GOALI: Stimulated Raman microscopy for sensitive real-time detection of membrane fouling

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A membrane provides a selective barrier or filter, allowing certain compounds to pass through but preventing others. Membranes separate salts from sea water to produce drinking water. In emissions control, membranes prevent pollutants from being released into the environment. In landfills, membranes stop contaminants from leaching into the groundwater. In the process of filtering contaminants, however, the retention of certain compounds can lead to fouling. Fouling is a serious and ubiquitous problem in purification processes that rely on membranes, as it decreases membrane performance, increases energy consumption, and can lead to permanent damage of the membrane. Combined, these effects increase the cost of membrane operation, and thus, fouling mitigation is of great interest for industrial membrane processes. A key part of the mitigation strategy is detection, in order to proactively prevent fouling before it proceeds unchecked. Existing detection techniques rely on bulk measurements, such as pressure drop across the membrane, which can give an early warning of fouling. However, these bulk techniques do not provide chemical specific information on what leads to fouling. It is anticipated that chemical identification could facilitate molecular-level design of membranes that are resistant to fouling. The research will demonstrate an innovative method to detect membrane fouling under realistic operating conditions. The work will demonstrate an effective, high-resolution, label-free, non-destructive, and non-invasive real-time method for fouling detection under realistic operating conditions. A number of fundamental questions will be answered, including the sensitivity of the proposed optical detection method to early-stage reverse-osmosis, scaling initiation and growth as manifested by an increase in lateral and thickness dimensions. The research is an interdisciplinary topic spanning physics, materials science and engineering. If successful, the project will enable higher efficiency and lower-cost operation of reverse-osmosis desalination systems; and will provide similar significant benefits for other membrane-based separation applications. The project will provide research opportunities for graduate and undergraduate students, as well as dissemination to under-represented students at the college and K-12 level through involvement with public scientific demonstrations, laboratory tours, K-12 courses, and involvement with the Women in Electrical, Computer and Energy Engineering group.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.