Abstract
Marine pollution caused by frequent oil spill accidents has brought about tremendous damages to marine ecological environment. Therefore, the facile large-scale preparation of three-dimensional (3D) porous functional materials with special wettability is in urgent demand. In this study, we report a low-cost and salt-tolerant superoleophobic aerogel for efficient oil/seawater separation. The aerogel is prepared through incorporating graphene oxide (GO) into alginate (ALG) matrix by using a facile combined freeze-drying and ionic cross-linking method. The 3D structure interconnected by ALG and GO ensures the high mechanical strength and good flexibility of the developed aerogel. The rough microstructure combined with the hydrophilicity of the aerogel ensures its excellent underwater superoleophobic and antifouling properties. High-content polysaccharides contained in the aerogel guarantees its excellent salt-tolerant property. More impressively, the developed aerogel can retain its underwater superoleophobicity even after 30 days of immersion in seawater, indicating its good stability in marine environments. Furthermore, the aerogel could separate various oil/water mixtures with high separation efficiency (>99%) and good reusability (at least 40 cycles). The facile fabrication process combined with the excellent separation performance makes it promising for practical applications in marine environments.
Highlights
In the past decades, the marine pollution caused by frequent oil spill accidents has brought about tremendous damages to marine ecological environment[1,2,3]
The discovery of unique underwater oil-repellent property of fish scale opened a new window for fabricating underwater superoleophobic materials such as hydrogels coatings[12,13,14,15] and inorganic metal oxide coatings[16,17,18,19]
To overcome the first obstacle, an effective approach is the incorporation of reinforcing fillers into the alginate matrix and here graphene oxide (GO) is chosen as reinforcing filler owing to its excellent mechanical property and remarkable flexibility[26,27,28], which can effectively resist the load transferred from the alginate matrix
Summary
The microstructural morphology of the ALG/GO aerogel was studied using a scanning electron microscopy (SEM). The ideal pore size and network-distribution of the as-prepared aerogel allow oil/water separation to be achieved in a gravity-driven process with high-flux. To further study the separation ability of the ALG/GO aerogel, Oil intrusion pressure and water flux were investigated. To illustrate the water/oil separation mechanism of the ALG/GO aerogel, the equation to calculate theoretical intrusion pressure was introduced[34,35,36]. The repulsive force between the trapped water and oil resulted in a significant reduction in the contact area between the oil and surface of the aerogel, leading to θ > 150° (underwater superoleophobicity) and Pt > 0, oil/water mixtures could be selectively separated efficiently using the developed underwater superoleophobic ALG/GO aerogel. The aerogel can be adapted to perform different types of oil/seawater separation and demonstrated both highly efficient and reusable in high-salinity environments. We believe that this kind of aerogel is a promising candidate material for oil/water separation in marine environments
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