Recovery of Oligosaccharides from Prehydrolysis Liquors of Poplar by

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Recovery of oligosaccharides from pre-hydrolysis liquors of poplar by microfiltration/ultrafiltration membranes and anion exchange resin Xiaoqian Chen, Qiulin Yang, Chuanling Si, Zhaojiang Wang, Dan Huo, Yimei Hong, and Zongquan Li ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b01029 • Publication Date (Web): 03 Feb 2016 Downloaded from http://pubs.acs.org on February 5, 2016

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ACS Sustainable Chemistry & Engineering

Recovery of oligosaccharides from pre-hydrolysis liquors of poplar by microfiltration/ultrafiltration membranes and anion exchange resin Xiaoqian Chen,

†

Qiulin Yang,

†,§

Chuan-Ling Si,

*,†,‡,#

Zhaojiang Wang,

║

Dan Huo,

†

Yimei Hong, † Zongquan Li ║

†

Tianjin Key Laboratory of Pulp & Paper, Tianjin University of Science & Technology, Tianjin 300457, China

‡

State Key Laboratory of Tree Genetics & Breeding, Northeast Forestry University, Harbin 150040, China

#

Jiangsu Province Biomass Energy and Materials Laboratory, Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China

║

Key Laboratory of Paper Science & Technology of Ministry of Education, Qilu University of Technology, Jinan 250353, China

§

State Key Laboratory of Pulp & Paper Engineering, South China University of Technology, Guangzhou 510640, China

*

Corresponding author: Tianjin Key Laboratory of Pulp & Paper, Tianjin University of Science & Technology, No.29 at 13th Avenue of TEDA, Tianjin 300457, China. E-mail: [email protected]; Tel: +86-22-60601313; Fax: +86-22-60602510 (C.L. Si)

1

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ABSTRACT: The recovery of oligosaccharides (OS) from pre-hydrolysis liquor (PHL) is of great economic significance and environmental benefits. In the present study, a novel and environmental friendly process using microfiltration/ultrafiltration membranes (MM/UM) and anion exchange resin was investigated to separate and purify OS from the PHL of poplar. The results showed that the addition of NaOH prior to filtration improved the filtration capacity and reduced fouling for MM (pore size 0.45 µm), and the removal rate of lignin was as high as 31%. On this basis, 36.8% of the remaining lignin was further removed by an ultrafiltration process using UM, while 39% of the remaining OS was recovered by ethanol or acid precipitation. The crude OS in the filtrate was then purified with anion exchange resin, and its purity was 96.4%. The current process recovered a total of 41.7% of the OS in the PHL and the obtained OS exhibited relatively stable molecular weight which was characterized by gel permeation chromatography (GPC).

Oligosaccharides; Pre-hydrolysis

KEYWORDS:

liquor;

Microfiltration/ultrafiltration

membranes; Anion exchange resin

INTRODUCTION Because of the diminishing of crude oil reserves and the shortage of energy, woody biomass is drawing a great deal of attention as an economical and sustainable source of future energy.

1

Biorefinery, a concept of converting plant-based biomass to chemicals,

energy and materials to instead of petroleum, coal, natural gas, and other non-renewable

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energy and chemicals, has very important significance for environmental protection and the development of sustainability. 2 The oligosaccharides (OS) derived from hemicelluloses is a potential feedstock for food and pharmaceutical production and raw material to produce biodegradable plastics, coatings, tablets, as well as chitosan-xylan hydrogels.

3,4

In the conventional pulping process, most of

the degraded products from hemicelluloses are primarily dissolved into spent liquor and ultimately combusted for recovering thermal energy. This caused an inefficient utilization of hemicellulose, thus cutting the economic benefits. Under this background, biorefinery concept is introduced into pulping process, which plays an important role for the whole components utilization and sustainable utilization of the biomass. Therefore, these degraded fractions can be utilized effectively, and the resulted wood chips after pre-hydrolysis can be subsequently used for pulping, while the pre-hydrolysis liquor (PHL) can be separated to produce the high value-added chemicals such as xylitol, furfural and acetic acid etc.

5-7

The

isolated residues mainly composed of lignins can also be used as a raw material for biofuels, polymers and surfactant production. The complexities of OS have further caused new challenges for the recovery of organics and their subsequent purification.

8

Shen et al. reported a combined process using activated

carbon, anion exchange resin and nanofiltration membranes to recover the dissolved organics from PHL.

