论文总字数：19898字

摘 要

将石墨相氮化碳化合物(g-C₃N₄)，活化的g-C₃N₄(O-g-C₃N₄)和聚多巴胺修饰的g-C₃N₄(PDA@O-g-C₃N₄）纳米片添加到聚乙烯醇(PVA)基质中，PVA和g-C₃N₄纳米片之间的非选择性聚合物/无机界面通道可分别通过氢键，刚性和柔性的化学键调节。在75 ℃下对90 wt.%乙醇水溶液脱水实验表明，随着聚合物/无机界面之间的结合力的增加，从氢键(CPVA-g-C₃N₄)到柔性化学键(CPVA-PDA@O-g-C₃N₄)，膜总通量从4634降至2328 g/(m²h)，分离因子从32.4增加至57.9。与纯交联PVA膜(CPVA)(总渗透通量和分离因子分别为2325 g/(m²h)和18.7)相比，加入g-C₃N₄，O-g-C₃N₄和PDA@O-g-C₃N₄均可导致CPVA膜的分离性能增加。此外，由于g-C₃N₄、O-g-C₃N₄和PDA@O-g-C₃N₄纳米片的有序排列以及这些纳米片与PVA和琥珀酸之间的相互作用，复合膜表现出较高的抗溶胀性和机械稳定性。

关键词：渗透汽化脱水，水选择性，聚多巴胺，石墨相氮化碳，聚乙烯醇

Abstract: Highly water-selective hybrid pervaporation membranes with excellent water/ethanol separation performance and superior water channels were fabricated by incorporating graphitic carbon nitride (g-C₃N₄), activated g-C₃N₄ (O-g-C₃N₄) and polydopamine modified g-C₃N₄ (PDA@O-g-C₃N₄) nanosheets into poly(vinyl alcohol) (PVA) matrix. The nonselective polymer/inorganic interface channels between PVA and g-C₃N₄, O-g-C₃N₄ and PDA@O-g-C₃N₄ in hybrid membranes were controllable constructed through hydrogen bonds, rigid and flexible chemical bonds, respectively. The membrane performances were tested in the pervaporation (PV) process for the dehydration of 90 wt % ethanol/water mixtures at 75 °C. The results revealed that with the increase of binding force among polymer/inorganic interface, from hydrogen bonds (CPVA-g-C₃N₄), to rigid (CPVA-O-g-C₃N₄) and flexible chemical bonds (CPVA-PDA@O-g-C₃N₄), the total flux decreased from 4634 to 2328 g/(m²h) and the separation factor increased from 32.4 to 57.9. It is implied that the nonselective polymer/inorganic interface channels were controlled successfully. Meanwhile, compared with the pure cross-linked PVA (CPVA) membrane(total flux 2325 g/(m²h) and separation factor 18.7), incorporation of g-C₃N₄, O-g-C₃N₄ and PDA@O-g-C₃N₄ could all lead to an increase of surface hydrophilicity of the CPVA membranes along with an increase in membrane tortuosity and membrane water-selective channels that was favorable to the selective permeation of water molecules. Namely, these new hybrid membranes can break the “trade-off effect” effectively. Moreover, due to the ordered alignment of g-C₃N₄, O-g-C₃N₄ and PDA@O-g-C₃N₄ nanosheets and the strong interfacial interactions among these nanosheets, succinic acid (Sa) and the PVA matrix, the hybrid composite membranes showed both high swelling resistance and mechanical stability.

Keywords: Pervaporation dehydration, water-selective, polydopamine, graphitic carbon nitride, poly(vinyl alcohol)

目录

1 前言 3

1.1 渗透汽化简介 3

1.2 基本分离原理 3

1.3 渗透汽化脱水膜 4

1.3.1 高分子分离膜的改性 4

1.3.2 渗透蒸发脱水膜的制备 4

2 实验 6

2.1 材料 6

2.2 合成g-C₃N₄和g-C₃N₄的改性 6

2.3 复合膜的制备 7

2.4 表征 7

3 结果与讨论 8

3.1 g-C₃N₄和修饰的g-C₃N₄纳米片的制备和表征 8

3.2 复合膜的制备与表征 10

3.3 膜性能 15

3.3.1 热性能 15

3.3.2 渗透蒸发性能 16

3.4 膜的长期运行稳定性 18

结论 20

参考文献 21

致谢 24

1 前言

1.1 渗透汽化简介

渗透汽化过程(Pervaporation, 简称PV, 国内又称为“渗透蒸发”) 是一种新型的膜分离过程, 是利用混合液中各组分被高分子膜选择吸附溶解, 及其在膜中扩散速度的不同, 通过渗透与蒸发将各组分分开, 从而分离或富集有机混合物中的某一组分。渗透汽化技术在石油化工、医药、食品、环保等工业领域中具有广阔的应用前景, 是目前处于开发期和发展期的技术, 国际学术界的专家们称之为21世纪最有前途的高技术之一。

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