Green synthesis of biomass-based SnO 2 – activated carbon composite from coffee husk for congo red detection using poly(niacin) functionalization

The present work describes a sensitive electrochemical method for the detection of congo red (CR) by modifying tin dioxide (SnO2), graphite powder and activated carbon (AC) composite paste (B(SnO2/GP/AC)) using poly niacin (PNCM(SnO2/GP/AC)). The green synthesis technique was applied to synthesize SnO2 using Azadirachta indica leaves extract and used as the electrode material. Techniques such as Fourier transform infrared (FTIR), X-Ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM) and linear scanning voltammetry (LSV) were utilized to study the surface characteristics of both B(SnO2/GP/AC) and PNCM(SnO2/GP/AC). A linear response was observed over the concentration range of 0.2–4.5 μM, with calculated limit of detection (LOD) of 0.875 μM and 0.793 μM for CV and LSV, respectively. The proposed electrode was applicable for the analysis of CR in tap water and effluent water with good recovery rates of 100.67%–101.06% and 97.67%–99.68%, respectively.