9

It was found that the concentrations of lignin, acetic acid and furfural were

reduced to 0.32%, 0.71% and 0.02%, respectively, while the content of hemicellulosic sugars was 22.13%. When activated carbon and strong anion-exchange resin were used for extracting xylo-oligosaccharides, 78.2% of non-carbohydrates and 22.2% of carbohydrates

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were removed from the PHL. 8 However, the utilization of these active carbons is limited.

10

Polymeric resins such as XAD-7 and XAD-16 can also be used for OS separation, while the selectivity of lignin and carbohydrates is weak. 11 The membrane technology has been recently proposed as an effective purification method because of the high treatment efficiency, low energy input, mild operating conditions, as well as better integration with other operating units.

12,13

According to the molecular

weight cut-off, namely pore sizes, the membrane can be divided into reverse osmosis membrane (ROM), nanofiltration membrane (NM), UM and MM, where the pore size of MM (0.02-10 µm) is much larger than that of the UM (0.001-0.02 µm) and is more difficult to block. Membrane technology had been used for recovering hemicellulose from the recycled water of pulp mill.

14-16

Liu et al. reported that sugars could be purified and

concentrated by NM, and the losses of yield were negligible.

17

While, the fouling and

blocking problems that were caused by lignin macromolecule influenced the membrane utilization.

16,18

The pre-treatment with activated carbon or laccase could improve the

membrane filterability. 8,19 Luo et al. investigated a two-stage process using UM/NM to treat dairy waste water, which could better increase the removal efficiency of lignin and decrease the membrane fouling comparing to a single stage process using NM. 20 In this study, a combined process containing MM/UM and anion exchange resin was proposed to extract OS from the PHL. At the first stage, NaOH was added into the PHL prior to filtrating with MM to remove the high-molecular-weight lignin, thus significantly improving the membrane filterability. At the second stage, the UM was focused on the removal of remained lignin fractions, which had a similar molecular weight to the OS and

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were difficult to remove. The purity of the crude OS was further increased by anion exchange resin. MATERIALS AND METHODS Materials. Poplar wood chips were provided by Huatai Paper Co. Ltd. (Dongying, China). The MM (polyvinylidene fluoride, pore size 0.22 µm and 0.45 µm) were purchased from Shanghai Aiybio Co. (China). The UM (cellulose acetate, diameter 76 mm) with a molecular weight cut-off >1000 Daltons was purchased from Alfa Laval Co (Shanghai, China). The resin D311 (macroporous acrylic acid series weak base anion exchange) and D201 (macroporous strong base styrene anion exchange resin) were provided by Huizhu Resin CO., Ltd. (Shanghai, China). Other chemicals were of analytical grade and purchased from Damao Chemical Reagent Factory (Tianjin, China). Hot water pre-hydrolysis process. The pre-hydrolysis was carried out in a pulp digester, 500 g of oven-dried poplar chips and 3000 mL of deionized water were thoroughly mixed in the reactor (solid/liquid ratio of 1/6). Heated the reactor to 170ºC at a heating rate of 1 ºC/min and kept for 1 h. At the end of pre-hydrolysis, the digester was cooled and depressurized. The PHL was separated, collected and kept under the temperature of 4ºC for further tests. Filtrating with MM/UM. The filtration experiment was performed in an Amicon stirred ultrafiltration cell (8400, Millipore, Billaica, USA) with membrane effective area of 4.18×10−3 m2, where the experimental set-up and the properties of ultrafiltration cell were listed in Table 1. The transmembrane pressure (TMP) was controlled at 58 psi by pressured-

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nitrogen during filtration, and the temperature was maintained at 20°C under the magnetic stirring rate of 100 rpm. The MM was directly used for filtrating, While the UM was soaked with ethanol solution (50%) for 30 min and washed with 300 mL of deionized water to remove the residual coating materials (glycerine and azide). And then it was compressed to a steady state, where a deionized water flux of 43.06 L/(m2·h) was emerged. 100 mL of samples were added into the flow cell, and the volume of the filtrate was recorded by measuring cylinder. The filtrate and the related residue were collected for subsequent analysis.

