-
纳滤(nanofiltration, NF)是一种介于超滤和反渗透之间的压力驱动型膜分离过程. 孔径约为1 nm,对二价及多价离子具有较高的截留率,对一价离子截留率低,适用于分离体系中含有相对分子质量为几百的有机物及二价、多价离子. 近年来,纳滤膜已从常规的污水处理体系,逐步向有机溶剂、高温、耐氯、自清洗等特种分离应用方向发展.
对于纳滤膜而言,超滤基膜性质、反应单体种类和浓度、聚合时间、热处理温度等均会对致密层结构(thin film composite, TFC)产生影响,进而影响复合膜结构性能[1-3]. 一般来说,具有使用价值的超滤基膜应具有孔径分布均匀、亲水性好、耐高温、耐溶剂、力学强度优良等特点. 2018年浙江大学张林教授团队在《Science》期刊上发表了一种具有特殊“脊谷状图灵(Turing)结构”的复合纳滤膜[4],详细介绍了控制得到高渗透通量、高截留率TFC致密层表面界面聚合反应机理,表明水相单体从基膜孔内迁移至界面聚合反应区域速度主要受“反应-扩散”机制控制.
目前商业化复合膜所使用基膜多以聚砜(PSf)或聚醚砜(PES)为成膜聚合物,采用浸没沉淀相转化(NIPS)法制备. PSf和PES基膜耐高温性能、亲水性能较差,且其膜孔径相对较大、孔径分布相对较宽,此皆不利于制备高性能复合膜. 虽无机膜对苛刻环境的耐受性较优异,但其制备成本较高且加工难度较大限制了其应用,因此,开发耐热性能优异的有机纳滤膜,将进一步拓展复合膜的应用领域. 此外,温度增加会降低水溶液黏度并加快水分子扩散速度从而提升复合膜通透性能. 故耐热有机复合膜的开发不仅可拓展有机复合膜的应用领域,也可使工业余热在得到充分利用的基础上提高复合膜通透性能[5]. 为获得耐热性能优异的有机纳滤膜,目前多数研究通过采用耐热性能优异的聚合物材料如聚醚酮类、聚酰亚胺类、聚芳醚酰胺类等为膜材料制备多孔基膜,然后采用界面聚合工艺制备耐热有机复合膜,并取得了可观效果[6]. 然而此类材料制备工艺比较复杂,价格较高,限制了耐热有机纳滤膜的开发与应用.
聚对苯二甲酰对苯二胺(PPTA)是一种高性能聚芳酰胺大分子,其纤维制品被称为“Kevlar(凯夫拉)”,在我国被称为“对位芳纶或芳纶1414”,是世界三大高性能纤维之一. 其主链含有大量苯环和亲水性酰胺基团,分子间作用力强,结晶度高,带有较强的电负性,这些特性赋予了PPTA材料高强高模、耐高温、耐酸碱、耐有机溶剂等优良性能[7-9]. 随着高性能对位聚芳酰胺全球市场的急速发展和市场需求量显著增加,多品种对位芳纶纤维、水处理膜、锂电隔膜及复合材料新一轮技术开发正在加速推进,但国产高性能芳纶纤维及其下游产品研发由于各种复杂原因仍发展缓慢,其产品性能稳定性、成本、规模及应用水平方面与日本和美国等发达国家相比竞争力较弱、差距明显,特别是高性能对位芳纶分离膜材料仍是空白,尚无国产化对位芳纶膜材料问世.
因此,本文以涤纶无纺布作为增强支撑体,PPTA超滤膜为多孔基膜,以无水哌嗪(PIP)为水相单体,1,3,5-苯三甲酰氯(TMC)为油相单体,采用界面聚合制得 PPTA/PA复合纳滤膜. 研究界面聚合过程中水相单体浓度、油相单体浓度、热处理温度等条件对 PPTA/PA复合纳滤膜结构与染料脱盐性能的影响,为苛刻环境下精细膜分离的应用提供了一种新型高性能高分子分离膜材料.
