查看更多>>摘要：In this study, an amphoteric magnetic chitosan (CS)-based flocculant MFe3O4@CS-g-PIA was prepared from CS, Fe3O4, and itaconic acid (IA), and its apparent morphology and characteristic structure were systematically studied. The flocculation performance and mechanism of the fabricated material were also investigated in different pollution systems, and the effects of total monomer concentration, m(CS):m(IA), IA pre-neutralization degree, reaction temperature, reaction time, and initiator concentration on the synthesis of MFe3O4@CS-g-PIA were studied. Characterization results showed that MFe3O4@CS-g-PIA forms a three-dimensional network with excellent magnetic induction. The optimal removal rates of Cu(II) and Disperse Blue 56 (DB56; 90.2% and 97.0%, respectively) were obtained under the conditions of 150 mg·L~(-1) MFe3O4@CS-g-PIA, pH 6.0, and 300 rpm stirring speed. MFe3O4@CS-g-PIA maintained removal rates of over 80.0% for Cu(II) and DB56 after five consecutive cycles of regeneration/flocculation and demonstrated excellent acid resistance stability. Changes in the particle size distribution, fractal dimensions, and zeta potentials of the flocs indicated that the relevant flocculation mechanism involves the synergistic functions of chelation, charge neutralization, and adsorption bridging. An artificial neural network model was finally established on the basis of the experimental flocculation data to predict the removal rates of Cu(II) (R = 0.97) and DB56 (R = 0.98) accurately.
查看更多>>摘要：Zero-valent iron microparticle (mZVI) is an excellent reductant for nitroaromatic compounds (NACs). However, it still faces severe challenges including easy agglomeration, oxidation, loss and difficult reuse. To overcome these drawbacks, a zero-valent iron microspheres/polyvinylidene fluoride (mZVI/PVDF) composite membrane using non-solvent induced phase separation (NIPS) method was constructed. Compared with bare mZVI, the mZVI/PVDF composite membrane limited agglomeration and oxidation of mZVI and slowed down the loss of mZVI and resultant iron (hydr)oxide, which made it maintain 100% nitrobenzene (NB) degradation in eight cycles. In the 1st use of mZVI/PVDF composite membrane, the NB degradation went through four steps dominated by adsorption, reduction by mZVI, formation of Fe~(2+) species associated with iron (hydr)oxide, reduction by Fe~(2+) species associated with iron (hydr)oxide. The captured iron (hydr)oxide by mZVI/PVDF composite membrane after 1st use accelerated the formation of Fe~(2+) species associated with iron (hydr)oxide, which made the NB degradation in 2nd-5th use faster than in 1st use. To promote NB diffusion, the cross-flow model was further applied and the NB removal amount was 11.63 times that in static model in 1st use. Our findings showed the NB degradation by mZVI/PVDF composite membrane in details, which would accelerate optimized use of mZVI.
查看更多>>摘要：In order to conquer the obstacle that increased CO2 selectivity in two-dimensional nanosheet incorporated-mixed matrix membranes (MMMs) is accompanied with sacrifice of CO2 permeability, CuBDC-ns was grown on multilayered MoS2 nanosheets via bottom-up synthesis strategy to obtain two-dimensional nanosheet composite, which was incorporated into Pebax-based MMM for efficient CO2 separation. The synthesized CuBDC-ns@MoS2 composite with abundant unsaturated metal sites (Cu-S and Cu-O) achieve superior CO2 adsorption capacity compared to pristine CuBDC-ns. This is attributed to formation of coordination complex between Cu ions on CuBDC-ns and S atoms in multilayered M0S2 nanosheets, as revealed on FTIR and XPS analysis. Therefore, the incorporated CuBDC-ns@MoS2 composites not only increase CO2 separation selectivity via lamellar morphology and narrow pore aperture, but also enhance CO2 solubility and diffusivity via coordination complex and unsaturated metal sites, boosting CO2 permeability and separation selectivity simultaneously. Gas permeation experiments demonstrate that Pebax-based MMMs incorporated with 2.5 wt% of CuBDC-ns@10MoS2 composite achieve CO2 permeability of 123 Barrers, as well as superior CO2/CH4 and CO2/N2 selectivities of 18 and 69. They are higher by 42.5 %, 19.2 %, and 80.2 %, respectively, than those of pristine Pebax membrane.
