Theoretical Studies of Methane Partial Oxidation to Methanol Catalyzed by Metal-Exchanged Zeolites

主1工学_物質創造工

Insight into the wheat residues-derived adsorbents for the remediation of organic and inorganic aquatic contaminants: A review

International audienceWheat is a major grain crop of the world that provides a stable food for human consumption. Large amounts of by-products/waste materials are produced after the harvesting and processing of wheat crop. Such materials can cause an environmental issue if not disposed of properly. Several studies have shown that wheat residues can be efficient precursors for adsorbents because of their availability, renewability, lignocellulosic composition, and surface active groups enriched structure. In the literature, there are few review articles that address wheat residues-based adsorbents. For instance, the use of raw wheat straw and bran as adsorbents for heavy metals and wheat bran-based adsorbents against dyes. However, these reviews were specific in terms of adsorbate or adsorbent and did not provide detailed information about the modification, properties, and regeneration of these adsorbents. This article extensively reviews the utilization of wheat biomass/waste including straw, bran, husk, and stalk as precursors for raw or untreated, chemically treated, carbonaceous, and composite adsorbents against various environmental pollutants. The influences of inlet pollutant amount, adsorbent dose, pH, temperature, and time on the performance of adsorbents against pollutants were considered. The maximum uptakes, equilibrium time, and adsorption nature were identified from isotherms, kinetic, and thermodynamic studies. The highest adsorbed amounts of most tested contaminants were 448.20, 322.58, and 578.13 mg/g for lead, chromium, and copper, 1374.6 and 1449.4 mg/g for methylene blue and malachite green, and 854.75, 179.21, and 107.77 mg/g for tetracycline, phosphate, and nitrate, respectively. For the studied adsorbate/adsorbent systems the adsorption mechanism and regeneration were also discussed. Significant results and future directions are finally presented

Synthesis of conch-like layered carbon nanosheets by ball-milling assisted ultrasonic exfoliation for highly selective removal of Cd(II) from multiple water matrices

International audienceDevelopment of carbonaceous materials from biomass have attracted tremendous research interest because their intriguing physicochemical properties and promising applications. However, endowing them with precisely controlled morphologies remains a formidable challenge. Herein, oxygen-functionalized biomass-derived carbon-nanosheets (CNSs) framework was synthesized using ball-milling ultrasonic exfoliation for application to remove cadmium Cd(II) water matrices. The obtained CNSs showed remarkably higher surface area (368.9 m2 g-1), thickness-range (∼6-8 nm) pore size (10.58 than pristine carbon (PC) (10.126 g-1, 1-2 µm 2.13 nm, respectively). demonstrated adsorption capacity (545.76 mg superior reusability (removal efficiency maintained >91% after 10 cycles) excellent selectivity (Kd = 4.7 × 106 mL g−1). isotherm kinetics data were better fitted by Langmuir pseudo-second order models. High led 97.7% in presence Cu(II), Zn(II), Pb(II) Ni(II) ions. strong also evident complex matrices including tap water, groundwater (Cd(II) removal >99%) river (98.97%). experimental analyses indicate that electrostatic attraction complexation as the prominent mechanisms. Overall, this work illustrates an applicable strategy develop successful toxic metal

Novel thiol-grafted composite of chitosan and rice straw biochar (TH@CT-BC): A two-step fabrication for highly selective adsorption of cadmium from contaminated water

International audienceThis study followed the one-step and two-step technologies to produce rice straw biochar (BC), chitosan-modified rice straw biochar (CT-BC), and thiol grafted chitosan-modified biochar (TH@CT-BC) for cadmium (Cd) removal from contaminated water. Here, chitosan and thiol were introduced by two-step combination to enhance the adsorption ability of biochar. Our results revealed the maximum Cd adsorption at pH 5.5 with TH@CT-BC (261.47 mg g−1) followed by CT-BC (103.14 mg g−1) and BC (29.64 mg g−1). Obtained data was best fitted by the Langmuir and pseudo-second-order kinetic models (with R2 values of 0.997 for TH@CT-BC) as compared to Freundlich and Temkin models (0.949 and 0.925, respectively). TH@CT-BC retained its efficiency in spiked river water system, removing up to 89% of Cd in river water spiked with 30 mg−1 L Cd. The experimental investigations and data calculations demonstrated the surface complexation and electrostatic interaction as dominant underlying mechanisms for Cd removal by TH@CT-BC. Moreover, it is essential to utilize the large amount of produced rice straw to develop new materials which would help in converting the waste to useable product for environmental remediation. Thus, this study demonstrates the production of TH@CT-BC from rice straw as an effective adsorbent of Cd from aqueous systems which can be studied as a potential candidate for practical wastewater treatment applications. © 2023 Elsevier Lt

Novel Mechanistic Insights into Methane Activation over Fe and Cu Active Sites in Zeolites: A Comparative DFT Study Using Meta-GGA Functionals

Fe- and Cu-exchanged zeolites are known to oxidize methane directly to methanol at low temperature and have been intensively discussed in recent literature studies including theoretical works based..