对位芳香族聚酰胺复合纳滤膜制备及高温纳滤性能
Preparation and thermal resistance performance for PPTA composite nanofiltration membrane
-
摘要: 本文以对位芳香族聚酰胺(PPTA)超滤膜为基膜,无水哌嗪(PIP)与1,3,5-苯三甲酰氯(TMC)分别作为水相单体和油相单体,采用界面聚合法制得高通量耐热PPTA/PA复合纳滤膜. 研究了反应条件对PPTA/PA复合纳滤膜高温纳滤性能影响,观察了复合纳滤膜表面形貌与致密层结构,考察了渗透通量、耐热性以及抗污染等性能. 结果表明,当PIP浓度为15%wt,TMC浓度为2.5%wt,热处理温度和时间分别为60 ℃和8 min时,所得PPTA/PA复合纳滤膜对不同染料分子截留率可达95%以上,对二价盐截留率可达90%以上. 在高温条件下,所得PPTA/PA复合纳滤膜表现出优良的染料脱盐性能,在刚果红染料与Na2SO4截留率保持在99%的同时,渗透通量可达50 L·m−2·h−1·MPa−1以上.Abstract: In this paper, high flux heat-resistant PPTA/PA composite nanofiltration membranes were prepared by interfacial polymerization using para-aromatic polyamide (PPTA) ultrafiltration membrane as the base membrane and Piperazine (PIP) and trimesoyl chloride (TMC) as the aqueous and oil phase monomers, respectively. The effects of interfacial polymerization on the high-temperature nanofiltration performance of PPTA/PA composite nanofiltration membranes were investigated. The surface morphology and dense layer structure of the composite nanofiltration membranes were observed, and the permeance, heat resistance and anti-pollution properties were investigated. The results showed that when the PIP concentration was 15%wt, the TMC concentration was 2.5%wt, the heat treatment temperature and time were 60 ℃ and 8 min, respectively, the PPTA/PA composite nanofiltration membrane could retain more than 95% of rejection for different dye molecules and more than 90% of rejection for divalent salts, Under high temperature conditions, the obtained PPTA/PA composite nanofiltration membranes exhibited excellent dye desalination performance, and the permeate flux could reach more than 50 L·m−2·h−1·MPa−1 while the rejection rate of Congo red and Na2SO4 remained at 99%.
-
Key words:
- PPTA /
- interfacial polymerization /
- nanofiltration membrane /
- heat-resistance.
-
表 1 PPTA/PA复合纳滤膜样品制备参数
Table 1. The parameter of PPTA/PA NF membranes
膜样品
SamplesTMC/ % wt
ConcentrationPIP浓度/ % wt
Concentration热处理温度/℃
Thermal treatment15P-0.5T-60 0.5 15 60 15P-1.0T-60 1.0 15 60 15P-1.5T-60 1.5 15 60 15P-2.0T-60 2.0 15 60 15P-2.5T-60 2.5 15 60 15P-3.0T-60 3.0 15 60 5P-2.5T-60 2.5 5 60 10P-2.5T-60 2.5 10 60 20P-2.5T-60 2.5 20 60 25P-2.5T-60 2.5 25 60 30P-2.5T-60 2.5 30 60 15P-2.5T-40 2.5 15 40 15P-2.5T-80 2.5 15 80 -
[1] PENG L E, YANG Z, LONG L, et al. A critical review on porous substrates of TFC polyamide membranes: Mechanisms, membrane performances, and future perspectives [J]. Journal of Membrane Science, 2022, 641: 119871. doi: 10.1016/j.memsci.2021.119871 [2] WANG K P, WANG X M, JANUSZEWSKI B, et al. Tailored design of nanofiltration membranes for water treatment based on synthesis-property-performance relationships [J]. Chemical Society Reviews, 2022, 51(2): 672-719. doi: 10.1039/D0CS01599G [3] CHEN M X, XIAO C F, WANG C, et al. Preparation and characterization of a novel thermally stable thin film composite nanofiltration membrane with poly (m-phenyleneisophthalamide) (PMIA) substrate [J]. Journal of Membrane Science, 2018, 550: 36-44. doi: 10.1016/j.memsci.2017.12.040 [4] TAN Z, CHEN S F, PENG X S, et al. Polyamide membranes with nanoscale Turing structures for water purification [J]. Science, 2018, 360(6388): 518-521. doi: 10.1126/science.aar6308 [5] HU L J, ZHANG S H, HAN R L, et al. Preparation and performance of novel thermally stable polyamide/PPENK composite nanofiltration membranes [J]. Applied Surface Science, 2012, 258(22): 9047-9053. doi: 10.1016/j.apsusc.2012.05.153 [6] LIANG S M, XU G Y, JIN Y, et al. Annealing of supporting layer to develop nanofiltration membrane with high thermal stability and ion selectivity [J]. Journal of Membrane Science, 2015, 476: 475-482. doi: 10.1016/j.memsci.2014.12.003 [7] WANG C, XIAO C F, HUANG Q L, et al. A study on structure and properties of poly(p-phenylene terephthamide) hybrid porous membranes [J]. Journal of Membrane Science, 2015, 474: 132-139. doi: 10.1016/j.memsci.2014.09.055 [8] ZSCHOCKE P, STRATHMANN H. Solvent resistant membranes from poly-(p-phenylene-terephthalamide) [J]. Desalination, 1980, 34(1/2): 69-75. [9] SINGH T J, SAMANTA S. Characterization of kevlar fiber and its composites: A review [J]. Materials Today:Proceedings, 2015, 2(4/5): 1381-1387. [10] 赖星, 王黎明, 王纯, 等. 