Generation of a Molecular Imprinted Membrane by Coating Cellulose

Article Cite This: Org. Process Res. Dev. 2018, 22, 278−285

pubs.acs.org/OPRD

Generation of a Molecular Imprinted Membrane by Coating Cellulose Acetate onto a ZrO2‑Modified Alumina Membrane for the Chiral Separation of Mandelic Acid Enantiomers Huichang Li, Qiang Huang,* Dan Li, Shujie Li, Xiaoru Wu, Longfei Wen, and Chunlan Ban School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001, P.R. China ABSTRACT: An alumina template modified with ZrO2 was coated with cellulose acetate (CA) containing imprinted molecules for a novel enantioselective membrane. The preparation, morphologies, and properties of the different membranes were introduced and investigated. The morphologies of the membranes were examined using a scanning electron microscope. The best performing CA amount in the casting solution was observed to be 15 wt %, and this was chosen as the preparation amount for the resulting membrane. (S)-(+)-Mandelic acid was used as imprinted molecules to prepare the molecular imprinted nanochannel membrane, which enhanced the permselectivity and flux compared with the traditional membrane, and the separation factor was as high as 35. And this membrane has the best separation effect on (R,S)-mandelic acid when compared with (R,S)-malic acid and (R,S)-lactic acid.

1. INTRODUCTION Mandelic acid (MA), which called α-hydroxybenzene acetic acid, is a chiral molecule (Figure 1). Obvious differences can be

This solid membrane can be prepared via molecular imprinting technology.20−23 The molecular imprinting technique (MIT) is a technique for preparation of polymer networks with selective recognition of the spatial structure of a particular molecule. The MIT has developed rapidly in recent years because of its predictability, recognizability, and practicability. So it has a good application prospect in the field of chiral separation, simulated enzyme catalysis, membrane separation, and so on. Cellulose acetate (CA) is a polysaccharide derivative which was widely used in separating and analyzing chiral samples12,24,25 because it exhibits high selectivity, easy processing, strong plasticity, and easy film formation, etc. In recent years, it has been reported that CA has been successfully incorporated into an asymmetric chiral polymer membrane, and the membrane has a selective permeation ability to trans-1,2two phenyl ethylene oxide enantiomers; however, while increasing the percentage of enantiomers excess (% e.e.), the flux decreased, suggesting a trade-off relationship. Therefore, the focus of the study is how to increase the flux and the percentage of enantiomers excess (e.e.(%)) at the same time. In this article, cellulose with imprinted molecules coated on the aluminum oxide template was studied, with the goal of increasing both enantiomers excess and flux.

Figure 1. Chemical structure of MA enantiomers.

discovered in the chiral isomers, such as physiological activity, efficacy, and toxicity. Available data shows that more than 50% of worldwide-approved drugs are chiral. Thus, an economical, practical, and convenient method for chiral separation of enantiomers is of importance. Currently, many classical approaches for the separation of racemic compounds are known,1,2 but these conventional methods have many procedural and financial shortcomings, particularly when processing small amounts of optically active compounds in a single operation.3−5 Because membrane technology has the advantages of good operability, this technology has been proved to be a robust approach for large-scale chiral separation with a good prospect.6,7 Considering the drawbacks of conventional methods and potential advantages of membrane processing, membrane technology has been an emerging technology for the chiral separation of racemic compounds.8−14 There are two types of membrane separation methods: liquid membrane separation and chiral solid membrane separation.15−18 However, liquid membrane processes have low stability and a short lifetime when tested under industrial separation conditions.5,16,19 Therefore, in recent years, a chiral solid film, called a chiral selective polymer film, has been used. © 2018 American Chemical Society

2. EXPERIMENTAL DETAILS 2.1. Materials. Cellulose acetate (CA), with an acetyl content of 54.5−56.0%, was purchased from Sinopharm Chemical Reagent Co., Ltd. and used without purification. (R,S)-Mandelic acid and (S)-(+)-mandelic acid were purchased from Heze Chenxu Chemicals Co., Ltd. (S)-(+)-Mandelic acid was used as print molecules without further purification. (R,S)Malic acid was purchased from Zhengzhou Tianshun Food Additive Co., Ltd. (R,S)-Lactic acid was purchased from Shanghai BaYuan Chemicals Co., Ltd. N,N-DimethylformaReceived: February 16, 2017 Published: January 31, 2018 278

