Optical resolution of <img src='/image/spc_char/alpha.gif' border=0>-amino acid derivative through membrane process

197-206The present study deals with preparation, characterization and performance of chiral selective composite membrane. The reported membranes are prepared by forming the chiral selective layer on polysulfone (PS) microporous membrane. The chiral selective layer is prepared in-situ on PS membrane by co-polymerization of dibasic amino acid (lysine) and piperazine with trimesoyl chloride. The membranes are characterized by ATR-FTIR spectroscopy and scanning electron microscopy (SEM). The membrane performance is determined by performing optical resolution of racemic lysine monohydrochloride in pressure driven transport. The influence of concentration and ratio of monomers in co-polymerization on the membrane flux, separation and enantioseparation is observed. The observation indicates that membranes perform enantioseparation achieving >95% enantiomeric excess (%ee) for D-lysine hydrochloride in permeate. The composite membrane prepared with equal proportions of L-lysine and piperazine exhibited highest %ee with reasonable flux of D-lysine hydrochloride (4.03 gm-2h-1 at 1034.21 kPa). High enantiomeric excess is obtained with feed solutions of low concentration

Enantiomeric separation of α-amino acids by imprinted terpolymer membrane

In this work, molecularly imprinted polymer membrane (d-arginine (Arg) imprinted terpolymer P(AN-co-AA-co-AAm) membrane) was prepared by the wet phase inversion method. Acrylamide (AAm) and acrylic acid (AA) were used as the functional monomers and acrylonitrile (AN) was used as a cross linker. The removal of template molecules from the membrane matrix increased the number of free –COOH groups and reduced dimerized –COOH groups, which is an indirect evidence of the formation of recognition sites. Optical resolution was performed in ultrafiltration cell using aqueous solutions of racemic mixtures of α-amino acids (arginine and asparagine). The imprinted membrane permeated d-enantiomers preferentially achieving 93% and 72% enantiomeric excess for d-arginine and d-asparagine, respectively

A Novel Approach for the Development of Low-Cost Polymeric Thin-Film Nanocomposite Membranes for the Biomacromolecule Separation

The separation of biomacromolecules, mainly proteins, plays a significant role in the pharmaceutical and food industries. Among the membranes’ techniques, thin-film nanocomposite nanofiltration membranes are the best choice due to their high energy efficiency, excellent productivity, cost-effective and tuneable properties that have captured the attention of the efficient separation of biomacromolecules, especially from the industrial perspective. The present work directs the efficient separation study of proteins, namely, lysozyme, trypsin, pepsin, bovine serum albumin (BSA), and cephalexin, using a thin-film nanocomposite membrane integrated with Arg-MMT (arginine-montmorillonite) clay nanoparticles. The surface morphology and cross-section images of the TFN membranes were studied using a field emission scanning electron microscope (FE-SEM) and a high-resolution transmission electron microscope (HR-TEM). The thermal stability and hydrophilicity of the membranes were examined using thermogravimetric analysis (TGA) and contact angle, respectively. The surface chemistry of the selective layer has different functional groups that were analyzed using FTIR spectroscopy. The performance of the membranes was studied at different trans-membrane pressures and permeation times. The effect of monomer concentration on the separation performance of the membranes was also studied at different permeation times. The membranes’ antibacterial activity was evaluated using the Muller–Hinton disk diffusion method using gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) bacteria. The highest rejection was achieved for BSA up to 98.92 ± 1%, and the highest permeation was obtained against lysozyme feed solution up to 26 L m–2 h–1 at 5 bar pressure. The membrane also illustrated excellent rejection of cephalexin antibiotics with a rejection of 98.17 ± 1.75% and a permeation flux of 26.14 L m–2 h–1. The antifouling study performed for the membranes exhibited a flux recovery ratio of 86.48%. The fabricated thin-film nanocomposite membrane demonstrated a good alternative for the separation of biomacromolecules and has the potential to be used in different sectors of industry, especially the pharmaceutical and food industry

Water vapor transport properties of interfacially polymerized thin film nanocomposite membranes modified with graphene oxide and GO-TiO2 nanofillers

Graphene oxide (GO) and its composite with TiO2 (GT) were utilized as nano-filler materials to prepare highly permeable and water vapor selective nanocomposite membranes. The nano-fillers were characterized using different analytical tools to determine their physicochemical properties. Nanocomposite membranes were prepared by dispersing the nano-fillers in aqueous phase monomer solution for interfacial polymerization reaction on the inner surface of Polysulfone hollow fiber membrane. Surface morphology and bonding chemistry of the nanocomposite membrane was analyzed using various analytical tools. The two types of nano-fillers were compared for their compatibility with the polyamide matrix, and consequently, the water vapor separation performance of the resulting membrane. Results revealed that both the nano-fillers are firmly attached to the polyamide layer via hydrogen and covalent bonds. GT based membranes have higher surface roughness and better hydrophilicity as compared to GO. In addition, GT membranes have more carboxyl groups and lesser degree of cross-linking due to the interference with interfacial polymerization reaction. This leads to a higher permeance (2820 GPU) and a water vapor/nitrogen selectivity when compared to other TFN membranes reported in literature. The nano-fillers act as active sites for preferential transport of water vapor molecules through the membrane thereby, significantly improving water vapor permeance

Development of Antifouling Thin-Film Composite/Nanocomposite Membranes for Removal of Phosphate and Malachite Green Dye

Nowadays polymer-based thin film nanocomposite (TFN) membrane technologies are showing key interest to improve the separation properties. TFN membranes are well known in diverse fields but developing highly improved TFN membranes for the removal of low concentration solutions is the main challenge for the researchers. Application of functional nanomaterials, incorporated in TFN membranes provides better performance as permeance and selectivity. The polymer membrane-based separation process plays an important role in the chemical industry for the isolation of products and recovery of different important types of reactants. Due to the reduction in investment, less operating costs and safety issues membrane methods are mainly used for the separation process. Membranes do good separation of dyes and ions, yet their separation efficiency is challenged when the impurity is in low concentration. Herewith, we have developed, UiO-66-NH2 incorporated TFN membranes through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) for separating malachite green dye and phosphate from water in their low concentration. A comparative study between thin-film composite (TFC) and TFN has been carried out to comprehend the benefit of loading nanoparticles. To provide mechanical strength to the polyamide layer ultra-porous polysulfone support was made through phase inversion. As a result, outstanding separation values of malachite green (MG) 91.90 &plusmn; 3% rejection with 13.32 &plusmn; 0.6 Lm&minus;2h&minus;1 flux and phosphate 78.36 &plusmn; 3% rejection with 22.22 &plusmn; 1.1 Lm&minus;2h&minus;1 flux by TFN membrane were obtained. The antifouling tendency of the membranes was examined by using bovine serum albumin (BSA)-mixed feed and deionized water, the study showed a good ~84% antifouling tendency of TFN membrane with a small ~14% irreversible fouling. Membrane&rsquo;s antibacterial test against E. coli. and S. aureus. also revealed that the TFN membrane possesses antibacterial activity as well. We believe that the present work is an approach to obtaining good results from the membranes under tricky conditions