Preparation and properties of hollow fibre nanofiltration membrane with continuous coffee-ring structure

doi:10.1007/s11705-020-1943-8

Front. Chem. Sci. Eng.

2021, Vol. 15

Issue (2) : 351-362 https://doi.org/10.1007/s11705-020-1943-8

RESEARCH ARTICLE

Preparation and properties of hollow fibre nanofiltration membrane with continuous coffee-ring structure

Xiuzhen Wei^1,²(

), Xufeng Xu^1,², Yi Chen^1,², Qian Zhang^1,², Lu Liu^1,², Ruiyuan Yang^1,², Jinyuan Chen^1,²(

), Bosheng Lv^1,²

¹. College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
². Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, Hangzhou 310014, China

Download: PDF(1475 KB) HTML
Export: BibTeX | EndNote | Reference Manager | ProCite | RefWorks

Abstract

Polyamide (PA) hollow fibre composite nanofiltration (NF) membranes with a coffee-ring structure and beneficial properties were prepared by adding graphene oxide (GO) into the interfacial polymerization process. The presentation of the coffee-ring structure was attributed to the heterogeneous, finely dispersed multiphase reaction system and the “coffee-stain” effect of the GO solution. When the piperazine concentration was 0.4 wt-%, the trimesoyl chloride concentration was 0.3 wt-%, and the GO concentration was 0.025 wt-%, the prepared NF membranes showed the best separation properties. The permeate flux was 76 L·m⁻²·h⁻¹, and the rejection rate for MgSO₄ was 98.6% at 0.4 MPa. Scanning electron microscopy, atomic force microscopy, and attenuated total reflectance-Fourier transform infrared spectroscopy were used to characterize the chemical structure and morphology of the PA/GO NF membrane. The results showed that GO was successfully entrapped into the PA functional layer. Under neutral operating conditions, the PA/GO membrane showed typical negatively charged NF membrane separation characteristics, and the rejection rate decreased in the order of Na₂SO₄>MgSO₄>MgCl₂>NaCl. The PA/GO NF membrane showed better antifouling performance than the PA membrane.

Keywords GO PA interfacial polymerization hollow fibre NF membrane

Corresponding Author(s): Xiuzhen Wei,Jinyuan Chen

Just Accepted Date: 15 May 2020 Online First Date: 19 June 2020 Issue Date: 10 March 2021

Cite this article:

Xiuzhen Wei,Xufeng Xu,Yi Chen, et al. Preparation and properties of hollow fibre nanofiltration membrane with continuous coffee-ring structure[J]. Front. Chem. Sci. Eng., 2021, 15(2): 351-362.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-020-1943-8
https://academic.hep.com.cn/fcse/EN/Y2021/V15/I2/351

Fig.1 SEM surface and cross-sectional images of M0, M1, M2, M3, M4, M5 NF membranes. 1: Inner surface morphology; 2: cross-sectional morphology.

Fig.2 AFM images of surfaces for M0, M2, M4.

Tab.1 Surface roughness values of the prepared M0, M2, M4 membranes

Fig.3 ATR-FTIR spectra of PSF, PA and PA/GO membranes.

Fig.4 SCA of PA and PA/GO membranes.

Fig.5 Zeta potentials of the PA/GO NF membranes at various pH values.

Fig.6 MWCO of PA/GO NF membranes.

Fig.7 Effect of GO concentration on PA/GO NF membrane performance.

Fig.8 Separation behaviour of NF membranes for four inorganic salts.

Tab.2 Radius and diffusion coefficient of different inos

Tab.3 Performance comparison of different NF membrane modified with GO

Fig.9 Flux change of M0 and M4 NF membranes with time prolonging in treatment LYS, BSA and HA solutions.

Fig.10 SEM of M0 and M4 membranes inner surface after treating with LYS, BSA and HA solutions. 1: LYS; 2: BSA; 3: HA.

Fig.11 Effect of operation time on water flux and salt rejection rate for M4 membrane.

