Microwave in-situ synthesis of 2D Ni-Fe MOF/diatomite composite and oil-water separation performance of modified polyvinyl alcohol hydrogel stainless steel screen
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摘要: 如何高效处理含油污水的问题,是如今世界科研人员共同关注的问题。聚乙烯醇(PVA)水凝胶作为高含水量及具有三维亲水网络的软材料在油水分离领域引起了广泛的关注。但是,和大多数具有超润湿性质的水凝胶一样,PVA水凝胶类油水分离材料不仅力学性能差,同时也存在化学稳定性差的问题。基于此,通过微波法制备了2D Ni-Fe金属-有机框架材料(MOF)-硅藻土(Dia)纳米材料及其PVA复合水凝胶。同时,不锈钢网经过浸泡2D Ni-Fe MOF-Dia/PVA水凝胶溶液得到2D Ni-Fe MOF-Dia/PVA水凝胶不锈钢筛网,表现出超亲水-水下超疏油性质。利用SEM、XPS分析2D Ni-Fe MOF-Dia及其复合水凝胶的化学组成和表面形貌。研究了2D Ni-Fe MOF-Dia/PVA复合水凝胶的力学性能及2D Ni-Fe MOF-Dia/PVA复合水凝胶不锈钢筛网的油水分离与乳液分离的分离效率及水通量,并对其耐盐性、耐酸耐碱性油水分离性能进行了测试。结果表明:2D Ni-Fe MOF-Dia/PVA复合水凝胶具有优异的力学性能,拉伸与压缩强度分别达到1.49 MPa及0.58 MPa,同时表现出超亲水-水下超疏油性质,2D Ni-Fe MOF-Dia/PVA不锈钢筛网的油水分离与乳液分离效率与通量分别可达99.2%和742.7 L·m−2·h−1。在酸性、碱性、盐性环境下均保持优异的分离效率与通量,并且在5次循环后,依旧保持稳定的分离效率与通量。
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关键词:
- 聚乙烯醇水凝胶 /
- 硅藻土 /
- 2D Ni-Fe 金属-有机框架材料(MOF) /
- 油水分离 /
- 力学性能
Abstract: How to efficiently treat oil-polluted water has been a common concern of researchers all over the world. Polyvinyl alcohol (PVA) hydrogel as a soft material with high water content and three-dimensional hydrophilic network had attracted wide attention in the field of oil-water separation. However, like most hydrogel with super wettability, PVA hydrogel oil-water separation materials have poor mechanical properties and poor chemical stability. Based on this, 2D Ni-Fe metal-organic frame material (MOF)-diatomite (Dia) nanomaterials and their PVA compo-site hydrogels were prepared by microwave method. After immersion in 2D Ni-Fe MOF-Dia/PVA solution, the 2D Ni-Fe MOF-Dia/PVA stainless steel mesh was obtained, showing super hydrophilic and super hydrophobic properties. The chemical composition and surface morphology of 2D Ni-Fe MOF-Dia and its composite hydrogels were analyzed by SEM and XPS. The mechanical properties of 2D Ni-Fe MOF-Dia/PVA composite hydrogel and the separation efficiency and water flux of 2D Ni-Fe MOF-Dia/PVA composite hydrogel stainless steel screen were studied. The salt resistance, acid and alkali resistance of oil-water separation were tested. The results show that 2D Ni-Fe MOF-Dia/PVA composite hydrogel has excellent mechanical properties, tensile strength and compressive strength reached 1.49 MPa and 0.58 MPa respectively, and exhibited super hydrophilic underwater super thinning oil. The efficiency and flux of 2D Ni-Fe MOF-Dia/PVA stainless steel screen are 99.2% and 742.7 L·m−2·h−1 respectively. It maintains excellent separation efficiency and flux in acidic, alkaline and salt environments, and still maintains stable separation efficiency and flux after 5 cycles. -
图 3 聚乙烯醇(PVA) (a)、2D Ni-Fe-MOF/PVA (b)、Dia/PVA (c) 和2D Ni-Fe MOF-Dia/PVA (d) 的截面SEM图像(图3(d)中插图为2D Ni-Fe MOF-Dia/PVA的TEM图像)
Figure 3. Cross sectional SEM images of polyvinyl alcohol (PVA) (a), 2D Ni-Fe MOF/PVA (b), Dia/PVA (c) and 2D Ni-Fe MOF-Dia/PVA (d) (Inset in Fig.3(d) is TEM image of 2D Ni-Fe MOF-Dia/PVA)
图 5 PVA (a)、2D Ni-Fe MOF/PVA (b)、Dia/PVA (c)、2D Ni-Fe MOF-Dia/PVA (d) 的亲水性及水滴在复合水凝胶表面完全铺展的时间;(e) 2D Ni-Fe MOF-Dia/PVA包覆的不锈钢筛网水下油的滑动过程
Figure 5. Hydrophilicity of PVA (a), 2D Ni-Fe MOF/PVA (b), Dia/PVA (c), 2D Ni-Fe MOF-Dia/PVA (d) and the time of water droplet spreading on the surface of the composite hydrogel; (e) Sliding process of underwater oil in 2D Ni-Fe MOF-Dia/PVA submerged stainless steel screen of the stainless steel mesh
图 6 PVA、2D Ni-Fe-MOF/PVA、Dia/PVA、2D Ni-Fe-MOF-Dia/PVA的力学性能:(a) 拉伸应力-应变曲线;(b) 抗拉强度和断裂伸长率;(c) 压缩应力-应变曲线;(d) 抗压强度(插图为压缩前后水凝胶高度差对比)
Figure 6. Mechanical properties of PVA, 2D Ni-Fe MOF/PVA, Dia/PVA, 2D Ni-Fe MOF-Dia/PVA: (a) Tensile stress-strain curves; (b) Tensile strength and elongation at break; (c) Compressive stress-strain curves; (d) Compressive strength (Illustrations for height difference ratio of hydrogel before and after compression)
图 8 (a) 石油醚-水混合循环分离效率及水通量;(b) 对于不同质量分数的NaCl溶液/石油醚油水混合物的分离效率及水通量;(c) 不同pH下的分离效率及水通量;(d) 不同pH值下分离后水下油的接触角
Figure 8. (a) Separation efficiency and water flux of petroleum ether water mixing cycle; (b) Separation efficiency and water flux for different mass fractions of NaCl solution/petroleum ether oil-water mixture; (c) Separation efficiency and water flux at different pH values; (d) Contact angle of underwater oil after separation at different pH values
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