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

Abstract

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 CO 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 via 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.