The Fabrication Of Hydrophobic Three-dimensional Porous Materials And Their Applications In Water/Oil Separation

With the development of international trade and marine petroleum exploitation, oil spill accidents are of common occurrence, doing catastrophic damage to the ocean and coast near the oil leakage area. Materials that can effective removal of oil from water are of significant in oceanography and environmental protection. Hydrophobic three-dimentional porous materials have been introduced as physical adsorbents for oilspill cleanup, because of of their low density, hydrophobility, high porosity, chemical inertness, and large specific surface area. In this thesis, we used different stratergies to fabricate various hydrophobic three-dimentsional porous materials, and apply them as oil absorbents to removal oils from water. Their surface wettability and oil-water performance were systematically investigated. The main contents and the results of the research are as follows:1. Templating by a lignin nanoparticle-stabilized oil-in-water Pickering high internal phase emulsions, a new material, termed nitrogen-rich carbon aerogels(NRC aerogels,) with highly porous structure and nitrogen-rich surfaces, were successfully fabricated. We demonstrate that the obtained NRC aerogels can also collect micrometer-sized oil droplets from an oil-water mixture with high efficiency that is well beyond what can be achieved by most existing separation methods, but is extremely important in practical marine oil-spill recovery because a certain amount of oils often shears into many micrometersized oil droplets by the sea wave, resulting in enormous potential destruction to marine ecosystem if not properly collected. Furthermore, our fabricated material can be used like a recyclable container for oils and chemicals cleanup because the oil/chemical-absorbed NRC aerogels can be readily cleaned for reuse by direct combustion in air because of their excellent hydrophobicity andfire-resistant property. We demonstrate that they keep 61.2% absorption capacity even after 100 absorption/combustion cycles, which thus has the highest recyclability of the reported carbon aerogels. All these features make these fabricated NRC aerogels suitable for a wide range of applications in water purification and treatment.2. Monolithic polyurethane organogel was first achieved by the condensation polymerization of lignin and modified dissocyanate in a THF solution, and then ambient pressure drying was applied to the as-prepared organogel resulting in a lignin-based xerogel. Interestingly, the obtained xerogels simultaneously possess low surface energy and great water repellence without any further chemical modification, with a water contact angle of 146.4o. The exrogels exhibited multifunctional characteristics including self-cleaning and selective oil absorption, demonstrating that they are ideal absorbents for removing oils or organic solvents from water for oil spill cleanup or industrial wastewater purification.3. An excellent oil/water separation material derived from commercially available PMF foam has been developed by a cost-effective, facile and scalable method via hydrophobic functionalization between pyrolyzed PMF foam and chlorotrimethylsilane. The resultant UFC foam simultaneously possesses great water repellency(with water contact angle of145.4o), ultralight weight(with density of 8-9.5 mg cm-3), excellent fire-resistance and good compressible properties. Compared with other absorbents, the present UFC foam not only effectively separates oils from water as expected, but also possesses a much higher absorption capacity for the removal of oils and organic liquids from water with maximum absorption capacities up to 158 times its own weight. More importantly, due to its fire resistance and compressibility, distillation, combustion and squeezing, or a combination of them can be applied for recycling the foams depending on the type of pollutants, making them a versatile and comprehensive absorbent to satisfy various practical separation requirements.4. A simple and general combustion-assisted in situ carbon deposition method was developed to prepare novel ultralight sponges with high hydrophobicity, fire-resistance, compressibility, and self-cleaning properties. The water contact angle truned out to be 149 o. The fabrication of this sponge is easy to be scaled up and functionalized, and this method can be extendable for different substrates. The sponges obtained can effectively separate oils from water even under harsh conditions, with maximum absorption capacities up to 145 times of their own weight. More importantly, excellent recyclability, outstanding oil recoverability, and good oil keeping efficiency make the sponge a versatile and comprehensive absorbent to satisfy various practical separation requirements. We believe that this simple and general method could be applied to fabricate far more excellent oil absorbents to settle the severe water pollution caused by the growing number of oil spill accidents and chemical leakages.5. A facile synthesis of ultralight, high-hydrophobic, and superoleophilic sponges(UHS sponges) was developed through a dip adsorbing process based on lignin and commercially available melamine sponges. The obtained UHS sponges consist of an interconnected structure with high porosity and ultra-low density(6.4 mg cm-3). As the hydrophobic carbon coating of the skeleton and its microstructure trapping the air, the UHS sponge exhibit superhydrophobicity and superholeophilicity, which is beneficial to its applications in oil-water separation. Besides lignin, other biomass like tannin is also suitable as the modification agent to prepare UHS sponges via a dip adsorbing method. As a result, this novel sponge exhibits excellent oil/water separation performance such as high selectivity, good recyclability, and oil absorption capacities up to 217 times of its own weight or 99 vol% of its own volume. We believe that this dip adsorbing method resultant sponge is highly promising as ideal oil absorbents in the spill oil recovery applications and environmental protections.6. On the basis of cellulose nancrycals(CNCs) and commercial available melamine foam, superhydrophobic, fire-resistant, and compressible sponge(SFC sponges) were succefully prepared by an immersing-adsorption-pyrolysis method. The obtained SFC sponges consist of a novel double network structure, an ultra-low density(7.3 mg cm-3) and a great water contanct value(155o). The SFC sponges exhibited excellent thermal stability in 450 oC under nitrogen atmosphere. This novel sponge exhibits excellent oil/water separation performance such as high selectivity, good recyclability, and oil absorption capacities up to 201 times of its own weight or 94 vol% of its own volume. Distillation, combustion and squeezing, or a combination of them can be applied for recycling the SFC sponges depending on the type of pollutants. Furthermore, the spilled oils coule be consecutively collected from the water surface to collecting vessel byour designed oil collection apparatus.