Extraction Process of Amino Acids with Deep Eutectic Solvents-Based

Subscriber access provided by - Access paid by the | UCSB Libraries

Separations

Extraction Process of Amino Acids with Deep Eutectic Solvents Based Supported Liquid Membranes Zhuo Li, Yingna Cui, Yongming Shen, and Changping Li Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 08 Mar 2018 Downloaded from http://pubs.acs.org on March 8, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Extraction Process of Amino Acids with Deep Eutectic Solvents Based Supported Liquid Membranes

Zhuo Li, † Yingna Cui,‡ Yongming Shen, § Changping Li * , †

† School of Ecological Environment and Civil Engineering, Dongguan University of Technology, Dongguan, 523808, China ‡ College of Chemical Engineering and Environment, Dalian University, Dalian, 116622, China §State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China

ABSTRACT: Separation and purification process of amino acids (AAs) accounts for 80% of the total production cost. So the development of new technology for the separation and purification of AAs is very important. In this research, supported liquid membranes (SLMs) based on deep eutectic solvents (DESs) was successfully applied for the extraction of AAs. Series of DESs were designed, synthesized and screened to get the suitable ones as supported phase. Some important factors, such as effect of types of DESs and membranes, pH and concentration of Trp were investigated. Higher extraction efficiency was achieved. ChCl/PTS was found to be the most efficient one. Results show that the initial concentration of Trp in feed phase is 0.1 mM, and pH=1.0 in feed phase and pH=13.0 in receiving phase is optimal for

ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

extraction, under which the extraction efficiency can reach 86.1%. ChCl/PTS/Asp (1/4/1) of SLM has the best stability, the weight loss of SLM is 0.38%. Finally, 1H NMR shows that the hydrogen bonding interaction between DESs and Trp is probably the main driven force for this specific process. This research would provide a new process for the separation and purification of AAs with SILMs technique. 1.

INTRODUCTION

Amino acids (AAs) are the basic unit of peptides, proteins, enzymes and biological macromolecules. They are very important in metabolism process and other physiological activities. AAs are widely used in food additives, pharmaceuticals and animal feeds. Furthermore, they can also be used as intermediates in the synthesis process, such as low calories sweeteners, chelating agent and polypeptide.1 However, compared to the fast development of the its production process, the separation and purification process has been lost. Traditional technologies, such as ion exchange, adsorption, crystallization, and extraction etc., were most adopted for the separation and purification of AAs.2 Especially, the ion exchange process is widely used as industrial separation process. But there still exist some problems, such as high cost of extraction process and serious environment pollution. 3 So the development of new technologies for the separation and purification of AAs can be urgent. Extraction based on supported liquid membranes (SLMs) has been widely studied during the past few years.4-9 The extraction and back-extraction can be realized on both sides of the SLMs at the same time, which can reduce the use of extraction solvents and consumption of energy greatly. Generally, SLMs system is composed of


Page 2 of 42

Page 3 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


three parts: the feed phase, SLMs and the receiving phase. The supported phase in SLMs is the most important one that determine the extraction process of SLMs. SLMs extraction has attracted great attention for its low cost, high extraction efficiency and simple operation process.10 However, there are still some problems posed by traditional supported phase of SLMs because of the use of traditional volatile organic compounds (VOCs). At the same time, its low stability and extraction efficiency have constrained its industrial application.11 Therefore, it can be of great significance to develop stable and green supported solvents for the realization of green separation process based on SLMs. As ionic liquids (ILs) analogues, deep eutectic solvents (DESs) are a new type of solvents that provide a new opportunity for the development of green solvents. DESs refers to the eutectic substance composed of two or three cheap, green components, namely hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), in combination with each other through hydrogen bond formation. Compared with the ionic liquids, it not only shares the advantages of ionic liquids, such as high chemical stability, low vapor pressure and designability etc. At the same time, it also pose many advantages such as its cheap and easily obtained raw materials, green and simple synthesis process without introducing other organic solvents. Therefore, DESs and ILs are considered equally important alternative to VOCs as green solvents.12-16 In recent years, DESs have been widely used in catalysis,17,18 organic synthesis,19 materials preparation,20 electrochemistry,21 substance dissolution,22,23 separation process24,25 etc. Furthermore, DESs can receive or give electron or proton to form



