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Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane

Shengming MA Zhihao LIANG Xingfan WANG Zaichao GUO Jie LIU Jinglai DUAN Dan MO Huijun YAO

马圣明, 梁志豪, 王星凡, 郭再超, 刘杰, 段敬来, 莫丹, 姚会军. 基于PET核孔膜制备有机无机复合纳滤膜[J]. 原子核物理评论, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
引用本文: 马圣明, 梁志豪, 王星凡, 郭再超, 刘杰, 段敬来, 莫丹, 姚会军. 基于PET核孔膜制备有机无机复合纳滤膜[J]. 原子核物理评论, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
Shengming MA, Zhihao LIANG, Xingfan WANG, Zaichao GUO, Jie LIU, Jinglai DUAN, Dan MO, Huijun YAO. Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane[J]. Nuclear Physics Review, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
Citation: Shengming MA, Zhihao LIANG, Xingfan WANG, Zaichao GUO, Jie LIU, Jinglai DUAN, Dan MO, Huijun YAO. Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane[J]. Nuclear Physics Review, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011

基于PET核孔膜制备有机无机复合纳滤膜

doi: 10.11804/NuclPhysRev.40.2022011
详细信息
  • 中图分类号: O571.6

Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane

Funds: Youth Innovation Promotion Association of CAS(Y850030YQO); National Natural Science Foundation of China(Y850020GJ0); National Key Research and Development Program of China(Y91O171KJ1)
More Information
  • 摘要: 纳滤膜在海水淡化及饮用水净化领域起着越来越重要的作用,核孔膜作为一种重要的分离材料,具有均匀的孔径、可调的孔密度及无缺陷的表面,在水处理及精确分离应用方面有着潜在的优势,高孔密度的超薄核孔膜在制备高性能纳滤膜上具有很大的潜力。基于此,利用氧化锆作选择层,核孔膜作为支撑层制备出了三层结构的有机无机复合纳滤膜,聚多巴胺(PDA)与聚乙烯亚胺(PEI)中间层促进无机纳米粒子在膜表面形成无机层。制备出的复合膜可实现对不同盐的部分截留,表现出的截留顺序为Na2SO4>MgSO4>MgCl2>NaCl。
  • Figure  1.  Schematic diagram for the fabrication process of PET ITM. (color online)

    Figure  2.  Schematic diagram of the preparation process for the organic-inorganic composite nanofiltration membranes with ultrathin ZrO2 film as the selective layer on the PDA-PEI coating ITM. (color online)

    Figure  3.  Surface morphologies of ITM support (a), PDA-PEI coating (b), ZrO2-ITM (c) and cross-section structure of ZrO2-ITM (d).

    Figure  4.  AFM image of the ZrO2-ITM composite membrane surface. (color online)

    Figure  5.  FT-IR/ATR of PET ITM, PEI-PDA coating and ZrO2-ITM composite membrane. (color online)

    Figure  6.  (a) Energy spectrum analysis results of the ZrO2-ITM composite membrane; SEM image (b) of the membrane surface and corresponding EDS image (c) of the distribution of Zr element (blue point) on the composite membrane. (color online)

    Figure  7.  The static contact angle of the ITM, the PDA-PEI coating surface and the ZrO2-ITM composite membrane. (color online)

    Figure  8.  Water flux (a) of before and after compositing and salt retention (b) of ZrO2-ITM composite membrane. (color online)

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出版历程
  • 收稿日期:  2022-01-29
  • 修回日期:  2022-04-12
  • 刊出日期:  2023-03-20

Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane

doi: 10.11804/NuclPhysRev.40.2022011
    基金项目:  Youth Innovation Promotion Association of CAS(Y850030YQO); National Natural Science Foundation of China(Y850020GJ0); National Key Research and Development Program of China(Y91O171KJ1)
    作者简介:

    (1996–), male, Tongwei, Gansu Province, Postgraduate, working on condensed matter physics and materials science; E-mail: mashengming@impcas.ac.cn

    通讯作者: E-mail: modan@impcas.ac.cnE-mail: yaohuijun@impcas.ac.cn
  • 中图分类号: O571.6

摘要: 纳滤膜在海水淡化及饮用水净化领域起着越来越重要的作用,核孔膜作为一种重要的分离材料,具有均匀的孔径、可调的孔密度及无缺陷的表面,在水处理及精确分离应用方面有着潜在的优势,高孔密度的超薄核孔膜在制备高性能纳滤膜上具有很大的潜力。基于此,利用氧化锆作选择层,核孔膜作为支撑层制备出了三层结构的有机无机复合纳滤膜,聚多巴胺(PDA)与聚乙烯亚胺(PEI)中间层促进无机纳米粒子在膜表面形成无机层。制备出的复合膜可实现对不同盐的部分截留,表现出的截留顺序为Na2SO4>MgSO4>MgCl2>NaCl。

