Xianghai Guo

Growth of two-dimensional silicalite-1 on graphene oxide with controllable electrical conductivity

Multi-quaternary ammonium surfactants are assembled co-operatively with graphene oxide (GO) to generate two-dimensional (2D) silicalite-1. The hybrid composites behave with controllable electrical conductivity and exhibit a specific surface area (SBET) as high as 643 m2 g−1.

Synthesis of b-oriented MFI nanosheets with high-aspect ratio by suppressing intergrowth with 2D GO nanosheets

High-aspect ratio b-oriented MFI nanosheets are synthesized by simply adding a suitable amount of graphene oxide (GO) nanosheets into a multilamellar MFI zeolite crystallization system. The GO nanosheets, serving as the building blocks for oriented attachment and in situ nucleation sites, positively induce the silicalite-1 nanosheet crystallization process and confine the over-growth of MFI crystals during the subsequent preparation. A two-dimensional (2D) induction mechanism of the GO nanosheets is discussed for the generation of the b-oriented MFI nanosheets. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), nitrogen adsorption, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA).

Advances in separation methods for large-scale production of silicon isotopes

For large-scale production of silicon isotopes, chemical exchange reaction and gas centrifugation are the most prospective methods. Advances in these two methods are reviewed in this article. With brief introduction of the principles, the progress and problems in these two methods are discussed. New donors and the benefits of the combination of these two separation methods are introduced. Among these donors trimethyl phosphate is more suitable in chemical exchange reaction due to its separation coefficient, freezing point and stability. Moreover, the combination of separation methods is a promising technology to massively perform silicon isotope.

Metal–organic frameworks (MOFs) as highly efficient agents for boron removal and boron isotope separation

The boron adsorption and isotopic separation on water-stable metal–organic frameworks (MOFs) were evaluated. These materials, to date, exhibit fairly high to highest adsorption capacities for boron. Furthermore, unprecedentedly high isotopic separation factors (S) were observed in some materials.

Theoretical study on complexes and reactions of boron isotopic exchange separation with fluorinated anisoles as novel donors

Semi-empirical and ab initio density-functional theory (DFT) methods were evaluated for the description of isotope exchange reactions to produce enriched 10B species. We found that DFT calculations using M06-2X/6-311+G(3d,2p) functional and basis sets in combination with the SMD implicit solvation model were able to correctly predict the performance of various anisole-derived donor molecules. We confirmed that fluorination results in greatly increased separation factors, and successfully identified the o- and 2,4-difluorinated anisole as superior donors for chemical exchange distillation. These findings provide the basis for an efficient approach to rapidly screen and design new donor species.

Nanosheet-based magadiite: a controllable two-dimensional trap for selective capture of heavy metals

Long-chain imidazolium-based surfactants are assembled cooperatively with silicate clathrate anions to generate magadiite nanosheets, where the imidazole acts as a structure-directing agent for specific structures, while the surfactant tails regulate the distance of layers. Four different tails are selected among linear alkyl chains (CnH2n+1, n = 12, 16, 18, 22) to evaluate structure-directing effects with the formula of [tail-N+C5H8N]Br−. The well-crystallized nanosheet-based magadiites with controllable 2-dimensional rectangular layered structure are reported for the first time. The adsorption performances of these materials are investigated by removal of heavy metals, including Cu(II), Zn(II), Pb(II) and Cd(II). These materials manifest high adsorption capacity and different selectivities, especially for Cu(II) and Pb(II). The space and assembly of interlayers as well as the properties of heavy metals determine the removal efficiency and selectivity. Through a controllable interface, the as-synthesized samples could overcome the diffusion limit with enhanced selectivity and adsorption capacity, compared to conventional rosette-like magadiites. Nanosheet-based magadiites are promising adsorbents with controlled interlayer space and well-defined 2D structure, which make them new candidates for heavy metal removal and a platform to study the 2-dimensional plane trap effects between the silicate and metals.

Dynamic-accumulative operation policy of continuous distillation for the purification of anisole

Abstract In the B10 isotope enrichment industry, the purification of anisole mixture makes great sense. A dynamic-accumulative operation policy of continuous distillation (DACD) with repeated filling and dumping of the still is proposed for the separation of trace heavy impurities in the recycled anisole. To simulate and optimize the purification process of anisole, a mathematical model of DACD is derived, and the computer codes are developed in the MATLAB environment. Moreover, the experiment is performed in a pilot-scale distillation column. The results show that the experimental date agrees well with simulation results. DACD could solve the difficulty of flow rate control when the bottom flow rate is very small in continuous distillation. The size of the still in this operation mode is also smaller than that in batch distillation. And the yield of anisole is raised to 99.91%. In a word, DACD is especially suitable for separating trace heavy impurities from the recycled anisole.