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Table 1. Properties of Amicon stirred ultrafiltration cell 8400 ultrafiltration cell and UM Properties

Values

Cell capacity (mL)

400

Stirred minimum volume (mL)

10.0

Membrane diameter (mm)

76

Effective membrane area (cm2)

41.8

Hold-up volume1 (mL)

1.5

Maximum operating pressure (psi)

75

Note: 1non-recoverable volume (below membrane surface) Treating with anion exchange resin. After the treatment by MM/UM, the samples were then subjected to anion exchange resin to further purification of OS by removing the low-molecule-weight impurities. 50 mL of the samples were added into a chromatographic column (2× 20 cm) packing with resin, where a pump was used to provide pressure and the effluent flow rate was kept at 3 mL/min. After adsorption equilibrium, the components such as lignin and sugar were prepared for analyzing. Each data point of analysis was reported as an average value, with the relative standard deviation less than 2%. Analysis methods. After dilution, the lignin content in the PHL was determined by an ultraviolet spectrophotometer (UV2800, SOPTOP, China) at 205 nm. For the detection of sugars, an indirect method was used. The liquid sample was quantitatively hydrolyzed with 4% w/w of H2SO4 at 120°C for 60 min, where the OS were present in the form of monosaccharides by the determination of high performance liquid chromatography (HPLC) (LC-20A, SHIMADZU, Japan).

21

The molecule weights of OS and lignin were analyzed by 7



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GPC (LC-20A, SHIMADZU, Japan) equipped with a SB-803 HQ column. The detection conditions were as follows: refraction index detector and ultraviolet detector at 280 nm, mobile phase ultrapure water at 35°C (flow rate 1.0 mL/min). Particle size was measured by Malvern zetasizer (Nano ZS90, Malvern Instruments, UK) at 25°C.

RESULTS AND DISCUSSION A combined process of MM/UM and anion exchange resin for recovering the OS from PHL. The poplar wood was extracted with hot water at 170ºC for 1 h to obtain the PHL, and the compositions of which included OS, lignins, monosaccharides and other degraded products. The chemical compositions of PHL are listed in Table 2. It was found that the compositions of PHL were very complex, and the concentration of OS were at a low level, which limited its recovery and utilization.

22

The OS were mainly composed by

xylooligosaccharides (XOS), and the contents of which were high to 31.0 mg/mL, indicating that the purification process was mainly related to the XOS. A combined process of MM/UM and anion exchange resin for separating and concentrating OS is proposed in Figure 1. The PHL was treated with MM first, to remove most of the macromolecular substances, which were precipitated by NaOH. Thus a pretreatment step using NaOH was critical for the subsequent operations, especially for the filtration with UM, since the removal of these substances could significantly decrease the membrane fouling. Then the resulted filtrate was further treated by UM for removing of the remained lignin fractions, where a small proportion of OS could be concentrated into the residue. The membrane with a certain strength and porous structure could be secondly used

8


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in this process. The UM filtrate was further subjected to a specific anion exchange resin to generate the OS with high purity. The anion exchange resin can be reused by desorbing process using sulfuric acid or NaOH. 23 Table 2. Characteristics of the PHL of poplar (mg/mL) Oligosaccharides Monosaccharides Degradation products GlcOS

2.6

Xylose

3.0

Formic acid

0.36

pH

3.6

XOS

31.0

Glucose 1.3

Acetic acid

0.49

Lignin

6.7

MOS

3.8

Mannose 1.2

Furfural

0.52

Total solid

56.8

Total

37.4

Total

HMF

0.2

5.5

Note: GlcOS, glucooligosaccharides; XOS, xylooligosaccharides; MOS, mannooligosaccharides

PHL

MM Assisted by NaOH

Filtrate

Repeated usage of membrane

Improved membrane filterability

Filtrate

UM

Anion exchange resin

Repeated usage of membrane

Residue

Concentrated OS and lignin

Highpurified

Regenerated resin Adsorption of micromolecular impurities Desorption

Macromolecule lignin

OS

Acetic acid

Figure 1. A combined process of MM/UM/anion exchange resin used for recovering the OS from PHL 9



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Filtrating with MM. The lignin with high-molecular-weight was considered as the main fouling, which could decrease the membrane filterability and lifetime. Therefore, removing of the lignin prior to filtrating with UM was an efficient method for the improvement of filterability. In the filtrating process with MM, the higher-molecular-weight components in PHL such as lignin and its derivatives could be effectively removed, with the lower-molecular-weight components including OS retained. The changes of filtrate volume during the filtrating with MM were recorded. The results are shown in Figure 2.

