查看更多>>摘要：? 2021Zeolite NaA was prepared from lithium leach residue (LLR) via the traditional hydrothermal synthesis method. The adsorption characteristics of zeolite on Pb2+ and Cd2+ were lucubrated to solve the problems caused by heavy metal wastewater and industrial waste LLR. The influence factors in the synthesis process were systematically explored. The cubic zeolite NaA was synthesized at 100 °C for 12 h when n(SiO2)/n(Al2O3) was 2 and the alkalinity was 60 g/L. The performance of zeolite NaA to adsorb Pb2+ and Cd2+ in the mixed solution was also assessed in detail. Results showed that zeolite NaA had excellent adsorption property for Pb2+ and Cd2+, and the maximum adsorption capacities of Pb2+ and Cd2+ were 487.805 and 193.798 mg/g. Moreover, the initial pH value of the solution and the adsorbent dosage greatly influenced the removal rates of Pb2+ and Cd2+. The isotherm and kinetic analysis of the adsorption process revealed that Langmuir model and pseudo-second-order model agreed well with the adsorption process. The adsorption mechanism was accredited to the ion exchange and hydroxyl groups on the zeolite NaA surface. This work provided a rational process route of synthesizing zeolite NaA adsorbent from LLR, and it was well applied to the removal of Pb2+ and Cd2+.
查看更多>>摘要：? 2021The specific surface area is key for various application fields of porous materials. Its reliable and fast determination is therefore crucial for materials development and product quality management. Surface area assessment is usually based on physical adsorption using the Brunauer-Emmett and Teller (BET) theory. However, the BET method/gas adsorption exhibits a number of limitations and challenges including (i) time consuming sample preparation and measurement time, and (ii) reliable surface areas only possible for non-porous and meso-/macroporous materials to obtain reliable surface areas. In addition, the accuracy of surface area data obtained from adsorption depends on the proper choice of adsorptive/probe. Within this context, this work evaluates in a rigorous way in-depth Small Angle X-ray Scattering (SAXS) as an alternative and complimentary approach for reliable and fast surface area assessment. To our knowledge, this work can be considered the first systematic study where the surface areas from SAXS are compared and validated with true benchmark surface area data. We utilize silica-based nanoparticles as well as a well-defined mesoporous controlled pore glass for systematic SAXS and adsorption studies (argon and nitrogen at 87 K and 77 K, respectively). Owing to the lack of micro- and narrow mesopores of these model materials, the BET method based on argon 87 K adsorption can be applied to determine benchmark surface areas. Indeed, excellent agreement was found between surface areas derived from argon 87 K adsorption and SAXS. In fact, we demonstrate that the determination of specific surface area can be brought with SAXS to a new level, where parameters such as size of the probing adsorptive, its orientation and thus its effective cross-sectional area (when adsorbed on the surface) are no longer affecting the value of the specific surface area determined. Furthermore, SAXS was shown to be significantly faster than gas adsorption. For the silica materials used, the study shows that SAXS does not require degassing and – along with analysis times of only few minutes per sample – provides an accurate and extremely fast, high-throughput approach. This fundamental study can be considered a major step in enabling SAXS for reliable surface area assessment for applications both in nanoporous materials development and quality control, thus boosting SAXS for surface area determination in general, but in particular also for materials, where the usage of gas adsorption is restricted or not possible at all.
查看更多>>摘要：? 2021 Elsevier Inc.Development of carbon-based oxygen reduction reaction (ORR) catalysts with performance superior to noble metals across a wide pH range has been a formidable challenge. Herein, porous hollow carbon spheres co-doped with N, P (NH3-NPCS-900) is directly synthesized from the herbal residues of Lasiosphaera seu Calvatia (LSC). Critically, the N content was significantly enhanced in the presence of ammonia (NH3) and formed a hierarchical porous structure and a large specific surface area (984.7 m2 g?1). With the synergistic effect of these contributions, the NH3-NPCS-900 catalyst exhibit excellent ORR catalytic activity across acidic (E1/2 = 0.615 V) and alkaline solutions (E1/2 = 0.862 V). Zn-air batteries with NH3-NPCS-900 exhibit high peak power density (188 mW cm?2) and better cycle durability (>180 h), showing its potential and promise in applications. This study provides valuable direction and insight into how to develop porous carbon with highly efficient ORR catalytic activity from biomass.
