Research Seminar: Light Driven Processes at the Water-Energy Nexus

January 19, 2023 @ 10:00 am – 11:00 am

Stephanie Loeb

Stephanie Loeb, Assistant Professor
Civil Engineering, McGill University

Abstract: Light is the most abundant and fastest moving energy resource on Earth. Sunlight is the primary driver of many environmental transformation and decay processes, while environmental remediation technologies that harness sunlight can be driven by a sustainable energy source, typically do not require consumable chemicals, and have greater mobility for use in isolated and off-grid locations. This seminar will discuss processes and technologies that harness solar energy for water treatment, with particular emphasis on disinfection of viral pathogens. Understanding light induced inactivation is key to predicting the fate of viral pathogens in the environment, while engineered light-based treatment systems provide opportunities to develop sustainable, practical, and effective methods for controlling viral pathogens.

A meta-analysis of available sunlight inactivation rate constants for viruses and their surrogates revealed little correlation between pathogens and their common surrogates, as well as knowledge gaps in the wavelength dependent damage mechanisms. To study these mechanisms, we used a genome-wide PCR approach to study photodamage in the genomes of human norovirus and a common surrogate bacteriophage MS2. In contrast to previous work indicating that UV inactivation occurs primarily through the formation of pyrimidine dimers which render the viral genome non-replicable after a single photon absorption event, we found that the single-hit inactivation assumption is invalid under simulated solar radiation, highlighting the need for further mechanistic analysis of genomic photoproducts and the contribution of non-genomic damage to viruses under environmentally relevant conditions.

Harnessing solar energy for water treatment is a highly desirable approach to provide safe water in resource limited locations. The preferred photocatalytic nanomaterial for water treatment applications, TiO2, has a relatively wide bandgap, limiting its spectral overlap with the most abundant solar wavelengths. Nanomaterials exhibiting surface plasmon resonance can act as light antennae when incoming resonant light radiation generates an intense electric-field enhancement leading to absorption cross-sections many times greater than the size of the particle ─ essentially, the particle can absorb more light than incident on it. Recently, we developed a novel nanomaterial enabled system for sustainable solar photothermal disinfection, leading to the first demonstration of direct solar nanoparticle-enhanced thermal inactivation of bacteria and viruses in drinking water. Likewise, we have synthesized composite plasmonic-photocatalytic nanomaterials that can enhance the light absorption properties of TiO2 permitting more effective degradation of organic contaminants. We further optimize these approaches through the fabrication of prototype reactors from immobilized nanomaterial films for application in flow-through validation tests.

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