查看更多>>摘要：The discharge of anionic surfactants stabilized oily wastewater is harmful to aquatic plants and animals, and the treatment of the wastewater is urgent. However, on account of the high stability of the oil-water interface, the wastewater is hard to be efficiently disposed. To destabilize the stability, superhydrophilic positively charged polyurethane (PU) sponge was fabricated by a simple cross-linking reaction between chitosan and glutaraldehyde. Through the electrostatic interaction, the positively charged PU sponge could absorb anionic surfactants molecules (sodium dodecyl sulfate, SDS) absorbed on the oil surface, resulting in the decline of the stability of the oil-water interface, sequentially the oil droplets could collide and coalesce in the three-dimensional pores of PU sponge. For SDS stabilized oil-in-water emulsion, the positively charged PU sponge can constantly work for 100 min to separate above 3500 mL emulsion with a favorable separation efficiency. Furthermore, the positively charged PU sponge can absorb dyes and metal ions in wastewater, due to a large number of amino groups and hydroxyl groups of the positively charged coating. Therefore, the prepared positively charged PU sponge could continuously separate oil/water emulsion and remove the dyes and metal ions in wastewater, which could be a promising candidate for oily wastewater treatment.
查看更多>>摘要：Flavonoid aglycones and flavonol aglycones, are difficult to be separated due to their similar structures and limited hydroxyls. Herein, Zr(IV) immobilized collagen fiber (ZCF) was prepared by immobilizing Zr(IV) on glutaraldehyde cross-linked collagen fiber (GCF) to separate apigenin and kaempferol, the representative compounds of flavonoid aglycones and flavonol aglycones. TG, DSC, SEM and element mapping were applied to characterize ZCF. The static adsorption suggested that when the amount of immobilized Zr(IV) reached only 0.3 mmol/g, the adsorption difference between apigenin and kaempferol on ZCF was highly improved compared with GCF without Zr(IV). The adsorption rate of apigenin increased from 2.21% to 14.31%, while that of kaempferol significantly increased from 22.35% to 87.17%. In addition, the spectroscopy (UV-Vis, FT-IR) were applied to analyze the binding sites of flavonoids with Zr(IV), indicating that the strong adsorption of ZCF to kaempferol may be related to the 3-hydroxyl on the C-ring, while apigenin only can conduct a weak binding with ZCF through 5-hydroxyl on the A-ring. In ZCF column chromatography separation, apigenin and kaempferol could be separated effectively with purities of 94.02% and 89.23% by stepwise elution of 50% aqueous ethanol followed by 50% aqueous ethanol containing 0.005 mol/L citric acid. In separation on ZCF and GCF combined columns, the purities of apigenin and kaempferol reached 95.59% and 92.56%, respectively, and the trace amount of Zr(IV) shedding from ZCF was completely adsorbed by GCF avoiding contaminating the target components. In addition, the effective separation of apigenin and kaempferol in apium gvaveolens (celery) extract by ZCF column was also achieved. The above results indicated ZCF could selectively adsorb flavonol aglycones with 3-hydroxyl on the C-ring from the mixture with flavonoid aglycones. This investigation provides a novel column chromatography packing material for the fast separation of flavonoid aglycones and flavonol aglycones.
查看更多>>摘要：Both sustainable storage of renewable energy using H2O2 as energy carrier and wastewater treatment by electro-Fenton are highly dependent on the efficiency of H2O2 electrosynthesis via 2-electron reduction of O2. Rational design of high-performance and cost-effective electrocatalysts with facile preparation is bear the brunt of scalable H2O2 electrosynthesis. Herein, for the first time, we synthesize a pitaya peel-derived formicary-like electrocatalyst employing facile pyrolysis and KOH activation. At the optimal mass ratio of biochar to KOH (1:3), the electrocatalyst exhibits prominent H2O2 activity and selectivity owing to its rich self-doped oxygen-containing functional groups as well as structural defects and sp3-C bonds serving as reactive sites, rational hierarchical pores boosting mass transfer of reactants and products, and ultrahigh specific surface area facilitating the exposure of reactive sites. Under natural air diffusion, the pitaya peel-derived catalyst-coated cathode achieves surprising H2O2 productivity of 41.6 mg h~(-1) cm-2 with current efficiency of 65.5% at large current density of 100 111A cm-2, meeting the near-industrial requirements for sustainable H2O2 production. Long-term operation stability at large current and rapid degradation of multiple high-concentration organic pollutants demonstrate tremendous potential of the pitaya peel-derived catalysts for H2O2-based renewable energy storage and environmental remethation.
