NSF-BSF: Precision Engineering of Functional Polymers for High Performance Silica Scale Inhibitors in Reverse Osmosis Desalination

Yale University, New Haven CT

Investigators

Abstract

Reverse osmosis (RO) is recognized as the most energy-efficient seawater desalination technology. To address increasing societal demands for water, RO is being used more broadly for water recovery from unconventional sources such as brackish groundwater and industrial wastewater. Despite RO’s advantages, mineral scale formation on RO membranes remains a critical challenge as it adversely affects membrane performance and lifespan. Scale formation is even more problematic for unconventional RO applications. This is due to the increased prevalence of silica-based scales in unconventional water that are resistant to commonly used scale inhibitor chemicals. The goal of this project is to address this problem by developing effective inhibitors for silica scales through an international collaboration with researchers at Ben Gurion University (Israel). The project aims to develop molecular design principles for high-performing polymeric inhibitors. The work is guided by the principle that reactive silica acid-containing molecules polymerize to form clusters (i.e., “scale”) that cover the RO membrane. This scale can thus be controlled by polymeric inhibitors that stabilize silicic acids, thus limiting the rate of silica scale formation. The key to winning the chemical “battle” between silica scale deposition and polymer inhibition is to better understand the molecular-level interactions between the antiscaling polymers and the soluble silica species at the membrane interface. To that end, the project will investigate a host of polymer chemical and physical design properties, followed by synthesis and evaluation of attractive candidates. Successful completion of this project will benefit society by improving RO separation technology for increased water supply, as well as the promotion of clean energy technologies to address critical environmental challenges. Additional benefits to society result from teaching, mentoring, and outreach activities that will create educational opportunities for a diverse group of students to improve the Nation’s STEM workforce. The development of precisely engineered polymers capable of inhibiting silica scale holds the potential to significantly improve the efficiency and extend the lifespan of RO membranes. The goal of this project is to elucidate the essential design principles for effective silica scale inhibitors under operational RO membrane conditions. The study will investigate the individual impact of polymer chain length, composition, and conformation on inhibition efficiency, as well as their detailed mechanistic role in stabilizing soluble silica species. Researchers will investigate scale formation utilizing a state-of-the-art quartz crystal microbalance in conjunction with localized surface plasmon resonance to elucidate mechanistic differences between homogeneous and membrane-based heterogeneous scaling processes. The research project encompasses functional polymer design and synthesis, antiscaling performance analysis in both homogeneous solutions and RO membranes, kinetic and computational studies on scaling and inhibition mechanisms, and the evaluation of RO desalination performance. The combined outcomes of this research will contribute to establishing a scalable and precise synthesis methodology for obtaining high-performance polymeric inhibitors for silica scaling. 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.