DOI: 10.1021/acs.oprd.7b00054 Org. Process Res. Dev. 2018, 22, 278−285

Organic Process Research & Development

Article

Figure 2. Flowchart of the process for the preparation of the molecularly imprinted nanochannel membrane.

added to the solution, while rapidly stirring, resulting in the gradual formation of a transparent sol (pH = 4). The sol was stored at room temperature for 48−72 h prior to the formation of a wet sol. The alumina film was immersed in the wet sol solution, followed by ultrasound for 30 min. The saturated wet sol was subsequently placed in air for 10 min. After sonicating in pure water for 3 min to remove the impurities adsorbed onto the channel, the ZrO2-modified alumina film was placed into a vacuum drying box. 2.2.3. Preparation of a molecular imprinted nanochannel membrane. The ZrO2-modified channel membrane was immersed in acetone, followed by ultrasonication for 5 min. After rinsing with water and drying, the membrane was immersed in a cast film liquid with (S)-(+)-mandelic acid used as imprinted molecules, followed by ultrasonication for 30 min. Next, the membrane was subjected to static evaporation for 5 min for the liquid phase separation of the cast film and subsequently immersed in pure water at 10 °C, followed by washing in an ethanol aqueous solution for 24 h to remove the acetone and DMF, and the imprinted molecules were barely detectable using UV analysis (Figure 2). The final prepared film was stored in water until further use. 2.3. Permeation experiment. The prepared membrane (effective area of 7.0 cm2) was fixed in the membrane test apparatus (Figure 3) with a 100 mL capacity. A total of 50 mL of (R,S)-mandelic acid at a concentration of 10 mmol/L was used as the feed solution. The received filtrate was sealed and stored to measure rotation using an optical instrument. In this experiment, the driving force was the pressure obtained after

mide (DMF) was purchased from The Recovery of Tianjin Science And Technology Development Co., Ltd. Acetone was purchased from Luoyang Chemical Reagent Plant. Alumina template was purchased from Hefei Primeton Nano Technology Co., Ltd. with pores of 40−70 nm, 80−100 nm, and 100− 150 nm. All reagents were analytical grade and used without any further purification. The water was purified using an ultrapure water system (Simpli Lab, Millipore S.A. Molsheim, France) and subsequently used as solvent in feed solutions. A scanning electron microscope (JEOLJSM-6700F) was used to examine the morphology of the membranes. The optical rotation of the receiving liquid measured using a digital optical instrument under 20 °C ± 2 °C was purchased from Shanghai Precision Science Co., Ltd. (WZZ-1S). 2.2. Membrane preparation. 2.2.1. Preparation of cast film liquid and molecular imprinted membrane. CA was dissolved in a mixture of acetone and DMF (16/6, v/v). Different thicknesses can be formed with different concentrations of CA, followed by stirring for 24 h with (S)(+)-mandelic acid used as imprinted molecules, ultrasound for 30 min, and deforming. The ratio of imprinted molecules to CA was 1:10. Under conditions of 40% humidity and 10 °C, the resulting uniform casting film liquid was coated onto a smooth flat glass plate using a casting knife, followed by static evaporation for 5 min for the phase separation of the cast film liquid and subsequent immersion in pure water at 10 °C. The membrane was detached from the glass plate and washed in an aqueous ethanol solution for 24 h. After washing five times, until the concentrations of acetone, DMF, and the imprinted molecules were changed to 0 with the analysis of UV at the wavelength of 210 nm, the membrane was washed with pure water and stored in pure water until further use. The membrane formation of the nonimprinted molecular membrane was found using the same procedures as that for the imprinted molecular membrane. 2.2.2. Preparation of the alumina nanochannel membrane modified with zirconia. According to the literature, because of the instability of alumina film, the most promising film for the application of nanofiltration is zirconia film.26,27 Compared with Al2O3 film materials, ZrO2 film has a higher mechanical strength and better thermal and chemical stability.28,29 The alumina nanochannel film was modified with ZrO2 through the deposition of ZrO2 onto the inner wall and all the surface of the alumina film nanopore using the sol−gel template synthesis method. A sol precursor solution was prepared after mixing anhydrous ethanol and distilled water at the mass ratio of 1:1, and the solution was subsequently added to the ZrOCl2·8H2O formulated Zr+ transparent solution at a concentration of 1 mol/L. Next, H2O2 was added to the solution mixture and stirred for 30 min. Ammonia was slowly