查看更多>>摘要：? 2021Siliceous Beta zeolite and its metal-containing counterparts are effective adsorption and catalysis materials. To develop facile and efficient synthesis strategy would facilitate their large-scale production and application. Herein, we report the fluoride-free hydrothermal synthesis of siliceous Beta achieved by an inorganic cation-driven strategy. It is found that the types of inorganic cations are more critical than anions in determining the product phase. Inorganic cations with smaller sizes (such as Li+, Na+ and Mg2+) facilitate the synthesis of siliceous Beta, while the larger ones (such as K+, Ca2+ and NH4+) tend to give rise to impurity or amorphous materials. Crystallization mechanism investigation based on the Na+-added system revealed that inorganic cations can effectively promote the fast polymerization of SiO2 colloids at the initial stage. The crystallization occurs on the polymerized composites, yielding siliceous Beta with high solid yield. The resultant material is well characterized, which possesses few framework defects, high hydrophobicity and large adsorption uptake for toluene (one of the common volatile organic compounds). Breakthrough experiments further evidence the dynamic toluene adsorption capacity of the material is 24% higher than that of siliceous Beta synthesized by fluoride route.
查看更多>>摘要：? 2021The shuttle effect of lithium polysulfides (LPSs) is the main issue which prohibits the practical use of Li–S batteries (LSBs). Therefore, a MnO decorated Nitrogen doped carbon/CNT (MnO/N–C/CNT) composite is synthesized and used as the barrier and accelerator for LPSs. The bi-metal Zn/Mn-MOF is firstly grown on carbon nanotubes (CNT) by a facile chemical reaction of Zn(NO3)2/Mn(NO3) and dimethylimidazole, then the precursor is calcined in nitrogen ambient at 910 °C to fabricate MnO/N–C/CNT composite. After coating on the polypropylene separator, the MnO/N–C/CNT layer can greatly alliviate the shuttle effect by its dual function. The N–C/CNT network can provide good conductivity and physical barrier, while the polar MnO can enhance the chemical adsorption and conversion rate for LPSs. As a result, when the sulfur areal loading is 3.5mg/cm2, an impressive specific capacity of 950 mAh/g at 0.5C is obtained by use of MnO/N–C/CNT modified separator, and it can cycle steadily for over 500 cycles at an average decay rate of 0.022%/cycle. Furthermore, the battery also displays a cycle stability for over 200 cycles even under the sulfur areal loading of 5.5mg/cm2, which demonstrate its application potential.
查看更多>>摘要：? 2021 Elsevier Inc.The zeolitic imidazolate framework (ZIF)-8/water-glycol slurry shows great potential in separating low carbon hydrocarbons. In the present study, the physical properties of the ZIF-8/water-glycol slurry were determined, and the hydrophobicity and glycophilicity of the ZIF-8 material were demonstrated by measuring the contact angle between liquid droplets with a ZIF-8 material, for the first time. It was observed that the increase in pressure could weaken the hydrophobicity of ZIF-8. In addition, the sorption kinetics of CH4 and C2H4 in the slurry were investigated. It was noted that the relatively high temperature and pressure could increase the dissolution rates of CH4 and C2H4 in the slurry. A kinetic model for describing the dissolution of CH4 and C2H4 in the slurry was proposed, wherein the diffusion of gas molecules in the glycol membrane around ZIF-8 particles and those in the inner pores of ZIF-8 were concurrently considered for the first time. The simulation results correlated with the experimental data. Finally, multistage simulation separation experiments for CH4/C2H4 gas mixtures using the slurry were performed. It was observed that after a four-stage simulation separation operation, the concentration of C2H4 decreased from 49.72 mol% in the feed gas to 4.68 mol%. The experimental and modeling results will be helpful for the practical separation application of the ZIF-8 slurry system.
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