hydrogen bonds. Therefore, it has good dissolution capability for many substances. So it has great potential to be applied in separation process. However, compared with the wide application of ILs in separation process, research on DESs in separation process is just at the beginning. Only few studies have focused on the separation of glycerol24-27 and phenol in biodiesel,28,29 separation of cellulose30 and CO2 adsorption.31 Nevertheless, up to now, the applications of DESs in SLMs extraction process has not been reported in literatures. During the past few years, we have been committed to the separation process with ionic liquids32,33 and DESs,34 especially the extraction of AAs.32,33 And higher extraction efficiencies more than 99% were obtained with amide based fuctionalized ionic liquids (FILs). So this inspires us to design new solvents combined with the SLMs process to optimize its extraction process. Our previous research shows that hydrogen bond formed between the AAs and FILs are the main driven force of the SLMs extraction process for AAs. How to design and synthesize more efficient and economic greener solvents can be of great importance. Compared with the ionic liquids, DESs are more suitable for the above criterions because of low cost, greener property and “potential” high efficiency. This inspires us to investigate the extraction of AAs with SLMs based on DESs systematically. In this research, choline chloride (ChCl), tetrabutyl ammonium chloride (TBAC) were chosen as typical HBA, and malonic acid (MA), tetraethylene glycerol (TEG), polyethylene glycol (PEG), propionate (Pr), p-toluenesulfonic acid (PTS), L-Threonine (Thr), Glycine (Gly), L-Valine(Val), DL-Aspartic acid (Asp) as HBD,


Page 4 of 42

Page 5 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and series of DESs were designed and synthesized, which were shown in Figure 1. Some amino acids, including Glutamic acid (Glu), Val, Asp, Gly, Thr, Histidine (His), Asparagine (Asn), Tyrosine (Tyr), Arginine (Arg), Phenylalanine (Phe), Tryptophan (Trp), were chosen as typical ones to perfect the extraction process. In preliminary experiments, some important factors that influence extraction process were optimized, such as operation time, initial concentration of Trp and stirring speed etc. Then the above synthesized DESs was used as supported phase in SLMs process to investigate the extraction of Trp. At the same time, series of porous membrane were also selected. After selection, the extraction process was optimized with DES choline chloride/p-toluenesulfonic acid (ChCl/PTS). Important factors, such as pH of feed and receiving phase and the stability of SLMs were investigated. The stability of SLM was greatly improved through design. Finally, the SLMs were characterized with scanning electron microscope (SEM). And its extraction mechanisms were probed in detail with 1H NMR. And the possible SLMs extraction process was illustrated. 2. EXPERIMENTAL SECTION 2.1. Synthesis Process of DESs. DESs used in this study were synthesized through the following procedures. Quaternary ammonium salts were chosen as HBA and some typical organic acids or alcohols were chosen as HBD. Synthesis process was carried out in a round-bottomed flask. Raw materials were purified and dried before use. Then HBA and HBD were mixed at a certain molar ratio (from 1:1 to 1:5). After two compositions become liquid with heating, then the system was stirred vigorously with a magnetic stirrer at certain temperature, ranging from 80 ℃ to 130 ℃. The reaction



process would be about 3～5 hours. With the above process, TBAC/Pr (1/2), TBAC/Pr (1/1), TBAC/PEG (1/2), TBAC/PTS (1/2), ChCl/TEG (1/2), ChCl/Pr (1/2), ChCl/MA (1/1), ChCl/PTS (1/2), ChCl/PTS/Thr (1/2/2), ChCl/PTS/Gly (1/2/2), ChCl/PTS/Val (1/2/2), ChCl/PTS/Asp (1/2/2), ChCl/PTS/PEG (1/2/2), ChCl/PTS/Asp (1/2/0.5), ChCl/PTS/Asp (1/3/2), ChCl/PTS/Asp (1/4/2), ChCl/PTS/Asp (1/5/2), ChCl/PTS/Asp (1/4/1), ChCl/PTS/Asp (1/4/0.5) were synthesized. Finally, the structures and purity of DESs were characterized by using 1H NMR, shown in Figure S1～Figure S14. The synthesis route was summarized in Figure 2. 2.2. Preparation of Supported Liquid Membranes. Porous membranes Nitrocellulose (NC), Poly(vinylidene fluoride) (PVDF) used in study were provided by Millipore Corporation (Shanghai, China), Poly(tetrafluoroethylene) (PTFE), mixed cellulose (MCE), Poly(ether sulfones) (PES) and Nylon (N66) were available from Anow Corporation (Hangzhou, China). Membranes PVDF and PTFE are hydrophobic ones, while MCE, NC, N66 and PES are hydrophilic ones. The size of porous membranes used in this study is 0.45 µm and 80% porosity. The following procedure was used to prepare SLMs. The surface of the membrane was smeared with DESs evenly. Then it was soaked in the DESs with a Petri dish for 24 h. After the above process, the membrane was wiped using filter paper and washed with deionied water to remove the excessive DESs remaining left on the membrane surface, and then dried for 12 h. After all these done, the membrane was weighed. Morphologies of the SLMs were characterized with SEM. 2.3. Separation Process. Separation process was carried out with our own


