Baruah Upama, Das Avijit, Manna Uttam
Department of Chemistry , Indian Institute of Technology-Guwahati , Kamrup, Guwahati , Assam 781039 , India.
Centre for Nanotechnology , Indian Institute of Technology-Guwahati , Amingaon , Kamrup, Assam 781039 , India.
ACS Appl Mater Interfaces. 2019 Aug 7;11(31):28571-28581. doi: 10.1021/acsami.9b10977. Epub 2019 Jul 26.
Fish-scale-mimicked super oil-repelling wettability that functions under water has emerged as an important avenue for developing various functional materials. Mainly, polymeric hydrogel, brittle metal oxides, and electrostatic multilayers have been utilized for synthesizing an artificial underwater superoleophobic interface, and most of these reported artificial bioinspired wettabilities are likely to be compromised under practically relevant severe settings. Moreover, a design of a dual-functional fish-scale-mimicked interface that would be capable of separating water-soluble organic pollutants, in addition to the eco-friendly removal of different forms of contaminated oils under severe settings, could be highly useful in addressing globally recognized severe water pollution problems. In this report, a dual-functional underwater superoleophobic membrane is introduced for simultaneous removal of contaminated dyes and oil/oily phase, where graphene oxide (GO) nanosheets were strategically integrated with naturally abundant and environmentally friendly cotton fibers by adopting mussel-inspired chemistry. The synthesized membrane was found to exhibit fish-scale-mimicked nonadhesive underwater superoleophobicity, and this super oil repellency remained unaffected even after prolonged exposures to various practically relevant harsh chemical and physical conditions. Moreover, this material was capable of rapid (within 2 min) adsorption of water-soluble cationic organic dyes with high adsorption capacity (136 mg/g for methylene blue), following linear pseudo-second-order kinetics. The biomimicked extreme oil repellency was exploited for separating different forms (bulk and emulsion) of oil/oily (both sedimenting and floating) contaminants with high separation efficiency (above 98%), and the immobilized GO in the biomimicked membrane parallely allowed cationic organic dyes (methylene blue and crystal violet) to be removed from the aqueous phase through a single-step gravity-driven filtration process. The performance of simultaneous removal of cationic dyes and oil/oily contaminants remained unaffected even under various practically relevant severe settings including extremes of pH, sea water, river water, and so forth. Furthermore, the dual-functional biomimicked membrane was repetitively (10 times) used for successful separation of both the contaminated cationic dye and oil/oily phase from the aqueous phase, without affecting the separation efficiency. This simple approach is likely to provide a facile basis for addressing the problem of water pollution under practically relevant diverse and severe settings.
具有水下功能的仿鱼鳞超疏油润湿性已成为开发各种功能材料的重要途径。主要地，聚合物水凝胶、脆性金属氧化物和静电多层膜已被用于合成人工水下超疏油界面，并且这些已报道的人工仿生润湿性中的大多数在实际相关的严苛条件下可能会受到影响。此外，设计一种双功能仿鱼鳞界面，除了在严苛条件下对不同形式的污染油进行环保去除之外，还能够分离水溶性有机污染物，这对于解决全球公认的严重水污染问题可能非常有用。在本报告中，引入了一种双功能水下超疏油膜，用于同时去除污染染料和油/油相，其中通过采用贻贝启发化学方法，将氧化石墨烯（GO）纳米片与天然丰富且环境友好的棉纤维进行了策略性整合。发现合成的膜表现出仿鱼鳞的非粘性水下超疏油性，并且即使在长时间暴露于各种实际相关的苛刻化学和物理条件下，这种超疏油性仍然不受影响。此外，该材料能够按照线性准二级动力学，在2分钟内快速吸附水溶性阳离子有机染料，吸附容量高（亚甲基蓝为136 mg/g）。利用这种仿生的极端疏油性以高分离效率（高于98%）分离不同形式（散装和乳液）的油/油性（沉降和漂浮）污染物，并且仿生膜中固定的GO同时允许通过单步重力驱动过滤过程从水相中去除阳离子有机染料（亚甲基蓝和结晶紫）。即使在包括极端pH值、海水、河水等各种实际相关的严苛条件下，同时去除阳离子染料和油/油性污染物的性能仍然不受影响。此外，双功能仿生膜可重复使用（10次），成功地从水相中分离出污染的阳离子染料和油/油相，而不影响分离效率。这种简单的方法可能为在实际相关的多样且严苛条件下解决水污染问题提供一个简便的基础。
