Totally found 1885 items.

  • [期刊] Preparation and gas separation performance of thermally rearranged poly (benzoxazole-co-amide) (TR-PBOA) hollow fiber membranes deriving from polyamides
    Flexible poly(benzoxazole-co-amide) (PBOA) gas separation hollow fiber membranes were successfully prepared deriving from ether-containing polyamide precursors by thermal densification with or without a supplementary coating treatment. Compared with polyimide precursors, thermally rearrangement in this work required lower treatment temperature but generated better mechanical properties. Both spinning process and thermal treatment conditions were systemically manipulated to intensify the membrane densification aiming at achieving greatly improved selectivity of the obtained TR-PBOA hollow fiber membranes. It was found that draft ratio had little contribution to selectivity enhancement. Separation performance was substantially improved when precursor fibers were dried using ethanol-hexane exchange method and then thermally treated at 350-390 degrees C TR hollow fibers obtained by combined thermal treatment with coating method exhibited the highest selectivity values in this study.
  • [期刊] Comprehensive permeation analysis and mechanical resistance of electroless pore-plated Pd-membranes with ordered mesoporous ceria as intermediate layer
    H-2-selective composite membranes, particularly those based on palladium films deposited onto porous stainless-steel supports, represent a promising technology to be practically included in both independent devices and membrane reactors. To reach thin H-2-selective films and hence high permeance values, the use of a wide variety of intermediate layers is usually adopted in the literature. However, an agreement about the best solution is not found up to now. In this context, the current study presents the use of Ordered Mesoporous Ceria (OMC) particles as intermediate layer for the improvement of permeation properties of Electroless Pore-Plated (ELP-PP) Pd-composite membranes. OMC was obtained by nanocasting from SBA-15 as temporary template and cerium nitrate (III) hexahydrate as metal precursor. Resultant OMC particles have around 100 nm spherical diameter, an average pore-size diameter of 10-12 nm, and a total BET surface of around 134 m(2)/g. This material was next deposited onto the external surface of tubular Porous Stainless-Steel (PSS) supports by vacuum-assisted dip-coating (VA-DC) to form an intermediate layer that makes the preparation of a defect-free and thin Pd-film easier. This procedure allows the preparation of Pd composite membranes (OMC-Pd) with Pd thicknesses around 10 mu m, H-2 permeances of 1.03.10(-3) mol m(-2) s(-1) Pa-0.5 at 400 degrees C, and high ideal selectivity alpha(H2/N2) >= 24,000. It should be noted that H-2 permeance has been increased up to 6 times in comparison with other ELP-PP membranes without any intermediate layer and 2 times in contrast to membranes containing dense CeO2 particles instead of the mesoporous ones for the intermediate layer. Moreover, Pd-membranes so prepared (OMC-Pd) have shown excellent mechanical resistance in a wide variety of operating conditions such as temperature, pressure, and permeate flux direction, maintaining a high H-2-selectivity without delamination or peeling. These properties were also maintained in case of feeding different H-2/N-2 mixtures, where the concentration-polarization effect seems to stabilize for lower H-2 concentration values in the feed stream, not being noticeably influenced by temperature.
  • [期刊] Purification of green fluorescent protein using fast centrifugal partition chromatography
    The green fluorescent protein (GFP) is a biomolecule used in many biological applications such as biomarkers and biosensors, which require high purity levels. It is usually obtained from recombinant Escherichia coli strains, which also produces other endogenous proteins, demanding multiple purification steps, and consequently, increasing the overall costs to obtain pure GFP. Simpler and cheaper purification methods like Aqueous Biphasic Systems (ABS) were already successfully applied to purify GFP at lab scale. Therefore, the development of automatized industrially compatible purification platforms, such as countercurrent chromatography using ABS, can potentially improve the GFP production. This work studied the continuous purification of the variant enhanced GFP (EGFP) by applying ABS composed of polyethylene glycol (PEG 8000), sodium polyacrylate (NaPA 8000) and sodium sulfate (Na2SO4) as electrolyte. An initial screening was carried by changing the electrolyte content in the ABS. The increase of this condition has demonstrated an increase on the EGFP partition for the PEG-rich phase. The most efficient ABS and, at the same time, with the most appropriate conditions, namely the system composed of 15 wt% PEG 8000 + 4.5 wt% NaPA 8000 + 2.5 wt% Na2SO4 was chosen and applied on the fast centrifugal partition chromatography (FCPC). After optimization, the best operational conditions were identified, i.e. a flow rate of 2.5 mL.min(-1) and rotation speed of 2000 rpm at ascending mode, and the best results obtained, meaning a purification of 89.93% and a recovery yield of 82.3%, confirming the potential of FCPC to the continuous purification of EGFP.