查看更多>>摘要：Plasticization greatly reduces the separation performance and shortens the service life of the polymer-based gas separation membranes, which is one of the most critical problems to be addressed. This phenomenon becomes more severe in thin films. In this work, metal-polymer complexes were designed in thin polymeric membranes via coordination interaction between transition metal ions and benzimidazole moieties of polyimide to improve the plasticization resistance. The metal-polymer complexes effectively enhanced the interchain interaction and provided abundant open metal sites. The gas permeation results revealed that the CO2 plasticization pressure of the metal-polymer complex thin films was sharply improved from 6 to 27-30 bar. Remarkably, the thin films containing metal-ion coordination demonstrated an enhanced CO2/CH4 selectivity from ~ 37 to ~ 50 with increasing the mixed gas pressure from 1 to 15 bar, which was attributed to many open metal sites that strongly enhanced the affinity of membranes to CO2 and yielded the selective CO2 permeation. This work provides a facile and effective strategy for designing plasticization-resistant polymer membranes for efficient CO2 capture.
查看更多>>摘要：Reactive extraction of carboxylic acids such as lactic acid with tertiary amines is a state-of-the-art process but suffers strongly from reduced extraction efficiency in buffered environments like fermentation broths. In order to increase the efficiency of in-situ product removal, we here propose the combination of a membrane-assisted reactive extraction with an electrochemical pH shift. Prior to extraction in the membrane module, the fermentation broth containing the lactic acid at neutral pH is treated by anodic electrolysis to reduce the pH and thereby improve the extraction yield. Additionally, the cathodic reaction is used to increase the pH of the aqueous stream used for back-extraction of the loaded organic phase. Model solutions were used to develop a mathematical model, capable of calculating the required membrane area for in-situ extractions, considering the effect of the aqueous pH on the extraction performance. Additionally, using electrochemical pH shift, we were able to concentrate lactic acid from 1 wt% in the dilute broth to 7 wt% in the back extract.
查看更多>>摘要：Di-benzo-18-crown-6 ether (DB18C6) functionalized polymethyl acrylic acid (PMA) resin was synthesized after screening by employing density functional theory (DFT) and molecular dynamics (MD) simulations for the enrichment of gadolinium isotopes, Gd-155 and Gd-157. Batch adsorption and column chromatography studies were performed at various pH, gadolinium ion concentration and temperatures to check its efficacy and validation of theoretical approach. The adsorption capacity of gadolinium ion with the PMADB18C6 resin was found to be quite modest with a value of 1.128 mg/g. Both MD simulations and adsorption experiments confirm the Temkin type of adsorption isotherm. The positive entropy change along with the positive enthalpy change indicates that sorption of the Gd~(3+) ion with PMADB18C6 is entropy driven process. From the chromatography experiments, the lighter isotope (Gd-155) is seen to be depleted in the breakthrough volume samples which specify that the resin phase is depleted with heavier isotope (e.g Gd-160) contrast to natural Gd composition. The separation coefficient (c) for Gd_(155/158), Gd_(156/158), Gd_(157/158), Gd_(155/160) and Gd_(157/160) isotopic pairs were found to be 1.67 x 10~(-3), 2.65 x 10~(-3), 5.40 x 10~(-4), 3.18 x 10~(-3) and 1.87 x 10~(-3) respectively. The experimental isotopic separation factor corroborates the DFT findings. Further, both DFT and MD simulations confirm the experimentally observed endothermic complexation of Gd~(3+) ion with PMADB18C6 resin. The present findings employing combined DFT, MD simulations and experimental approaches are expected to benefit in the fundamental understanding of molecular complexation based isotope separation and design and development of future gadolinium isotopic enrichment technologies using chemical exchange methods.