Tab.4 Rejection behavior of M0 and M4 for dye aqueous solutions

1	C J Wei, Q Cheng, L G Lin, Z F He, K Huang, S S Ma, L Chen. One-step fabrication of recyclable polyimide nanofiltration membranes with high selectivity and performance stability by a phase inversion-based process. Journal of Materials Science, 2018, 53(15): 11104–11115 https://doi.org/10.1007/s10853-018-2369-2
2	J Miao, R Zhang, R Bai. Development and characterization of quaternized poly(vinyl alcohol) composite nanofiltration membranes. Journal of Materials Science, 2016, 51(4): 1855–1863 https://doi.org/10.1007/s10853-015-9492-0
3	A L Ahmad, B S Ooi, A Wahab Mohammad, J P Choudhury. Development of a highly hydrophilic nanofiltration membrane for desalination and water treatment. Desalination, 2004, 168: 215–221 https://doi.org/10.1016/j.desal.2004.07.001
4	H W Liang, X Cao, W J Zhang, H T Lin, F Zhou, L F Chen, S H Yu. Robust and highly efficient free-standing carbonaceous nanofiber membranes for water purification. Advanced Functional Materials, 2011, 21(20): 3851–3858 https://doi.org/10.1002/adfm.201100983
5	H J Zhang, C C Cai, Y Z Wu, D D Shao, B H Ye, Y Zhang, J Y Liu, J Wang, X Y Jia. Mitochondrial and endoplasmic reticulum pathways involved in microcystin-LR-induced apoptosis of the testes of male frog (Rana nigromaculata) in vivo. Journal of Hazardous Materials, 2013, 252-253: 382–389 https://doi.org/10.1016/j.jhazmat.2013.03.017
6	E F Krivoshapkina, A A Vedyagin, P V Krivoshapkin. Preparation of catalytic membranes with a nanostructured layer based on alumina. Nanotechnologies in Russia, 2014, 9(7-8): 423–429 https://doi.org/10.1134/S1995078014040107
7	M Jahanshahi, A Rahimpour, M Peyravi. Developing thin film composite poly(piperazine-amide) and poly(vinyl-alcohol) nanofiltration membranes. Desalination, 2010, 257(1–3): 129–136 https://doi.org/10.1016/j.desal.2010.02.034
8	L Y Liu, H Kang, W Wang, Z W Xu, W Mai, J Li, H M Lv, L H Zhao, X M Qian. Layer-by-layer self-assembly of polycation/GO/OCNTs nanofiltration membrane with enhanced stability and flux. Journal of Materials Science, 2018, 53(15): 10879–10890 https://doi.org/10.1007/s10853-018-2317-1
9	L Tessier, P Bouchard, M Rahni. Separation and purification of benzylpenicillin produced by fermentation using coupled ultrafiltration and nanofiltration technologies. Journal of Biotechnology, 2005, 116(1): 79–89 https://doi.org/10.1016/j.jbiotec.2004.09.002
10	K Y Wang, T S Chung. The characterization of flat composite nanofiltration membranes and their applications in the separation of cephalexin. Journal of Membrane Science, 2005, 247(1-2): 37–50 https://doi.org/10.1016/j.memsci.2004.09.007
11	S Y Cheng, D L Oatley, P M Williams, C J Wright. Positively charged nanofiltration membranes: Review of current fabrication methods and introduction of a novel approach. Advances in Colloid and Interface Science, 2011, 164(1-2): 12–20 https://doi.org/10.1016/j.cis.2010.12.010
12	N Heshmati, B Wagner, X Cheng, T Scholz, M Kansy, G Eisenbrand, G Fricker. Physicochemical characterization and in vitro permeation of an indirubin derivative. European Journal of Pharmaceutical Sciences, 2013, 50(3-4): 467–475 https://doi.org/10.1016/j.ejps.2013.08.021
13	L Yu, Y Zhang, B Zhang, J Liu, H Zhang, C Song. Preparation and characterization of HPEI-GO/PES ultrafiltration membrane with antifouling and antibacterial properties. Journal of Membrane Science, 2013, 447: 452–462 https://doi.org/10.1016/j.memsci.2013.07.042
