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近年来,油类泄漏造成的水污染事件频发,对水环境和生态系统造成严重影响[1-2]。目前适用于油类污染的治理方法包括原位燃烧法[3]、机械围栏法[4]、膜分离技术[5]、和生物处理法[6-8]等,但这些传统方法往往存在各自的局限性,如二次污染、耗时长和效率低等问题[9]。物理吸附相对而言具有简单高效的优势,是处理油类污染最常用的方法之一[10],常见的吸附材料,如大麦秸秆[11]、织物[12]、聚氨酯[13]、沸石[14]和气凝胶[15-16]等已被用于油类污染的治理,然而限制这些多孔材料实际应用的主要原因是油污的黏度高,流动性差,导致其在多孔材料内孔的扩散速率低,进而影响分离和处理效率等问题[17- 18]。因此,目前的挑战之一在于如何设计材料实现在吸附的同时降低油污的黏度,增加流动性从而实现高效的吸附和回收[19-20]。
基于油污黏度与温度成反比的特性,目前已有研究表明提高吸附体系的温度有助于突破现有吸附材料对高黏度油污处理的限制。Ge等[21]提出了一种焦耳加热的海绵,通过电加热提高温度可以降低石油黏度,用于快速清理原油泄漏。由于电热转换需要额外的电力输入,研究进一步转向设计具有光热转化特性的材料。目前光热材料已应用于各种不断发展的领域,例如光催化[22]、海水淡化[23]和癌症治疗[24]等。氧化石墨烯(GO)具有一定的光热特性及热稳定性,Wang等[25]通过简便的一锅水热法,将氧化石墨烯(GO)还原为还原氧化石墨烯(RGO)并加载到三聚氰胺海绵(MS)上,在模拟阳光下,RGO-MS的表面温度迅速升高,并在60 s内上升至~70 ℃。然而,考虑到负载的光热材料常常存在不稳定、易剥落等问题,可能导致环境暴露及次生风险[26],因此后续需考虑将光热材料与载体的成型步骤融于一体,实现光热材料在载体内部的有效掺杂。鉴于气凝胶良好的吸油能力,制备过程的可调控性,本研究选择探索氧化石墨烯基的复合气凝胶的制备及其吸油性能。
基于以上研究背景,本研究旨在合成稳定的,具有光热转化特性的吸附材料。通过水热法及定向冷冻法制备氧化石墨烯(GO)掺杂的聚氨酯丙烯酸酯复合气凝胶,在光照条件下,利用其光热特性使温度升高,进一步降低油污黏度,从而提高吸附性能。
氧化石墨烯复合气凝胶吸附油类污染应用的基础研究
Graphene oxide-polyurethane acrylate nanocomposite aerogel for oil absorption
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摘要: 油类污染对生态环境会造成严重且长期的影响,目前已成为世界性的挑战之一。在常用的处理方式中,原位燃烧易造成二次污染,生物修复手段往往是耗时的,而传统的吸油材料在应对高黏度的油污时具有较大的局限性。为此,本研究通过简单的60 ℃水热反应配合冷冻干燥,设计并制备了一种由氧化石墨烯和聚氨酯丙烯酸酯组成的复合气凝胶。利用SEM和拉曼光谱等技术表征了氧化石墨烯(GO)-聚氨酯丙烯酸酯复合气凝胶的微观结构和化学组成,结果表明氧化石墨烯成功嵌入到聚氨酯丙烯酸酯气凝胶中,且该复合气凝胶具有疏松多孔的结构。利用氧化石墨烯的光热效应,该复合气凝胶在光照下将太阳能转化为热能,降低油污的黏度,提升流动性,从而有效提高复合气凝胶对油污的吸附速率。在光照5 min条件下,该复合气凝胶可吸收约24倍自重的高黏度硅油。这项工作针对高黏度油污吸附的难点,设计了一种合成简便,具有一定应用价值的新型纳米复合气凝胶。Abstract: Oil pollution can cause serious and long-term ecological damage, which has become a worldwide challenge. Traditional treatment methods, such as in-situ burning and bioremediation are limited due to the generation of secondary pollution and the time-consuming procedure. Traditional oil absorbent materials often fail in absorbing high-viscosity oil. To this end, we designed and prepared an nanocomposite aerogel comprised of graphene oxide (GO) and polyurethane acrylate through a simple hydrothermal reaction at 60°C followed by freeze-drying. The microstructure and chemical composition of the graphene oxide (GO)-polyurethane acrylate nanocomposite aerogel were analyzed using SEM and Raman spectroscopy. The results showed that the graphene oxide (GO)-polyurethane acrylate nanocomposite aerogel possess highly porous structure, and graphene oxide was successfully embedded in the polyurethane acrylate aerogel. Due to the photothermal effect of graphene oxide, the nanocomposite aerogel converts solar energy into heat, leading to the increase of oil fluidity. As a result, the adsorption rate of the nanocomposite aerogel to oil is significantly improved. Meanwhile, the nanocomposite aerogel absorbs approximately 24 times of its own weight of high viscosity silicone oil under 5 min of light irradiation. This work demonstrated a facile method to fabricate a GO-based nanocomposite aerogel to overcome the challenge of high-viscosity oil adsorption, which could pave the way for developing new adsorbents with real-life application value.
