Cellulose derivatives crosslinked by citric acid on electrode surface as a heavy metal absorption/sensing matrix

Hypothesis: Modification of cellulose derivatives with citric acid leads to gain in sorption capacity towards metal ions, which has been many times applied for heavy metal sequestration. This work, for the first time, investigated the in-situ coating of a carbon electrode with citric acid-crosslinked cellulose derivatives. The occurrence of crosslinking bonds was revealed using infrared spectroscopy and thermogravimetric analysis, while other features were investigated using electrochemical methods. Experiments: Electrodes were modified by casting of aqueous solutions of cellulose derivatives (hydroxyethyl cellulose, HEC and thermally pre-treated carboxymethyl cellulose, T-CMC) mixed with citric acid (CA) on the electrode surface, followed by thermal treatment (110 degrees C, 1 h) to reach the requested HEC-CA and T-CMC-CA hydrogels coated on glassy carbon electrodes. Findings: After the absorption of metal cations from solution, the electrodes coated by both HEC-CA and T-CMC-CA exhibited stripping voltammetry peaks for Pb, Cd and Cu, contrary to electrodes prepared without crosslinking. It was also observed that HEC-CA surface change its electrochemical impedance reversibly after deposition and acid-induced removal of Pb2+. Assessment of Pb2+ sensing properties revealed the detection limit of 0.39 mg L-1 and sensitivity of 9.91 mu A L mg(-1). Therefore, the citric acid-crosslinked cellulose derivatives can be employed for the preparation of cheap and sustainable heavy metal sensors and similar surfaces.

Automated summary

This study investigated the in-situ coating of carbon electrodes with citric acid-crosslinked cellulose derivatives for improved sorption capacity towards metal ions, showing promising results for heavy metal sequestration applications. The electrodes coated with the crosslinked cellulose derivatives exhibited stripping voltammetry peaks for Pb, Cd, and Cu, as well as reversible changes in electrochemical impedance after metal ion absorption. The detection limit for Pb2+ sensing was found to be 0.39 mg L-1 with a sensitivity of 9.91 μA L mg(-1), suggesting the potential for cheap and sustainable heavy metal sensors.