Carbon nitride-doped melamine-silver adsorbents with peroxidase-like catalysis and visible-light photocatalysis: Colorimetric detection and detoxification removal of total mercury

Abstract Mesoporous melamine-silver (MA-Ag) nanocomposites doped with carbon nitride quantum dots (CNQDs) were fabricated simply by the controlled supramolecular self-assembly. It was discovered that the resulting nanoflower-like CNQDs@MA-Ag nanocomposites could exhibit the peroxidase-like catalysis, which could be specifically enhanced by Hg2+ by forming Ag@Hg alloys. A double catalysis-based colorimetric method was thereby developed for the fast detecting of Hg2+ and Hg0 in wastewater samples, with the levels down to 0.050 nM and 18.3 nM, respectively. Moreover, strong visible-light-driven photocatalysis of the nanocomposites was demonstrated for oxidizing Hg0 into Hg2+ through photocatalytic H2O2 production so as to realize the detoxification of Hg0 in the environmental wastewater. Besides, the fabricated mesoporous CNQDs@MA-Ag nanocomposites with large specific surface areas might facilitate the high Hg adsorption through the powerful MA-Hg chelate interaction, showing the efficient adsorption and/or removal of total Hg. The catalysis-selective colorimetric analysis and photocatalysis-based detoxification removal of total mercury may promise for wide applications in the environmental monitoring and wastewater treatment of toxic heavy metals of mercury.