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染料废水具有毒性强、难降解、对人类和环境危害大的特点,常规处理方法难以达到理想效果[1]。纳滤膜分离技术近年来在染料废水处理引起了广泛的关注[2]。原因是纳滤膜的截留分子质量为200~1 000 Da,可以将染料废水中的染料和盐进行有效的分离,有利于染料回收或生化降解,且纳滤(NF)膜分离技术还具有分离效率高、能耗低的优点。目前常见的纳滤膜材料为复合纳滤膜,其制备方法通常为界面聚合法,即将聚乙烯亚胺(PEI)、哌嗪(PIP)等含胺基的化合物在基膜上沉积后,再与均苯三甲酰氯(TMC)等含酰氯的化合物进行界面聚合得到厚度为纳米级的致密聚酰胺(PA)选择层[3-4]。界面聚合法存在选择层与基膜之间粘附不牢固,容易剥离的现象,因此,采用含酚羟基官能团的物质如多巴胺(DA)[5-7]、单宁酸TA等[8-28]与含胺基的物质进行共沉积,沉积过程中,在弱碱性条件下,多酚类物质中的酚羟基与胺基发Michael 加成反应或Schiff 碱反应生成粘附性较强的蒽醌类物质,然后再进行界面聚合制备复合纳滤膜,这样解决了选择层容易剥离的问题。
植物多酚单宁酸(TA)、没食子酸(GA)等与多巴胺相比具有价廉易得、环境友好、沉积时间短且涂层颜色浅等优点,因此,近年来在复合纳滤膜的研究中越来越引起人们的关注[8-25, 27-28]。目前采用TA、GA制备复合纳滤膜的方法主要有共沉积法[8-18, 27-28]和共沉积法与界面聚合组合法[21-25]。已有许多采用TA通过共沉积法制备复合纳滤膜的研究报道。LI等[10]用TA与PEI在PES上沉积制得一种高效的复合纳滤膜。XU等[12]用TA与胺类物质在聚丙烯腈(PAN)表面共沉积制得高效的复合纳滤膜。LI等[13]用单宁酸(TA)和聚乙烯吡咯烷酮(PVP)在聚偏二氟乙烯(PVDF)表面沉积制得复合纳滤膜有良好的截留效果。CHEN等[14]用TA与两性离子聚合物在PES表面沉积制得一种高效的复合纳滤膜。SHI等[16]用聚乙二醇(PEG)和单宁酸(TA)在聚醚砜(PES)表面沉积制得的复合纳滤膜具有良好的过滤性能。XIAO等[17]用TA与Fe3+在PAN表面沉积制得的TA-Fe3+复合纳滤膜具有良好的亲水性与截留效果。LIU等[18]用TA,Fe3+和两性离子聚合物在PAN表面制得的复合纳滤膜具有良好的过滤效果。关于采用TA通过共沉积与界面聚合组合法制备复合纳滤膜的研究主要有:LI等[25]用TA与哌嗪(PIP)在聚醚砜(PES)膜表面沉积后,再与TMC进行界面聚合制备了复合纳滤膜。没食子酸是由单宁酸水解产生的天然多酚类化合物,具有抗龋、抗氧化、抗菌等多种生物活性,在食品、医药等领域有着广泛的应用[26]。关于采用GA制备复合纳滤膜的研究报道较少。XUAN等[27]用没食子酸(GA)与Ag+在膜表面原位合成颗粒提高了膜的通量和防污能力。WANG等[28]采用没食子酸接枝壳聚糖沉积在聚砜(PFS)膜表面制备了PFS复合纳滤膜。TA与GA在分子结构和分子质量上存在较大差别,TA分子结构复杂,GA的分子结构简单。TA 分子质量和酚羟基含量远远大于GA,因此,TA与GA作为植物多酚类沉积物时,对PVDF复合纳滤膜选择层的结构和性能可能会产生不同的影响。
综上所述,采用TA制备复合纳滤膜的研究以沉积法较多,采用沉积法与界面聚合组合法制备复合纳滤膜的研究较少。而关于TA及GA与PEI共沉积与界面聚合组合法制备PVDF复合纳滤膜的研究,目前未见报道。为此,本研究通过将TA、GA与PEI在膜表面共沉积后与TMC交联在PVDF基膜上制备了高性能PA/蒽醌/PVDF复合纳滤膜,通过ATR-FTIR、SEM、AFM、水接触角一系列方法表征了复合纳滤膜的结构,研究了TA:GA比例对PA/蒽醌/PVDF复合纳滤膜微观结构和分离性能的影响。
PA/蒽醌/PVDF复合纳滤膜结构与性能及其应用
Structure, properties and application of PA/Anthraquinone/ PVDF composite nanofiltration membrane
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摘要: 以聚偏二氟乙烯(PVDF)超滤膜为基膜,采用聚乙烯亚胺(PEI)与单宁酸(TA)和没食子酸(GA)的混合物共沉积后,再与均苯三甲酰氯(TMC)进行界面聚合的方法制备了PVDF复合纳滤膜,探讨了TA与GA的混合质量比例对PVDF复合纳滤膜选择层的微观结构和性能的影响,分别采用FTIR、AFM、SEM和水接触角测量仪对复合纳滤膜选择层的化学结构、表面粗糙度、微观结构和表面亲水性进行了表征,考察了PVDF复合纳滤膜在模拟RB5-NaCl染料废水处理中的性能和稳定性。结果表明:随着TA:GA比例的增加,选择层的表面粗糙度增加、水接触角减小,纯水通量增加,PEG1000截留率略有降低;染料废水通量和截留率呈相同的变化趋势,染料和盐的分离因子达到12.97;PVDF复合纳滤膜在运行时间内表现出良好的稳定性。
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关键词:
- PA/蒽醌/PVDF复合纳滤膜 /
- 单宁酸 /
- 没食子酸 /
- 共沉积与界面聚合组合法 /
- 模拟RB5染料废水
Abstract: PVDF composite nanofiltration membrane was prepared by a co-precipitation between the base membrane of polyvinylidene fluoride (PVDF) ultrafiltration membrane and a mixture of PEI and tannic acid (TA) and gallic acid (GA) at first, then the interfacial polymerization with homophthalic chloride (TMC). The effects of the mixing ratio of TA and GA on the microstructure and properties of the selective layer of PVDF composite nanofiltration membranes were investigated. FTIR, AFM, SEM, and water contact angle measurement instruments were used to characterize the chemical structure, surface roughness, microstructure and surface hydrophilicity of the composite nanofiltration membrane selective layer. The performance and stability of the PVDF composite nanofiltration membrane on simulated RB5-NaCl dye wastewater treatment were investigated. The results showed that with the increase of TA:GA ratio, the surface roughness of the selective layer increased, the water contact angle decreased, the pure water flux increased, and the retention rate of PEG1000 decreased slightly; the flux and retention rate of dye wastewater showed the same trend, and the separation factor of dye and salt reached 12.97. PVDF composite nanofiltration membrane showed a good stability during the operation. -
表 1 药物添加量和反应时间
Table 1. Drug addition and reaction time
TA:GA TA/(g·L−1) GA/(g·L−1) PEI/(g·L−1) TMC/% 交联时间 /min 沉积时间/min 10:0 0.75 0 2.25 0.2 5 60 8:2 0.6 0.15 2.25 0.2 5 60 6:4 0.45 0.3 2.25 0.2 5 60 4:6 0.3 0.45 2.25 0.2 5 60 2:8 0.15 0.6 2.25 0.2 5 60 0:10 0 0.75 2.25 0.2 5 60 -
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