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The design and synthesis of porous carbons with unique structures and diverse functionalities as CO2 adsorbents constitute a challenging and intriguing research topic. In this study, the synthesis of hollow micro-mesoporous nitrogen-doped carbon nanoparticles (NPCS) and its adsorption of CO2 were investigated. Highly porous nitrogen-doped carbon nanoparticles were successfully synthesized by using economically available resorcinol and formaldehyde as carbon precursors, with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792) as a soft template and silica sol as a hard template. The hollow nitrogen-doped carbon nanoparticles exhibit an evident microporous-mesoporous structure and have two different scales of mesopores with 9 nm and 12 nm, respectively. The effects of various synthetic parameters on the formation of hollow nitrogen-doped carbon nanoparticles were analyzed. The hollow nitrogen-doped carbon nanoparticles exhibited specific surface area of 1090 to 1716 m2/g and nitrogen content of 2.83 to 5.28%. At 273 K and 1 bar, the experimental results demonstrated the positive effects of the enriched pore structure and nitrogen doping on CO2 adsorption. The optimum adsorption capacity of activated NPCS (ANPCS) was 5.11 mmol/g with excellent CO2/N2 selectivity value of 20.44 at 273 K and 1 bar. The initial heat of adsorption value for ANPCS was 30.90 KJ/mol. Additionally, the hollow nitrogen-doped carbon nanoparticles retained 99.2% of the initial adsorbed amount after 5 cycles of adsorption. The excellent adsorption performance of the material can be ascribed not only to its extensive specific surface area and enriched nitrogen but also to its mesoporous and hollow structure, which facilitates rapid CO2 transport. Highlights: The combination of soft and hard templates was used to prepare hollow micro-mesoporous nitrogen-doped carbon nanoparticles. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is used not only as structure-directing and pore-forming agent, but also nitrogen source. The carbon nanoparticles have excellent CO2 adsorption due to their large specific surface area, high nitrogen content and mesoporous hollow structures. The mesoporous and hollow structures leads to high CO2 transport rates in carbon nanoparticles. [ABSTRACT FROM AUTHOR]

Nitrogen-rich hollow carbon microspheres were successfully synthesized using resorcinol and formaldehyde as carbon sources, tetraethylenepentamine (TEPA) as a catalyst, and nitrogen source, with SiO2 microspheres as a hollow template. The hollow carbon microspheres were prepared by adding varying amounts of SiO2 hollow templates to a fixed amount of TEPA. The shell thickness increased as the amount of SiO2 template decreased and the shell thicknesses of AHMCS-2(1), AHMCS-2(3), and AHMCS-2(5) were 28.5 nm, 17.3 nm, and 12.7 nm, respectively. The activated hollow carbon microspheres (AHMCS-2(1), AHMCS-2(3) and AHMCS-2(5)) contained 4.66%, 5.05%, and 3.27% nitrogen, respectively. Due to the sufficient activation process, the specific surface area and microporous volume of hollow carbon microspheres are greatly increased compared to solid carbon microspheres, therefore, their CO2 adsorption performance is superior as well. As the shell layer thickens, the specific surface area and micropore volume of the activated hollow carbon microspheres increased, among which AHMCS-2(1) showed the largest specific surface area and micropore volume of 1146 m2/g and 0.45 cm3/g, respectively. Similarly, the CO2 adsorption capacity of activated hollow carbon microspheres increased with the increasing thickness of the shell layer, and that of AHMCS-2(1) reached 5.54 mmol/g at 0 °C. High specific surface area, high micropore volume, high nitrogen content, and small micropore pore size are favorable for CO2 adsorption by carbon microspheres. The hollow carbon microspheres exhibit high CO2 dynamic adsorption capacity, excellent selective adsorption, and good cyclic stability. Highlights: Nitrogen-rich hollow carbon microspheres with different shell layer thicknesses were prepared using the template method. The thicker shell thickness retains more micropores and nitrogen content. The nitrogen-rich hollow carbon microspheres have high CO2 adsorption performance due to large specific surface area and high nitrogen content. The effect of activation process on the nitrogen-rich hollow carbon microspheres with different shell thicknesses is investigated. [ABSTRACT FROM AUTHOR]

