Gulbalkan, Hasan CanHaslak, Zeynep PinarAltintas, CigdemUzun, Alper...
14页
查看更多>>摘要：Covalent organic frameworks (COFs) have emerged as novel adsorbents and membranes for gas separation. Incorporation of ionic liquids (ILs) into COFs is important to exceed the current performance limits of COFs. However, synthesis and testing of a nearly unlimited number of IL/COF combinations are simply impractical. Herein, we used a multi-scale computational screening approach combining COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) method, Grand Canonical Monte Carlo (GCMC), molecular dynamics (MD) simulations, and density functional theory (DFT) calculations to unlock both the adsorption-and membrane based CO2/N-2 separation performances of IL/COF composites. Several adsorbent and membrane performance assessment metrics including selectivity, working capacity, regenerability, adsorbent performance score, and permeability were computed. Our results revealed that IL incorporation into COFs significantly improves CO2/N-2 adsorption selectivities (from 12 to 26) and adsorbent performance scores (from 3.7 to 12 mol/kg). By performing DFT calculations, the nature of the interactions between CO2, N-2, COFs, and their IL-incorporated composites was evaluated. The high CO2 selectivity of IL/COF composites was attributed to the cooperative intermolecular effects induced by the COF and the IL. Finally, IL/COF membranes were studied, and results showed that they achieve significantly higher CO2 permeabilities (2.4 x 10(4)-9.4 x 10(5) Barrer) than polymeric and zeolite membranes with comparable selectivities (up to 15.7). This shows a great promise of IL/COF composites to replace the conventional membrane materials for flue gas separation. Our results will be useful in accelerating the experimental efforts to design new IL/COF composites that can achieve high-performance CO2 separation.
查看更多>>摘要：Due to the high presence of active functional groups, two-dimensional transition metal carbide/nitride materials that are usually named MXene have been thought as an efficient adsorbent for the removal of organic contaminants from wastewater. However, the poor stability of MXene originated from the high oxidization performance greatly restricts their application. In this work, few-layered MXene was firstly prepared and then the in situ polymerization of polypyrrole (PPy) was induced in the MXene solution to prepare the MXene/PPy composite particles. The microstructure, adsorption behaviors toward methylene blue (MB) and the stability during the storage process were systematically investigated. The results show that introducing PPy nanoparticles promotes the further exfoliation of MXene. Consequently, the adsorption ability of the MXene/PPy composite particles is significantly enhanced, and the maximum adsorption capacity reaches 553.57 mg/g. The MXene/PPy composite particles also show high adsorption selectivity and it can exclusively remove MB from the solution mixing both cationic and anionic dyes simultaneously. The stability of the MXene is greatly enhanced and nearly no oxidization is observed for the MXene/PPy composite particles. This study offers an additional way to fabricate the MXene-based adsorbents with high stability, and the composite particles exhibit promising applications in effluent water remediation.
查看更多>>摘要：In this study, a split-and-recombine (SAR) microreactor which is composed of convergent-divergent arc channel and rectangular obstacles was designed, and its enhancement characteristics in gas-liquid rapid chemical ab-sorption system were explored. In the SAR microreactor, the deformation, splitting, stretching and breakup of bubbles are monitored by a high-speed camera. Accordingly, the bubble velocity pulsation caused by SAR structure is analyzed. The squeezing mechanism for bubble breakup located on the front surface of the obstacle is revealed. Two breakup patterns, namely complete and partial breakup, are observed, and the mass transfer performance is highly related to them. The mass transfer enhancement factor (E-ka) of SAR structure increases with gas/liquid flow rate in complete breakup pattern while decreases in partial breakup pattern. The increase of gas-liquid flow rates and the number of SAR units, or slower reaction rate strengthens the velocity fluctuation and bubble breakup, resulting in an increase in E-ka, with a maximum value of 2.74. Overall, the SAR micro-reactor performs comparable to Corning Advanced Flow Reactor in term of mass transfer energy efficiency. This work guides the application of SAR microreactor in rapid gas-liquid chemical reaction system.