Page 6 of 42

Page 7 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


designed equipment, and its schematic diagram was shown in Figure 3. It consists of two independent quartz diffusion cells with 120 mL volume each. The prepared SLMs with DESs were sandwiched between the two cells by applying grease in the bushings to prevent leakage and bushings sliding. The membrane contact area between the quartz cells is 5.0 cm2. HCl solution (pH=1.0±0.1) was used to adjust the pH of feed phase. NaOH solution (pH=13.0±0.1) was used to adjust the pH of receiving phase. The initial concentration of Trp in feed phase was 0.1 mM which was adjusted to pH=1, and the receiving phase was adjusted to pH=13 except for otherwise defined. Both the feed and receiving phases were stirred at 400 rpm throughout the experiment. After the extraction process was done, the membrane was dried in the drying oven for 2 h. Then weighed and its weight was recorded. All experiments were carried out in triplicates and the standard deviation of extraction efficiency is less than ± 5%. 2.4. Analytical Methods. The absorbance of the Trp solution in the feed and receiving phases were measured using a UV-visible spectrophotometer at 278 nm, and the concentrations of Trp were determined by the standard curve, shown in Figure S15. The samples were obtained by sampling (0.3 mL) from each phase at regular time intervals of 1 h during a period of 4 h. The extraction efficiency of Trp based supported liquid membrane system was obtained by the following Eq. (1). 3. RESULTS AND DISCUSSION 3.1. Selection of Amino Acids. To investigate the selectivity of amino acids with the above mentioned deep eutectic solvents, eleven typical AAs were chosen as separation samples. From the results, tryptophan gets the highest extraction efficiency



(Figure 4). The sequence of extraction efficiencies are listed as follows: Trp>Phe>Arg> Tyr>Asn>His>Thr>Gly>Asp>Val>Glu. So, from the above results, it is indicated that the deep eutectic solvent ChCl/PTS (1/2) has special selectivity for tryptophan, which can be of great significance for the separation of AAs. The diversity of DESs provides more choice for the selective separation of AAs. Here the extraction process of tryptophan was investigated systematically to perfect the extraction process. 3.2. Optimization of Extraction Factors. Some important factors, including operation time, initial concentration of Trp in feed phase, and stirring speed were optimized as preliminary experiments. Operation time is an important factor that influences the extraction process. The result was listed in Figure 5. For this specific extraction process, the concentration of Trp in feed phase decrease with the increase of operation time. After 4 h, the concentration of Trp did not change because of their equilibrium reached. Compared with the traditional ILs based SLMs, the equilibrium time can be much shorter, which result from the lower viscosity of DESs. Initial concentration of Trp is also the main factor that determines whether the SLMs can be adopted for the separation and purification process of specific Trp systems with certain concentration. So optimization of the initial concentration of Trp on extraction efficiency was also investigated. Different Trp concentration ranging from 0.1 mM to 0.5 mM was studied. And results were shown in Figure 6. It can be seen that the extraction efficiency is influenced greatly by the initial concentration. The increase of concentration will result in the decrease of the extraction efficiency.


Page 8 of 42

Page 9 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The extraction efficiency while the initial concentration is 0.1 mM can reach 86.1% which is higher than 44% while the initial concentration is 0.5 mM. Therefore, this specific DES based SLMs extraction system can be more suitable for the system with lower AAs concentration due to the limit of effective membrane area and flux for transport. To attain homogeneous mixing, stirring would be necessary for feed and receiving phases. And minimum thickness of diffusion boundary layer should be maintained to minimize the resistance to aqueous mass transfer. As illustrated in Figure 7, the extraction efficiency was not influenced by stirring speed. And this demonstrates that the thickness of aqueous boundary layer had become minimum. Moreover, the higher stirring speed has more tendencies to result in the loss of membrane35 and shorten the utilization lifecycle of SLMs. 400 rpm was adopted as stirring speed throughout the investigation. 3.3. Selection of DESs. The designable property makes the diversity of DESs. So the proper choice of DESs would be beneficial for the separation process. For the new supported phase DESs, the construction of fundamental theory for the chosen of the suitable DESs as supported phase of SLMs is very valuable. The MCE membrane was used as supporting carrier to investigate the extraction performance of Trp with different DESs based SLMs. The selection of DESs was probed and the result was shown in Figure 8. From results, HBA and HBD both influence the extraction process. It can be seen that the sequence of extraction efficiencies is listed as follows: ChCl/PTS (1/2) >ChCl/Pr (1/2) > TBAC/Pr (1/2) > TBAC/PEG (1/2) > TBAC/ Pr