Figure 3. Schematic diagram of the membrane cell used: (1) N2; (2) pressure release valve; (3) nut; (4) inlet of feed solution; (5) feed solution; (6) stirring bar; (7) porous plate; (8) lampstand; (9) compacting bar; (10) membrane; (11) permeate. 279



Article

adjusting the rotation of the measuring device using nitrogen. The permeation experiments were performed under 2 kgf/cm2 pressure18 at room temperature, and all membranes were only used once. 2.4. Membrane performance definitions. The flux of the aqueous mandelic acid solution was measured according to the following equation:4 Flux (mg/cm 2·min) =

Q At

(1)

where Q is the mass of the solute permeated for a given time, t is the permeation time, and A is the effective membrane area. The selective permeation of the membrane is represented as the percentage enantiomers excess [e.e.(%)], using the following equation: e. e. (%) =

CPR − CPS × 100 CPR + CPS

(2)

where CPS is the S-enantiomer concentration and CPR is the Renantiomer concentration in the permeation. The separation factor α is determined based on the upstream and downstream concentration, using the equation α = (CPS/ CPR)/(CFS/CFR), where CPR and CPS represent the concentrations of the R- and S-isomers in the permeation, respectively, and CFR and CFS represent the concentrations of R- and Sisomers in the feed solution, respectively. Because CFS and CFR are equal, the formula can be simplified as α=

CPS CPR

Figure 4. SEM images of Al2O3 film (a and b, the pore is 80−100 nm) and Al2O3 film modified with ZrO2 (c and d).

(3)

The separation of series (N) was calculated according to the equation as follows: ⎡ 1 ⎤N O. P. % = 1 − ⎢ ⎥ ⎣α⎦

(4)

where O.P.% is the optical purity to be achieved, α is the separation factor, and N is the separation of the series.

Figure 5. Results and data of the elemental analysis of the Al2O3 film modified with ZrO2 (High voltage: 20.5 kV, Pulse: 1.87 kcps).

3. RESULTS AND DISCUSSION 3.1. The morphology of the ZrO2-modified Al2O3 membrane. A scanning electron microscope (SEM) was used to characterize the top surface and the cross section of Al2O3 film before and after ZrO2 modification. To investigate the cross-section, the area of the alumina template film where ZrO2 was deposited was placed onto the vertical surface, demonstrating that the thickness of ZrO2 on the Al2O3 surface was 6.00 μm (Figure 4(c)). The membrane of the loaded ZrO2, whether from a cross section or top surface perspective, was not the same as that of the crude channel film (Figure 4(a) and (b)). The top surface was inhomogeneous, and some holes on the top surface had been covered with zirconium oxide compared with the crude channel film. 3.2. Elemental analysis. 3.2.2. Elemental analysis of the Al2O3 film channel. The chemical component was determined through elemental analysis using a large membrane (insets in Figures 5 and 6), and the results are elaborated in Figures 5 and 6 and in Tables 1 and 2. Table 1 shows that the surface of the ZrO2-modified Al2O3 film contains oxygen, aluminum, carbon, zirconium, and chlorine, with 53.76 at.%, 28.86 at.%, 15.45 at.%, 0.95 at.%, and 0.98 at.%, respectively. The carbon content on the film was high, likely reflecting the conductive adhesive under the film, which contains carbon

Figure 6. Results and data of the elemental analysis of a Al2O3 film channel modified with ZrO2 (High voltage: 20.5 kV, Pulse: 1.87 kcps).

element. Table 2 shows that the channel of the Al2O3 film contains oxygen, aluminum, carbon, zirconium, and chlorine, with 55.71 at.%, 26.67 at.%, 15.04 at.%, 1.54 at.%, and 1.03 at.%, respectively. 280



Article

Table 1. Data of the Elemental Analysis of the Top Surface El

AN

Series

Unn.[wt %]

Norm.[wt %]

Atom.[at.%]

O Al C Zr Cl

8 13 6 40 17

K-series K-series K-series L-series K-series Total:

