Laccase-immobilized biochar as a unique host matrix for electrochemical detection of gallic acid: a sustainable engineering approach

An electrochemical platform for the detection of organic persistent polyphenolic pollutant, gallic acid (GA), was fabricated using an enzyme-immobilization approach over acid-functionalized biochar (f-BC) modified carbon fiber electrode (CFP) electrode. The f-BC was synthesized from dried pineapple leaves and was characterised using X-ray diffraction analysis (XRD), Raman spectroscopy, scanning electron microscopy (SEM), Fourier Transform-Infrared Spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) for analysing the physicochemical characteristics. The SEM image of Lac/f-BC/CFP confirmed the presence of a porous and granulated surface upon laccase immobilization, while the FTIR spectrum confirmed the presence of C[double bond, length as m-dash]O stretch and N-H bend, indicating amide bond formation. The acid treatment of biochar introduced -OH and -COOH groups that further aided in the successful immobilization of laccase <i>via</i> covalent bonding. The fabricated electrode could demonstrate a linear response within the concentration range of 0.012-40 μM and a low detection limit (LOD) of 9 nM with high selectivity. The fabricated electrode also showcased high practical utility as it could attain high recovery percentage during real sample analysis in tap, pond, sewage and industrial effluent samples.