(1/1) > TBAC/PTS (1/2) >ChCl/MA (1/1) >ChCl/TEG (1/2). ChCl/PTS (1/2) gets the highest extraction efficiency, which can reach up to 86.1%. It is much higher than SLMs based on traditional ILs and solvents. 3.4. Selection of Membranes. In addition to selection of DESs, membranes are also critical to SLMs extraction process. There are two main standards for the selection of membranes. On the one hand, as the formation mechanism of SLMs depends on the capillary force, pore size of membrane is an essential measure. The decrease of the pore size will lower trans-membrane pressure and enhance the capillary force between membrane pore and supported phase of SLMs, which will reinforce the stability of SLMs. On the other hand, the hydrophilicity of membranes and DESs should be consistent in order to ensure DESs full access to the membranes channels and improve the stability of SLMs. Therefore, the porous membranes should have lower swelling capacity, smaller pore size and higher capillary force with DESs, which can improve the stability of SLMs and make DESs dispersed evenly in the membrane pore, thereby obtaining excellent separation performance. With the above analysis, six commercial membranes were chosen as typical ones to investigate their extraction capabilities. The selection of membranes was shown in Figure 9. With the same DES ChCl/PTS (1/2) as supported phase, MCE membrane as supported carrier achieves the highest extraction efficiency more than 86%. The permeation rate of Tryptophan, J, is defined in the following flux Equation (2), where k, C and K are the overall mass transfer coefficient, the concentration of Trp and the partition coefficient of Trp between the membrane and aqueous phases. Subscripts f and r denote feed and


Page 10 of 42

Page 11 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


receiving phases, respectively. It can be easily assumed that Kf>>Kr. Therefore, Eq. (2) is simplified to Eq. (3), where A, V, and t are the effective area of the membrane, the volume of the feed phase, and equilibration time, respectively. The k is obtained by Eq. (4) where superscript 0 denotes the initial state. The permeation rate of all SLMs with different membranes was listed as Table 1. From results, MCE membrane gets the highest permeation rate. Combined with its high extraction efficiency, MCE was chosen as the typical supporting carrier in the following experiments. 3.5. Effect of pH. pH is always one of the most important factors that affects the extraction process. Then the effect of the pH on the extraction efficiency was studied and the result is shown in Figure 10. It can be found that pH influences the extraction efficiency greatly. For the influence of pH in feed phase, pH=13 in receiving phase, while for influence of pH in receiving phase, pH=1 in receiving phase. Results show that the extraction efficiency increases with the decrease of pH in feed phase, while it is contrary for the receiving phase. It was also observed that the extraction efficiency of Trp was appreciably higher when pH=1.0 in feed phase and pH=13.0 in receiving phase. This may be interrelated to the charged characteristics of the Trp at different pH. And the Trp existing in the state of cationic form would be beneficial for the extraction process. 3.6. Reuse of SLM. In this study, reuse of DESs based SLMs were also investigated to confirm the stability of SLMs. Figure 11 describes the extraction efficiency of Trp with SLMs based on ChCl/PTS (1/2) for multiple extraction cycles. It was observed that the extraction efficiency decrease with the increase of extraction



cycles. However, as shown in Figure 11, the extraction efficiency is still more than 60% after the seventh cycle. In other words, the SLMs based on ChCl/PTS (1/2) are still effective for the extraction of Trp. This successful recycling would be very important for its future industrial application. 3.7. The Stability of SLM. The stability of SLM is one of the most important factors which restricts its industrial and engineering applications. The ChCl/PTS of SLM is not very stable, and the weight loss of SLM is 7.04%. It mainly result from the SLM’s swelling in aqueous solution and DES’s viscosity. Therefore, three-components ChCl/PTS based DESs were synthesized to increase its viscosity, which can improve the stability of SLM and has high extraction efficiency. Different three-components DESs were synthesized and SLMs were prepared with the MCE membrane used as supporting carrier. The selection of DESs was probed and the result was shown in Figure 12. ChCl/PTS/Asp (1/2/2) shows the best stability, the weight loss of SLM is only 0.66%, but extraction efficiency is only 44.88%. To improve the stability and extraction of SLM, ChCl/PTS/Asp (1/4/1) was prepared, the extraction efficiency is reached 73.49%, while the weight loss of SLM is 0.38%, which is shown in Figure 13. 3.8. SEM Characterization. Morphologies of the MCE membrane and ChCl/PTS (1/2) with SLMs were studied by scanning electron microscope (SEM), which were shown in Figure 14. It can be seen from Figure 14a, the pores of the MCE membrane were completely unfilled and no material is present inside the pores. However, from Figure 14b, the pores of SLMs were completely filled with ChCl/PTS (1/2). At the