Figure 2. Effects of membrane and feed type on the ultrafiltration rate It was shown that the filtration rate of PHL by MM (pore size of 0.22 µm) was slower than that with MM (pore size of 0.45 µm). Meanwhile, no obvious improvement in the removal rate of lignin and OS was found when the pore size of MM reduced from 0.45 to 0.22 µm. Considering the blocking phenomenon, the MM with a pore size of 0.45 µm was suitable for the first-stage filtration. For removing of the high-molecular-weight lignin and the remaining OS from PHL, the treatment methods, pH conditions, the removal rates of lignin and the OS were investigated. As showed in Table 3, 43.8% of the lignin and 26% of the OS were removed from the PHL during the treatment with MM. Furthermore, a relatively high removal rate of the lignin 10


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could be realized in the treatment with poly aluminium chloride, whereas the removal rate of the OS was as high as 17%, obviously higher than that with NaOH, demonstrating that the separation effect of NaOH was more superior.

24

When NaOH was added into PHL, the

removal rate of lignin and OS were 28.8% and 2% at the pH of 9, respectively. After the PHL treated with NaOH, the further filtration with MM still removed 59.8% of lignin and 28% of OS. Though the removal rate of OS was slightly higher when the NaOH was added into the PHL prior to filtrating with MM, the filtration rate of the PHL, the removal rate of lignin and membrane lifetime were improved significantly, demonstrating that NaOH had a better effect for the filtrating (Figure 2).

Table 3. The removal rate of OS and lignin after treating with different strategies Strategies

pH

Removal rate of OS, %

Removal rate of lignin, %

MM

3.6

26.0

43.8

NaOH

9.0

2.0

28.8

MM (NaOH)a

9.0

28.0

59.8

AlCl3

3.6

1.8

21.9

AlCl3

9.0

17.0

46.9

Note: a NaOH was added into the PHL to adjust the pH and remove some precipitates prior to filtrating with MM. The effects of NaOH dosage on the pH and particle size of the PHL are shown in Figure 3. It was found that the pH and particle size were gradually increased with the increase of NaOH dosage, which had positive effects on the lignin removal. It was mainly because that the PHL had negative charges and colloidal stability.

25

The ionization of the colloidal

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substances in the PHL was depended on the pH values. The zeta potential analysis was showed that more anionic charges were available with the addition of hydroxyl ion, which caused a high pH value and promoted the ionization.

24

When the sodium ions were added

into the system, the structure of electrical double layer formed by lignin colloid was destroyed, then the sodium ions combined with the ionized phenolic lignin by electrostatic interaction and formed flocculent precipitations, and these precipitations could be removed by the MM. The similar results were observed as the electrostatic binding undermined the colloidal stability and led to 28% of the lignin being removed.

19, 26

To confirm it, the AlCl3

was added into the PHL, with the pH values being changed. The results showed that when the pH value was raised from 3.6 to 9.0, the removal rate of lignins was increased from 21.9% to 46.9%, demonstrating that the NaOH played dual roles for the lignin removal, promoting ionization by changing the pH value and forming flocculent precipitations by electrostatic interaction.

Figure 3. Responses of pH and particle size to the addition of NaOH Note: NaOH treatment is conducted by gradual addition of 0.2 M NaOH into 50 mL PHL under the room temperature.

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Filtrating with UM. After filtrating with MM, a certain amount of the uncharged lignin impurities were still present in the filtrate and were difficult to be removed by the MM filtration, which had the similar molecular weight and charge density to the OS. In this study, the UM with 1000 MWCO was used to remove the remaining lignin and impurities in the PHL. The characteristics of the filtrate and residue after treating with UM and MM/UM are summarized in Table 4. Table 4. Characteristics of the filtrate and residue after filtrating with UM and MM/UM Treatment

UM

MM/UM

pH

Components

Filtrate, %a

Residue, %

Loss, %

OS

59(41.0)b

37.0

4.0

Lignin

83.2(16.8)

12.8

4.0

OS

61(39.0)

34.0

5.0

Lignin

63.6(36.4)

33.6

2.8

3.6

9

Note: a The percentage is relative to the PHL before treated by the treatments as mentioned in the table. b