查看更多>>摘要：Solar vapor generation (SVG) has emerged as a promising technique of harvesting solar energy for producing fresh water from seawater. However, two main problems of insufficient energy utilization and salt accumulation on evaporation surfaces are still challenging issues for the broad application of this technique. In this work, we demonstrate a hierarchically structured bilayer aerogel by in situ deposition of polypyrrole (PPy) inside the top layer of cellulose. The light-absorbing PPy/cellulose composite with three-dimensional (3D) hierarchical structures served to convert solar energy into thermal energy and localize the heat to power the vaporization of water contained in the cellulose network. While the porous and hydrophilic cellulose matrix enabled continuous water transport and replenishment to the upper evaporative layer. Moreover, several microcracks were formed at the PPy/cellulose surface, which assisted vapor escape and salt re-dissolution. As a result, the prepared PPy/cellulose aerogel enabled a high seawater evaporation rate of 1.42 kg m- 2 h-1 at energy efficiency of 97.8% under one sun illumination. The SVG system also exhibited highly efficient and stable evaporation performance in seawater without surface salt accumulation over one week.
查看更多>>摘要：Thermal reduction of CO2 by green H-2 is one of the most effective strategies for CO2 utilization and preparation of value-added C1 chemicals, which is highly dependent on the catalyst compositions and structures. In this work, hollow mesoporous nickel phyllosilicate (mNiSiO(3)) with an average size of 250 nm was used as catalysts for CO2 hydrogenation after the partial extraction of Ni ions from nickel phyllosilicate. After the reduction treatment by H-2 at 400 degrees C, the mNiSiO(3)-R-400 showed CO2 conversion of 22.9% and CH4 selectivity of 80.9% (300 degrees C, 0.1 MPa). Interestingly, by functionalization of two-dimensional graphene oxide (GO) onto the nickel phyllosilicate to obtain mNiSiO(3)/GO catalyst, more CO product was obtained and the CO/CH4 ratio in the products can be easily tuned via the change of GO loading amount. It was found that the functionalization of GO nanosheets on mNiSiO(3) would affect the reduction degree of nickel phyllosilicate and stabilize the structure against collapse during high-temperature reduction. In accordance, the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in different transient states suggested that the formation of bidentate carbonate species may play a vital role in the high selectivity of CO and that CH3O* was the key intermediate species over the Ni site for CH4 formation. Due to the electronic interaction between GO and Ni-0, it might weaken the interaction between Ni-0 and H-2, which prevents the direct decomposition of CO* into C* and the further hydrogenation of C* into methane over the Ni-0 sites. This work will provide new references for adjusting the CO/CH4 selectivity in CO2 hydrogenation over the Ni-based catalysts.
Napolitano, Erasmo S.Di Renzo, AlbertoDi Maio, Francesco P.
15页
查看更多>>摘要：Design, scale-up and operation of cyclone gas-solid separators are mostly based on simplified models and experience. Previous single-phase or one-way coupled simulations are not applicable to cyclones operating with relatively big particles and under high loadings, as used for example in circulating fluidized beds for the polymer and energy industry. Simulations based on the DEM-CFD allow for four-way coupled dense flow, including dissipation, friction, and rotational particle motions. However, the computational cost becomes easily prohibitive. Coarse-graining methods based on lumping smaller particles into parcels or grains have been recently proposed to reduce the number of elements and increase the time-step. Yet, much remains to be characterized in terms of accuracy vs. speed-up. In the present work, a coarse-grain DEM-CFD approach to simulate the two-phase flow in a Stairmand high-efficiency cyclone at gas velocities in the range 10-20 m/s and solid loading in the range 0.1% to 0.5%vol is investigated. In particular, the focus is on the effect that the coarse graining degree (up to 64 particles per coarse grain) exerts on the replicability of the results compared to pure DEM-CFD simulations. It is shown that the macroscopic quantities characterizing the cyclone performances, such as pressure drop, inner vortex length and collection efficiency, are generally maintained even with coarse graining degree up to 64, with an approximation that improves with the increase in the solids loading. However, detailed features of the gas and solids flow (e.g. strand formation) appear significantly affected by the coarse graining degree, already at coarse graining degree 8 and 27.