14	X Peng, J Jin, Y Nakamura, T Ohno, I Ichinose. Ultrafast permeation of water through protein-based membranes. Nature Nanotechnology, 2009, 4(6): 353–357 https://doi.org/10.1038/nnano.2009.90
15	Z J Cai, C Zhu, P Xiong, J Guo, K Y Zhao. Calcium alginate-coated electrospun polyhydroxybutyrate/carbon nanotubes composite nanofibers as nanofiltration membrane for dye removal. Journal of Materials Science, 2018, 53(20): 14801–14820 https://doi.org/10.1007/s10853-018-2607-7
16	D Zhou, L Zhu, Y Fu, M Zhu, L Xue. Development of lower cost seawater desalination processes using nanofiltration technologies—A review. Desalination, 2015, 376(1219): 109–116 https://doi.org/10.1016/j.desal.2015.08.020
17	L Wang, J P Corriou, C Castel, E Favre. A critical review of cyclic transient membrane gas separation processes: State of the art, opportunities and limitations. Journal of Membrane Science, 2011, 383(1-2): 170–188 https://doi.org/10.1016/j.memsci.2011.08.052
18	P Bernardo, E Drioli, G Golemme. Membrane gas separation: A review/state of the art. Industrial & Engineering Chemistry Research, 2009, 48(10): 4638–4663 https://doi.org/10.1021/ie8019032
19	M Wu, J Yuan, H Wu, Y Su, H Yang, X You, R Zhang, X He, N A Khan, R Kasher, Z Jiang. Ultrathin nanofiltration membrane with polydopamine-covalent organic framework interlayer for enhanced permeability and structural stability. Journal of Membrane Science, 2019, 576: 131–141 https://doi.org/10.1016/j.memsci.2019.01.040
20	E S Kim, Q Yu, B Deng. Plasma surface modification of nanofiltration (NF) thin-film composite (TFC) membranes to improve anti organic fouling. Applied Surface Science, 2011, 257(23): 9863–9871 https://doi.org/10.1016/j.apsusc.2011.06.059
21	Y Zhao, N Li, S Xia. Polyamide nanofiltration membranes modified with Zn-Al layered double hydroxides for natural organic matter removal. Composites Science and Technology, 2016, 132: 84–92 https://doi.org/10.1016/j.compscitech.2016.06.016
22	M Safarpour, V Vatanpour, A Khataee, M Esmaeili. Development of a novel high flux and fouling-resistant thin film composite nanofiltration membrane by embedding reduced graphene oxide/TiO2. Separation and Purification Technology, 2015, 154: 96–107 https://doi.org/10.1016/j.seppur.2015.09.039
23	H Zarrabi, M E Yekavalangi, V Vatanpour, A Shockravi, M Safarpour. Improvement in desalination performance of thin film nanocomposite nanofiltration membrane using amine-functionalized multiwalled carbon nanotube. Desalination, 2016, 394: 83–90 https://doi.org/10.1016/j.desal.2016.05.002
24	T Kamada, T Ohara, T Shintani, T Tsuru. Controlled surface morphology of polyamide membranes via the addition of co-solvent for improved permeate flux. Journal of Membrane Science, 2014, 467: 303–312 https://doi.org/10.1016/j.memsci.2014.03.072
25	G S Lai, W J Lau, P S Goh, A F Ismail, N Yusof, Y H Tan. Graphene oxide incorporated thin film nanocomposite nanofiltration membrane for enhanced salt removal performance. Desalination, 2016, 387: 14–24 https://doi.org/10.1016/j.desal.2016.03.007
26	Z Tan, S Chen, X Peng, L Zhang, C Gao. Polyamide membranes with nanoscale Turing structures for water purification. Science, 2018, 360(6388): 518–521 https://doi.org/10.1126/science.aar6308
27	S Kondo, T Miura. Reaction-diffusion model as a framework for understanding biological pattern formation. Science, 2010, 329(5999): 1616–1620 https://doi.org/10.1126/science.1179047