  • [期刊] Reactive extraction of gallic acid from aqueous solution with Tri-n-octylamine in oleyl alcohol: Equilibrium, Thermodynamics and optimization using RSM-rCCD
    Concern of the recovery of important constituents found in nature, industrial waste streams and fermentation broth, the present study is aimed to recover gallic acid (HGA) from aqueous solution using tri-n-octylamine (TOA) in a non-toxic diluent, oleyl alcohol (OA). The optimal conditions for maximum extraction of HGA (90.1%) are determined as (i) initial concentration of HGA (C-HGA,C-o) = 0.0588 mol/L, (ii) initial TOA concentration (C-TOA,C-o) = 0.2762 mol/L, (iii) pH = 2.0 and (iv) temperature (T) = 25.0 degrees C, at atmospheric pressure (101.325 kPa), using response surface methodology (RSM) with rotatable central composite design (rCCD). The statistical analysis with ANOVA is used to model fitness and shows a high coefficient of determination (R-2 = 97%). At optimum conditions, the insights of reactive extraction are determined using differential evolution (DE) approach, a bio-inspired algorithm. The apparent stoichiometric coefficient (number moles of acid per mole of extractant, m = 1.28) of reactive extraction, overall equilibrium constant (K-E = 85.77) and individual equilibrium constants (K-11 = 110.32 and K-21 = 1106.77) are calculated. Thermodynamic study at four different temperatures (20, 30, 40 and 50 degrees C) is also carried out to determine enthalpy (Delta H = -12.97 J/mol), entropy (Delta S = -3.77 J/mol.K) and Gibb's energy change (Delta G = -12370.44 to - 5399.96 J/mol.K) of reactive extraction.
  • [期刊] Efficient separation of V(V) and Cr(VI) in aqua by microemulsion extraction
    Separation of V(V) and Cr(VI) in aqua is intensively demanded in consideration of full resource utilization and environmental safety of vanadium extraction industry, which is however a challenge due to their highly similar chemical properties. In this work, chromium transformation is firstly conducted to convert Cr(VI) anions into Cr (III) cations that are differentiable from V(V) anions. Then, the microemulsion system of Aliquat 336/isoamyl alcohol/n-heptane/NaCl is utilized to selectively extract V(V) anions by method of microemulsion extraction and leave Cr(III) cations in the raffinate, leading to the separation of V and Cr. In optimal conditions of microemulsion extraction, the extraction efficiency of V is as high as 98.45% while that of Cr is only 4.44%, confirming the efficient separation of V and Cr in aqua. Extracted V is retrieved back to aqueous solution by stripping V-loaded microemulsion and simultaneously concentrated by 4 times with total recovery of 97.91%; Cr (III) left in the raffinate is environmentally safe and ready for direct precipitation recovery. The achieved separation of V(V) and Cr(VI) is thus not only efficient, but also beneficial to their subsequent recovery. This work has demonstrated a powerful separation method for V(V) and Cr(VI) with high separation capacity, efficiency and speed, which lays the essential foundation for the recovery and comprehensive utilization of V and Cr resources in vanadium metallurgy industry.
  • [期刊] Biocompatible amino acid-based ionic liquids for extracting hormones and antibiotics from swine effluents
    The generalized use of antibiotics and hormones in swine feed has triggered a growing concern on their presence in wastewater effluents and manure. Therefore, the implementation of strategies for their removal is a matter of practical significance and the synthesis of biocompatible ionic liquids to be used as segregation agents in aqueous waste effluents could be a suitable means for removing these emerging contaminants. In this work, the salting out capacity of cholinium alaninate, (N(1112OH)Ala) in aqueous streams containing surfactants (Triton X-100) was demonstrated. Afterwards, its ability to separate a hormone (17-beta estradiol) and antibiotics belonging to tetracycline and fluoroquinolone families was investigated in an aqueous synthetic swine effluent at environmental conditions. It was checked that the cautious selection of the feed compositions allowed high levels of hormone extraction (E) and partition coefficients (K): E > 90% and K > 13.86, in surfactant rich-phase. Antibiotics migrated to any of the two phases depending on system compositions. However, the decisive addition of a cationic surfactant (2% CTAB) led to increased extraction efficiencies of chlortetracycline (K = 15.77 and E = 92.5%), proving the versatility of the process.