Maria C. IliutaValex Raul Mollo-VarillasFrancis Bougie
11页
查看更多>>摘要：CO2 valorization by chemical recycling into useful chemicals and alternative fuels is often accompanied by the production of water as by-product, which limits thermodynamically the CO2 conversion and has a negative effect on catalyst activity. Water removal from the reaction medium through the intensified sorption enhanced reaction process (SERF) is an effective way to significantly increase the conversion of reactants and the selectivity of desired products. We have previously revealed that FAU-13X and LTA-4A zeolites have adequate water adsorption capacity in the temperature range of 100-250 °C. To study the competitive adsorption of water in the presence of CO2 and the corresponding adsorption kinetics, essential for SERP, experiments using combinations of water vapor and CO2 were carried out in the range of 100-250 °C by using an Intelligent Gravimetric Analyzer (IGA) integrated with an infrared (IR) CO2 analyzer. The results showed that FAU-13X zeolite presents a significant adsorption selectivity for water vapor over CO2, which is 1.2 times higher compared to LTA-4A. In addition, water vapor is adsorbed on FAU-13X 46 and 20 times (on average) more than CO2 at 100 °C and 250 °C, respectively. The double stretched exponential model was applied to determine the kinetic parameters, which represent key data in modeling, design, and simulation of sorption enhanced reaction processes involving CO2 catalytic conversion.
查看更多>>摘要：Mg/Al-LDH is widely used in the removal of aqueous pollutants due to the large surface and high anion exchange capacity, but the traditional Mg/Al-LDH for arsenic removal has a narrow range of pH application. The present study focused on the modifying of the lamellar Mg/Al-LDH to synthesize flower-like nanoparticles for arsenate removal in a wide pH range. Results showed that Mg/Al/Fe-CLDH (calcined Mg/Al/Fe-LDH) exhibited an extremely high arsenate removal efficiency (e.g., reducing As(V) from 10 mg/L to 1 ng/L) in a wide pH range (2-12). Furthermore, it can keep excellent removal efficiency for arsenate under a complex anions environment (co-existing with CO_3~(2-), SO_4~(2-), PO_4~(3-), and F~-), and maintain 80% removal efficiency for arsenate after 4 regeneration cycles. SEM, XRD, and XPS results unveiled the following enhancing mechanism, for arsenate removal by using this modified Mg/Al-LDH: 1) partial content of ferric ions were successfully insert into the layers of Mg/Al-LDH and substituted by aluminium ions, which produce more affiliative sites for arsenate and expand its feasibility in a wide pH ranges; 2) the flower-like structures facilitate to offer more adsorption sites for arsenate due to its larger specific surface area. In brief, this flower-like Mg/Al/Fe-CLDH has great application potential for eco-friendly purity of arsenate from complicated industrial wastewater.
查看更多>>摘要：Salbutamol (SAL) and Atenolol (ATL), two common medical ingredients acting on adrenal receptor, are often used for treating chronic illnesses. However, the incomplete metabolism in organism and widespread utilization lead to unneglected problems of water pollution, which the traditional treatment plant cannot satisfactorily deal with. For efficient removal of SAL and ATL, a kind of silanized p-cyclodextrin compound adsorbents (GD-EDTS) was designed based on the ionization features of two pollutants. Through an introduction of rich carboxyl groups by N-[(3-Trimethoxysilyl)propyl]ethylenediamine triaceticacid trisodium salt (EDTS), GD-EDTS surface obtains an appropriate electronegativity to meet different forms of IOCs and maintain a good adsorption performance in a wide pH range. The maximum adsorption capacities of SAL and ATL are 140.24 mg/g and 236.92 mg/g, respectively. And a remarkable rise is known from the adsorption capacity of SAL and ATL increasing to 162% and 706%, respectively, after EDTS modification. Adsorption data fit the Sips adsorption isotherms and the pseudo second-order kinetic model, and a weak competitive behavior between SAL and ATL indicates two pollutants can be removed simultaneously by GD-EDTS in their binary system. In this work, GD-EDTS is suggested to be an efficient adsorbent in the removal of SAL and ATL.
