查看更多>>摘要：Big transition state (TS) energy barriers of free-state CO2 molecules getting adsorbed on different sites of MgO are one of the most difficult issues to accomplish fast CO2 adsorption. In order to solve this problem, cerium (Ce) atoms are used as a dopant to modify MgO's surface potential fields with the purpose of quicker CO2 adsorption processes. In this study, TS processes of CO2 getting adsorbed on pure, Ca-doped, Fe-doped and Al-doped MgO are firstly investigated to analyze the relationship between TS processes and TS energy barriers. Since Al-doped MgO shows the best compromise feature in the relationship, thus, Ce is adopted as single-atom promoters to facilitate CO2 adsorption processes over Al-doped MgO. According to density functional theory (DFT) calculations, the average TS energy barrier of CO2 adsorption over Ce/Al-doped MgO is nearly reduced to 0 with 146.82% bigger average adsorption energy in contrast with Al-doped MgO. What is more, effects of temperatures on CO2 adsorption traits and adsorption kinetics of different TS processes are explored to reflect promotion effects of single-atom Ce. The relevant consequences present that doping of Ce atoms could simultaneously reduce the activation energy by 74.74% and improve the temperature power exponent by 0.11%. The whole results of this study would supply crucial information for stable/fast CO2 adsorption over MgO-based adsorbents in industries.
查看更多>>摘要：The synthesis of three amino-functionalized polyacrylonitrile/bentonite (PAN/BT) composite membranes and the removal strategies of Pb2+ and Congo Red (CR) from water were put forward. The successful synthesis of PAN/BT was confirmed by scanning electron microscopy, X-ray energy spectrum, differential thermogravimetric analysis, specific surface area and contact angle tests. In addition, although having a similar composition to PAN/BT, the functionalized membrane materials have more N-H and C = N groups and stronger wettability. The influences of the optimal contaminant type, adsorbent dosage, temperature, contaminant concentration and contact time on the adsorption process of the modified membrane materials were systematically investigated. The adsorption processes were in good agreement with the Langmuir model, in which the theoretical maximum adsorption capacities of gamma-aminopropyl triethoxysilane (KH550)-modified PAN/BT (K-PAN/BT), diethylenetriamine (DETA)-modified PAN/BT (D-PAN/BT) and hydroxylamine hydrochloride (NH3OHCl)-modified PAN/BT (N-PAN/BT) for Pb2+ were 200.1, 332.9 and 182.8 mg/g, and the theoretical maximum adsorption of CR was 346.9, 156.2 and 579.2 mg/g, respectively, which were higher than 88 and 149 mg/g of bentonite, exhibiting excellent component synergy. The adsorption equilibrium was reached within 100 min for both Pb2+ and CR, and the adsorption processes were in accordance with the pseudo-second-order kinetics, involving chelation, cation exchange and 'pi-pi' interactions. It is worth mentioning that the N-PAN/BT membranes can remove high concentrations of anionic and cationic dyes with a difference of up to 100 times, with selective adsorption potential and excellent contaminant indicating ability, which has an application prospect in the field of environmental protection.
查看更多>>摘要：The evaluation of collection efficiencies of aerosol samplers becomes challenging with high pressure drops. The evaluation approaches applied at various conditions deserve further development, especially when a high pressure drop is induced by the sampler. In this work, an elution-based method using NaCl aerosol was proposed to estimate the size-resolved collection efficiency which was not affected by the pressure drop. More specifically, a Condensation Particle Counter (CPC) was used to count the upstream particle number, and the collected NaCl particles were eluted and determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for estimating the collected particle number. The relationship between number-based concentration and mass-based concentration of NaCl particles was established. A stainless steel impactor for Differential Mobility Analyzer (DMA), polydimethylsiloxane (PDMS)-based microchannel, and a homemade impactor containing 151 nozzles with a diameter of 0.1 mm were employed to investigate the feasibility of the elution method. DMA-selected particles with a nominal size are considered to be the monodisperse aerosol, which was commonly used for estimating the collection efficiencies of samplers, but size redistribution of downstream monodisperse aerosol with the particle size smaller than 100 nm and larger than the cutoff size (D-50) was revealed through the elution method, which affected the collection efficiency measured by either conventional CPC-or elution-based method. It was found that the elution method was dependent on the D-50 value of the sampler, and the applicable size range was from 100 nm to D-50 (D-50 < 500 nm) or from 100 nm to 500 nm (D-50 greater than 500 nm). This study provided insights into the size-dependent particle transport through aerosol samplers, and the development of an elution based method to estimate pressure drop-independent collection efficiencies.