37.00 33.51 7.98 3.73 1.49 83.72

44.20 40.02 9.54 4.45 1.79 100.00

53.76 28.86 15.45 0.95 0.98 100.00

Error (1σ) [wt %] 5.29 1.56 2.24 0.20 0.10

These results demonstrate that ZrO2 is not only loaded onto the surface but also coated in the channels of the film. 3.3. Effect of CA concentration on the morphologies and properties of the CA membrane. To demonstrate the morphology of the membranes, the surface and cross section of the membranes were characterized through SEM. Representative images are shown in Figure 7. Prior to the scanning analysis, the wet membrane was prepared and treated with propanol and heptane to retain the original structures. The surface and cross sectional structure of the film were observed on the SEM after coating with gold using an ion sputtering apparatus. As we can see in Figure 7(b, d, f) clearly, the surface has obvious holes and a homogeneous structure. As the amount of CA increased, on the one hand, the number of holes decreased, which could be described in the flux of Figure 8. On the other hand, the film thickness, which is shown on the cross section of the membrane, increased in Figure 7(a, c, e), and the film thickness is 1.69, 17.1, and 28.1 μm, respectively. To detect the effect of the CA concentration on transmission selection, membranes with three different CA concentrations in the casting solution were prepared at cellulose acetate concentrations of 10, 15, and 20 wt %, respectively. Figure 8 shows that the flux of the membrane decreased with increasing cellulose acetate concentration and test duration. This finding likely reflects the fact that the number of membrane pores decreased, indicating that the structure of the membrane became increasingly more compact with increasing CA concentration in the casting solution and the flux of the membrane decreased. Figure 9 shows that when the CA concentration was 15 wt %, the membrane exhibited the best selectivity, and when the CA concentration was 10 wt %, the membrane exhibited the worst selectivity. In Figure 10, the small gray diamond represents the chiral recognition site and the denser the number of diamonds, the more chiral recognition sites on the membrane. When the cellulose content in the casting solution was 10 wt %, after formation of the membrane, the chiral recognition sites were limited. That is, the feed solution from one chiral site was too far to reach another site (Figure 10(a)), thereby decreasing the e.e.(%). When the cellulose content in the casting solution was 15 wt %, the distance between the two chiral sites was

Figure 7. SEM images of the CA membrane prepared with 10 wt % (a and b), 15 wt % (c and d), and 20 wt % CA (e and f).

Figure 8. Flux and e.e.(%) in the enantioseparation of (R,S)-mandelic acid through CA membranes fabricated with 10, 15, and 20 wt % CA. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Table 2. Data of the Elemental Analysis of the Cross Section El

AN

Series

Unn.[wt %]

Norm.[wt %]

Atom.[at.%]

Error (1σ) [wt %]

O Al C Zr Cl

8 13 6 40 17

K-series K-series K-series L-series K-series Total:

39.47 31.87 8.00 6.22 1.62 87.17

45.27 36.55 9.18 7.14 1.86 100.00

55.71 26.67 15.04 1.54 1.03 100.00

5.2 1.6 1.9 0.3 0.1

281



Article

3.4. Effect of molecular imprinting on the morphologies and properties of molecular imprinted CA membrane. Figure 11 shows the SEM images of the top

Figure 11. SEM images of a CA membrane prepared with 15 wt % CA using molecular imprinting.

surface and cross section (22.5 μm) of the imprinted membrane (nonimprinted membranes in Figure 7). These images suggest that both the imprinted membrane and the nonimprinted membrane have the same structure, indicating that both the imprinted and nonimprinted membranes have normal infiltration membrane structures. Figure 12 shows that both the flux and e.e.(%) of cellulose membranes containing molecular imprinted molecules are

Figure 9. Separation factors in the enantioseparation of (R,S)mandelic acid through CA membranes prepared with 10, 15, and 20 wt % CA. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Figure 12. Flux and e.e.(%) in the enantioseparation of (R,S)mandelic acid through a CA membrane fabricated with 15 wt % CA using molecular imprinting. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

better than those without molecular imprinting. Several holes were formed when the imprinted molecules were gradually washed off, resulting in a higher flux than that of the ordinary CA membrane, and because the molecular imprinting increased, the number of chiral recognition sites and e.e.(%) also increased. 3.5. Effect of the pore size on the morphologies and properties of the molecular imprinted nanochannel membrane. Figure 13 shows the SEM images of channel membranes modified with zirconia and loaded at 15 wt % CA. It can be seen from the cross section, CA with imprinted molecules covers the pores of the upper surface of the alumina and the thickness of CA and the alumina template is 75.5 and 80.6 μm, respectively, so it can be proved that most of the CA is only loaded on the upper surface. The top surface of the membrane is not much different from other membranes.