Ana Paula Floriano SantosFabio GozziAdriana Evaristo de Carvalho
10页
查看更多>>摘要：The effectiveness of using solar photo-Fenton-like processes to degrade sanitary landfill leachates was investigated. Leachate samples exhibited varying composition, owing to a mixture of older and younger effluents from a former dump site subsequently converted into a sanitary landfill. Coagulation assays (jar test) using Al~(3+), Fe~(2+), and Fe~(3+) in the 240-800 mg L~(-1) range were performed to evaluate optimal coagulant concentration for abatement of chemical oxygen demand (COD) and dissolved organic carbon (DOC). A high COD (53%) and DOC (72%) removal rates were obtained for Al~(3+) but there was a very substantial increase in the turbidity. Optimal coagulant concentration was then adopted, and the effluents were subjected to photo-Fenton processes at laboratory scale. At this scale, coagulation by Fe~(3+) at 240 mg L~(-1) combined with a photo-Fenton-like method exhibited superior performance, with 66% DOC removal by coagulation and over 70% DOC removal using the photo-Fenton-like process. Solar photodegradation was conducted for 180 min at [Fe~(3+)] = 100 mg IT1, pH = 3.0 ± 0.3, and [H2O2] = 50-250 mg L~(-1) at a solar pilot plant. Use of solar photo-Fenton-like processes improved effluent biodegradability, irrespective of coagulation pretreatment, and also reduced leachate toxicity, as shown by acute ecotoxicity tests using Lactuca sativa seeds, Allium cepa bulbs, and Artemia salina, proving to be a promising treatment method in line with the National Solid Waste Policy, which promotes and encourages non-generation, reduction, reuse, recycling, the treatment of solid waste, and the environmentally appropriate final disposal of tailings.
查看更多>>摘要：Highly CO2 permeable membranes with good selectivity are ideal candidates for CO2 separation. Herein, we, for the first time, designed different polymeric membrane systems for CO2 removal from the air-fed anion-exchange membrane fuel cells (AEMFCs) by UniSim simulation under different operating conditions. The results indicate that the operations with higher feed pressure and permeate vacuum degree reduce the required membrane areas but increase the power demands. In addition, the single-stage facilitated transport membrane system (CO2 permeance of 3000 GPU) with an area of<10 m is feasible to reach a low CO2 content of < 5 ppm for automotive AEMFCs with an air flow rate of 30 Nm /h at 87 °C. It was also found that pursuing an extremely high CO2 removal ratio dramatically increases the required membrane area and the O2 loss, and sweep gas is more applicable for automotive vehicles. Nevertheless, highly permeable membranes should be further developed to enhance their competitiveness for CO2 removal from the air-fed AEMFCs.
查看更多>>摘要：Mixed matrix membranes (MMMs) have received numerous interests as promising membrane configurations for dealing with the energy-intensive gas separation processes. In this study, MMMs were fabricated by incorporating novel ZnO@MOF nanocomposites (ZnO@ZnBDC) into Matrimid (PI) matrix. The physico-chemical properties and microstructures of ZnO@ZnBDC nanocomposites and ZnO@ZnBDC/PI MMMs were characterized. The CO2/CH4 separation performance of MMMs was evaluated and analyzed according to the solution-diffusion mechanism. ZnBDC in the nanocomposites increased CO2 permeability by providing mass transfer pathways with low resistance in the MMMs, while ZnO increased the CO2/CH4 selectivity via high CO2 affinity. Owing to the synergistic effect of the nanocomposites, MMMs with 0.75 wt% ZnO@ZnBDC showed CO2 permeability of 11.5 Barrer and CO2/CH4 selectivity of 39.5, which increased by 67% and 33%, respectively, by comparing with control PI membrane.
查看更多>>摘要：The reduced T1O2 nanotube arrays (RTNA) electrode is a cost-effective anode, but its limited electrocatalytic activity is an obstacle for the application. To solve this problem, a reduced TiO2 nanotube arrays-based titanium membrane (RTNA/TM) was fabricated by a facile electrochemical method to promote the electrocatalytic performance. The one-dimensional nanostructure and reduction treatment increased the electrocatalytic capacity and reduced the energy consumption, resulting in the sulfamethoxazole (SMX) removal rate of 86.1% and electrical efficiency per order of 0.55 kWh/m for RTNA/TM. Compared with the batch mode, the SMX removal efficiency of the flow-through mode was significantly increased by 71%, verifying the superiority of a porous flow-through anode. The SMX degradation performances of RTNA/TM were strongly affected by the fluid velocity, current density and initial SMX concentration, except for pH. Both hydroxyl radicals and direct electron transfer were responsible for the SMX removal, while the contribution of sulfate radicals could be ignored. Furthermore, RTNA/TM displayed stable performances for five experimental cycles and showed remarkable degradation efficiencies of SMX spiked into the natural water (76.5%) and wastewater effluent (75.4%). Therefore, RTNA/TM has been proven to be a promising flow-through anode for electrochemical oxidation.
NSTL