28	R Zimmermann. Condensation Polymers: By Interfacial and Solution Methods. Von P. W. Morgan. John Wiley & Sons, New York London-Sydney 1965. 1. Angewandte Chemie, 1966, 78(16): 787 https://doi.org/10.1002/ange.19660781632
29	T Bánsági, V K Vanag, I R Epstein. Tomography of reaction-diffusion microemulsions reveals three-dimensional turing patterns. Science, 2011, 331(6022): 1309–1312 https://doi.org/10.1126/science.1200815
30	N Tompkins, N Li, C Girabawe, M Heymann, G B Ermentrout, I R Epstein, S Fraden. Testing Turing’s theory of morphogenesis in chemical cells. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111(12): 4397–4402 https://doi.org/10.1073/pnas.1322005111
31	R Ding, H Zhang, Y Li, J Wang, B Shi, H Mao, J Dang, J Liu. Graphene oxide-embedded nanocomposite membrane for solvent resistant nanofiltration with enhanced rejection ability. Chemical Engineering Science, 2015, 138: 227–238 https://doi.org/10.1016/j.ces.2015.08.019
32	Y Qin, H L Liu, Y M Liu, M X Chen, K K Chen, Y Huang, C F Xiao. Design of a novel interfacial enhanced GO-PA/APVC nanofiltration membrane with stripe-like structure. Journal of Membrane Science, 2020, 604: 118064 https://doi.org/10.1016/j.memsci.2020.118064
33	A Anand, B Unnikrishnan, J Y Mao, H J Lin, C C Huang. Graphene-based nanofiltration membranes for improving salt rejection, water flux and antifouling—A review. Desalination, 2018, 429: 119–133 https://doi.org/10.1016/j.desal.2017.12.012
34	S Bano, A Mahmood, S J Kim, K H Lee. Graphene oxide modified polyamide nanofiltration membrane with improved flux and antifouling properties. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2015, 3(5): 2065–2071 https://doi.org/10.1039/C4TA03607G
35	R Hu, R Zhang, Y He, G Zhao, H Zhu. Graphene oxide-in-polymer nanofiltration membranes with enhanced permeability by interfacial polymerization. Journal of Membrane Science, 2018, 564: 813–819 https://doi.org/10.1016/j.memsci.2018.07.087
36	C Cheng, P Li, T Zhang, X Wang, B S Hsiao. Enhanced pervaporation performance of polyamide membrane with synergistic effect of porous nanofibrous support and trace graphene oxide lamellae. Chemical Engineering Science, 2019, 196: 265–276 https://doi.org/10.1016/j.ces.2018.11.019
37	H Lian, L Qi, J Luo, R Zhang, K Hu. Uniform droplet printing of graphene micro-rings based on multiple droplets overwriting and coffee-ring effect. Applied Surface Science, 2019, 499: 143826 https://doi.org/10.1016/j.apsusc.2019.143826
38	D S Eom, J Chang, Y W Song, J A Lim, J T Han, H Kim, K Cho. Coffee-ring structure from dried graphene derivative solutions: A facile one-step fabrication route for all graphene-based transistors. Journal of Physical Chemistry C, 2014, 118(46): 27081–27090 https://doi.org/10.1021/jp507451b
39	L Lin, R Lopez, G Z Ramon, O Coronell. Investigating the void structure of the polyamide active layers of thin-film composite membranes. Journal of Membrane Science, 2016, 497: 365–376 https://doi.org/10.1016/j.memsci.2015.09.020
40	W Fang, L Shi, R Wang. Mixed polyamide-based composite nanofiltration hollow fiber membranes with improved low-pressure water softening capability. Journal of Membrane Science, 2014, 468: 52–61 https://doi.org/10.1016/j.memsci.2014.05.047
41	M Hu, B Mi. Enabling graphene oxide nanosheets as water separation membranes. Environmental Science & Technology, 2013, 47(8): 3715–3723 https://doi.org/10.1021/es400571g
42	C Zhao, X Xu, J Chen, F Yang. Effect of graphene oxide concentration on the morphologies and antifouling properties of PVDF ultrafiltration membranes. Journal of Environmental Chemical Engineering, 2013, 1(3): 349–354 https://doi.org/10.1016/j.jece.2013.05.014