Figure 10. Chiral recognition sites schematics of the membrane. a, b, and c represent CA membranes prepared with 10, 15, and 20 wt % CA, respectively.

appropriate, and the feed liquid could be sequentially identified according to each chiral recognition site (Figure 10(b)), thereby increasing the e.e.(%). However, when the cellulose content in the casting solution was 20 wt %, many chiral recognition sites were observed in the membrane and the feed solution flowed to the next chiral recognition site, having more selections, which might promote partial feed solution flow in the vertical direction or even in the opposite direction (Figure 10(c)). However, because of the relatively high recognition sites, these results were better than the findings at 10 wt %. 282



Article

Figure 13. SEM images of a channel membrane modified with zirconia and loaded with 15 wt % CA.

The separation efficiency of mandelic acid enantiomers through functionalized membrane channels obtained at different pores of 40−70 nm, 80−100 nm, and 100−150 nm was investigated. The results (Figure 14) showed that not only flux but also the separation efficiency of mandelic acid enantiomers increased with the increasing pore size.

Figure 15. Separation factors in the enantioseparation of (R,S)mandelic acid through a nanochannel membrane prepared with pores of 40−70 nm, 80−100 nm, and 100−150 nm. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Figure 14. Flux and e.e.(%) in the enantioseparation of (R,S)mandelic acid through membranes fabricated with pores of 40−70 nm, 80−100 nm, and 100−150 nm. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Figure 16. Flux and e.e.(%) in the enantioseparation of (R,S)mandelic acid through a nanochannel membrane fabricated with 110− 150 nm using molecular imprinting. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Figure 15 shows the separation factors of nanochannel membranes with different pores at an optical resolution of (R, S)-mandelic acid. The separation factors of membranes with a pore of 100−150 nm were higher than others, suggesting that the structure of membranes with large pores might promote increased CA loading, thereby increasing the chiral recognition sites and separation factors of the membrane, whereas smaller pores decrease flux and influence the diffusion selectivity. 3.6. Comparison of molecular imprinted nanochannel membrane and nonmolecular imprinted nanochannel membrane. From Figure 16 we can see that the fluxes of the molecular imprinted nanochannel membrane and the nonmolecular imprinted nanochannel membrane are roughly the same. However, the value of the enantiomers excess was higher than that of the nonmolecular imprinted nanochannel film. It is possible that the molecular imprinted nanochannel membrane has stereo spaces which are matched with the mandelic acid enantiomers, which leads to a high value of the enantiomers excess. 3.7. Recognition performance of the molecular imprinted nanochannel membrane on the target molecule. The separation efficiency of different target

molecules through functionalized aluminum oxide nanochannels obtained with a 100−150 nm pore was investigated. Figure 17 shows that different target molecules exhibited different flux and e.e.(%) values under the same conditions. The e.e.(%) values of lactic acid were roughly similar to those of mandelic acid, suggesting that the chiral recognition of a single carboxylic acid was better than that of others, as both lactic acid (Figure 18(c)) and mandelic acid (Figure 18(a)) have only one carboxylic acid group, while malic acid (Figure 18(b)) has two carboxylic acid groups, reflecting the distinction of the e.e.(%) for lactic acid and mandelic acid from those of malic acid. Mandelic acid had a higher flux through the membrane than lactic acid, likely reflecting the similar ring structures between mandelic acid and CA (Figure 18(d)), which was not available in the structure of lactic acid. Thus, the flux of mandelic acid was relatively higher than that of lactic acid. The highest flux was observed with malic acid, likely reflecting its structure. Although lactic acid and mandelic acid had similar e.e.(%), the flux of mandelic acid was relatively 283



Article

35, and after computing with formula 4 we can get the ideal optical purity of 99% with a double-stage operation.

