Electro‐membrane process for the separation of amino acids by iso‐electric focusing

BACKGROUND: Amino acids (AAs) are usually produced commercially using chemical, biochemical and microbiological fermentation methods. The product obtained from these methods undergoes various treatments involving extraction and electrodialysis (ED) for salt removal and AA recovery. This paper describes an electro‐membrane process (EMP) for the charge based separation of amino acids. RESULTS: Iso‐electric separation of AAs (GLU–LYS) from their mixture, using ion‐ exchange membranes (IEMs) has been achieved by an efficient and indigenous EMP. It was observed that electro‐transport rate (flux) of glutamic acid (GLU) at pH 8.0 (above its pI) was extremely high, while that for lysine (LYS) (pH 9.6) across the anion‐exchange membrane (AEM) was very low, under similar experimental conditions. Under optimum experimental conditions, separation of GLU from GLU–LYS mixture was achieved with moderate energy consumption (12.9 kWh kg^?1), high current efficiency (CE) (65%) and 85% recovery of GLU. CONCLUSIONS: On the basis of the electro‐transport rate of AA and membrane selectivity, it was concluded that the separation of GLU–LYS mixture was possible at pH 8.0, because of the oppositely charged nature of the two amino acids due to their different pI values. Moreover, any type of membrane fouling and deterioration in membrane conductivity was ruled out under experimental conditions. This work clearly demonstrates the great potential of EMP for industrial applications. Copyright © 2010 Society of Chemical Industry     

Comparative Studies on Electro-Membrane Processes for Recovery of Ascorbic Acid from its Sodium Salt

This article presents an efficient electro-membrane reactor with three compartments (EMR-3) for in situ ion substitution and recovery of ascorbic acid (ASH) from its sodium salt (ASNa). In situ ion substitution, separation, and recovery of ASH from ASNa were achieved by EMR–3 using the ion-exchange membranes (cation-exchange membranes: CEMs), based on the principle of electro-electrodialysis. Process performances of EMR–3 and electrodialysis (ED) were compared. Under optimum operating conditions for EMR–3 at 3.0 V cm^?1 applied voltage (after passage of 3.41 × 10³ Coulombs), current efficiency (CE), and energy consumption (W) were found to be 94.3% and 2.63 kWh kg^?1, respectively, corresponding to 95% recovery of ASH. While by ED, under the similar experimental conditions, CE and W were found to be 59.1% and 5.44 kWh kg^?1, respectively corresponding to 86.3% recovery of ASH. It was concluded that EMR–3 showed high CE, recovery, and low W, in comparison with ED under similar experimental conditions. Thus the proposed EMR–3 is an efficient alternate for producing ASH from ASNa in an by economical and environmentally-friendly manner. Also, the production of NaOH in cathode stream is a spinoff of EMR–3.     

A robust mixed‐conducting multichannel hollow fiber membrane reactor

To accelerate the commercial application of mixed‐conducting membrane reactor for catalytic reaction processes, a robust mixed‐conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction‐tolerant and CO₂‐stable SrFe_0.8Nb_0.2O_3‐δ (SFN) oxide not only possesses a good mechanical strength but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 mL min^?1 cm^?2, hydrogen production rate of 54.7 mL min^?1 cm^?2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2592–2599, 2015     

DNA adsorption on a poly‐L‐lysine‐immobilized poly(2‐hydroxyethyl methacrylate) membrane

