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Fouling due to biofilms composed primarily of microorganisms and extracellular polymeric substances is a significant hindrance to membrane filtration in water treatment. The goal of this work was to use a reactive membrane surface to reduce membrane biofouling by coating a ceramic ultrafiltration membrane with the nanoparticulate photocatalyst, TiO2. 10-Day biofilm growth experiments were conducted to determine the effect of photocatalytic coatings on the formation of a Pseudomonas putida biofilm and subsequent changes in membrane flux. Results indicate that a highly hydrophilic, photoreactive coating of mixed phase TiO2 nanoparticles is effective for the control of biofouling on ceramic ultrafiltration membranes.

Bacterial attachment is an initial stage in biofilm formation that leads to flux decline in membrane water filtration. This study compares bacterial attachment among three photocatalytic ceramic ultrafiltration membranes for the prevention of biofilm formation. Zirconia ceramic ultrafiltration membranes were dip-coated with anatase and mixed phase titanium dioxide photocatalysts to prevent biofilm growth. The membrane surface was characterized in terms of roughness, hydrophobicity, bacterial cell adhesion, and attached cell viability, all of which are important factors in biofilm formation. The titanium dioxide coatings had minimal impact on the membrane roughness, reduced the hydrophobicity of membranes, prevented Pseudomonas putida attachment, and reduced P. putida viability. Degussa P25 is a particularly promising reactive coating because of its ease of preparation, diminished cell attachment and viability in solutions with low and high organic carbon concentrations, and reduced flux decline. These reactive membranes offer a promising strategy for fouling resistance in water filtration systems.

Electron-hole recombination limits the efficiency of TiO2 photocatalysis. We have investigated the efficacy with which anatase/carbon nanotube (CNT) composite materials reduce charge recombination and enhance reactivity. We synthesized nanostructured assemblies composed of different proportions of anatase (5 or 100 nm) and either single-or multi-walled CNTs. The composites were prepared using a simple low temperature process in which CNTs and anatase nanoparticles were dispersed in water, dehydrated at 80 degrees C, and dried at 104 degrees C. The structures of the various TiO2/CNT composites were characterized by scanning electron microscopy (SEM) and their function was tested by phenol oxidation. Charge recombination was compared by measuring the photoluminescence spectra of select composites. We found that a nanostructured composite assembled from the 100 nm anatase and single-walled CNTs (SWCNTs) exhibited enhanced and selective photocatalytic oxidation of phenol in comparison to both pure anatase and Degussa P25. A mechanism for the enhanced reactivity is proposed in which electrons are shuttled from TiO2 particles to the SWCNTs as a result of an optimal TiO2/ CNT arrangement that stabilizes charge separation and reduces charge recombination. In addition, the SWCNT assembly provides better catalyst-support (dispersal and connection) than multi-walled CNTs.

Mixed-phase titanium dioxide (TiO2) materials, such as Degussa P25, show high photocatalytic activity due largely to the synergistic effect between anatase and rutile phases, in which spatial charge separation hinders charge recombination. Our previous studies indicate that a particular nanostructured assembly of anatase and rutile crystallites is necessary for the synergy. In this paper, we apply this structure-function understanding to the synthesis of highly active TiO2 nanocomposite photocatalysts. Using simple synthetic procedures, we demonstrate an ability to design a highly active nanocomposite that shows enhanced photoactivity in both oxidative and reductive chemistry. Studies by electron paramagnetic resonance spectroscopy indicate the existence of the critical nanostructured assembly and thus the optimization of charge transfer between anatase and rutile phases in the synthesized nanocomposite. These results illustrate the potential of rationally designing photocatalysts for energy applications.

This paper describes a model for a virtual community of practice (VCP) to support faculty efforts to adopt research-based instructional strategies in Chemical, Materials and Biological Engineering courses. The VCP was built on published recommendations for successful faculty development programs. The VCP program began with a 10 week virtual training period for five pairs of VCP leaders, during which they acquired the skills and knowledge needed to lead the faculty VCP. The faculty VCPs focused on one of five technical disciplines and were led by a pair of leaders having expertise in a specific technical focus area as well as in engineering pedagogy. Workshops were held using Internet conferencing software: the first 8 weekly workshops provided training in research-based pedagogy, and the second 8 biweekly workshops supported faculty efforts to implement chosen strategies in their courses. The participants were full-time faculty members with a range of teaching experience and pedagogical expertise, ranging from novice to expert. Improvement was measured via pre/post survey in the areas of familiarity and use of research-based pedagogy, as well as in perceived student motivation. The second part of the paper focuses on the translation of faculty participant experiences from the VCP into the classroom as they implemented a variety of instructional methods in their courses. We describe their approaches and preliminary results using different instructional methods such as flipping the classroom, using game-based pedagogy, promoting positive interdependence in cooperative-learning teams, peer instruction, small group discussion, Process Oriented Guided Inquiry Learning (POGIL), and using Bloom’s Taxonomy to structure a course.