4. COMPARISON Compared with previous studies on enantioselective membranes (Table 3), the molecular imprinted nanochannel membrane developed in the present study is more suitable for the separation of mandelic acid enantiomers, because the chiral polymer coating on the channel film of Al2O3 modified with ZrO2 increased the membrane flux while the enantiomers excess (e.e%) values have little effect when compared with previous studies in this area. 5. CONCLUSIONS A molecular imprinted nanochannel membrane was successfully incorporated using the sol−gel template synthesis method, and the membrane was characterized using SEM and other analyses. The effects of different substrates on the flux and permselectivity of the membrane was examined using aqueous solutions of (R,S)-mandelic acid, (R,S)-malic acid and (R,S)lactic acid as feed solutions. And the results showed that the membrane separation performance was optimum with mandelic acid enantiomer since structures of (R,S)-mandelic acid, (R,S)malic acid, and (R,S)-lactic acid are different. The e.e.(%) values for lactic acid and mandelic acid were distinct from that of malic acid. Notably, with a cellulose content of 15 wt %, the membrane separation performance peaked. In addition, switching from a nonmolecular imprinted cellulose acetate membrane to a molecular imprinted membrane increased both the flux and e.e.(%). Furthermore, imprinted cellulose membrane on metal oxide films with 110−150 nm wide pores exhibited a higher flux, while the e.e.(%) was not affected. Thus, this method simultaneously enhanced the permselectivity and flux of the membrane, suggesting a trade-off relationship. The experiment indicates that the molecular imprinted nanochannel membrane can separate (R,S)-mandelic acid very well.

Figure 17. Flux and e.e.(%) in target molecule through membranes fabricated with 20 wt %. The operating pressure and feed concentration were 2 kgf/cm2 and 10 mmol/L, respectively.

Figure 18. Chemical structures of the materials used in the present study.

■

larger, suggesting that the membrane works better on mandelic acid. 3.8. Design for practical applications. Due to an unmatched preponderance over traditional methods, such as low energy consumption, high operability, time saving, large processing capacity, and the possibility to be used in continuous mode, membrane separation is widely believed to be a potential approach for large-scale chiral separation, with a good application prospect. Compared with other chiral membranes, the most prominent feature of the membrane used by us in practice is large flux. Owing to the fact that one-time separation is not up to the optical purity that we need, we can carry out a series of membranes to make the enantiomers flow through each membrane in turn until they reached the ideal optical purity. The separation factor α obtained by the experiments was

AUTHOR INFORMATION

Corresponding Author

*Tel.: +86 871 67781292. E-mail addresse: Huangqwen609@ sohu.com. ORCID

Qiang Huang: 0000-0003-3496-9947 Notes

The authors declare no competing financial interest.

■

NOMENCLATURE Q = mass of the solute permeated (mg) t = permeation time (min) Flux = (mg/cm2·min) CS = S-enantiomer concentration (g/L)

Table 3. e.e.(%), Flux and Separation Factors (α) of the Membranes Generated in This and Previous Studies No.

Membrane

Isolated substance

Conc

e.e.(%)

Q (mg/cm2·min)

1 2 3 4 5 6

Cellulose acetate butyrate membrane Cellulose acetate butyrate membranes Cellulose membranes Cellulose acetate propionate/cellulose acetate Molecular imprinted cellulose membrane Molecularly imprinted nano Channel membrane

trans-stilbene oxide (R,S)-2-phenyl-1-propanol mandelic acid trans-stilbene oxide mandelic acid mandelic acid

5.2 mmol/L 15 mmol/L 0.5 mg/mL 0.5 mg/mL 10 mmol/L 10 mmol/L

96 97 93 97 92 94.5

4.563 × 10−5 5.952 × 10−5 1.587 × 10−4 1.7 × 10−4 0.01545 0.1597

284

α 38 63 25 35

Refs 30 18 31 32 (This study) (This study)