查看更多>>摘要：For a massive uranium recovery from seawater, designing an adsorbent with ultrahigh uranium uptake capacity and good biofouling-resistant activity is crucial, but difficult. Here, a facile and eco-friendly freeze-thawing strategy was explored for the first time to create a physically crosslinked poly(amidoxime) (PAO)-chitosan (CS) hybrid hydrogel (PAO@CHM) with excellent interfacial compatibility, superior uranium uptake capacity and good anti-biofouling activity. The porous 3D network architecture of PAO@CHM, combined with its good hydrophilicity as well as antibacterial property, synergistically constructs numerous hydrophilic and biofoulingresistant ion channels for the rapid diffusion of uranyl ions into the interior of the hydrogel, achieving maximum use of adsorption active sites on PAO@CHM. Consequently, superior uranium uptake capacities (743.87, 865.27, and 1091.53 mg g(-1) for PAO fixed on hydrogel) were obtained in 8, 16, and 32 ppm U-spiked water, respectively. Benifiting from the enhanced uranium adsorption activity and good antibacterial property, the uranium extraction capacity of PAO@CHM reached 7.46 mg g(-1) after 28 days of exposure in 500 L of natural seawater, which is significantly higher than that of most of adsorbents. The O and N atoms in amidoxime group act as main bonding sites for uranium uptake. The finding of this study provides a facile and eco-friendly strategy to construct hydrophilic and biofouling-resistant amidoxime-based adsorbent for efficient uranium recovery from seawater.
查看更多>>摘要：Menaquinone (vitamin K2) is an essential fat-soluble vitamin for bone and cardiovascular health. Long-chain menaquinones are exclusively synthesised by bacteria, and Lactococcus lactis appears promising as a microbial production platform. Menaquinone exists in the bacterial cytoplasmic membrane protected by a thick cell wall, thus requiring efficient cell lysis and extraction for its recovery. In this work, several potential solvents that are ranked as "recommended " for pharmaceutical manufacture were screened for their effectiveness, with the aid of external heating, to simultaneously disrupt cells and extract menaquinone from wet biomass. These results were compared with those obtained by traditional two-step strategies and extraction approaches using dry biomass. Ethanol appeared to be the most effective extractant, and the technique was then optimised using response surface methodology. Under optimal conditions (75 degrees C, biomass concentration of 0.199 g mL(-1) and extraction time of 36.8 min), the extraction yields for menaquinone-7 and menaquinone-8 were 6.73 +/- 0.17 and 179.6 +/- 3.59 mu g g(-1) dry cell weight, respectively. In addition, the use of ethanol as the extraction solvent coupled with microwave heating and bead-beating was investigated. Enhanced extraction was achieved using microwave assisted extraction at an elevated temperature of 125 degrees C for 5 min, with a 1.15- and 1.2-fold increase in menaquinone-7 and menaquinone-8 yields, respectively. This work proposes the development of an integrated single-step process for the sustainable and efficient recovery of menaquinone from biomass, with the advantage of using ethanol as a green extraction solvent.
查看更多>>摘要：UV/chlorine is an emerging process that can simultaneously control waterborne bacteria and disinfection byproducts (DBPs). In this study, performance of UV365/chlorine process on bacterial inactivation was comprehensively investigated, which showed better performance than UV365 alone and chlorine alone processes. The better performance could be attributed to the reactive species (especially O-3 and HO center dot) generated in UV365/chlorine process. Inactivation of E. coli, S. aureus, and B. subtilis was further reflected via the evaluation of membrane permeability, leakage of adenosine-triphosphate (ATP), and damage of cell surface morphology. The results also demonstrated that bacterial inactivation generally follow the order of E. coli, S. aureus, B. subtilis. To ensure the disinfection efficiency, reactivation of three bacteria after complete treatment by UV(365 )alone, chlorine alone and UV365/chlorine processes was evaluated, and the combined process showed the lowest reactivation potential. Further, formation of disinfection byproducts (DBPs) from the bacterial suspensions with/ without UV365/chlorine pretreatment was determined. Bacterial suspensions treated with UV365/chlorine process generated fewer DBPs than that in direct chlorination. Overall, our present study could provide much useful information on the actual application of UV365/chlorine process in drinking water treatment plants.
