CAREER: Harnessing Mineralogy and Polymer Science to Elucidate Mechanisms and Mitigation Strategies for Mineral Scaling in Membrane Desalination

Membrane-based technologies such as reverse osmosis (RO) are increasingly being utilized to provide clean water in the United States and worldwide under a rapidly changing climate and growing water scarcity. Currently, RO is the best available commercial technology for extracting and recovering clean water from a wide range of impaired water sources including seawater, inland brackish water, and municipal/industrial wastewater.

However, the formation and precipitation of inorganic scales at the surface of RO membranes severely limit their water recovery and adversely impact the overall process efficiency and cost of water produced by RO desalination and water reuse plants. Compared to organic/biological membrane fouling, the mechanisms of formation and precipitation of inorganic scales at RO membrane surfaces are poorly understood as they involve complex chemical reactions and nucleation phenomena at polymer-mineral-water interfaces.

The overarching goal of this CAREER project is to advance the fundamental understanding of mineral scaling at the surface of RO membranes. The successful completion of this project will benefit society through the development of new fundamental knowledge to advance the development and implementation of more efficient and cost-effective solutions to control and mitigate mineral scaling in RO desalination and water reuse systems.

Further benefits to society will be achieved through student education and training including the mentoring of a graduate student and an undergraduate student at Colorado State University.

Membrane scaling remains an important and unresolved challenge that limits the water recovery and overall system efficiency of commercial reverse osmosis (RO) desalination and water reuse plants. There are still critical knowledge gaps in the fundamental understanding of RO membrane scaling. First, the key physical/chemical processes and factors that control the extent of mineral scaling in RO membranes are not well understood.

Second, the utilization of surface modification to mitigate mineral scaling in RO membranes has met with only limited success. Third, there is a lack of fundamental knowledge and principles to guide the design of antiscalants to mitigate the formation and precipitation of amorphous silica scales in RO membranes. This CAREER proposal will address these critical knowledge gaps.

The guiding hypothesis of the proposed research is that polymers used as RO membrane surface modifiers or antiscalants can control the extent of mineral scaling by altering the thermodynamics and kinetics of scale nucleation events at membrane-water interfaces and the subsequent attachments of nascent mineral scales to membrane surfaces. Two key goals of the research are to: (1) Characterize and unravel the roles of scale nucleation thermodynamics, kinetics, and mineral-membrane affinity on the extent of RO membrane scaling and (2) Develop structure-property-performance relationships to guide and inform the design of scaling-resistant RO membranes and polymeric antiscalants to minimize and prevent RO membrane scaling.

The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge to advance the development of more effective strategies to control and mitigate membrane scaling in RO desalination and water reuse plants. To implement the educational and training goals of this CAREER project, the Principal Investigator (PI) will work with the Native American STEM Institute of Colorado State University (CSU) to develop and implement lectures and hands-on experiments for Native American high school students to learn about the critical science and engineering of challenges around water sustainability including the desalination of seawater and brackish water.

In addition, the PI plans to partner with the ENpower Bridge program of CSU’s Engineering College to encourage and recruit students from underrepresented groups to pursue undergraduate/graduate education in Environmental Engineering.

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.