Page 12 of 42

Page 13 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


same time, there is still small amount of DES accumulated on the surface of the membrane due to the viscosity of DESs. It is known that the greater viscosity of DESs, the higher amount will be left on the surface of the membrane. In this case, lower viscosity DESs are more preferable. Nevertheless, low viscosity of DESs will encounter with the problem of mechanical stability. Therefore, the finding of suitable DESs with proper viscosity that can completely fill the pores of the membrane, while not accumulate on the membrane surface are always challengeable. 3.9. Extraction Mechanisms. The mass transfer process of Trp through SLMs can be described by the following model, which was shown in Figure 15. Trp diffuses in the feed phase, and transfers to the phase interface between feed phase and SLMs. Then it is followed by mass transfer process in the SLMs, the most important extraction process. Finally, Trp transfers to the interface of SLMs and receiving phase, and releases into the receiving phase. Certainly the most important process would be mass transfer process in SLMs. To learn more detail of transfer process of Trp in DESs based SLMs, interaction between DES and Trp was characterized with 1H NMR listed in Figure 16. It can be seen that compared with the spectrum of the pure Trp and DES, the mixture of Trp and DES displays obvious changes. From Figure 16a and 16c, the chemical shift of hydrogen 9’ in Trp moves from 7.51 ppm to 8.31 ppm, which probably results from hydrogen bond interaction between the Trp and DES. This can be explained as follows: when the DES mixed with Trp, the hydrogen bond formed between the oxygen atom in sulfonyl group of the DES and the hydrogen atom in amino group of



Trp. The strong electron-withdrawing effect of oxygen atom will result in the hydrogen atom in amino group of Trp moving to the lower field. Furthermore, from Figure 16b and Figure 16c, the chemical shift of hydrogen 7 in DES moves from 7.08 ppm to 6.35 ppm, and the peak shape becomes lower and wider. This can be illustrated that the hydrogen bond also formed between the hydrogen atom in sulfo group of DES and oxygen atom in carbonyl group of Trp, which will lead to the increase of the relaxation time and the decrease of the peak intensity. And then results in the hydrogen atom in sulfo group of DES moving to the higher field. Therefore, it can be safely drawn the conclusion that hydrogen bonding interaction between DES and Trp would probably be the main driven force for the higher extraction efficiency with our specific DES based SLMs. At the same time, electrostatic interactions between DES and charged Trp and ion exchange would probably another reason that account for extraction mechanisms. 4. CONCLUSIONS Higher extraction efficiency of Trp was achieved with our new designed SLMs process based on deep eutectic solvents. A series of DESs were screened to get the suitable DESs as supported phase. DES ChCl/PTS (1/2) was found to be the most efficient supported phase. MCE were selected as supporting membrane. The result shows that pH and the initial concentration of Trp in feed phase both influence the extraction process greatly. The initial concentration of Trp in feed phase is 0.1 mM, and pH=1.0 in feed phase and pH=13.0 in receiving phase is optimal for extraction. And the extraction efficiency can reach up to 86.1%. So properly designed DESs


Page 14 of 42

Page 15 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


would be valuable for the SLMs extraction process to improve the extraction efficiency. By the reuse of SLMs based on ChCl/PTS (1/2), it exhibits good extraction capability and mechanical stability. ChCl/PTS/Asp (1/4/1) of SLM has best stability, the weight loss of SLM is 0.38%. Finally, The mechanism study shows that the hydrogen bonding interaction between DESs and Trp would probably the main driven force. This research provides new greener solvents for SLMs as supported phase and new process for the separation and purification of AAs with SLMs technique. ASSOCIATED CONTENT Supporting Information The 1H NMR spectra of DESs and analysis of standard curve. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *School of Ecological Environment and Civil Engineering, Dongguan University of Technology, Dongguan, 523808, China, E-mail: [email protected] ORCID Changping Li: 0000-0003-1084-4023 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS



Sincere thanks should be given to National Natural ScienceFoundation of China (NSFC Grant NO. 21176033, 21306016 and 21546007), Dalian Outstanding Scholar Project (Grant No. 2016RJ11) and Dalian Technology Star Project (Grant No. 2016RQ079) for financial support of this project.

