Sustainable Biochar–Alumina Composites for Electroanalytical Sensing of Herbicide and Antibiotic

The problem of water pollution by various xenobiotics has gained a lot of interest due to their persistence, bioaccumulation potential, and toxic effects on ecosystems and humans. Electrochemical sensors offer a rapid, sensitive, and cost-effective method for on-site monitoring. In this research, an electrochemical sensor for xenobiotics based on a biochar–alumina composite is developed. The biochar–alumina composites were obtained by the air-limited pyrolysis of oak sawdust in the presence of alumina. Two types of alumina were mixed with oak sawdust in three ratios and subjected to thermal treatment. The resulting composites were characterized by SEM, N2 adsorption isotherm, XRD, and electrochemical characterization. The detection of the herbicide pendimethalin and the antibiotic ciprofloxacin was investigated, and the composite with the optimal biochar/alumina ratio was selected for each of the xenobiotics studied. A linear current response was obtained for pendimethalin in the concentration range 0.7 μM to 70.0 μM with an LOD of 0.5 μM. A linear current response was obtained for ciprofloxacin in the concentration range 1.6 μM to 55.4 μM with an LOD of 0.63 μM. A comparison of the characterization results with the electroanalytical performance implied the importance of the hydrophobic/hydrophilic nature of the electrode surface for detecting the analyte under investigation.