Experimental and theoretical studies of spherical hydroxylamine hydrochloride intercalated molybdenum disulfide for the removal of U(VI), Eu(III), and Cr(VI)

Abstract

The current environmental problem is the coexistence of multiple pollutants rather than a single pollutant. In this study, U(VI), Eu(III), and Cr(VI) are selected as representatives of the actinides, lanthanide elements, and heavy metal elements for removal study. The hydroxylamine hydrochloride intercalated molybdenum disulfide (HAH/MoS₂) was prepared to remove these contaminants. The insertion of hydroxylamine hydrochloride increased layer spacing, which was conducive to the pollutant molecules entering the molybdenum disulfide layer. HAH/MoS₂ revealed a spherical shape with a rough surface and relatively high anti-interference. The maximum adsorption capacities of HAH/MoS₂ for U(VI), Eu(III), and Cr(VI) reached 104.9 mg/g, 72.9 mg/g, and 81.4 mg/g, respectively. The adsorption mechanism of U(VI) was interlayer adsorption at pH < 6.2 and surface complexation at pH > 6.2. Similarly, the removal of Eu(III) was interlayer adsorption at pH < 5.0, interlayer adsorption and surface complexation at pH 5.0–7.7, and forming precipitation Eu(OH)₃(s) at pH > 7.7. The removal of Cr(VI) depended on surface complexation at pH < 4.0 and interlayer adsorption at pH > 4.0. These ions were more likely to be adsorbed between layers instead of at the surface. Compared to U(VI) and Cr(VI), Eu(III) was more easily adsorbed at the interlamination of HAH/MoS₂. From the point of view of charge transfer, U(VI) and Eu(III) tended to give away electrons, and Cr(VI) tended to gain electrons in the removal process. This work can offer a new perspective for the design and application of two-dimensional materials for multiple pollutants removal.