43	Z Wang, H Yu, J Xia, F Zhang, F Li, Y Xia, Y Li. Novel GO-blended PVDF ultrafiltration membranes. Desalination, 2012, 299: 50–54 https://doi.org/10.1016/j.desal.2012.05.015
44	X Kong, Y Zhang, S Y Zeng, B K Zhu, L P Zhu, L F Fang, H Matsuyama. Incorporating hyperbranched polyester into cross-linked polyamide layer to enhance both permeability and selectivity of nanofiltration membrane. Journal of Membrane Science, 2016, 518: 141–149 https://doi.org/10.1016/j.memsci.2016.07.037
45	J Yin, E S Kim, J Yang, B Deng. Fabrication of a novel thin-film nanocomposite (TFN) membrane containing MCM-41 silica nanoparticles (NPs) for water purification. Journal of Membrane Science, 2012, 423-424: 238–246 https://doi.org/10.1016/j.memsci.2012.08.020
46	E S Kim, B Deng. Fabrication of polyamide thin-film nano-composite (PA-TFN) membrane with hydrophilized ordered mesoporous carbon (H-OMC) for water purifications. Journal of Membrane Science, 2011, 375(1-2): 46–54 https://doi.org/10.1016/j.memsci.2011.01.041
47	R K Joshi, P Carbone, F C Wang, V G Kravets, Y Su, I V Grigorieva, H A Wu, A K Geim, R R Nair. Precise and ultrafast molecular sieving through graphene oxide membranes. Science, 2014, 343(6172): 752–754 https://doi.org/10.1126/science.1245711
48	J P Ambre, K B Dhopte, P R Nemade, V H Dalvi. High flux hyperbranched starch-graphene oxide piperazinamide composite nanofiltration membrane. Journal of Environmental Chemical Engineering, 2019, 7(6): 103300 https://doi.org/10.1016/j.jece.2019.103300
49	Y Kang, M Obaid, J Jang, I S Kim. Sulfonated graphene oxide incorporated thin film nanocomposite nanofiltration membrane to enhance permeation and antifouling properties. Desalination, 2019, 470: 114125 https://doi.org/10.1016/j.desal.2019.114125
50	W Shao, C Liu, H Ma, Z Hong, Q Xie, Y Lu. Fabrication of pH-sensitive thin-film nanocomposite nanofiltration membranes with enhanced performance by incorporating amine-functionalized graphene oxide. Applied Surface Science, 2019, 487: 1209–1221 https://doi.org/10.1016/j.apsusc.2019.05.157
51	P Wen, Y Chen, X Hu, B Cheng, D Liu, Y Zhang, S Nair. Polyamide thin film composite nanofiltration membrane modified with acyl chlorided graphene oxide. Journal of Membrane Science, 2017, 535: 208–220 https://doi.org/10.1016/j.memsci.2017.04.043
52	H Li, W Shi, Q Du, R Zhou, H Zhang, X Qin. Improved separation and antifouling properties of thin-film composite nanofiltration membrane by the incorporation of cGO. Applied Surface Science, 2017, 407: 260–275 https://doi.org/10.1016/j.apsusc.2017.02.204
53	T Ma, Y Su, Y Li, R Zhang, Y Liu, M He, Y Li, N Dong, H Wu, Z Jiang. Fabrication of electro-neutral nanofiltration membranes at neutral pH with antifouling surface via interfacial polymerization from a novel zwitterionic amine monomer. Journal of Membrane Science, 2016, 503: 101–109 https://doi.org/10.1016/j.memsci.2015.12.038
54	Y Li, Y Su, X Zhao, X He, R Zhang, J Zhao, X Fan, Z Jiang. Antifouling, high-flux nanofiltration membranes enabled by dual functional polydopamine. ACS Applied Materials & Interfaces, 2014, 6(8): 5548–5557 https://doi.org/10.1021/am405990g
55	T Szabó, E Tombácz, E Illés, I Dékány. Enhanced acidity and pH-dependent surface charge characterization of successively oxidized graphite oxides. Carbon, 2006, 44(3): 537–545 https://doi.org/10.1016/j.carbon.2005.08.005

