the conversion of pomegranate peel powder biochar and its post-functionalization by phosphoric acid treatment, followed by arylation organic reaction. The latter was conducted using 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 using thermal gravimetric analysis (TGA) and Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). SEM pictures showed micrometer-sized biochar particles with tubular structure having about 10–20 μm-wide channels. SEM studies have shown that arylation did not affect the morphology upon arylation. The porous structure did not collapse and withstood the arylation organic reaction in acid medium did not collapse upon arylation. TGA and Raman indicated gradual changes in the arylation of biochar at initial concentrations 10– 5, 10– 4 and 10– 3 mol L− 1 of 4-aminobenzoic acid. The detailed Raman spectra peak fittings indicate that the D/G peak intensity ratio leveled off at 3.35 for 4-aminobenzoic acid initial concentration of 10– 4 mol L− 1, and no more change was observed, even at higher aryl group mass loading. This is in line with formation of oligoaryl grafts rather than the grafting of new aryl groups directly to the biochar surface. Interestingly, Azure A diazonium salt induced much lower extent of surface modification, likely due to steric hindrance. To the very best of our knowledge, this is the first report on diazonium modification of agrowaste-derived biochar and opens new avenues for arylated biochar and its applications.

    Abstract
        Graphical abstract
    1 Introduction
    2 Experimental
        2.1 Chemicals
        2.2 Biochar preparation
        2.3 Arylation of biochar
        2.4 Characterization of biochar samples
    3 Results and discussion
        3.1 Raman spectroscopy
    4 Conclusion
    Acknowledgements 
    References

• Ahmed M. Khalil(Photochemistry Department, National Research Centre, Université Paris Est, CNRS, ICMPE, Faculté Des Sciences, Unité de Recherche Électrochimie, Matériaux Et Environnement UREME)
• Radhia Msaadi(Faculté Des Sciences, Unité de Recherche Électrochimie, Matériaux Et Environnement UREME (UR17ES45))
• Wafa Sassi(Faculté Des Sciences, Unité de Recherche Électrochimie, Matériaux Et Environnement UREME (UR17ES45))
• Imen Ghanmi(Faculté Des Sciences, Unité de Recherche Électrochimie, Matériaux Et Environnement UREME (UR17ES45))
• Rémy Pires(Université Paris Est, CNRS, ICMPE (UMR 7182))
• Laurent Michely(Université Paris Est, CNRS, ICMPE (UMR 7182))
• Youssef Snoussi(Université Paris Cité, CNRS, ITODYS (UMR 7086))
• Alexandre Chevillot‑Biraud(Université Paris Cité, CNRS, ITODYS (UMR 7086))
• Stéphanie Lau‑Truong(Université Paris Cité, CNRS, ITODYS (UMR 7086))
• Mohamed M. Chehimi(Université Paris Est, CNRS, ICMPE (UMR 7182), Université Paris Cité, CNRS, ITODYS (UMR 7086))