The first value represents the percentage of the compounds in the filtrate, and the following

value in the bracket is the corresponding removal. It was found that the removal rate of lignin was only 16.8% when the PHL was only treated by UM (pH= 3.6). However, when the MM/UM was used for the purification (pH= 9), the removal rate was increased by 20% compared with the MM treatment. The reason was that the molecular weights of lignins were increased under alkaline conditions, and these lignins could be removed by the filtration with MM/UM. Meanwhile, the characteristics of residues were tested, and the results were shown in Table 4. There were some concentrated 13



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OS and lignins in the residue, which could be separated by ethanol or acidification precipitation. The filtration process with UM was critical that would not only remove the remaining lignin, but also possess a good shield of OS. In our previous study, a dialysis filtration method was used to replace the filtrating with UM, which caused 60% loss of the OS, indicating that the filtrating with UM was more suitable for the purification. 24 Moreover, the OS could be recovered from both of the residue and filtrate. The MM/UM process not only improved the removal rate of lignin, but also relieved the membrane fouling phenomenon. In this study, the effects of filtration time on the volume reduction factors (VRF, initial feed volume/retention volume) were investigated. The results are shown in Figure 4. Comparing to the treatment only by UM, the filtration with MM/UM performed better in the improvement of the filterability of UM. It was found that 25 of the VRF could be achieved in the filtrating with MM/UM, which was higher than that treated with UM. The improved membrane filterability could enhance the working stability and greatly satisfied the demand for industrial application. In addition, an inflection point was emerged in the filtration with MM/UM, where the VRF was greatly raised with the time longer than 80 min, demonstrating that the membrane fouling problem was mainly generated at the late stage of filtration. It was mainly related to the pH value which had a significant effect on the membrane fouling. It could be concluded that, the two-stage process with MM/UM had a higher efficiency for purifying the OS and decreasing the membrane fouling.

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Figure 4. Effect of filtration time on the volume reduction factor Anion exchange resin for OS purification. After the MM/UM treatment, the filtrate still contained a certain amount of impurities with smaller-molecular-weight, including lignin and degraded products, which had an inhibitory effect on the application of OS. The filtrate was then subjected to anion exchange resin to the further purification of OS. These degraded products containing phenolic lignin, monosaccharide, organic acid, furfural and HMF could be released with the degradation of hemicellulose and cellulose under a high temperature condition, where the treatment with anion exchange resin had a positive effect to remove these products.

10

It was found that the adsorbing efficiency of anion exchange resin was

increased at an optimum pH value of 9-10. 23-27 From the previous research, it was found that the wheat straw hydrolysate treated with anion exchange resin D311 and Ca(OH)2 could remove 90.36%, 77.44% and 96.29% of the furfural, phenolic and acetic acid, respectively. 28 According to the research of Nilvebrant, strong-base anion exchange resin was applied as adsorbent to remove the residual lignin in the PHL after lime treatment, since it had a high adsorption capacity for phenolic compounds.

29

The OS in the PHL was purified with anion

exchange resins D311 and strong-base anion exchange resin D201, respectively. The effects

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of anion exchange resin on the recovery rate of OS and removal rate of lignin were determined, and the results were shown in Table 5. Table 5. Effect of pH values and resin types on the removal rate of OS and lignin Method

Resin

pH

Removal rate of OS, %

Removal rate of lignin, %

D201

7

0

72.1

NaOH/

D201

9

5.0

73.0

MM/UM

D201

10

10.0

73.0

D311

7

3.0

72.1

D201

5

27.0

59.6

D311

5

36.0

77.4

MM/UM

Compared with OS, the removal rate of lignin was higher, when the D311 and D201 anion exchange resigns were used for absorption. The addition of NaOH could negatively affect the removal of OS. The recent research showed that the OH- not only provided an alkaline condition for the anion exchange, but also facilitated the mass transfer, which could promote the lignin adsorption. 19 It was reported that the treatment with resin could cause the HMF and furfural decreasing, without being changed the sugars. 30 The analysis showed that furfural and HMF in the PHL were completely removed after resin treatment. The photographs of the ion exchange resins before and after adsorbing were shown in Figure 5. It was found that the colors of resins were getting darker, with the adsorbed lignin increasing. As reported, the resins could be regenerated by using 4% of NaOH.

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Prior to adsorbing

After adsorbing

Figure 5. The photographs of the D311 ion exchange resins

It was demonstrated that the concentrations of inhibitors could be significantly reduced in the treatment with anion exchange resin at pH of 10, and a small amount of sugars could be removed from the hydrolyzate.