Article

(14) Zhong, L.; Gao, Y.; Li, B.; Zhang, L. Preparation of hydrophilic polysulfone porous membrane by use of amphiphilic cellulose. J. Appl. Polym. Sci. 2015, 132. (15) Yang, Q.; Chung, T. S. Modification of the commercial carrier in supported liquid membrane system to enhance lactic acid flux and to separate l,d-lactic acid enantiomers. J. Membr. Sci. 2007, 294, 127−131. (16) Yue, Y.; Jiang, X. Y.; Yu, J. G.; Tang, K. W. Enantioseparation of mandelic acid enantiomers in ionic liquid aqueous two-phase extraction systems. Chemical Papers 2014, 68, 465−471. (17) Zhao, Y.; Song, J.; Sun, J.; Yuan, X.; Guo, X. [Chiral separation of six tetralone derivative enantiomers using immobilized cellulose chiral stationary phase]. Sepu 2014, 32, 832−836. (18) Xie, S. M.; Wang, W. F.; Ai, P.; Yang, M.; Yuan, L. M. Chiral separation of (R,S)-2-phenyl-1-propanol through cellulose acetate butyrate membranes. J. Membr. Sci. 2008, 321, 293−298. (19) Yang, M.; Zhao, M.; Xie, S. M.; Yuan, L. M. Optical resolution of (R,S)-2-phenyl-1-propanol through enantioselective ethycellulose membranes. J. Appl. Polym. Sci. 2009, 112, 2516−2521. (20) Chen, J.; Liang, R. P.; Wang, X. N.; Qiu, J. D. A norepinephrine coated magnetic molecularly imprinted polymer for simultaneous multiple chiral recognition. Journal of Chromatography A 2015, 1409, 268−276. (21) Farber, S.; Green, B. S.; Domb, A. J. Selective 17-β-estradiol molecular imprinting. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 5534−5542. (22) Saifuddin, N.; Yasumira, A. A. N. Microwave Enhanced Synthesis of Chitosan-graft Molecularly Imprinted Polymer (MIP) for Selective Extraction of Antioxidants. E-J. Chem. 2010, 7, 1362− 1374. (23) Whitcombe, M. J.; Kirsch, N.; Nicholls, I. A. Molecular imprinting science and technology: A survey of the literature for the years 2004−2011. J. Mol. Recognit. 2014, 27, 297−401. (24) Nguyen, T. P. N.; Yun, E. T.; Kim, I. C.; Kwon, Y. N. Preparation of cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis. J. Membr. Sci. 2013, 433, 49−59. (25) Yang, Z. Y.; Wang, W. J.; Shao, Z. Q.; Zhu, H. D.; Li, Y. H.; Wang, F. J. The transparency and mechanical properties of cellulose acetate nanocomposites using cellulose nanowhiskers as fillers. Cellulose 2013, 20, 159−168. (26) Gao, N.; Li, M.; Jing, W.; Fan, Y.; Xu, N. Improving the filtration performance of ZrO2 membrane in non-polar organic solvents by surface hydrophobic modification. J. Membr. Sci. 2011, 375, 276−283. (27) Maximous, N.; Nakhla, G.; Wan, W.; Wong, K. Performance of a novel ZrO 2 /PES membrane for wastewater filtration. J. Membr. Sci. 2010, 352, 222−230. (28) Salahi, E.; Esfahani, H.; Mobasherpour, I.; Bijarchi, M. A.; Taheri, M. Sintering behavior and mechanical properties of alumina/ zirconia multilayers composite via nano-powder processing. Ceram. Int. 2014, 40, 2717−2722. (29) Pulgarin, H. L. C.; Albano, M. P. Sintering, microstrusture and hardness of different alumina−zirconia composites. Ceram. Int. 2014, 40, 5289−5298. (30) Blachechen, L. S.; Mesquita, J. P. D.; Paula, E. L. D.; Pereira, F. V.; Petri, D. F. S. Interplay of colloidal stability of cellulose nanocrystals and their dispersibility in cellulose acetate butyrate matrix. Cellulose 2013, 20, 1329−1342. (31) Ma, C.; Xu, X. L.; Ai, P.; Xie, S. M.; Lv, Y. C.; Shan, H. Q.; Yuan, L. M. Chiral separation of D,L-mandelic acid through cellulose membranes. Chirality 2011, 23, 379−382. (32) Flores-López, L. Z.; Caloca, J.; Rogel-Hernández, E.; EspinozaGomez, H. Development of an enantioselective membrane from cellulose acetate propionate/cellulose acetate, for the separation of trans-stilbene oxide. Cellulose 2014, 21, 1987−1995.

