Porous Defect-Modified Graphitic Carbon Nitride as an Effective Adsorbent for the Removal of Hg From Surface Water

The presence of mercury in water bodies has been identified as one of the major pollutants of immense concern. This is due to their carcinogenic and mutagenic nature. This ion easily finds its way into the human system where they interact and alter the functionality of the DNA. Therefore, methods of their removal have garnered a lot of interest. Hence, in this study, a porous defect-modified graphitic carbon nitride (PD-gCN) was constructed and utilized as an effective adsorbent for the removal of mercury from water. The porosity and the defect modification of the adsorbent were achieved by a process involving thermal polymerization of a freeze-dried mixture of melamine and ammonium chloride (NH 4 Cl) under an inert atmosphere of nitrogen. During the process, a simultaneous introduction of both a porous feature and two types of defects (cyano group and nitrogen vacancy) occurred within the frame-. work of graphitic carbon nitride (gCN). The structural and morphological properties were established using X-ray diffraction, Fourier transform infrared spectroscopy, and microscopic techniques. The amount of Hg adsorbed was determined by ICP-OES spectroscopy. The involvement of cyano group and nitrogen vacancy in PD-gCN adsorbent was confirmed by the characterization techniques and the gCN properties was found to be influenced by the nature of the modification method. The percentage removal of Hg by PD-gCN in synthetic water was found to be 97.5%, and the residual concentration of Hg, Pb, Fe, Mn, Co, Cu, Zn, Se, Sc, Ti, V were below the drinking water standard recommended by the World Health Organization. This, thus, confirm that PD-gCN is a promising, and highly-efficient adsorbent that could be used to purify water of a low Hg ions concentration. The Langmuir maximum adsorption capacity of Hg ions by PD-gCN was found to be 46.50 mg/g. Furthermore, the performance achieved by PD-gCN in the treatment of real surface water confirms its robustness in water treatment.