English Abstract

马圣明, 梁志豪, 王星凡, 郭再超, 刘杰, 段敬来, 莫丹, 姚会军. 基于PET核孔膜制备有机无机复合纳滤膜[J]. 原子核物理评论, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
引用本文: 马圣明, 梁志豪, 王星凡, 郭再超, 刘杰, 段敬来, 莫丹, 姚会军. 基于PET核孔膜制备有机无机复合纳滤膜[J]. 原子核物理评论, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
Shengming MA, Zhihao LIANG, Xingfan WANG, Zaichao GUO, Jie LIU, Jinglai DUAN, Dan MO, Huijun YAO. Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane[J]. Nuclear Physics Review, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
Citation: Shengming MA, Zhihao LIANG, Xingfan WANG, Zaichao GUO, Jie LIU, Jinglai DUAN, Dan MO, Huijun YAO. Fabrication of Organic-inorganic Composite Nanofiltration Membrane Based on PET Ion Track Membrane[J]. Nuclear Physics Review, 2023, 40(1): 92-98. doi: 10.11804/NuclPhysRev.40.2022011
    • The shortage of fresh water and the deterioration of water environment resulting from economic and population growth have seriously threatened the continuous development of human beings and limited sustainable development, which urgently requires suitable water treatment technology to alleviate the current situation[1]. With the increasing demand for clean water, membrane technologies have been widely applied in purification and separation due to their commendable separation efficiency[2-6].

      In the pressure-driven membrane technology, nanofiltration technology with separation characteristics between ultrafiltration and reverse osmosis is widely used in drinking water and waste water treatments due to the low energy consumption and the high retention for multivalent ions and organic molecules ($ 200 \sim 1\,000 $ Da). In general, the nanofiltration membrane possesses the asymmetric structure consisting of selective layer and support substrate[7] or the triple-layered structure with a interlayer[8-10], which can be fabricated by interfacial polymerization[7], layer-by-layer assembly[11] and so on.

      The ion track membrane (ITM), as a kind of important separation membrane with uniform pore size, regulable pore density, and free-defect surface, has potential permission in water treatments and precise separation. ITM can be effectively prepared by two procedures, swift heavy ion irradiation and chemical etching. During swift heavy ion irradiation, the latent ion tracks along the ion projectile will form in the polymer film. The next procedure is chemical etching in which the latent tracks are transformed into pores with defined size[12]. Up to date, the ITM has been widely used in the fields of biology, medicine[13], ion separation[14-15] and water treatments including microfiltration[16], ultrafiltration[17-18] and membrane distillation[19-20]. However, the ITM used as selective layer with the pore size in the range of 1 to 10 nm is extremely difficult to be obtained, which limits the application of ITM in nanofiltration that requires ultrathin selective layer to acquire high water flux. To the best of our knowledge, the ITM has not been used in nanofiltration as a special membrane material up to now. Thus, it can be a feasible solution to prepare the nanofiltration membrane by using the ITM acting as the support layer.

      Besides, inorganic membrane materials are combination of excellent chemical, mechanical, and thermal stability, which can improve the chemical and mechanical stability of polymer ITM. It is reported that the organic-inorganic composite nanofiltration membranes have been realized in other polymeric substrates[21-22]. The mussel-inspired polydopamine (PDA) coating method has attracted much interest and been widely adopted due to its simplicity, versatility and strongly adhere to almost any substrate surface on account of multiple covalent and non-covalent interaction[23-25]. At the same time, the PDA coating can facilitate a combination between polymeric support and metal oxides for constructing inorganic films on various substrates. polyethyleneimine (PEI) has great potential for preparing membrane-separation materials thanks to the dendritic structure[25]. Compared with PDA coating in acidic, alkaline and oxidizing environments, the PEI introduced into the co-deposition system of ITM can further provide better stability of the PDA/PEI coating due to the covalent reaction between PEI and dopamine. Moreover, because of the existence of carboxyl groups on the surface of the polyethylene terephthalate (PET) ITM, PDA/PEI co-deposition in carboxyl surface has higher initial adsorption rate than hydroxyl, alkyl and phenyl[25]. This further shows that it is feasible to prepare organic-inorganic composite membranes by PDA/PEI co-deposition method.

