John Hoffman (Phillip Group)

Spatially-Controlled Functionalization of Nanofiltration Membranes

September 15, 2021


John Hoffman recently graduated under the advisement of Prof. William Phillip in the Department of Chemical and Biomolecular Engineering. He presented “Spatially-Controlled Functionalization of Nanofiltration Membranes” in September 2021 during ND Energy’s monthly seminar series for postdoctoral scholars and graduate students.

Hoffman received a 2021 Patrick and Jana Eilers Graduate Student Fellowship for his research on developing membranes for purifying water. Hoffman uses polymers to make films with selective permeability – to filter out salts, heavy metals, and other toxic chemicals but still allow water to flow through.

“If we can develop more energy efficient ways to produce clean water, it will not only provide more drinking water to those who need it, but will also reduce the energy demands needed to produce it,” Hoffman said. “I hope this work can develop better and cheaper membranes to help provide clean water to the people who need it.”

The codependency between clean water and energy, which is referred to as the water-energy nexus, presents a global challenge as hundreds of millions of people around the world still lack access to clean drinking water.

“This is a big problem that we need to address and will only get worse if we don’t act now,” Hoffman said.

More specifically, Hoffman’s Eilers fellowship project was focused on developing a way to produce a multi-functional membrane which consists of small domains of different functionality.

“In this way, we can enhance the utility of these membranes by incorporating more interactions between solutes in water and produce cleaner water with less energy,” Hoffman said. “This was evaluated by introducing two separate domains of different functionality, which each capture different heavy metals.”

Hoffman collaborated with Prof. Ruilan Guo’s group to synthesize polymers for his membrane research.

“Her group is very skilled in polymer chemistry and has been a great partner,” Hoffman said.

Using a laser-etched photomask, Hoffman and collaborators were able to develop a process to pattern the membrane surface. This process produced stripes, around 200 micrometers in size, capable of capturing a specific heavy metal. In this case, they were able to capture copper, which is toxic if consumed.

“Beyond improving the membrane performance, introducing these patterns can help improve sensing applications by making barcode or QR patterns, which can alert waste management systems if a high degree of toxic material is present,” Hoffman said.

Along with instrumentation in the Center for Environmental Science and Technology (CEST) and Notre Dame Integrated Imaging Facility (NDIIF), Hoffman’s research was supported by the capabilities at ND Energy’s Materials Characterization Facility (MCF). He used the FTIR to demonstrate the success of the chemical modifications to the membranes.

“Notre Dame fosters a great environment in which research can be done. Beyond the help we get from our advisors and departments, there are many great organizations that assist and provide meaningful support to us throughout our graduate careers,” Hoffman said, citing ND Energy’s seminar series and annual research symposium as examples.

Now that he has graduated, Hoffman has accepted a two-year postdoctoral fellowship at the National Institute of Standards and Technology (NIST) and will start his new position in December 2021.

“I will be working on membranes for the application of direct-air carbon capture. This is similar in respect to the capture of heavy metals from wastewater but will focus on the capture of carbon dioxide from the air. Many of the skills I learned at Notre Dame will be used, including experimental techniques such as FTIR. I’ll also learn more skills which will help me to grow as a researcher,” Hoffman said.