REFERENCES (1) Wu, G. Amino acids: metabolism, functions, and nutrition. Amino Acids 2009, 37, 1-17. (2) Ward, W. W.; Swiatek, G. Protein purification. Curr. Anal. Chem., 2009, 5, 85-105. (3) Chen, H. L.; Juang, R. S. Recovery and separation of surfactin from pretreated fermentation broths by physical and chemical extraction. Biochem. Eng. J. 2008, 38, 39-46. (4) Panigrahi, A.; Pilli, S. R.; Mohanty, K. Selective separation of Bisphenol A from aqueous solution using supported ionic liquid membrane. Sep. Purif. Technol. 2013, 107, 70-78. (5) Chakraborty, M.; Dobaria, D.; Parikh, P. A. The separation of aromatic hydrocarbons through a supported ionic liquid membrane. Pet. Sci. Technol. 2012, 30, 2504-2516. (6) Yahaya, G. O.; Hamad, F.; Bahamdan, A.; Tammana, V. V. R.; Hamad, E. Z. Supported ionic liquid membrane and liquid-liquid extraction using membrane for removal of sulfur compounds from diesel/crude oil. Fuel Process. Technol. 2013, 113, 123-129.


Page 16 of 42

Page 17 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(7) Plaza, A.; Merlet, G.; Hasanoglu, A.; Isaacs, M.; Sanchez, J.; Romero, J. Separation of butanol from ABE mixtures by sweep gas pervaporation using a supported gelled ionic liquid membrane: Analysis of transport phenomena and selectivity. J. Membr. Sci. 2013, 444, 201-212. (8) Zarca, G.; Ortiz, I.; Urtiaga, A. Copper(I)-containing supported ionic liquid membranes for carbon monoxide/nitrogen separation. J. Membr. Sci. 2013, 438, 38-45. (9) Lan, W. J.; Li, S. W.; Xu, J. H.; Luo, G. S. Preparation and carbon dioxide separation performance of a hollow fiber supported ionic liquid membrane. Ind. Eng. Chem. Res. 2013, 52, 6770-6777. (10) Kocherginsky, N. M.; Yang, Q.; Seelam, L. Recent advances in supported liquid membrane technology. Sep. Purif. Technol. 2007, 53, 171-177. (11) Bao, L.; Trachtenberg, M. C. Facilitated transport of CO2 across a liquid membrane: comparing enzyme, amine, and alkaline. J. Membr. Sci. 2006, 280, 330-334. (12) Zhang, Q. H.; Vigier, K. D. O.; Royer, S.; Jérôme, F. Deep eutectic solvents: syntheses, properties and applications. Chem. Soc. Rev. 2012, 41, 7108-7146. (13) Francisco, M.; Bruinhorst, A.; Kroon, M. C. Low-transition-temperature mixtures (LTTMs): a new generation of designer solvents. Angew. Chem. Int. Ed. 2013, 52, 3074-3085. (14) Liu, L.; Yang, J. F.; Li, J. P.; Dong, J. X.; Sisak, D.; Luzzatto, M.; McCusker, L. B. Ionothermal synthesis and structure analysis of an open-framework zirconium



phosphate with a high CO2/CH4 adsorption ratio. Angew. Chem. Int. Ed. 2011, 50, 8139-8142. (15) Abbott, A. P.; Barron, J. C.; Frisch, G.; Gurman, S.; Ryder, K. S.; Fernando, S. A. Double layer effects on metal nucleation in deep eutectic solvents. Phys. Chem. Chem. Phys. 2011, 13, 10224-10231. (16) Vigier, K. O.; Benguerba, A.; Barrault, J.; Jérôme, F. Conversion of fructose and inulin to 5-hydroxymethylfurfural in sustainable betaine hydrochloride-based media. Green Chem. 2012, 14, 285-289. (17) Serrano, M. C.; Gutierrez, M. C.; Jiménez, R.; Ferrer, M. L.; Monte, F.Synthesis of novel lidocaine-releasing poly(diol-co-citrate) elastomers by using deep eutectic solvents. Chem. Commun. 2012, 48, 579-581. (18) Hu, S. Q.; Zhang, Z. F.; Zhou, Y. X.; Song, J. L.; Fan, H. L.; Han, B. X. Direct conversion of inulin to 5-hydroxymethylfurfural in biorenewable ionic liquids. Green Chem. 2009, 11, 873-877. (19) Zhang, Z. H.; Zhang, X. N.; Mo, L. P.; Li, Y. X.; Ma, F. P. Catalyst-free synthesis of quinazoline derivatives using low meltingsugar-urea-salt mixture as a solvent. Green Chem. 2012, 14, 1502-1506. (20) Cooper, E. R.; Andrews, C. D.; Wheatley, P. S.; Webb, P. B.; Wormald, P.; Morris, R. E. Ionic liquids and eutectic mixtures as solvent and template in synthesis of zeolite analogues. Nature 2004, 430, 1012.