Temperature-induced orbital polarizations and tunable charge dynamics in layered double perovskite thin films

The realization of lead-free all-inorganic perovskites in emergent materials requires an in-depth understanding of strongly correlated systems toward optoelectronics or spintronics applications. Herein, we report the electronic and optical variation of the -oriented layered double perovskites (LDP) family with the formula of Cs4MIIBi2Br12 thin films (where MII: Cu, Mn, Pb, or Sr). The element and shell-specific orbital polarization based on soft X-ray linear dichroism spectroscopy probes the Cs M4,5- and Mn L2,3- edges of Cs4MnBi2Br12 thin films as a function of temperature. A strong reversal orbital polarization at the respective edges at 150 K indicates a thermally induced orbital-selective rearrangement at low temperature. In addition, the valence band analysis indicates different orbital admixtures of Br 4p and MII d states, corroborated by the density functional theory calculations. In terms of the transient charge dynamics, we observe the photoluminescence peak maxima position trend line is shifted toward a longer wavelength. In addition, the longest average lifetime is recorded for Cs4CuBi2Br12 at 27.40 ± 1 μs. As the LDP structural integrity is lead-free, therefore, these all-inorganic perovskites hold promising potentials as sustainable and green materials for photophysics applications.Ministry of Education (MOE)The authors acknowledge research grants from Ministry of Education, Singapore with numbers MOE Tier 3 (MOE2014-T3-1-004) and MOE Tier 2 (MOE2018-T2-1-088, MOE2016-T2-1-052, and MOE2019-T2-1-163) and MOE2019-T1-002-063. A. acknowledges funding support from NRF-NSFC grant R-144-000-405-281. M.H.M. acknowledges a research grant no. 139/IT1.B07.1/TA.00/2021 from Institut Teknologi Bandung under the ‘Riset ITB 2021’ scheme

Photodetection and scintillation characterizations of novel lead-bismuth double perovskite halides

International audienceDouble perovskite materials with large effective atomic numbers and high mass densities generate short absorption length for radiation detection. Bromide and iodide variants were characterized for their scintillation and photodetection properties

Lattice expansion in Rb-doped hybrid organic-inorganic perovskite crystals resulting in smaller band-gap and higher light-yield scintillators

Two-dimensional hybrid-organic-inorganic perovskite (2D-HOIP) lead bromide perovskite crystals have demonstrated great potential as scintillators with high light yields and fast decay times while also being low cost with solution-processable materials for wide energy radiation detection. Ion doping has been also shown to be a very promising avenue for improvements of the scintillation properties of 2D-HOIP crystals. In this paper, we discuss the effect of rubidium (Rb) doping on two previously reported 2D-HOIP single crystals, BA2PbBr4 and PEA2PbBr4. We observe that doping the perovskite crystals with Rb ions leads to an expansion of the crystal lattices of the materials, which also leads to narrowing of band gaps down to 84% of the pure compounds. Rb doping of BA2PbBr4 and PEA2PbBr4 shows a broadening in the photoluminescence and scintillation emissions of both perovskite crystals. Rb doping also leads to faster γ-ray scintillation decay times, as fast as 4.4 ns, with average decay time decreases of 15% and 8% for Rb-doped BA2PbBr4 and PEA2PbBr4, respectively, compared to those of undoped crystals. The inclusion of Rb ions also leads to a slightly longer afterglow, with residual scintillation still being below 1% after 5 s at 10 K, for both undoped and Rb-doped perovskite crystals. The light yield of both perovskites is significantly increased by Rb doping with improvements of 58% and 25% for BA2PbBr4 and PEA2PbBr4, respectively. This work shows that Rb doping leads to a significant enhancement of the 2D-HOIP crystal performance, which is of particular significance for high light yield and fast timing applications, such as photon counting or positron emission tomography.Ministry of Education (MOE)Published versionF.M. and C.D. acknowledge financial support from the Singapore Ministry of Education(T2EP50121-0025) and the MERLION Project. M.H.M. and M.D.B. acknowledge research funds from the Institut Teknologi Bandung under the “Penelitian, Pengabdian Masyarakat, dan Inovasi (PPMI) 2022” scheme (6A/IT1.C07.2/TA.01/2022)and Lukasiewicz Research Network-PORT, respectively

A2Bn-1PbnI3n+1 (A = BA, PEA; B = MA, n = 1, 2): Engineering Quantum-well Crystals for High Density and Fast Scintillators

Quantum-well (QW) hybrid organic-inorganic perovskite (HOIP) crystals, e.g. A2Pb2X4 (A = BA, PEA, X = Br, I), demonstrated significant potentials as scintillating materials for wide energy radiation detection compared to their individual three-dimensional (3D) counterparts, e. g. BPbX3 (B = MA). Inserting 3D into QW structures resulting new structures namely A2BPb2X7 perovskite crystals and they may have promising optical and scintillation properties towards higher mass density and fast timing scintillators. In this article, we investigate the crystal structure, optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with fastest PL decay time 3.0 g/cm3, and tunable smaller band gaps 7 photons/keV) at 10 K, while at room temperature are still low > 0.6 photons/keV compared to our previously reported QW bromide crystals (10-40 photons/keV). Thus, promising results of our study on iodide-based QW HOIP scintillators provide the right pathway for further enhancement towards fast-timing applications