Application of biochar prepared from wheat bran as the binding phase in diffusive gradient in thin films technique for determination of mercury in natural waters

A novel binding gel for the DGT technique, containing biochar produced through the pyrolysis of wheat bran, was developed. The results of this study indicate that wheat bran biochar (WBBC) is a porous material with a surface area of 25 m²/g. The primary functional group on the surface of WBBC was identified as a carbonyl group, although some hydroxyl and imino groups were also detected. Furthermore, the findings demonstrate that the accumulation of Hg on WBBC was significantly influenced by an increase in ionic strength, particularly in NaCl solution, owing to Hg’s high affinity for chloride ions. The performance of the DGT with WBBC binding gel was also affected by solution pH, with the optimal pH for WBBC application falling within the range of 3–7. The diffusion coefficient of Hg, depending on the matrix environment, varied between 5.44 and 6.99 × 10⁻⁶ cm²/s. When applying the newly designed DGT technique to spiked samples of river water, an R value of 0.68 was achieved. The results of this work proved that modified DGT technique allows for a cost-effective analysis of Hg in natural waters with lower salinity, while retaining the fundamental properties of the binding gel incorporating a particulate adsorbent with anchored functional groups.

Graphical Abstract