      In this work, organic-inorganic composite nanofiltration membranes were prepared with an inorganic selective layer on PET ion track membranes and a PDA-PEI coating platform as an interlayer. The combination with ultrathin ZrO2 selective layer and the PET ITM is a successful attempt for modifying and preparing composite membrane based on PET ITM, which opens the window of the application of PET ITM in nanofiltration.

    • 8 µm thick PET films were purchased from DuPont Co., Ltd, US. Dopamine hydrochloride, PEI (MW = 600 Da), Zirconium sulfate tetrahydrate, tris(hydroxymethyl) aminomethane were purchased from Aladdin Chemistry Co., Ltd, China. Other reagents, including ethanol, sodium chloride (NaCl), magnesium chloride (MgCl2), sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), sodium hydroxide (NaOH) and concentrated hydrochloric acid (HCl) were obtained from Tianjin Damao Chemical Reagent Co., Ltd, China.

    • The fabrication process for PET ITM is shown in Fig. 1. First, the PET membrane was irradiated by $ ^{129}{\rm{Xe}} $ ions (19.5 MeV/u) with the beam normal to the membrane surface at the Heavy Ion Research Facility in Lanzhou (HIRFL, China), and the ion latent tracks highly parallel to each other were formed. Herein, the ion fluence of $ 1\times 10\ {{\rm{ions}}/{\rm{cm}}^2} $ was adopted. Subsequently, both sides of the irradiated PET membranes were exposed to the ultra-violet (UV) light (MUA-165, MEJIRO GCNOSSEN, Japan) with 365 nm peak wavelength for 1 h. The radiation intensity of the UV light was adjusted to $ 30\ {{\rm{mW}}/{\rm{cm}}^{2}} $. Then, the sensitized PET membrane was immersed in the solution of 2 M 50 °C NaOH for 4 min to carry out chemical etching. After the etching, the ITM was washed in deionized water for three times to remove the chemical residuals completely.

      Figure 1.  Schematic diagram for the fabrication process of PET ITM. (color online)

    • The fabrication process of composite nanofiltration membrane was performed according to the reports from Lv $et~al$.[21], and is shown in Fig. 2. The PET ITM was firstly immersed in hydrochloric acid solution (2 mol/L) for 10 min at room temperature, and then transferred into ethanol and treated for 10 mins. PDA and PEI were dissolved in Tris-HCl buffer solution (pH = 8.5, 50 mmol/L). The mass ratio of PDA and PEI was fixed at 1:1 with a total concentration of 2 mg/mL. After that, the ITM pre-wetted by ethanol were moved into the freshly as-prepared PDA/PEI solution and gently stirred at room temperature for 1 h. The resulting composite membrane was washed with deionized water several times and dried naturally. 0.7 g Zirconium sulfate tetrahydrate was dissolved in 500 mL hydrochloric solution with the concentration of 40 mmol/L. Subsequently, the PDA-PEI coating ITM was immersed in the solution at room temperature for 10 h. Finally, the resulting organic-inorganic composite nanofiltration membrane was washed in deionized water several times and dried in oven at 40 °C for 5 h to further evaluate its performance and characterization. The thin ZrO2-layer obtained from the hydrolysis process of zirconium sulfate tetrahydrate (Zr(SO4)2) under equilibrium reactions as follows:

      Figure 2.  Schematic diagram of the preparation process for the organic-inorganic composite nanofiltration membranes with ultrathin ZrO2 film as the selective layer on the PDA-PEI coating ITM. (color online)

      $$ {2[{\rm{Zr}}({\rm{SO_4^{}}})_2^{}]} + 3{{\rm{H_2^{}O}}}\to {[{\rm{Zr_2^{}}}({\rm{OH}})_3^{}({\rm{SO_4^{}}})_4^{}]^{3-}} + 3{{\rm{H}}^+}, $$ (1)
      $$ {[{\rm{Zr_2^{}}}({\rm{OH}})_3^{}({\rm{SO_4^{}}})_4^{}]^{3-}} + 3{{\rm{OH}}^-} \to {{\rm{Zr_2^{}}}({\rm{OH}}){\rm{_6^{}SO_4^{}}}} + 3{{\rm{SO_4}}^{2-}}, $$ (2)
      $$ {{\rm{Zr_2}}^{}({\rm{OH}})_6^{}{\rm{SO_4}}^{}} + 2{{\rm{OH}}^-} \to {\rm{ZrO_2}}^{} + {{\rm{SO_4^{}}}^{2-}}+4{{\rm{H_2}}^{}{\rm{O}}}. $$ (3)
    • The chemical structures and detailed components of membrane surfaces were analyzed by attenuated total reflectance Fourier transform infrared spectrometer (FT-IR/ATR, vertex 70, Bruker, Germany). Scanning electron microscopy (SEM, Nano-SEM 450, FEI, US) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the morphologies and elemental distribution of the membrane. The morphology and roughness of the membranes were observed by atom force microscopy (AFM, Cypher S, Asylum Research, UK). The water contact angles before and after composite were measured by a contact angle system (SZ-CAMB, Sunzern, China) at room temperature.