查看更多>>摘要：The CO2 adsorption performance of most adsorbents were inhibited by water vapor which is a ubiquitous component of flue gas. It is critical to find an adsorbent with long-term stability in the presence of water vapor. In this study, both theoretical and experimental study were carried out to investigate the CO2 capture capacity in humid flue gas of PEI impregnated ZIF-8. Grand canonical Monte Carlo (GCMC) simulation was performed to calculate the co-adsorption of CO2 and H2O on ZIF-8-PEI. The simulation result indicates that water vapor has no negative impact on CO2 adsorption of ZIF-8-PEI. Then, ZIF-8 with different PEI weight was synthesized and characterized. It is found that ZIF-8 with 30 wt.% PEI not only shows the highest CO2 uptake of 1.4 mmol/g in dry condition but also exhibits excellent CO2/N-2 separation performance. More important is that the adsorption capacity of ZIF-8-PEI30% was improved to 1.7 mmol/g when the adsorbents were imposed to humid flue gas with 50% relative humidity (RH). Moreover, it only shows a slight decrease after 50 adsorption/desorption cycles. Hence, water plays an excellent promoter role in CO2 capture of ZIF-8-PEI30%, and it is a promising adsorbent to be used in humid flue gas.
查看更多>>摘要：Oily wastewater treatment is an arduous and urgent global problem. Electrospinning has wide applications in construction of high-efficiency oil-water separation membranes. Herein, electrospinning and electrospraying technology were combined to construct a Polytetrafluoroethylene (PTFE) nanofiber membrane (NFM) with multileveled structure for oily wastewater treatment. The separation performance (driven by gravity) of the NFM to oil-water mixture was studied. In addition, the demulsification performance of the NFM to water-in-oil surfactant-stabilized emulsions (W/O SSEs) under gravity and oil-in-water surfactant-stabilized emulsions (O/W SSEs) at 0.5 bar were studied subsequently. The results showed that the flux of the 9% D-H-PTFE to the oil-water mixture reached 4909 L m(-2) h(-1), with a separation rate of 99.99%; the flux to the CCl4 W/O SSE reached 1867.93 L m(-2) h(-1) with the separation rate of 98.46%. The flux to the CCl4 O/W SSE was 122 L m-(2) h(-1) and the separation rate was 98.40% in multiple cycles. Therefore, these NFMs are expected to be practically applied to a low-pressure driven membrane separation system for preliminary separation of different types of oily wastewater.
查看更多>>摘要：In this study, the pressure drops and mass transfer performance of a improved tridimensional rotational flow sieve tray (TRST) manufactured by 3D printing under the condition of gas-liquid concurrent flow were investigated experimentally. Results suggest that the pressure drops of the improved TRST are much lower than that of the original TRST due to the transition of the arc surface of the blades is smoother. Dry pressure drop of the TRST is within 12 Pa, and wet pressure drop is within 80 Pa. A volumetric overall mass transfer coefficient of the tray section was proposed, which increased first and then decreased with increased superficial flow factor and concentrations of NaOH solution, increased with the increasing spray density and decreased with the increasing partial pressure of CO2. For tray geometric parameters, the influence of blade numbers is strongest, twist angle of the blades is weakest, and tray heights and sieve hole diameters are the middling. We also designed an energy efficiency factor to reasonably evaluate the comprehensive performance of TRST. Through comparative analysis, TRST with 8 blades, a 60 degrees or 90 degrees twist angle of the blades, a tray height of 15 mm, and sieve holes of 2 mm diameter were found to has the optimal geometry.
查看更多>>摘要：Photo-Fenton performance of Fe-based metal-organic frameworks needs to be further improved owing to little coordinatively unsaturated metal sites (Lewis acid sites) and poor photogenerated carrier separation and migration efficiency. In view of this problem, this work has developed missing-linker metal-organic framework with mix-valence coordinatively unsaturated metal site (abbreviated as CUS-Pac-MIL-100 (Fe)) for photo-Fenton degradation by thermal activation and introducing missing linker. The structure of catalysts was characterized by SEM, XRD, XPS, in-situ DRIFT, TG, BET, and EPR, which proves abundant mixed-valence coordinatively unsaturated metal sites are introduced by vacuum thermal activation and plenty of ligand vacancies are introduced by missing-linker. The conditions for TC-HCl degradation were optimized. The results indicate that CUS-Pac-MIL-100 (Fe) exhibits remarkable removal rate of TC-HCl within 80 min at 10 mL/L H2O2 dosage, 0.2 g/L catalyst dosage, and a wide pH range (4.0-7.0). The total organic carbon (TOC) removal rate also reaches 52.3% within 80 min. Such remarkable improvement in the photo-Fenton activity is attributed to the mix-valence coordinatively unsaturated metal sites improving the adsorption and activation ability of H2O2, and the ligand vacancies promoting the separation efficiency of carriers to accelerate Fe2+ regeneration. The catalyst also exhibits excellent cyclability and stability after multiple cycles. Further, the degradation mechanism and degradation pathways of TC-HCl in the photo-Fenton reaction has been proposed on the basis of radical quenching, electron paramagnetic resonance, and LC-MS tests. This work provides a worthy insight for the construction of high-efficiency MOF-based photo-Fenton materials.
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Elsevier