Highly Porous PMMA-TiO2 Fibers for Photocatalytic Degradation of Water Pollutants

Description:

­Background
Ever-increasing pollution calls for the development of a robust and cheap solution for environmental remediation. Numerous methods that can be employed to tackle this problem, including harnessing the photocatalytic activity of titanium dioxide (TiO2). TiO2 is a wideband semiconductor material that possesses a redox potential capable of decomposing organic contaminants into carbon dioxide and water. This advanced oxidation capability not only makes it suitable for purification applications, such as pollutant capture, treatment of industrial waste, and wastewater disinfection, but also for the reformation of hydrocarbon fuels. The commercial adaptation of TiO2 has thus far been limited by a low throughput and the high cost of photoreactors. These limitations can be addressed by a fixed-bed reactor where nanoscale TiO2 is immobilized on inert substrates. Nanoparticles of TiO2 provide a high surface-to-volume ratio, improving the transport of contaminants. Additionally, immobilization eliminates the need for expensive post-treatment separation of TiO2. However, this system suffers from poor light distribution and hindered charge transfer, due to the encapsulation of TiO2 in substrates. A cost-effective solution is to use polymers as a substrate, since they can be easily molded to the desired shape, size, and microstructure. Past research has reported anchoring TiO2 on polymeric beads, membranes, and electrospun fibers. Incorporating porosity in these substrates enhances mass transport. Another approach is to coat radially emitting optical fibers with TiO2. This architecture creates a greater surface area by utilizing the fiber’s longitudinal morphology and enables remote light accessibility through optical fibers.



Invention Description
Researchers at Arizona State University have developed methods to fabricate polymethyl methacrylate (PMMA)-TiO2 fibers, manufactured by a combination of fiber spinning and immersion precipitation. A porosity of up to 33.2 m2/g was achieved. Two fixed-bed fiber architectures are used, namely: (1) Dispersed phase fiber (D-phase) which is a porous PMMA fiber containing dispersed TiO2, and (2) Multiphase fiber (M-phase) with a solid PMMA core and a porous PMMA-TiO2 sheath. Internally illuminated M-phase fibers result in a compact reactor design, since the fibers can be bundled together, whereas light distribution in externally illuminated D-phase can be a limiting factor.

These fibers when tested using 3.2 mg/L methylene blue and reported a highest degradation rate of 0.116 min−1.


Potential Applications
•  Water purification
•  Pollutant capture
•  Hydrocarbon fuel reformation 


Related Publication: PMMA-TiO2 Fibers for the Photocatalytic Degradation of Water Pollutants


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