31

From the previous research, it was found that 95.2% of

the lignin was removed and only 21.2% of the sugar was extracted when the PHL was treated with anion exchange under alkaline conditions,

32

which confirmed that the anion exchange

resin exhibited a better selectivity for the removal of lignin. And the OS loss was not significant when the pH was increased from 7 to 10, which was shown in Table 5. 5% and 10% of the OS could be removed when the D201 anion exchanges were performed at pH of 9.0 and 10.0, respectively. Meanwhile there was no loss of OS when the anion exchange resin was used at pH of 7, which demonstrated that the pH value had little effect for the OS loss in the range of pH 7 to 10. It is necessary here to point out that this pH value of the PHL was same as the filtrate after pre-treatment with NaOH. In conclusion, the treatment with D201 resin could remove 73% of the lignin and 5% of the OS at the pH of 9.

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Table 6. The contents of the OS and lignins after each step of treatment. Treatment Original

MM

UM

Exchange resin

OS

37.4

26.93 (28) a

16.43 (39)

15.6 (5)

Lignin

6.7

2.69 (59.8)

1.71 (36.4)

0.46 (73)

Total solid, mg/mL

56.8

33.12

19.94

16.18

Compound

Recovery rate, %

41.7

Purity, %

96.4

Note:

a

the first value represents the concentration of the compounds in the PHL after

treatment (mg/mL), and the following value in the bracket is the corresponding removal (%).

The original PHL and combined treated (NaOH/UM/MM/anion exchange resin) PHL were analyzed by GPC. The two peaks were disappeared when the PHL was treated with the current combined process, verifying that most of the lignin could be removed from the liquor. The combined treatment process did not change the molecular structure of OS, but only reduced its content. The statistics of the results after each step of treatment are shown in Table 6. 16.18 mg/mL of the solid content, 15.60 mg/mL of the OS and 0.46 mg/mL of the remaining lignin were obtained by the combined treatment process of MM/UM and anion exchange resin, and the total yield and purity of the OS came up to 41.7% and 96.4%, respectively.

CONCLUSION 18


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The proposed process, consisting of MM/UM/anion exchange resin, was applied to recover the OS from the PHL of poplar, which removed 93.1% of the lignin by a good membrane permeability. The addition of NaOH before the filtration enhanced the lignin removal due to effective lignin coagulation. The recovery of OS and lignin from the concentrated residue between the stages of MM and UM was achieved by the ethanol precipitation or acidification. The filtrate was then treated with anion exchange resins, resulting in a 41.7% recovery rate of OS with 96.4% purity. The two-stage process of using MF/UF had less membrane fouling and longer service life comparing to the single UF process. And the ion-exchange resins had high efficiency in separation and purification and could be regenerated by using of 4% NaOH. So it is a potential and promising technology for commercialization using advanced technology to produce high value-added OS.

AUTHOR INFORMATION Corresponding author. Tel.: +86 22 60601313, Fax: +86 22 60602510. E-mail address: [email protected] (C.L. Si). Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS The authors are grateful for financial supports from the State Key Laboratory of Tree Genetics and Breeding (Northeast Forestry University) (K2013101), National and Natural

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Science Foundation of Tianjin City (13JCZDJC29400, 13JCZDJC33700), Jiangsu Province Biomass Energy and Materials Laboratory in Institute of Chemical Industry of Forest Products, CAF (JSBEM201601), National Natural Science Foundation of China (31170541), Open Foundation of the State Key Laboratory of Pulp and Paper Engineering in South China University of Technology (201359), and the Innovation Foundation for Young Teachers in Tianjin University of Science & Technology (2014CXLG14).

REFERENCES (1) Xu, J.; Sun, Y.; Sun, R. Ionic liquid pretreatment of woody biomass to Facilitate biorefinery: structural elucidation of alkali-soluble hemicelluloses. ACS Sustain. Chem. Eng. 2014, 2(4), 1035-1042. (2) Liu. J.; Shonnard, D.R. Life cycle carbon footprint of ethanol and potassium acetate produced from a forest product wastewater stream by a co-located biorefinery. ACS Sustain. Chem. Eng. 2014, 2(8), 1951-1958. (3) Zampa, A.; Silvi, S.; Fabiani, R.; Morozzi, G.; Orpianesi, C.; Cresci, A. Effects of different digestible carbohydrates on bile acid metabolism and SCFA production by human gut micro-flora grown in an in vitro semi-continuous culture. Anaerob. 2004, 10, 19-26. (4) Gabrielii, I.; Gatenholm, P.; Glasser, W.; Jain, R.; Kenne, L. Separation, characterization and hydrogel-formation of hemicellulose from aspen wood. Carbohyd. Polym. 2000, 43(4), 367-374.

