The Removal Mechanism of U(VI) on nZVI/MoS₂ Composites Investigated by Batch, Spectroscopic, and Modeling Techniques

Abstract

A novel nanoscale zero-valent iron/molybdenum disulfide (nZVI/MoS 2 ) composite was synthesized and well characterized in detail. The as-prepared materials were applied for the removal of U(VI) from water solutions under various experimental conditions. The characterizations showed that nZVI/MoS 2 composites exhibited a high surface area and uniform distribution of nZVI. The maximum adsorption capacities of nZVI/MoS 2 obtained from the Langmuir model (71.8 mg/g at pH 4.0 and 25 °C) were higher than that of MoS 2 (39.92 mg/g) due to the synergistic effect. According to the fitting of surface complexation modeling, U(VI) removal on nZVI/MoS 2 included cation exchange and inner-sphere surface complexation at low and high pH, respectively, whereas the adsorbed U(VI) was partly reduced into U(IV) by nZVI/MoS 2 composites. According to analysis of XPS analysis, the enhanced removal of U(VI) on nZVI/MoS 2 was due to the complexation of U(VI) with various oxygenated functional groups (e.g., −OH, Fe−O, and Mo−O functional groups) and then adsorbed U(VI) was reduced to U(IV) by Fe 0 and/or Fe(II). These findings showed that nZVI/MoS 2 could be used as efficient adsorbents for the high elimination of U(VI) from contaminated wastewater in environmental pollution cleanup.

Synergistic Removal of U (VI), Pb(II), and HA on nZVI/MoS2 Composites Investigated by Batch, Spectroscopic, and Modeling Techniques

“…The BET specific surface areas of MoS 2 and nZVI/MoS 2 were 25 and 31 m 2 /g, respectively. The large BET surface area of nZVI/MoS 2 could be ascribed to the incorporation of nZVI nanoparticles, which effectively prevented the aggregation of nZVI and significantly enhanced its dispersion. , Overall, the characterizations showed that nZVI was evenly deposited on the MoS 2 surface, which increased the specific surface area and uniform distribution.…”

“…The crystal composition of the nZVI/MoS 2 composite was further confirmed using XRD patterns (Figure C). The diffraction peaks of nZVI at 2θ = ∼58.3, 33.6, and 14.2° were indexed into the (110), (100), and (002) planes of MoS 2 , respectively . The appearance of new diffraction peaks of nZVI/MoS 2 at 2θ = ∼44.8 and 34.2° were attributed to the (110) plane of Fe 0 and the (023) plane of Fe 3 O 4 , respectively .…”

“…Additionally, the significant increase in the relative intensity of Fe-O groups after the reaction signified the transformation of nZVI into iron oxides . N 2 adsorption–desorption isotherms revealed a type-IV hysteresis of MoS 2 and nZVI/MoS 2 , indicating a significant number of mesopores . The BET specific surface areas of MoS 2 and nZVI/MoS 2 were 25 and 31 m 2 /g, respectively.…”

“…SEM analysis was conducted to characterize microstructures of the nZVI/MoS 2 composite. , As depicted in Figure A, the pristine MoS 2 nanosheets displayed lateral dimensions within 50–100 nm. In contrast, nZVI was evenly deposited on the MoS 2 surface (Figure B), featuring substantial porosity and amorphous defects .…”

“…Nano-zerovalent iron (nZVI) as a versatile and green material has been extensively introduced into the treatment of various contaminants (e.g., organics, radionuclides, and heavy metals) from agricultural and industrial wastewater due to its small particle size, large surface area, excellent chemical reactivity, abundant surface sites, and strong redox. − However, the tight agglomeration of nZVI and the rapid production of iron corrosion limit its application. , Interestingly, the unique dispersion of nZVI on various supports has been specifically designed with superior removal capacity and ease of separation. − So far, nZVI-based composites (e.g., metal (hydr)­oxides, chitosan/biopolymer, clay, , and carbon-bearing materials − ) as environmentally friendly and effective adsorbents have been extensively employed to remove U­(VI), Pb­(II), and HA from wastewater in different conditions. Among nZVI-based materials, nZVI/MoS 2 exhibited a high adsorption performance, fast adsorption efficiency, and strong redox due to the exposure of unsaturated S in MoS 2 (2D hexagonal transition metal dichalcogenide). ,,− To the authors’ knowledge, the simultaneous removal of Pb­(II), U­(VI), and HA on nZVI/MoS 2 composites in a complicated system is not available.…”