The nitrogen-rich carbon microspheres were prepared by the one-pot hydrothermal synthesis in the presence of resorcinol formaldehyde as the carbon precursor and tetraethylenepentamine (TEPA) as nitrogen precursor as well as the base catalyst, followed by carbonization and activation. Their nitrogen content and microstructure of the nitrogen-rich carbon microspheres could be adjusted by varying the addition of TEPA. The significant enhancement of the microstructure and the nitrogen doping leads to high CO2 adsorption in the activated carbon microspheres. The high nitrogen content of activated sample AMPS-4 was 5.61%, and the large specific surface area and micropore volume were 786.5 m2/g and 0.28 cm3/g, respectively. The activated sample AMCS-4 had the highest CO2 adsorption reaching 5.52 mmol/g and 2.97 mmol/g at 0 and 25 °C, respectively. Compared with EDA-prepared carbon microspheres AMCS-4E, TEPA-prepared carbon microspheres AMCS-4 have stabler chemical adsorption to CO2 due to their higher nitrogen content, which is in corresponds to the higher adsorption heat. The introduction of polyvinylpyrrolidone (PVP) into the system as a stabilizer not only improved the monodispersity of carbon microspheres but also improved the adsorption performance of CO2 by increasing the micropore volume and decreasing the micropore size of the microspheres. The CO2 adsorption of the PVP-assisted prepared sample AMCS-2-P1 reached 4.48 mmol/g and 2.95 mmol/g at 0 °C and 25 °C respectively, which is 0.72 mmol/g and 0.25 mmol/g higher than that of AMCS-2. The carbon microspheres have high CO2 dynamic adsorption capacity, excellent selective adsorption, and good cyclic stability. Highlights: Monodisperse highly N-rich carbon microspheres were prepared by a one-step hydrothermal method. The microspheres have a good monodisperse, improved microstructure, and high N content. The microspheres have high CO2 adsorption capacity, good selective adsorption, and cycling stability. [ABSTRACT FROM AUTHOR]

A novel hollow network magnetic Fe3O4/SiO2/meso-TiO2 (FSmT) composite microsphere photocatalyst, with network Fe3O4 nanorods as a magnetic layer, a dense SiO2 layer as an electronic barrier, and a mesoporous TiO2 as the active layer, was synthesized by sol–gel and hydrothermal process. The as-synthesized FSmT microspheres possess a high specific surface area (122 m2/g), a large mesoporous size (diameter = 5.47 nm), and pore volume (0.27 cm3/g). Further, the photocatalytic activity of the FSmT microspheres for methyl orange degradation was demonstrated and the degradation rate of methyl orange could reach up to 93.5% after 1 h under UV light. The good photocatalytic activity was attributed to the hollow network and mesoporous composite structures. The FSmT microspheres could be separated conveniently and well redispersed for further reuse because of their excellent magnetic property (Ms = 11.4 emu/g). Schematic diagram for the photocatalytic reaction of methyl orange solution with the FSmT microspheres. Highlights: The hollow structure of the composite microspheres is a warehouse for methyl orange and the channel of mesoporous TiO2 is as a reactor for photocatalytic reaction. The photocatalytic reaction with TiO2 began as methyl orange in warehouse entered the mesoporous channel. As the reaction continues, more and more methyl oranges enter the pore canal and react successively until the end of the reaction. Mesoporous titanium dioxide provides high specific surface area, and many photocatalytic reaction active sites for the photocatalytic reaction, it improves the photocatalytic efficiency by reducing the combination of the electron and the cavity so the composite microspheres possess high catalytic efficiency. [ABSTRACT FROM AUTHOR]

During the decommissioning of the nuclear facilities, the radioactive gases in pressure vessels may leak due to the demolition operations. The decommissioning site has large space, slow air circulation, and many large nuclear facilities, which increase the difficulty of workers' inhalation exposure assessment. In order to dynamically evaluate the activity distribution of radionuclides and the committed effective dose from inhalation in nuclear decommissioning environment, an inhalation exposure assessment method based on the modified eddy-diffusion model and the inhaled dose conversion factor is proposed in this paper. The method takes into account the influence of building, facilities, exhaust ducts, etc. on the distribution of radioactive gases, and can evaluate the influence of radioactive gases diffusion on workers during the decommissioning of nuclear facilities.

Ethyl-bridged organic–inorganic hybrid silica particles were prepared via a sol–gel and hydrothermal synthesis approach using 1,2-bis(triethoxysilyl)ethane (BTESE) as the sole precursor, and triblock copolymer poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (P123) and dodecyltrimethylammonium bromide (DTAB) as combined templates. The morphology, pore structure, chemical composition and liquid chromatographic performance of the obtained materials were investigated in detail. The particles exhibit a high surface area of 1136.40 m2/g, together with a pore volume of 0.39 cm3/g and an average pore size of 2.30 nm. Used as stationary phase for high-performance liquid chromatography (HPLC), the particles without extra bonding either C18 or C8 can successfully separate a mixture of uracil, phenol, pyridine, methylbenzene, ethylbenzene and tert-butylbenzene. The obtained materials also show practical application in the separation of phthalate acid esters (PAEs), which are harmful to environment and human health. Although the columns packed with ethyl-bridged organic–inorganic hybrid silica show lower column efficiency and peak symmetry compared to commercial column, they have considerably higher chemical stability in alkaline mobile phase. The HSS column also possesses high mechanical stability which is similar to that of the commercial column. [ABSTRACT FROM AUTHOR]