Co(II)–Co(III) hydrotalcite-like compounds

Enhanced Catalytic Hydrogenation Performance of Rh-Co2O3 Heteroaggregate Nanostructures by in Situ Transformation of Rh@Co Core-Shell Nanoparticles

In this work, poly(vinylpyrrolidone)-stabilized 3-5 nm Rh@Co core-shell nanoparticles were synthesized by a sequential reduction method, which was further in situ transformed into Rh-Co₂O₃ heteroaggregate nanostructures on alumina supports. The studies of XRD, HAADF-STEM images with phase mappings, XPS, TPR, and DRIFT-IR with CO probes confirm that the as-synthesized Rh@Co nanoparticles were core-shell-like structures with Rh cores and Co-rich shells, and Rh-Co₂O₃ heteroaggregate nanostructures are obtained by calcination of Rh@Co nanoparticles and subsequent selective H₂ reduction. The Rh-Co₂O₃/Al₂O₃ nanostructures demonstrated enhanced catalytic performance for hydrogenations of various substituted nitroaromatics relative to individual Rh/Al₂O₃ and illustrated a high catalytic stability during recycling experiments for o-nitrophenol hydrogenation reactions. The catalytic performance enhancement of Rh-Co₂O₃/Al₂O₃ nanocatalysts is ascribed to the Rh-Co₂O₃ interfaces where the Rh-Co₂O₃ interaction not only prevents the active Rh particles from agglomeration but also promotes the catalytic hydrogenation performance.

Arsenic removal from water/wastewater using layered double hydroxide derived adsorbents, a critical review

Arsenic pollution has become a worldwide environmental concern. Dangerous arsenic concentrations in natural waters threaten the health of millions of people, and this has received significant attention. Among the various technologies that have been developed for arsenic removal from water, the use of adsorption technology is considered to be a prevailing method, because the adsorption approach usually has high removal efficiency and the advantage of convenience of handling. In recent years, layered double hydroxides (LDHs) have become prime candidates for arsenic removal, due to their hydrophilic nature and cationic layered structures. Research on arsenic removal using LDHs is mainly focused on (1) the influence of the synthesis method and composition of the LDH, (2) the influence of the particle size of the LDH, (3) the influence of the Mg/Al ratio in LDHs, (4) LDH-based hybrids and (5) the competition with other anions. This paper provides a review of the currently available literature focusing on arsenic removal using LDHs for the five parts mentioned above. In addition, based on this overview, a closing section will suggest research efforts for future work. It is expected that this review will provide a summary of the main research in this area, and will also shed light on the direction of future development.

B, V. G, D. S, Kulal N, A. S. Framework of ruthenium-containing nickel hydrotalcite-type material: preparation, characterisation, and its catalytic application

The framework ruthenium-containing nickel (NiRu) hydrotalcite (HT)-type materials were prepared by a co-precipitation method for the first time in this study. Fourier-transform infrared spectroscopy and X-ray diffraction analysis revealed the formation of a layered hydrotalcite-type phase. DRUV-Vis and X-ray photoelectron spectroscopic studies revealed the presence of nickel in the +2 and +3 oxidation states along with the presence of ruthenium as Ru³⁺ ions. Temperature-programmed desorption studies of the NiRu-HT-type materials indicated a two-stage reduction with a decrease in T_max, supporting the presence of Ni²⁺ and Ru³⁺ in the framework of hydrotalcite. The obtained NiRu-HT-type materials proved to be promising catalysts for the reduction of aromatic nitro compounds in the presence of hydrazine as a hydrogen source under ambient conditions. The NiRu-HT-type material demonstrated enhanced activity and selectivity during the reduction of nitrobenzene and its derivatives due to the synergistic effect of nickel and ruthenium ions.

The framework ruthenium-containing nickel (NiRu) hydrotalcite (HT)-type materials were prepared for the first time without organics and the resultant materials were found to be promising catalysts for nitro-benzene reduction.