The DNA adsorption properties of poly‐L ‐lysine‐immobilized poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane were investigated. The pHEMA membrane was prepared by UV‐initiated photopolymerization and activated with epichlorohydrin. Poly‐L ‐lysine was then immobilized on the activated pHEMA membrane by covalent bonding, via a direct chemical reaction between the amino group of poly‐L ‐lysine and the epoxy group of pHEMA. The poly‐L ‐lysine content of the membrane was determined as 1537 mg m^?2. The poly‐L ‐lysine‐immobilized membrane was utilized as an adsorbent in DNA adsorption experiments. The maximum adsorption of DNA on the poly‐L ‐lysine‐immobilized pHEMA membrane was observed at 4 °C from phosphate‐buffered salt solution (pH 7.4, 0.1 M; NaCl 0.5 M) containing different amounts of DNA. The non‐specific adsorption of DNA on the plain pHEMA membrane was low (about 263 mg m^?2). Higher DNA adsorption values (up to 5849 mg m^?2) were obtained in which the poly‐L ‐lysine‐immobilized pHEMA membrane was used. Copyright © 2003 Society of Chemical Industry     

Electro-membrane reactor for separation and in situ ion substitution of glutamic acid from its sodium salt

An electro-membrane reactor with four compartments (EMR-4) (anolyte, catholyte and comp. 1 and 2) based on in-house-prepared cation- and anion-exchange membrane (CEM and AEM, respectively) was developed to achieve separation and recovery of glutamic acid (GAH) from its sodium salt by in situ ion substitution and acidification. The physicochemical and electrochemical properties of CEM and AEM were characterized and its suitability was assessed in operating environment. The separation of GA⁻ from the mixture of nonionic organic compounds and further ion substitution was achieved by EMR-4. But the higher energy consumption (5.75 kWh/kg of GAH produced), low current efficiency (50.5%) and recovery of GAH (57.2%) in this process were main obstacles for the industrial exploration of the process. Latter, electro-membrane reactor with three compartments (EMR-3) (anolyte, catholyte and central compartment) was developed based on CEMs for only in situ ion substitution of GANa to achieve GAH, in which GA⁻ was not allowed for electro-migration from its feed compartment. CE and recovery of GAH were close to 73% and 96% that indicate the suitability of the EMR-3 process for industrial application over the EMR-4. It was concluded that EMR-3 was efficient as compared to EMR-4 for separation and recovery of GAH from fermentation broth by in situ ion substitution in eco-friendly manner.     

A novel porous‐dense dual‐layer composite membrane reactor with long‐term stability

A porous‐dense dual‐layer composite membrane reactor was proposed. The dual‐layer composite membrane composed of dense 0.5 wt % Nb₂O₅‐doped SrCo_0.8Fe_0.2O_3‐δ (SCFNb) layer and porous Ba_0.3Sr_0.7Fe_0.9Mo_0.1O_3‐δ (BSFM) layer was prepared. The stability of SCFNb membrane reactor was improved significantly by the porous‐dense dual‐layer design philosophy. The porous BSFM surface‐coating layer can effectively reduce the corrosion of the reducing atmosphere to the membrane, whereas the dense SCFNb layer permeated oxygen effectively. Compared with single‐layer dense SCFNb membrane reactor, no degradation of performance was observed in the dual‐layer membrane reactor under partial oxidation of methane during continuously operating for 1500 h at 850°C. At 900°C, oxygen flux of 18.6 mL (STP: Standard Temperature and Pressure) cm^?2 min^?1, hydrogen production of 53.67 mL (STP) cm^?2 min^?1, CH₄ conversion of 99.34% and CO selectivity of about 94% were achieved. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4355–4363, 2013     

Partial Oxidation of Methane to Syngas in a Packed Bed Catalyst Membrane Reactor

The planar membrane reactor configuration was explored for partial oxidation of methane (POM) to syngas. A supported membrane composed of yttria‐stabilized zirconia and La_0.8Sr_0.2Cr_0.5Fe_0.5O_3‐δ was sealed to a stainless holder, and a Ni/Al₂O₃ catalyst bed was placed under the membrane plane with a small slit between them. This reactor configuration would facilitate the POM reaction via oxidation‐reforming mechanism: the oxidation reaction occurring at the membrane surface and the reforming reaction taking place in the catalyst bed. At 800°C and a methane feed rate of 32 mL min^?1, the reactor attained methane throughput conversion over 90%, CO and H₂ selectivity both over 95%, and an equivalent oxygen permeation rate 1.4 mL cm^?2 min^?1. The membrane and catalyst remained intact after the POM testing. The planar membrane reactor configuration explored in this study may lead to the development of a compact reactor for syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2170–2176, 2016     

