Scientific publications
Ruth Valerie Ngnokam Nkouonga
Emmanuel Ngameni
Hervé L. Tcheumi* (Corresponding author)
International Journal of Environmental & Analytical Chemistry
The development of analytical tools for pesticide pollution control is an important challenge to monitor pollution associated to these widely used compounds. In the present work, sawdust, a waste biomass, was modified using concentrated phosphoric acid. The resulting material was used to modify a glassy carbon electrode, and applied for the electrochemical detection of paraquat, a non-selective herbicide, known for its extremely harmful effects on living organisms. Characterisation of the phosphoric acid modified sawdust by XRD, FTIR spectroscopy, XPS and SEM/EDX reveals a structure close to that of hydrochars obtained by hydrothermal treatment of biomass. Electrochemical characterisations (cyclic voltammetry and electrochemical impedance spectroscopy) showed that this material also contains anionic groups (mainly phosphonate and carboxylate) which facilitated the selective accumulation of cationic species such as paraquat. Adsorption studies demonstrated the material’s high affinity for paraquat, with an adsorption capacity of 0.45 mmol g−1, at least 12-folds higher than that recorded on the untreated sawdust. Used as an electrode modifier, the sensor obtained showed a detection limit of 0.24 nM in the investigated concentration range (5 nM to 60 nM). This sensor was effective for the detection of this pesticide in real samples (river and tap water) and in commercial formulation with excellent precision and recovery capacity. These results highlight the dual potential of the synthesised material as both an efficient adsorbent for the removal of paraquat as well as an electrode modifier for trace-level sensing of paraquat in aqueous environments.