Page 18 of 42

Page 19 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(21) Abbott, A. P.; Ttaib, K. E.; Frisch, G.; Ryder, K. S.; Weston, D. The electrodeposition of silver composites using deep eutectic solvents. Phys. Chem. Chem. Phys. 2012, 14, 2443-2449. (22) Abbott, A. P.; Frisch, G.; Hartley, J.; Ryder, K. S. Processing of metals and metal oxides using ionic liquids. Green Chem. 2011, 13, 471-478. (23) Mamajanov, I.; Engelhart, A. E.; Bean, H. D.; Hud, P. N. V. DNA and RNA in anhydrous media: duplex, triplex, and G-quadruplex secondary structures in a deep eutectic solvent. Angew. Chem. Int. Ed. 2010, 49, 6310-6314. (24) Abbott, A. P.; Cullis, P. M.; Gibson, M. J.; Harris, R. C.; Raven, E. Extraction of glycerol from biodiesel into a eutectic based ionic liquid. Green Chem. 2007, 9, 868-872. (25) Shahbaz, K. A.; Mjalli, F. S.; Hashim, M. A.; AINashef, I. M. Using deep eutectic solvents based on methyl triphenyl phosphunium bromide for the removal of glycerol from palm-oil-based biodiesel. Energy and Fuels 2011, 25, 2671-2678. (26) Hayyan, M.; Mjalli, F. S.; Hashim, M. A.; AINashef, I. M. A novel technique for separating glycerine from palm oil-based biodiesel using ionic liquids. Fuel Process. Technol. 2010, 91, 116-120. (27) Shahbaz, K. A.; Mjalli, F. S.; Hashim, M. A.; AINashef, I. M. Using deep eutectic solvents for the removal of glycerol from palm oil-based biodiesel. J. Appl. Sci. 2010, 10, 3349-3354.



(28) Guo, W. J.; Hou, Y. C.; Wu, W. Z.; Ren, S. H.; Tian, S. D.; Marsh, K. N. Separation of phenol from model oils with quaternary ammonium salts via forming deep eutectic solvents. Green Chem. 2013, 15, 226-229. (29) Pang, K.; Hou, Y. C.; Wu, W. Z.; Guo, W. J.; Peng, W.; Marsh, K. N. Efficient separation of phenols from oils via forming deep eutectic solvents. Green Chem. 2012, 14, 2398-2401. (30) Francisco, M.; Bruinhorst, A.; Kroon, M. C. New natural and renewable low transition temperature mixtures (LTTMs): screening as solvents for lignocellulosic biomass processing. Green Chem .2012, 14, 2153-2157. (31) Li, X. Y.; Hou, M. Q.; Han, B. X.; Wang, X. L.; Zou, L. Z. Solubility of CO2 in a choline chloride + urea eutectic mixture. J. Chem. Eng. Data 2008, 53, 548-550. (32) Li, H. X.; Li, Z.; Yin, J. M.; Li, C. P.; Chi, Y. S.; Liu, Q. S.; Zhang, X. L.; Welz-Biermann U. Liquid–liquid extraction process of amino acids by a new amide-based functionalized ionic liquid. Green Chem. 2012, 14, 1721-1727. (33) Li, C. P.; Li, Z.; Wang, A. L.; Yin, J. M.; Wang, J.; Li, H. X.; Liu, Q. S. Aqueous two phase extraction process of tryptophan based on functionalized ionic liquids. RSC. Adv. 2013, 3, 6356-6361. (34) Li, C. P.; Li, D.; Zou, S. S.; Li, Z.; Yin, J. M.; Wang, A. L.; Cui, Y. N.; Yao, Z. L.; Zhao, Q. Extraction desulfurization process of fuels with ammonium-based deep eutectic solvents. Green Chem. 2013, 15, 2793-2799. (35) Welton, T. Room-temperature ionic liquids solvents for synthesis and catalysis. Chem. Rev. 1999, 99, 2071-2083.