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Key words:
- aerogels /
- graphene oxide /
- polyurethane acrylate /
- photothermal conversion /
- nanocomposite
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图 6 (a-c) GO-聚氨酯丙烯酸酯复合气凝胶对不同黏度硅油的润湿性能; (d-f) GO-聚氨酯丙烯酸酯复合气凝胶与水/油混合物接触时的液体吸收行为
Figure 6. (a-c) Wettability of GO-polyurethane acrylate nanocomposite aerogel with different viscosity silicone oil; (d-f) The liquid absorption behavior of GO-polyurethane acrylate nanocomposite aerogel when in contact with a water/oil mixture.
图 10 (a) 模拟阳光照射,聚氨酯丙烯酸酯气凝胶和GO-聚氨酯丙烯酸酯复合气凝胶对高黏度油吸附行为示意图; (b) 模拟太阳光(1.0 kW·m−2)照射,对比GO-聚氨酯丙烯酸酯气凝胶和聚氨酯丙烯酸酯复合气凝胶对100 mPa·s和500 mPa·s的硅油的吸附行为
Figure 10. (a) A schematic illustration of the adsorption behavior of high viscosity oils on the polyurethane acrylate aerogel and GO-polyurethane acrylate nanocomposite aerogel under simulated sunlight irradiation; (b) Successive optical images showing distinct absorbing behavior for the GO-polyurethane acrylate nanocomposite aerogels vs polyurethane acrylate aerogels. Liquids with various viscosities were used: Silicone oil-100.0 mPa·s and Silicone oil-500.0 mPa·s (simulated sunlight irradiation, power density: 1.0 kW·m−2).
图 12 (a) 光照射下定量吸收硅油的方法示意图; (b) 对比聚氨酯丙烯酸酯气凝胶与GO-聚氨酯丙烯酸酯复合气凝胶对硅油-1000 mPa·s的吸附能力(% W/W)
Figure 12. (a) Schematic illustration on the quantification method of crude oil absorption under light irradiation; (b) Silicone oil-1000 mPa·s absorption capacity (% W/W) of polyurethane acrylate aerogel vs GO-polyurethane acrylate nanocomposite aerogel.
图 13 (a) 光照射下,硅油-1000 mPa·s的红外热像图; (b) 模拟光照下,GO-聚氨酯丙烯酸酯复合气凝胶吸附硅油-1000 mPa·s过程中的红外热像图
Figure 13. (a) Infrared thermal image of silicone oil under light irradiation; (b) Infrared thermal image of GO-polyurethane acrylate nanocomposite aerogel during adsorption of silicone oil -1000 mPa·s under the light irradiation.
表 1 不同掺杂量的GO-聚氨酯丙烯酸酯复合气凝胶在模拟光照下(功率:1.0 kW·m−2,时间:5 min)的表面温度
Table 1. Surface temperature of GO-polyurethane acrylate composite aerogels with different doping amounts under simulated illumination (power: 1.0 kW·m−2, time: 5 min).
GO 浓度 (W/V)
GO concentration0.005% 0.006% 0.007% 0.008% 温度
Temperature48.0 ℃ 49.7 ℃ 53.1 ℃ 56.8 ℃ -
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