  • [期刊] Synthesis of divalent metal-silicalite MEL zeolites as efficient bi-functional adsorbents/catalysts for non-methane hydrocarbon in cooking oil fumes elimination
    Divalent metallic ions (M2+ = Fe2+, Mn2+, Cu2+) have been successfully introduced into silicalite-2 via a crystallization process control method. When applied in Non-methane Hydrocarbon (NMHC) removal from cooking oil fumes, these synthesized M-S2 (M = Fe, Mn, Cu) samples present both higher adsorption capacity and good catalytic oxidation performance compared with Al-S2 composed of silicon and aluminum. XRD, FTIR, UV-Vis, SEM, STEM, N-2 sorption, TG-DTA, Si-29 MAS NMR and XPS were used to characterize the incorporation and dispersion of different divalent metallic ions in silicalite framework. It was found Fe2+ can be well incorporated into the zeolite framework as similarly as Al3+, then followed by Mn2+ and Cu2+, respectively. Mn2+ can exist in the form of extra-framework oxidized metallic species despite of the framework Mn species, while Cu species are mainly in the form of CuOx nanoparticles or clusters. Due to lacking Si-OH-Al, these divalent metal-MEL zeolites possess superior hydrophobicity compared with Al-MEL and this endows the former's superior NMHC adsorption performance from cooking oil fumes. Moreover, owing to possess active metallic species with variable valence states, these divalent metal-MEL zeolites display good oxidation ability to VOCs. Particularly, Mn-S2 displays the best catalytic activity for NMHC, which can be attributed to both the good dispersion and the various valence states of Mn species in silicalite.
  • [期刊] Copper extraction from waste printed circuit boards by glycine
    The metal recycling processes in the waste printed circuit boards (WPCBs) are mainly pyrometallurgy and hydrometallurgy, whereas hydrometallurgy is considered as an efficient but less environmentally friendly process. In this study, a green amino acid, glycine, was used to replace traditional inorganic acids to extract Cu from WPCBs by investigating the effects of temperature, H2O2 volume, solid-liquid ratio and glycine concentration on Cu leaching efficiency. The kinetics and thermodynamics of the leaching process were also studied. The maximum leaching efficiency is up to 94.08% when the temperature is 30 degrees C, initial H2O2 volume is 10%, the solid-liquid ratio is 1:100 and the initial glycine concentration is 1 mol/L. After leaching, sky blue crystal, cupric-glycinate, could obtain by adding absolute ethyl alcohol. The leaching process is controlled by diffusion and chemical reactions. All these results show that the green glycine could successfully replace traditional inorganic acids to extract Cu from WPCBs, providing a feasible and perspective future for industrial application.
  • [期刊] Immobilization of lipase AYS on UiO-66-NH2 metal-organic framework nanoparticles as a recyclable biocatalyst for ester hydrolysis and kinetic resolution
    Lipase AYS was immobilized onto various metal-organic frameworks (MOFs) and diverse immobilization methods were compared. The immobilized lipase of AYS@UiO-66-NH2 via precipitation-crosslinking linkage method was characterized by XRD, SEM, N-2 adsorption/desorption analysis, TGA, and FT-IR. Application of AYS@UiO-66-NH2 in kinetic resolution of 2-(4-Methylphenyl) propanoic acid (MPA) enantiomers by hydrolysis of the methyl ester of MPA was further investigated to test the application ability. In comparison to free lipase AYS, AYS@UiO-66-NH2 shows enhanced tolerance to pH and temperature. Moreover, after 4 cycles of reuse, no significant decrease in its initial activity was observed and the enantioselectivity was well retained. Under optimal conditions, the yield of (R)-MPA was 72.57% with 93.20% of enantiomeric excess, where good improvement of catalytic performance from free lipase AYS was successfully achieved. The present work provides a simple and efficient method for enzyme immobilization, which may be well-adapted to prepare enzymatic biocatalyst for industrial applications.
  • [期刊] On the conceptual modeling, economic analysis and life cycle assessment of partial dealcoholization alternatives of bitter extracts
    In this paper, we will analyze the economic and environmental performance of three different technologies for the on-site concentration of a bitter extract of herbs with simultaneous reduction of its alcoholic content to be able to obtain a beverage without alcohol off-site through the addition of deionized water. A base case, in which the bitter extract from the herbs extraction process is transported to the blending-bottling plant without any treatment is also considered.
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