Hydrothermal Synthesis of 1T-MoS2/Pelagic Clay Composite and Its Application in the Catalytic Reduction of 4-Nitrophenol

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS2/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS2 nanosheets are evenly dispersed on the surface of the clay minerals, significantly reducing the agglomeration of MoS2. Compared with pure 1T-MoS2, the 1T-MoS2 nanosheets generated on the surface of pelagic clay have significantly smaller lateral dimensions and thicknesses. Moreover, the specific surface area is much larger than that of the pure 1T-MoS2 nanosheets fabricated by the same method, indicating that the active sites of the MoS2 sheets are fully exposed. In addition, the composite exhibited excellent hydrophilicity, leading to a high dispersibility in aqueous solutions. In this work, the composite was used as a catalyst in the reduction of 4-nitrophenol (4-NP), and the conversion of 4-NP reached up to 96.7%. This result shows that the 1T-MoS2/pelagic clay composite is a promising catalyst in a variety of reactions.

Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay: implications for mineral flux estimates

<p>Deep-sea sediment sometimes lacks biostratigraphic or radiometric age constraints. Chemical stratigraphy and magnetostratigraphy is useful for dating it. Oxic pelagic clay contains Fe-Mn oxyhydroxides that can retain seawater <sup>187</sup>Os/<sup>188</sup>Os values, and its age can be estimated by fitting the isotopic ratios to the seawater <sup>187</sup>Os/<sup>188</sup>Os curve. On the other hand, the stability of Fe-Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original <sup>187</sup>Os/<sup>188</sup>Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of <sup>187</sup>Os/<sup>188</sup>Os ages of pelagic clay have never been tested. Magnetostratigraphy is often unsuccessful for pelagic clay older than a few Ma, which has been attributed to diagenesis. Here we report multiple polarity reversals in ca. 35 Ma pelagic clay around Minamitorishima Island, which is inconsistent with a <sup>187</sup>Os/<sup>188</sup>Os age model. In a ~5 m thick interval, previous studies correlated <sup>187</sup>Os/<sup>188</sup>Os data to a brief (<1 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a >2.9 – 6.9 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the <sup>187</sup>Os/<sup>188</sup>Os chronology leads unrealistically high values. These results suggest that the low <sup>187</sup>Os/<sup>188</sup>Os signal has diffused from an original thin layer to the current ~5 m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic re-distribution of Fe-Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island. It is also indicated that old oxic pelagic clay can be a faithful paleomagnetic recorder, and success of magnetostratigraphy depends on sedimentation rate and polarity length rather than diagenesis.</p><p>Usui, Y., Yamazaki, T. <em>Earth Planets Space</em> <strong>73, </strong>2 (2021). https://doi.org/10.1186/s40623-020-01338-4</p>

Magnetostratigraphic evidence for post-depositional distortion of osmium isotopic records in pelagic clay and its implications for mineral flux estimates

Chemical stratigraphy is useful for dating deep-sea sediments, which sometimes lack radiometric or biostratigraphic constraints. Oxic pelagic clay contains Fe–Mn oxyhydroxides that can retain seawater 187Os/188Os values, and its age can be estimated by fitting the isotopic ratios to the seawater 187Os/188Os curve. On the other hand, the stability of Fe–Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original 187Os/188Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of 187Os/188Os ages of pelagic clay has never been tested. Here we report inconsistency between magnetostratigraphic and 187Os/188Os ages in pelagic clay around Minamitorishima Island. In a ~ 5-m-thick interval, previous studies correlated 187Os/188Os data to a brief (< 1 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a > 2.9–6.9 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the 187Os/188Os chronology leads to unrealistically high values. These results suggest that the low 187Os/188Os signal has diffused from an original thin layer to the current ~ 5-m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic redistribution of Fe–Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island.

Symbiotic composite composed of MoS2 and pelagic clay with enhanced disinfection efficiency

A symbiotic composite MoS2/PC was prepared and showed an enhanced disinfection efficiency to E. coli 8739 under visible light.

Magnetostratigraphic Evidence for Post-Depositional Distortion of Osmium Isotopic Records in Pelagic Clay and Its Implications for Mineral Flux Estimates

Chemical stratigraphy is useful for dating deep sea sediments which sometimes lack radiometric or biostratigraphic constraints. Oxic pelagic clay contains Fe-Mn oxyhydroxides that can retain seawater 187Os/188Os values, and its age can be estimated by fitting the isotopic ratios to the seawater 187Os/188Os curve. On the other hand, the stability of Fe-Mn oxyhydroxides is sensitive to redox change, and it is not clear whether the original 187Os/188Os values are always preserved in sediments. However, due to the lack of independent age constraints, the reliability of 187Os/188Os ages of pelagic clay have never been tested. Here we report inconsistency between magnetostratigraphic and 187Os/188Os ages in pelagic clay around Minamitorishima Island. In a ~ 5 m thick interval, previous studies correlated 187Os/188Os data to a brief (< 2 million years) isotopic excursion in the late Eocene. Paleomagnetic measurements revealed at least 12 polarity zones in the interval, indicating a > 3.3–7.4 million years duration. Quartz and feldspars content showed that while the paleomagnetic chronology gives reasonable eolian flux estimates, the 187Os/188Os chronology leads unrealistically high values. These results suggest that the low 187Os/188Os signal has diffused from an original thin layer to the current ~ 5 m interval, causing an underestimate of the deposition duration. The preservation of the polarity patterns indicates that a mechanical mixing such as bioturbation cannot be the main process for the diffusion, so diagenetic re-distribution of Fe-Mn oxyhydroxides and associated Os may be responsible. The paleomagnetic chronology presented here also demands reconsiderations of the timing, accumulation rate, and origins of the high content of rare-earth elements and yttrium in pelagic clay around Minamitorishima Island.