20


Page 20 of 25

Page 21 of 25

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


(5) Yang, G.; Jahan, M.S.; Ahsan, L.; Zheng, L.; Ni, Y. Recovery of acetic acid from prehydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine. Bioresource Technol. 2013, 138, 253-258. (6) Kaur, I.; Ni, Y. A process to produce furfural and acetic acid from pre-hydrolysis liquor of kraft based dissolving pulp process. Sep. Purif. Technol. 2015, 146, 121-126. (7) Fatehi, P.; Catalan, L.; Cave, G. Simulation analysis of producing xylitol from hemicelluloses of pre-hydrolysis liquor. Chem. Eng. Res. Des. 2014, 92, 1563-1570. (8) Montané, D.; Nabarlatz, D.; Martorell, A.; Torné-Fernández, V.; Fierro, V. Removal of lignin and associated impurities from xylo-oligosaccharides by activated carbon adsorption. Ind. Eng. Chem. Res. 2006, 45(7), 2294-2302. (9) Shen, J.; Kaur, I.; Baktash, M.M.; He, Z.; Ni, Y. A combined process of activated carbon adsorption, ion exchange resin treatment and membrane concentration for recovery of dissolved organics in pre-hydrolysis liquor of the kraft-based dissolving pulp production process. Bioresource Technol. 2013, 127, 59-65. (10) Chandel, A.K.; Singh, O.V.; da Silva, S.S. Detoxification of lignocellulosic hydrolysates for improved bioethanol production. In Biofuel Production-Recent Developments and Prospects; Chandel, A.K., Singh, O.V., da Silva, S.S. InTech Open Access Publisher: Brazil, 2011，Pages 225-246. (11) Koivula, E.; Kallioinen, M.; Sainio, T.; Antón, E.; Luque, S.; Mänttäri, M. Enhanced membrane filtration of wood hydrolysates for hemicelluloses recovery by pretreatment with polymeric adsorbents. Bioresource Technol. 2013, 143, 275-281.

21



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

(12) Amidon, T.E.; Wood, C.D.; Shupe, A.M.; Wang, Y.; Graves, M.; Liu, S. Biorefinery: conversion of woody biomass to chemicals, energy and materials. J. Biobased. Mater. Bio. 2008, 2(2), 100-120. (13) Arkell, A.; Olsson, J.; Wallberg, O. Process performance in lignin separation from softwood black liquor by membrane filtration. Chem. Eng. Res. Des. 2014, 92(9), 1792-1800. (14) Al Manasrah, M.; Kallioinen, M.; Ilvesniemi, H.; Mänttäri, M. Recovery of galactoglucomannan from wood hydrolysate using regenerated cellulose ultrafiltration membranes. Bioresource Technol. 2012, 114, 375-381. (15) Persson, T.; Krawczyk, H.; Nordin, A-K.; Jönsson, A-S. Fractionation of process water in thermomechanical pulp mills. Bioresource Technol. 2010, 101(11), 3884-3892. (16) Sainio, T.; Kallioinen, M.; Nakari, O.; Mänttäri, M. Production and recovery of monosaccharides from lignocellulose hot water extracts in a pulp mill biorefinery. Bioresource Technol. 2013, 135, 730-737. (17) Liu, S.; Amidon, T.E.; Wood, C.D. Membrane filtration: concentration and purification of hydrolyzates from biomass. J. Biobased. Mater. Bio. 2008, 2(2), 121-134. (18) Koivula, E.; Kallioinen, M.; Preis, S.; Testova, L.; Sixta, H.; Mänttäri, M. Evaluation of various pretreatment methods to manage fouling in ultrafiltration of wood hydrolysates. Sep. Purif. Technol. 2011, 83, 50-56. (19) Wang, Q.; Liu, S.; Yang, G.; Chen, J. Improvement membrane filterability in nanofiltration of prehydrolysis liquor of kraft dissolving pulp by laccase treatment. Bioresource Technol. 2015, 181, 124-127.