    • Nanofiltration performance of composite membrane was evaluated by measurement of pure water flux and salt rejection using a lab-scale cross-flow filtration apparatus (effective membrane area is $ 7.1\ {{\rm{cm}}^2} $). Membranes were pre-compacted under 0.65 MPa for over 30 min before evaluation and tested under 0.6 MPa at room temperature. Various salts including NaCl, MgCl2, Na2SO4, MgSO4 were dissolved in deionized water and used as feed solutions with a concentration of 1 g/L. The permeate flux was calculated by the following equation:

      $$ F = \frac{V}{A\times t}, $$

      where $ V $ is the volume of permeated solution; $ A $ is the effective membrane area; $ t $ is the filtration time. The salt rejection was calculated as follow:

      $$ R = \left( { 1-\frac{c_{\rm{p}}^{}}{c_{\rm{f}}^{}} } \right)\times 100\text{%}, $$

      where $ c_{\rm{p }}^{} $ and $ c_{\rm{f}} ^{}$ are the concentration of the permeated and feed solution, respectively. The concentration of the salt solution was determined by the solution conductivity monitored using the electrical conductivity meter (METTLER TOLEDO S230, Switzerland).

    • The morphology of prepared ITM support, PDA-PEI coating and ZrO2-ITM composite membrane were first characterized by SEM as shown in Fig. 3. The nanopores of ITM with diameter in 35 nm are obtained when the chemical etching was optimized as 4 min Fig. 3(a). When chemical etching time is 3.5 min, it is difficult to acquire effective data due to the extremely low water flux of the related ZrO2-ITM composite membrane. Once the chemical etching time is 4.5 min, the mechanical property of ITM substrate will become weaker and the ITM substrate is easily to crack. Thus, the 4-min is chosen as the optimal chemical etching time in our current experiments. Due to the high ion irradiation fluence, the overlapping of the nanopores in ITM support happens. After PDA-PEI coating, the pore size significantly shrinks from 35 to 20 nm Fig. 3(b). After ZrO2 growing on the PDA-PEI coated ITM, the surface of the ZrO2-ITM composite membrane changes significantly due to the formation of the top layer, which can act as the selective layer during the nanofiltration process. The thickness of the selective layer was confirmed as 130 nm from the cross-section of the ZrO2 composite membrane [as Fig. 3(d) shown]. Furthermore, the roughness of the top layer was obtained through AFM measurement and the peak-to -valley roughness is about 38 nm as shown in Fig. 4.

      Figure 3.  Surface morphologies of ITM support (a), PDA-PEI coating (b), ZrO2-ITM (c) and cross-section structure of ZrO2-ITM (d).

      Figure 4.  AFM image of the ZrO2-ITM composite membrane surface. (color online)

      FT-IR/ATR and EDS are used for obtaining the chemical structure of the membrane surface. As shown in Fig. 5, the main absorption bands for the bare PET ITM are determined as $ 2\,970\ {{\rm{cm}}^{-1}} $ (aromatic CH), $ 2\,912\ {{\rm{cm}}^{-1}} $ (aliphatic CH), $ 1\,710\ {{\rm{cm}}^{-1}} $ (C = O group), 1 615, 1 470, $ 1\,407\ {{\rm{cm}}^{-1}} $ (aromatic vibrations of the carbon skeleton), $ 1\,340\ {{\rm{cm}}^{-1}} $ (OCH bending), stretching vibrations of C(O)-O bonds of ether groups ($ 1\,238\ {{\rm{cm}}^{-1}} $), $ 1\,096\ {{\rm{cm}}^{-1}} $ (C-O stretching), $ 1\,017\ {{\rm{cm}}^{-1}} $ (ring CCC bending) and $ 970\ {{\rm{cm}}^{-1}} $ (O-CH2)[19]. After the composite process, there is no significant new adsorption peaks appeared in the FT-IR/ATR spectra besides the significantly strengthen on the absorption peak of ZrO2.