Page 20 of 42

Page 21 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure Captions: Table 1. Permeation rate of SLMs with different membranes Figure 1. Hydrogen bond donor and acceptor of DESs used Figure 2. Synthesis route of DESs Figure 3. Separation equipment Figure 4. Selection of Amino Acids Figure 5.Effect of operation time Figure 6. Effect of initial Trp concentration in feed phase on extraction efficiency Figure 7. Effect of stirring speed on extraction efficiency Figure 8. Selection of DESs Figure 9. Selection of membranes Figure 10. Effect of pH of feed phase and receiving phase on extraction efficiency Figure 11. Reuse of SLM Figure 12. Extraction efficiency and the weight loss of ChCl/PTS based SLMs Figure 13. Extraction efficiency and the weight loss of ChCl/PTS/Aspof SLMs Figure 14. SEM of the MCE membranes Figure 15. The transport mechanism of Trp across SLM Figure 16. 1H NMR of (a) Pure Trp, (b) Pure DES ChCl/PTS (1/2), (c) ChCl/PTS (1/2) and Trp mixture Eq.1 The equation of extraction efficiency of Trp Eq.2 The equation of permeation rate of Trp Eq.3 The equation of permeation rate of Trp Eq.4 The equation of permeation rate of Trp Eq.5 The equation of weight loss of SILMs



Table 1. Table 1. Permeation rate of SLMs with different membranes SLMs

Permeation rate/J (L/(h·cm2))

PES

537

PVDF

584

N66

600

NC

693

PTFE

714

MCE

927


Page 22 of 42

Page 23 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1.

Figure 1. Hydrogen bond donor and acceptor of DESs used



Figure 2.

Figure 2. Synthesis route of DESs


Page 24 of 42

Page 25 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3.

1. Feed phase2. Receiving phase3. SLM 4.Stirrer 5. Glass lids Figure 3. Separation equipment



Figure 4.

Figure 4. Selection of Amino Acids


Page 26 of 42

Page 27 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5.

Figure 5. Effect of operation time



Figure 6.

Figure 6. Effect of initial Trp concentration in feed phase on extraction efficiency


Page 28 of 42

Page 29 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7.

Figure 7. Effect of stirring speed on extraction efficiency



Figure 8.

Figure 8. Selection of DESs:a. Effect of different DESs on extraction efficiency b. Screening of DESs


Page 30 of 42

Page 31 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 9.

Figure 9. Selection of membranes: a. Effect of different membranes on extraction efficiency b. Screening of membranes



Figure 10.

Figure 10. Effect of pH of feed phase and receiving phase


Page 32 of 42

Page 33 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 11.

Figure 11. Reuse of SLM



Figure 12.

Figure 12. Extraction efficiency and the weight loss of ChCl/PTS based SLMs


Page 34 of 42

Page 35 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure13.

Figure 13. Extraction efficiency and the weight loss of ChCl/PTS/Asp of SLMs



Page 36 of 42

Figure 14.

a

b

Figure 14. SEM of the MCE membranes: a. without DESs

b. with ChCl/PTS(1/2) 36


Page 37 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 15.

a

b Figure 15. The transport mechanism of Trp across SILM (a) Extraction mechanisms by SLMs based on DES

(b) Interaction of DES and Trp

37



Page 38 of 42

Figure 16.

a

b

38


Page 39 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


c

Figure16. 1H NMR of(a) Pure Trp (b) Pure DES ChCl/PTS (1/2) (c) DES ChCl/PTS (1/2) and Trp mixture

39



Page 40 of 42

Eq.1 E(%) =

[ Trp ] feed,0 − [ Trp ] feed ,t [ Trp ] feed ,0

× 100%

(1)

where[Trp]feed,0and [Trp]feed,t are initial concentration and final concentration of Trp in feed phase.

Eq.2

 K   J = k C f −  r C r  K    f   

(2)

where k, C and K are the overall mass transfer coefficient, the concentration of Trp and the partition coefficient of Trp between the membrane and aqueous phases. Subscripts f and r denote feed and receiving phases, respectively.

Eq.3, 4

J =−

ln

Cf C

0 f

V dC f = kC f A dt

(3)

A kt V

(4)

=−

where A, V, and t are the effective area of the membrane, the volume of the feedphase, and equilibration time, respectively. Eq.5 Wt .loss(%) =

[ wt ]membrane ,before − [ wt ]membrane ,after [ wt ]membrane ,before

× 100%

(5)

where[wt] membrane,beforeand [wt]membrane,afterare the weights of SLMs before and after extraction process.

40


Page 41 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC

41



Graphics for manuscript


Page 42 of 42

Extraction Process of Amino Acids with Deep Eutectic Solvents-Based

Recommend Documents