22


Page 22 of 25

Page 23 of 25

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


(20) Luo, J.; Ding, L.; Qi, B.; Jaffrin, M.Y.; Wan, Y. A two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater. Bioresource Technol. 2011, 102(16), 7437-7442. (21) Sluiter, A.; Hames, B.; Ruiz, R.; Scarlata, C.; Sluiter, J.; Templeton, D. Determination of sugars, byproducts, and degradation products in liquid fraction process samples. National Renewable Energy Laboratory, Golden, CO. 2006. (22) Shi, H.; Fatehi, P.; Xiao, H.; Ni, Y. A combined acidification/PEO flocculation process to improve the lignin removal from the pre-hydrolysis liquor of kraft-based dissolving pulp production process. Bioresource. Technol. 2011, 102(8), 5177-5182. (23) De Mancilha, I.M.; Karim, M.N. Evaluation of ion exchange resins for removal of inhibitory compounds from corn stover hydrolyzate for xylitol fermentation. Biotechnol. Progr. 2003, 19(6), 1837-1841. (24) Chen, X.; Wang, Z.; Fu, Y.; Li, Z.; Qin, M. Specific lignin precipitation for oligosaccharides recovery from hot water wood extract. Bioresource. Technol. 2014, 52, 3137. (25) Duarte, G.; Ramarao, B.; Amidon, T. Polymer induced flocculation and separation of particulates from extracts of lignocellulosic materials. Bioresource. Technol. 2010, 101(22), 8526-8534. (26) Ragnar, M.; Lindgren, C.T.; Nilvebrant, N-O. pKa-values of guaiacyl and syringyl phenols related to lignin. J. Wood. Chem. Technol. 2000, 20(3), 277-305 (27) Ranjan, R.; Thust, S.; Gounaris, C.E.; Woo, M.; Floudas, C.A.; von Keitz, M.; Valentas, K.J.; Wei, J.; Tsapatsis, M. Adsorption of fermentation inhibitors from lignocellulosic

23



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

biomass hydrolyzates for improved ethanol yield and value-added product recovery. Micropor. Mesopor. Mat. 2009, 122(1-3), DOI 10.1016/j.micromeso.2009.02.025. (28) Zhuang, J.; Liu, Y.; Wu, Z.; Sun, Y.; Lin, L. Hydrolysis of wheat straw hemicellulose and detoxification of the hydrolysate for xylitol production. Bioresources 2009, 4, 674-686. (29) Nilvebrant, N-O.; Reimann, A.; Larsson, S.; Jönsson, L.J. Detoxification of lignocellulose hydrolysates with ion-exchange resins. Appl. Biochem. Biotech. 2001, 91(1), 35-49. (30) Nilvebrant, N-O.; Persson, P.; Reimann, A.; de Sousa, F.; Gorton, L.; Jönsson, L.J. Limits for alkaline detoxification of dilute-acid lignocellulose hydrolysates. Appl. Biochem. Biotech. 2003, 107(1), 615-628. (31) Larsson, S.; Reimann, A.; Nilvebrant, N-O.; Jönsson, L.J. Comparison of different methods for the detoxification of lignocellulose hydrolyzates of spruce. Appl. Biochem. Biotech. 1999, 77(1), 91-103. (32) Wang, Z.; Jiang, J.; Wang, X.; Fu, Y.; Li, Z.; Zhang, F.; Qin, M. Selective removal of phenolic lignin derivatives enables sugars recovery from wood prehydrolysis liquor with remarkable yield. Bioresource. Technol. 2014, 174, 198-203.

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For Table of Contents Use Only Recovery of oligosaccharides from pre-hydrolysis liquors of poplar by microfiltration/ultrafiltration membranes and anion exchange resin

Xiaoqian Chen, Qiulin Yang, Chuanling Si, Zhaojiang Wang, Dan Huo, Yimei Hong, Zongquan Li

Synopsis A novel technology with MM/UM and exchange resin was used to purify OS from PHL. The MM/UM and resin were environmentally-friendly that could be repeatedly used. 40.3% of the OS could be purified from the PHL, with a high purity of over 96%.

A combined process of MF/UF/anion exchange resin used for recovering the OS from PHL

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Recovery of Oligosaccharides from Prehydrolysis Liquors of Poplar by

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