Preconcentration and selective extraction of trace Hg(ii) by polymeric g-C3N4 nanosheet-packed SPE column

Abstract

In this study, we successfully synthesized polymeric graphitic carbon nitride (g-C₃N₄) nanosheets through thermal means and proposed their application in solid-phase extraction (SPE) for the enrichment of trace Hg(II). The nanosheets underwent characterization using scanning electron microscopy, tunnelling electron microscopy, and energy-dispersive X-ray spectroscopy. The column packed with polymeric carbon nitride nanosheets demonstrated effective extraction of trace Hg(II) ions from complex samples. The g-C₃N₄ nanosheets possess a zeta potential value of −20 mV, enabling strong interaction with positively charged divalent Hg(II) ions. This interaction leads to the formation of stable chelates with the nitrogen atoms present in the polytriazine and heptazine units of the material. The proposed method exhibited a high preconcentration limit of 0.33 μg L⁻¹, making it suitable for analysing trace amounts of Hg(II) ions. Moreover, the method's applicability was confirmed through successful analysis of real samples, achieving an impressive preconcentration factor of 200. The detection limit for trace Hg(II) ions was determined to be 0.6 μg L⁻¹. To assess the accuracy of the method, we evaluated its performance by recovering spiked amounts of Hg(II) and by analysing certified reference materials. The results indicated excellent precision, with RSD consistently below 5% for all the analyses conducted. In conclusion, the thermally synthesized polymeric carbon nitride nanosheets present a promising approach for solid-phase extraction and preconcentration of trace Hg(II) from real samples. The method showcases high efficiency, sensitivity, and accuracy, making it a valuable tool for environmental and analytical applications.