聚吡咯/凯夫拉中空纤维复合纳滤膜的制备及其染料脱盐性能 [J]. 环境化学, 2023, 42(4): 1239-1248. doi: 10.7524/j.issn.0254-6108.2021112101 LAI X, WANG L M, WANG C, et al. Fabrication of polypyrrole/kevlar hollow fiber composite nanofiltration membrane for dye desalination [J]. Environmental Chemistry, 2023, 42(4): 1239-1248(in Chinese). doi: 10.7524/j.issn.0254-6108.2021112101
[11] WANG C, XIAO C F, CHEN M X, et al. Unique performance of poly(p-phenylene terephthamide) hollow fiber membranes [J]. Journal of Materials Science, 2016, 51(3): 1522-1531. doi: 10.1007/s10853-015-9473-3 [12] FU M J, WANG C, SUN G W, et al. Controllable preparation of acid and alkali resistant 3D flower-like UiO-66-NH2/ZiF-8 imbedding PPTA composite nanofiltration membrane for dye wastewater separation [J]. Journal of Water Process Engineering, 2022, 50: 103320. doi: 10.1016/j.jwpe.2022.103320 [13] AN Q F, LI F, JI Y L, et al. Influence of polyvinyl alcohol on the surface morphology, separation and anti-fouling performance of the composite polyamide nanofiltration membranes [J]. Journal of Membrane Science, 2011, 367(1/2): 158-165. [14] SONG Y J, SUN P, HENRY L L, et al. Mechanisms of structure and performance controlled thin film composite membrane formation via interfacial polymerization process [J]. Journal of Membrane Science, 2005, 251(1/2): 67-79. [15] BUCH P R, JAGAN MOHAN D, REDDY A V R. Preparation, characterization and chlorine stability of aromatic–cycloaliphatic polyamide thin film composite membranes [J]. Journal of Membrane Science, 2008, 309(1/2): 36-44. [16] WEI X Z, KONG X, SUN C T, et al. Characterization and application of a thin-film composite nanofiltration hollow fiber membrane for dye desalination and concentration [J]. Chemical Engineering Journal, 2013, 223: 172-182. doi: 10.1016/j.cej.2013.03.021 [17] PRAKASH RAO A, JOSHI S V, TRIVEDI J J, et al. Structure–performance correlation of polyamide thin film composite membranes: Effect of coating conditions on film formation [J]. Journal of Membrane Science, 2003, 211(1): 13-24. doi: 10.1016/S0376-7388(02)00305-8 [18] HAN R L, ZHANG S H, HU L J, et al. Preparation and characterization of thermally stable poly(piperazine amide)/PPBES composite nanofiltration membrane [J]. Journal of Membrane Science, 2011, 370(1/2): 91-96. [19] ALSALHY Q F. Hollow fiber ultrafiltration membranes prepared from blends of poly (vinyl chloride) and polystyrene [J]. Desalination, 2012, 294: 44-52. doi: 10.1016/j.desal.2012.03.008 [20] SHI Q, NI L, ZHANG Y F, et al. Poly(p-phenylene terephthamide) embedded in a polysulfone as the substrate for improving compaction resistance and adhesion of a thin film composite polyamide membrane [J]. Journal of Materials Chemistry A, 2017, 5(26): 13610-13624. doi: 10.1039/C7TA02552A [21] MI Y F, WANG N, QI Q, et al. A loose polyamide nanofiltration membrane prepared by polyether amine interfacial polymerization for dye desalination [J]. Separation and Purification Technology, 2020, 248: 117079. doi: 10.1016/j.seppur.2020.117079 [22] WEI X Z, WANG S X, SHI Y Y, et al. Application of positively charged composite hollow-fiber nanofiltration membranes for dye purification [J]. Industrial & Engineering Chemistry Research, 2014, 53(36): 14036-14045.