Fabrication of a novel polyhedral oligomeric silsesquioxanes/polyether‐block‐amide nano‐hybrid membrane for pervaporative separation of model fuel butanol

The present study reports the pervaporative separation capability of the pristine and polyhedral oligomeric silsesquioxanes (POSS) loaded hybrid polyether‐block ‐amide (PEBA) membranes for n ‐butanol recovery from the dilute n ‐butanol–water mixtures. It is the first study to produce POSS‐loaded PEBA membranes for n ‐butanol recovery. The morphology and crosslinking structure of the pristine and hybrid membrane were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The thermal stability and crystallization behaviors of the pristine and hybrid membranes were investigated using thermogravimetric analysis and differential scanning calorimetry methods. Swelling experiments were also done to determine the affinity of the membranes to the n ‐butanol–water mixture. The effect of increasing amount of POSS on pervaporation performance was investigated in terms of flux and the n ‐butanol separation factor at 40 °C and a given n ‐butanol. All the hybrid membranes exhibited high flux and n ‐butanol separation factor than that of the pristine PEBA membrane. The best n ‐butanol separation factor of 27.2 was obtained accompanied with 1.33 Kg m^?2 h^?1 of flux, when the POSS amount was 4 wt %. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45211.     

High‐rate hydrogen separation using an MIEC oxygen permeable membrane reactor

In this study, we propose using mixed ionic‐electronic conducting (MIEC) oxygen permeable membrane to separate hydrogen via the water splitting reaction. To do that, steam was fed to one side of the membrane (side I) and a low‐purity hydrogen was fed to the other side (side II). Oxygen from water splitting on side I permeates through the membrane driven by an oxygen chemical potential gradient across the membrane to react with the low‐purity hydrogen on side II. After condensation and drying, high‐purity hydrogen is acquired from side I. Thus, the hydrogen separation process is realized based on the fact that the low‐purity hydrogen is consumed and high‐purity hydrogen is acquired. We achieved a high hydrogen separation rate (13.5 mL cm^?2 min^?1) at 950°C in a reactor equipped with a 0.5‐mm‐thick Ba_0.98Ce_0.05Fe_0.95O_3‐δ membrane. This research proofed that it is feasible to upgrade hydrogen purity using an MIEC oxygen permeable membrane. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1278–1286, 2017     

Lysine Adsorption on Cation Exchange Resin. IV. Temperature Effects on Equilibrium and Kinetics in Batch and Column Systems

Abstract

Ion exchange equilibria and kinetics are determined for lysine adsorption on the strong acid cation exchanger DIAION SK‐1B at temperatures of 25, 40, and 60°C. The ion exchange equilibrium is found to be independent of temperature. Conversely, the kinetics of ion exchange increases dramatically as the temperature is increased. Average ion exchange selectivity coefficients of 6.0 g/cm³ and 0.52 are obtained for the ion exchange of divalent and monovalent cationic lysine with hydrogen ion, respectively. Resin phase diffusivities are determined by fitting batch binary ion‐exchange data with a mass transfer model based on the Nernst‐Planck equations. As the temperature is increased from 25 to 60°C, the resin phase diffusivity increases from 0.04×10^?6 to 0.14×10^?6 cm²/s for divalent lysine and from 0.16×10^?6 to 0.55×10^?6 cm²/s for monovalent lysine. The combination of temperature‐independent ion exchange equilibria and faster mass transfer at higher temperatures results in higher dynamic binding capacity and more efficient desorption of lysine when ion exchange is operated at an elevated temperature. This behavior is confirmed by means of column adsorption/desorption experiments whose results are found to be in agreement with a model incorporating the equilibrium and mass transfer data obtained in this work.