      Figure 5.  FT-IR/ATR of PET ITM, PEI-PDA coating and ZrO2-ITM composite membrane. (color online)

      In order to obtain the element distribution and morphology information of ZrO2 on the surface of the composite membrane further, the EDS analysis and SEM observation were adopted and the corresponding results are shown in Fig. 6. Three elements including carbon (C), oxygen (O) and zirconium (Zr) are confirmed Fig. 6(a). From the SEM image of the composite membrane Fig. 6(b) and the corresponding EDS mapping image Fig. 6(c), it can be confirmed that the Zr element is uniformly distributed on the membrane surface. These demonstrate the dopamine hydrochloric in Tris-HCl buffer solution plays a key role acting as bio-glue well since it promotes the deposition of the top layer of zirconium and polydopamine coating. The hydrolysis process of zirconium sulfate tetrahydrate to the ZrO2 is explained by Eqs. (1~3).

      Figure 6.  (a) Energy spectrum analysis results of the ZrO2-ITM composite membrane; SEM image (b) of the membrane surface and corresponding EDS image (c) of the distribution of Zr element (blue point) on the composite membrane. (color online)

      The surface wettability is an important parameter of the separation membrane, which can affect the water flux and fouling resistance of the membrane. In general, the hydrophilic surface is preferred because it can not only promote the water permeation but also improve the fouling resistance of the membrane[26]. To evaluate the surface wettability of the membranes, the contact angles of the membranes before and after compositing were measured. As shown in Fig. 7, the ITM membrane exhibits good hydrophilicity due to the existence of carboxyl groups and porous structure, and the surface contact angle is about 62.2°. After PDA/PEI deposition, the surface contact angle decreases to about 46.5°. This is attributed to the hydrophilic nature of PEI. When hydrophilic PDA-PEI coating surface was covered by the ZrO2 selective layer, the surface becomes smooth and dense, which results in an increased contact angle (around 70°).

      Figure 7.  The static contact angle of the ITM, the PDA-PEI coating surface and the ZrO2-ITM composite membrane. (color online)

      The filtration performance of the ZrO2-ITM composite membrane was evaluated with a typical cross-flow process. First, the pure water flux of prepared PET ITM with 35 nm pore diameter was measured and the water flux is $148~{{\rm{L}}\boldsymbol\cdot {\rm{m}}^{-2}\boldsymbol\cdot {\rm{h}}^{-1}}$ as shown in Fig. 8(a). After PDA/PEI coating, the pure water flux decreases to $114~{{\rm{L}}\boldsymbol\cdot {\rm{m}}^{-2}\boldsymbol\cdot {\rm{h}}^{-1}}$, which attributes to the decreasing pore size caused by PDA-PEI coating. Further, the water flux of the ZrO2-ITM composite membrane significantly drops to $6.1~{{\rm{L}}\boldsymbol\cdot {\rm{m}}^{-2}\boldsymbol\cdot {\rm{h}}^{-1}}$ due to the formation of dense selective layer. In addition, the retention of the membrane for Na2SO4 was also measured before and after compositing. It is found that the ITM and PDA/PEI coating membrane have no rejecting effect on Na2SO4. The main reason is that the pore sizes in ITM and PDA-PEI coating are too large to reject salts. However, the ZrO2-ITM composite membrane has 53% retention on Na2SO4, which further shows that the top layer of the ZrO2-ITM composite is compact enough to reject salts. At the same time, the retention effect for other salts including MgSO4, MgCl, NaCl was also investigated and the corresponding results are shown in Fig. 8(b). As displayed in Fig. 8(b), the salts retention follows the order of Na2SO4>MgSO4>MgCl2>NaCl, which is similar to other nanofiltration system and mainly caused by Donnan and size exclusion effects[27].

      Figure 8.  Water flux (a) of before and after compositing and salt retention (b) of ZrO2-ITM composite membrane. (color online)

    • PET ion track membranes (ITMs) were prepared by heavy ions irradiation, UV sensitization and ion track etching procedures. Organic-inorganic composite nanofiltration membranes with an inorganic selective layer were prepared on PET ion track membranes with a PDA-PEI coating platform as an interlayer. The ZrO2 layer with thin thickness and low roughness was prepared on the interlayer acting as selective layer. The prepared ZrO2-ITM composite membrane can achieve partial rejection for various kinds of salts including Na2SO4, MgSO4, MgCl, NaCl. The combination with ultrathin organic selective layer and PET ITM can be a successful attempt to modify and produce composite membrane based on PET ITM, which achieves the application of PET ITM in nanofiltration filed and broaden the application area of ITM.

      Acknowledgments We gratefully acknowledge finance support from the Youth Innovation Promotion Association of CAS (Grant No. Y850030YQO), the National Nature Science Foundation of China (Grant No. Y850020GJ0) and National Key Research and Development Program of China (Grant No. Y91O171KJ1). We would like to thank the members of Materails Research Center and the accelerator staff of HIRFL of IMP for preparation and irradiation of PET films.

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