[Show abstract][Hide abstract] ABSTRACT: The effects of pH and cell immobilization on acetone-butanol-ethanol (ABE) production coupled with a pervaporation membrane have been investigated using Clostridium acetobutylicum XY16. The solvent productivity of 0.29 g/L/h was obtained using a two-stage controlled-pH in the coupled process, which was 11% higher than a previous process without pH control, nevertheless, membrane was still fouled. Furthermore, butanol in the fermenter remained below the critical concentration using a larger membrane, solvent productivity achieved 0.38 g/L/h. However, these methods could not prevent membrane fouling, the average permeation flux and butanol separation factor decreased by 41.6% and 31.3%. Then, sugarcane bagasse was used as a cell immobilization carrier and applied to the coupled process; many cells aggregated and adsorbed on sugarcane bagasse surface, the dry cell weight (DCW) in broth was maintained at 1.1 g/L. Membrane fouling was relieved, the pervaporation maintained a steady state for more than 90 h, the average permeation flux was 0.676 kg/m2/h, which only decreased by 13.9% compared to that in the initial stage, and the butanol separation factor remained stable. A maximum solvent productivity of 0.62 g/L/h was also obtained. Thus, the pH control and cell immobilization are efficient methods for high-intensity ABE production with in-situ recovery.
Full-text · Article · Dec 2014 · PROCESS BIOCHEMISTRY
[Show abstract][Hide abstract] ABSTRACT: PDMS/ceramic composite membrane was directly integrated with acetone-butanol-ethanol (ABE) fermentation using Clostridium acetobutylicum XY16 at 37 °C and in situ removing ABE from fermentation broth. The membrane was integrated with batch fermentation, and approximately 46 % solvent was extracted. The solvent in permeates was 118 g/L, and solvent productivity was 0.303 g/(L/h), which was approximately 33 % higher compared with the batch fermentation without in situ recovery. The fed-batch fermentation with in situ recovery by pervaporation continued for more than 200 h, 61 % solvent was extracted, and the solvent in penetration was 96.2 g/L. The total flux ranged from 0.338 to 0.847 kg/(m(2)/h) and the separation factor of butanol ranged from 5.1 to 27.1 in this process. The membrane was fouled by the active fermentation broth, nevertheless the separation performances were partially recovered by offline membrane cleaning, and the solvent productivity was increased to 0.252 g/(L/h), which was 19 % higher compared with that in situ recovery process without membrane cleaning.
Full-text · Article · Mar 2012 · Bioprocess and Biosystems Engineering
[Show abstract][Hide abstract] ABSTRACT: A low-dimensional compound [C(6)-Apy][Ni(mnt)(2)] (1, where mnt(2-) = maleonitriledithiolate, C(6)-Apy(+) = 4-amino-1-hexylpyridinium) has been designed and synthesized, which has layer arrangement of anions and cations and shows two steps of magnetic transitions. The low temperature magnetic transition has an uncommon hysteresis loop, while the crystal structure investigations disclosed no structural transition with the magnetic transition. The high temperature magnetic transition exhibits two remarkable features: (1) it synchronously occurs with a crystalline-to-mesophase transition in the first heating process and (2) the structural changes that accompany the solid-mesophase transition are irreversible. A diamagnetic and isostructural compound, [C(6)-Apy][Cu(mnt)(2)], is further characterized by structure, DSC and POM techniques, which revealed also the existence of an irreversible crystalline-to-mesophase transition in the same temperature interval of [C(6)-Apy][Ni(mnt)(2)]. Therefore, the high-temperature magnetic transition in 1 is driven by release of the structural strains, but not magnetoelastic interactions. The mesophase exhibits the characteristic of smectic A phase, and the alkyl chain melting in the cation layers probably lead to the formation of mesophase. It is noticeable that the finding of a mesophase occurring in a hexyl hydrocarbon chain molecular system is in contrast to a suggested rule that at least a dodecyl chain is required. Our results will shed a light on the design and preparation of a new low-dimensional molecular system combining magnetic transition and liquid crystal properties.
No preview · Article · Mar 2011 · Dalton Transactions
[Show abstract][Hide abstract] ABSTRACT: Eight inorganic-organic hybrid compounds with a formula of [R-Bz-1-APy][PbI(3)] (R-Bz-1-APy(+) = mono-substituted benzylidene-1-aminopyridinium Schiff base derivative; R = m-CN (1), m-CH(3) (2), H (3), p-F (4), p-Cl (5), p-Br (6), o-Cl (7), o-Br (8)) have been synthesized and characterized structurally. The common characteristic of the crystal structures of 1-8 is that the inorganic components form straight and face-sharing octahedral [PbI(3)](∞) chains and the Schiff base cations surround the [PbI(3)](∞) chains to form molecular stacks. The substituent (R) on the phenyl ring of the Schiff base cation clearly influences the packing structures of 1-8, and the hybrid compound crystallizes in the space group P6(3) when R = CN (1) in the meta-position of the phenyl ring, and in a central symmetric space group when R is in the ortho- or para-position of the phenyl ring. The conformation of the Schiff base cation is related to the R position, and the dihedral angle between the phenyl and pyridyl rings increases in the order of para- < meta- < ortho-position substitution of the phenyl ring. The long molecular axis of the Schiff base cation adopts a manner approximately parallel to the straight inorganic [PbI(3)](∞) chain in the para-substituted hybrid compounds, and perpendicular to the straight inorganic [PbI(3)](∞) chain in the ortho-substituted hybrid compounds. 1 is second harmonic generation (SHG) active with a comparable response as that of urea and also exhibits ferroelectricity with larger P(s) and P(r) values; 1-8 emit multi-band luminescence in the 300-650 nm regions under the excitation of ultraviolet light.
No preview · Article · Feb 2011 · Dalton Transactions
[Show abstract][Hide abstract] ABSTRACT: Four isostructural inorganic-organic hybrid ferroelectric compounds, assembled from achiral 3-R-benzylidene-1-aminopyridiniums (R = NO(2), Br, Cl, or F for 1-4, respectively) and [PbI(3)](-) anions with the chiral Kagomé-shaped tubular aggregating architecture, show larger spontaneous polarizations.
No preview · Article · Dec 2009 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: Nitrogen-doped and pure TiO2 photocatalysts were synthesized by precipitation method using TiCl4 as titanium precursor. Both X-ray diffraction (XRD) and N-2 adsorption-desorption isotherms show that the as-prepared samples consis of anatase phase except for trace brookite phase with mesoporous structure. X-ray photoelectron spectroscopy (XPS) confirms that the Incorporated nitrogen element exists as the chemical state of NOx. The UV-Vis diffuse reflection absorption spectra (UV-Vis) reveal that the nitrogen-doped TiO2 shows a new absorption region at 400-550 nm. The photocatalytic activities of the nitrogen-doped TiO2 utilized for the photodegradation of 4-chlorophenol (4-CP) are higher than those of the pure TiO2 Under UV and visible light irradiation. The improved photocatalytic activities under UV light irradiation of the nitrogen-doped TiO2 are attributed to the presence of NOx With no influence on the energy gap of TiO2, NOx can extend the optical response of TiO2 excite more photoinduced electrons-holes for photocatalysis and reduce the recombination probabilities of carriers.
No preview · Article · May 2009 · Journal of Inorganic Materials