查看更多>>摘要：In this work, carbon-doped CoMn2O4/Mn3O4 (C-CoMnO) composite catalyst were prepared via calcining solvothermal product of Mn2+ , Co2+ , and 2-methylimidazole in air. The catalytic performance of activating peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation was discussed. The results showed that the 0.1 g L-1C-2CoMnO could effectively activate PMS, resulting in 96.18% CIP was degraded within 60 min. The corresponding total organic carbon removal ratio and apparent rate constant were 81.33% and 0.043 min(-1) , respectively. The influencing factors, such as Co/Mn molar ratios, calcination temperature, PMS concentration, solution pH, and coexisting ions were explored. The optimal catalytic system exhibited good recycling performance, wide pH adaptation and high resistance to salt interference. SO4 center dot(-) , center dot OH, and center dot O-2(-) -basedradicals, as well as O-1(2) and surface complexes-based nonradicals were participated in CIP degradation. The CIP degradation pathways were proposed. Density functional theory calculations (DFT) indicated that PMS was more easily activated via Co/Mn synergism. The doped carbon was also contributed to PMS activation via facilitating electron transfer. This study may shed light toward the synergistic effect of metal oxides in PMS activation.
查看更多>>摘要：This paper presented an experimental study for a noticeable phenomenon named by the self-cleaning in a granular bed filter-cyclone coupled gas-solid separator. This phenomenon brought about positive effects on the dust cake destruction and the operating time extension in the separation process. It was analyzed under different inlet gas velocity, inlet dust concentration as well as the bed operating modes. The inner tangential velocity distribution was also measured with the five-hole probe. The dust cake porosity was deduced by combing the pressure, the deposited dust mass as well as the proposed correlations in published literatures. The experimental results showed that the inner/outer self-cleaning phenomenon resulted in significant improvement on the collection efficiency and the pressure drop. The tangential velocity played the most important role in the outer self-cleaning. The friction effect induced by the downward-moving collector particles was the other key to restrain the formation of the dust cake on the inner Johnson screen, which was conducive to the inner selfcleaning phenomenon. Only the dense particle packed dusts left on the screen surface under the full-bed operating mode and a high collection efficiency was achieved by the self-cleaning phenomenon.
查看更多>>摘要：A flow-by fixed bed bioelectrochemical reactor was used for zinc removal from an aqueous solution. Response surface methodology (RSM) based on central composite design (CDD) was employed to study the effect of process parameters, such as applied voltage, initial zinc concentration, and pH, on the efficiency of zinc removal. To predict the relationship between the response of zinc removal efficiency (RE%) and its independent variables and to maximise this response, a quadratic model equation was established. The reliability of the quadratic model was confirmed by the high R-2 value (98.61%). The optimisation study revealed that the initial concentration of zinc was the most effective parameter in the zinc removal process because of its highest F-statistic value (331.59). Using RSM, the optimum conditions for maximum zinc removal were an applied voltage of 1.8 V, an initial zinc concentration of 15.9 mg/L, and a pH of 7.6. With these conditions, a high zinc RE% (90.5%) could be achieved at a specific energy consumption of 0.65 kWh/kg Zn with cathodic current efficiency of 99%.
查看更多>>摘要：Traditional Fenton reaction is limited by the problem of free radical scavenging and always requires pre acidification, which seriously hinders its practical application. In this study, an oxygen vacancy (OVs) assisted Fenton-like catalyst (Mn-CuO) was designed to degrade ciprofloxacin (CIP). Results showed that Mn10CuO exhibited 3 times decomposition rate of H2O2 than that of CuO, and can make decent performances under a wide pH ranges (pH = 3.01-10.00). This can be ascribed to the Cu-Mn binary synergism and formation of OVs after addition of Mn2+, which not only improved the adsorption capacity of catalyst, but also promoted H2O2 activation. Moreover, different radical scavenging experiments and characterization shows that Cu(III) rather than center dot OH dominated the degradation process in Mn10CuO/H2O2 system. The degradation intermediates were analyzed by LC-MS, and proposed the possible degradation pathways. Moreover, this system can work efficiently in tap water, river water as well as lake water without adjusting pH. This work indicates that it is an efficient strategy to constructing Fenton-like systems by using surface defect engineering to develop efficient catalyst.
NSTL
Elsevier