[1]

FCE-19086-OF-WX_suppl_1

Download

[1]	Wei Zhang, Boren Xu, Caihong Gong, Chunwang Yi, Shen Zhang. Antibacterial and anti-flaming PA6 composite with metathetically prepared nano AgCl@BaSO₄ co-precipitates[J]. Front. Chem. Sci. Eng., 2021, 15(2): 340-350.
[2]	Hasan Oliaei Torshizi, Ali Nakhaei Pour, Ali Mohammadi, Yahya Zamani, Seyed Mehdi Kamali Shahri. Fischer-Tropsch synthesis by reduced graphene oxide nanosheets supported cobalt catalysts: role of support and metal nanoparticle size on catalyst activity and products selectivity[J]. Front. Chem. Sci. Eng., 2021, 15(2): 299-309.
[3]	Boa Jin, Hyunmin Park, Yang Liu, Leijing Liu, Jongdeok An, Wenjing Tian, Chan Im. Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current[J]. Front. Chem. Sci. Eng., 2021, 15(1): 164-179.
[4]	Feng Sun, Jinren Lu, Yuhong Wang, Jie Xiong, Congjie Gao, Jia Xu. Reductant-assisted polydopamine-modified membranes for efficient water purification[J]. Front. Chem. Sci. Eng., 2021, 15(1): 109-117.
[5]	Wenqian Chen, Vikram Karde, Thomas N. H. Cheng, Siti S. Ramli, Jerry Y. Y. Heng. Surface hydrophobicity: effect of alkyl chain length and network homogeneity[J]. Front. Chem. Sci. Eng., 2021, 15(1): 90-98.
[6]	Yingjie Ma, Nan Zhang, Jie Li, Cuiwen Cao. Optimal design of extractive dividing-wall column using an efficient equation-oriented approach[J]. Front. Chem. Sci. Eng., 2021, 15(1): 72-89.
[7]	Huaiwei Shi, Teng Zhou. Computational design of heterogeneous catalysts and gas separation materials for advanced chemical processing[J]. Front. Chem. Sci. Eng., 2021, 15(1): 49-59.
[8]	Wenjie Sun, Jiale Mao, Shuang Wang, Lei Zhang, Yonghong Cheng. Review of recent advances of polymer based dielectrics for high-energy storage in electronic power devices from the perspective of target applications[J]. Front. Chem. Sci. Eng., 2021, 15(1): 18-34.
[9]	Weihong Zhang, Dan Wang, Jie-Xin Wang, Yuan Pu, Jian-Feng Chen. High-gravity-assisted emulsification for continuous preparation of waterborne polyurethane nanodispersion with high solids content[J]. Front. Chem. Sci. Eng., 2020, 14(6): 1087-1099.
[10]	Uthen Thubsuang, Suphawadee Chotirut, Apisit Thongnok, Archw Promraksa, Mudtorlep Nisoa, Nicharat Manmuanpom, Sujitra Wongkasemjit, Thanyalak Chaisuwan. Facile preparation of polybenzoxazine-based carbon microspheres with nitrogen functionalities: effects of mixed solvents on pore structure and supercapacitive performance[J]. Front. Chem. Sci. Eng., 2020, 14(6): 1072-1086.
[11]	Guoting Xia, Yinuo Huang, Fujiang Li, Licheng Wang, Jinbo Pang, Liwei Li, Kai Wang. A thermally flexible and multi-site tactile sensor for remote 3D dynamic sensing imaging[J]. Front. Chem. Sci. Eng., 2020, 14(6): 1039-1051.
[12]	Jiang-Wei Shen, Xue Cai, Bao-Juan Dou, Feng-Yu Qi, Xiao-Jian Zhang, Zhi-Qiang Liu, Yu-Guo Zheng. *Expression and characterization of a CALB-type lipase from Sporisorium reilianum* SRZ2 and its potential in short-chain flavor ester synthesis**[J]. Front. Chem. Sci. Eng., 2020, 14(5): 868-879.
[13]	Jun Wei, Jianbo Zhao, Di Cai, Wenqiang Ren, Hui Cao, Tianwei Tan. Synthesis of micro/meso porous carbon for ultrahigh hydrogen adsorption using cross-linked polyaspartic acid[J]. Front. Chem. Sci. Eng., 2020, 14(5): 857-867.
[14]	Hongzhe Hou, Yiqing Luo. A novel method for generating distillation configurations[J]. Front. Chem. Sci. Eng., 2020, 14(5): 834-846.
[15]	Edward Mohamed Hadji, Bo Fu, Ayob Abebe, Hafiz Muhammad Bilal, Jingtao Wang. Sponge-based materials for oil spill cleanups: A review[J]. Front. Chem. Sci. Eng., 2020, 14(5): 749-762.

Viewed

Full text

Abstract

Cited

Shared

Discussed