查看更多>>摘要：Decreasing crystal size and introducing more electronegative extraframework metal cations to small-pore zeolites provide clear-cut advantages for small gas adsorption and separations. Here, nanocrystalline (~100 nm) silver-exchanged ZK-5 (Ag-ZK-5) has been prepared and studied as an adsorbent for CH4/N2 separation. Nanocrystalline Ag-ZK-5 was found to show a CH4 uptake of 1.6 mmol g~(-1) at 298 K and 1.0 bar and an LAST CH4/N2 selectivity of 11.8 in vacuum-swing adsorption mode, which are the highest values ever reported for zeolite-based adsorbents for CH4/N2 separation. This zeolite is also characterized by fast adsorption kinetics and excellent regenerability, revealing its high potential for practical applications. It appears that nanocrystalline Ag-ZK-5 may have a more homogenous Ag~+ distribution than the macrocrystalline one, providing the former zeolite with a better CH4/N2 separation performance.
Nishel SainiKamlendra AwasthiDepartment of Physics, Malaviya National Institute of Technology Jaipur, Rajasthan
25页
查看更多>>摘要：The industrial gas hydrogen has showcased its utility in a variety of processes, including those in die steel and petrochemical industries. However, synthetically produced hydrogen contains other impurities and some unreacted substituents like CO2, N2, CH4, etc. that needs to stamp out. For this purpose, efficient and environmentally friendly, polymer membrane technology provides tremendous potential.The core objective of this paper is to analyze several key rules regarding material engineering and the separation mechanism used for the betterment of hydrogen separation membranes. In this review, we have highlighted the ongoing research using different polymer membrane materials to design matrices with better characteristics than the previous one. We have focused on different polymers which are involved as the main matrix while a variety of organic/inorganic particles are appended in the role of fillers to conquer the well-established trade-off. The principle criteria's are- (1) the phenomenology and regularities of hydrogen transfer through polymeric membranes, and (2) polymer membrane materials with favourable hydrogen separation properties in terms of permeability and selectivity. The results from the critical analysis of the published data over the potential of polymeric membranes towards hydrogen separation are also discussed. Furthermore, as per the conclusions of a thorough review, these polymer nanocomposite membranes can compete with or eventually replace the conventional approaches.
查看更多>>摘要：Membrane separation technology is playing a prominent role in treatment of suspension wastewater, but its efficiency is limited by membrane fouling. Here, a self-cleaning piezoelectric ceramic membrane (PCM) coupled with in-situ ultrasound functionality was developed. The PCM consists of a porous piezoelectric quartz (a-SiO2) support and a ZrO2 microfiltration (MF) layer. The MF layer serves as a separation membrane, and it possesses a smooth and negatively charged surface, which is beneficial to weaken the interaction between membrane and foulants. The a-SiO2 support provides mechanical strength to the membrane and can generate internal ultra-sound to mitigate fouling. In MF process, particulate foulants are inevitably deposited on the membrane surface, forming a cake whose permeance resistance is 3.9 times of pristine membrane. With the assistance of internal ultrasound, the thickness of cake decreased from 64.2 to 48.4 μm, and porosity increased from 39.5% to 42.5% due to the formation of shear force. Higher cross-flow velocity and more vigorous ultrasound intensity are helpful to strengthen turbulence, which can improve stationary membrane flux by 41.7%. The fouling removal efficiency of internal ultrasound is superior to the outer one, and the economic evaluation indicates that the cost of water production can be saved in the presence of ultrasound.
查看更多>>摘要：A series of anion exchange membranes (AEMs) based on poly(arylene piperidinium) with bis-cation strings were prepared by a simple synthetic method for diffusion dialysis (DD). Through Menshutkin reaction, l-(6-bromo-hexyl)-l-methylpiperidinium bromide was grafted onto the hydrophobic poly(arylene piperidine) backbone to produce side-chain-type AEMs with bis-piperidinium strings (QPBPipXAc). The self-assembled nanostructure of these AEMs was verified by SAXS and AFM images. The properties and DD performance of QPBPipXAc AEMs with different contents of bis-piperidinium ionic groups were systematically studied, including mechanical properties, ionic conductivity, thermal stability. The prepared AEMs demonstrated favorable overall properties due to the formation of self-assembled nanostructured hydrophilic-hydrophobic phase separation morphology, The hydrophilic domains provide more efficient ion transport channels for high acid flux, whereas the hydrophobic domains restrict the AEMs swelling and Fe~(2+) ion transport. The prepared QPBPipXAc AEMs displayed high H~+ dialysis coefficients (U_H~+, 10 × 10~(-3) - 65 × 10~(-3) m/h) and separation coefficients (S, 15.67-25.38). Compared with the commercial membrane DF-120 (U_h~+ = 9 × 10~(-3) m/h, S = 18.5), the prepared AEMs have better diffusion dialysis performance, indicating that they could be the potential candidates for application for acid recovery.
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