CR = R-enantiomer concentration (g/L) AS = S-enantiomer peak area (%) AR = R-enantiomer peak area (%) α = separation factor CFR = feed concentrations of R-isomer (g/L) CFS = f concentrations of S-isomer (g/L) Phrase Explanation

Flux: liquid volume of a nanoscale membrane which was flowed through within a unit area per unit time that reflects the transport strength of the membrane. Separation efficiency: the ratio of (S)-mandelic acid to racemate during a membrane separation which reflects the output rate of (S)-mandelic acid C −C Enantiomers excess [e.e.(%)]: e. e. (%) = CPR + CPS × 100 PR

PS

Alumina nanochannel film: longitudinal make of which channels with different diameters on the aluminum oxide membrane, and the membrane is a merchandise Separation factor α: α = (CPS/CPR)/(CFS/CFR), the greater α, the better selectivity Raceme: an equimolar mixture of levorotatory molecule and dextrorotatory molecule

■

REFERENCES

(1) Hatanaka, M.; Nishioka, Y.; Yoshikawa, M. Chiral Separation with Polyurea Membrane Consisting of L-Lysinyl Residue: Proposal of Facile Method for Prediction of Permselectivity. J. Appl. Polym. Sci. 2013, 128, 123−131. (2) Son, S. H.; Jegal, J. Chiral separation of D,L-serine racemate using a molecularly imprinted polymer composite membrane. J. Appl. Polym. Sci. 2007, 104, 1866−1872. (3) Stancu, A. D.; Hillebrand, M.; Tablet, C.; Mutihac, L. βCyclodextrin derivative as chiral carrier in membrane transport of some aromatic amino acids. J. Inclusion Phenom. Macrocyclic Chem. 2014, 78, 71−76. (4) Xiong, W. W.; Wang, W. F.; Li, Z.; Song, Q.; Yuan, L. M. Chiral separation of (R,S)-2-phenyl-1-propanol through glutaraldehyde-crosslinked chitosan membranes. J. Membr. Sci. 2009, 328, 268−272. (5) Zhong, T. S.; Yin, Z. F.; Liu, Y.; Huang, S. S. Chiral Separation and Identification of D,L-Histidine Based on Nanochannels Membrane Coupling with Surface Enhanced Raman Scattering Spectroscopy. Chin. J. Anal. Chem. 2015, 11, 1695−1700. (6) Wang, H. D.; Rui, X.; Niu, C. H.; Hang, S.; Mei, Y.; Shuai, L.; Chu, L. Y. Chitosan chiral ligand exchange membranes for sorption resolution of amino acids. Chem. Eng. Sci. 2009, 64, 1462−1473. (7) Kwon, H. T.; Jeong, H. K. Improving propylene/propane separation performance of Zeolitic-Imidazolate framework ZIF-8 Membranes. Chem. Eng. Sci. 2015, 124, 20−26. (8) Hadik, P.; Szabó, L. P.; Nagy, E.; Farkas, Z. Enantioseparation of d,l-lactic acid by membrane techniques. J. Membr. Sci. 2005, 251, 223− 232. (9) Ingole, P. G.; Bajaj, H. C.; Singh, K. Preparation of Enantioselective Membranes for Optical Resolution of Chiral Compounds. Procedia Eng. 2012, 44, 358−360. (10) Zhao, M.; Xu, X. L.; Jiang, Y. D.; Sun, W. Z.; Wang, W. F.; Yuan, L. M. Enantioseparation of trans-stilbene oxide using a cellulose acetate membrane. J. Membr. Sci. 2009, 336, 149−153. (11) Sueyoshi, Y.; Fukushima, C.; Yoshikawa, M. Molecularly imprinted nanofiber membranes from cellulose acetate aimed for chiral separation. J. Membr. Sci. 2010, 357, 90−97. (12) Xu, X.; Chemistry, D. O.; University, Q. N. Enantiomeric separation of(R,S)- mandelic acid using cellulose acetate membrane. Ind. Technol. Innovation 2014, 2, 192−196. (13) Yang, Z. G.; Zhen liang, X. U.; Wang, X. J. Study on the Separation of Ethanol/Water Using L-DBTA Molecular Imprinted Composite Membranes. Polymer Materials Science & Engineering 2006, 22, 220−224. 285


Generation of a Molecular Imprinted Membrane by Coating Cellulose

Recommend Documents