Polymeric porous material for oil-water separation

In the last years, the world is facing significant challenges due to the continuously decreasing freshwater resources caused by climate change and water pollution. With industrial development, multicomponent oily wastewater creates severe water pollution problems mainly due to ineffective treatment or to the direct discharge without any treatment. Conventional oil-water separation techniques are often constrained by their low efficiency, the generation of secondary pollutants, their inefficacy to remove other pollutants together with the oil, and their space, energy, and cost requirements. For these reasons, extensive studies are being performed to explore alternative separation methods or improve existing ones. This Thesis tackles some of the constraints mentioned above by developing novel polymeric porous materials with special surface functionalities and wettability and using them as 3D filters for the gravity-driven filtration of oil-water mixtures. In particular, 3D porous functional polymeric filters with hydrophilic and underwater superoleophobic properties are developed and proved to be a feasible alternative for the fast and efficient gravity-driven filtration of multicomponent oily wastewater. In particular, in the first study, robust porous foams able to efficiently treat oily wastewater through gravity-driven filtration have been fabricated by combining expanded graphite and waterborne polyurethane through direct mixing processes. The composite foams are hydrophilic and underwater oleophobic and present a porous interconnected structure. It is explored how the pore characteristics of these foams affect the separation performance during the oil-water filtration process. It is also proved that the as-prepared foams can separate non-stabilized oil-water mixtures and oil-in-water emulsions through gravity-driven filtration with high separation efficiencies and fast flow rates, which vary according to the type of foam. The foams can be used in several filtration cycles and harsh environmental conditions without affecting their filtration performance. The second polymeric 3D filters presented herein are composed of polydimethylsiloxane (PDMS) with a surface decorated with a polydopamine layer and silver nanoparticles. These materials present hydrophilic, underwater superoleophobic, and antibacterial properties and are used to separate oil-bacteria-water mixtures and simultaneous disinfection of the permeate. The foams can be used for various operation cycles, as it maintains their high separation efficiency and flow rate over twenty filtration cycles. Additionally, the filters display bactericidal efficacy, disinfecting the permeate after and during the oil-water filtration. The third purposed 3D filters are Poly(sodium acrylate)-ZnO composite cryogels able to simultaneously remove oil and dye from an oil-dye-water mixture through gravity-driven filtration and adsorption processes. Preliminary results show that the formed cryogels have a highly interconnected porous structure and are superhydrophilic and underwater superoleophobic. The swollen cryogels can efficiently separate the mixtures at very fast flow rates. In addition to their filtration performance, the composite cryogels present photocatalytic self-cleaning properties under UV light. The developed 3D polymeric porous materials used as filters can separate oil-water mixtures with high flow rates and rejection efficiencies in a gravity-driven process, which is energy-efficient. These porous materials can perform an integrated removal process that gives them great potential to be used as 3D filters for multicomponent oil-water separation in practical applications.