Sometimes separating things, instead of mixing them, is the goal in chemical engineering. But some systems prove difficult to separate, as is the case when trying to remove salt from water, or contaminants from natural gas (such as CO2 or other flammable impurities). Membranes are an effective way to remove contaminants from liquids or gases. They can act like filters to “screen” the objectionable component out, and provide a purified fluid. But it is a challenge to produce an effective membrane for a given application. In some cases the substance to be extracted is molecularly too small and easily passes through, or perhaps it is chemically too harsh and degrades the membrane. What is needed is a system that can be highly selective in separating components; tough enough to withstand extreme pH, oxidation, or elevated temperatures; and still “porous” enough to allow the gas or liquid product to come through fast enough.
About a year ago, a single conversation between two chemical engineering researchers about the problems designing such a system for a very important application resulted in an idea proving to be a viable solution. Sanat K. Kumar, professor and chair of the Department of Chemical Engineering, and Christopher J. Durning, professor of chemical engineering, are creating “designer” nanoparticle membranes that can screen out very specific components of a gas mixture.
“I have been working on polymer and nanoparticle design, and Chris has been working on membranes for gas and water purification, for a long time,” explains Kumar. “It was the case of the right people talking to each other at the right time about a shared challenge. That conversation resulted in us being able to take some fundamental science and platform technology and adapt it to a specific application.”
What Kumar and Durning have been able to do is control the structure and dynamics of nanoparticle-polymer assemblies by combining the two in a very specific way, and add the understanding emerging from this work to a growing knowledge of how gas separation membranes work. This combination has resulted in a new class of gas separation membranes that can potentially overcome the performance limitations of the best current membrane systems.
“The designer nanoparticle membranes let certain chemical species pass through faster than the native polymer membrane,” explains Durning. “It’s as if the presence of the nanoparticles that are decorated with chemically attached polymers open pathways for transport of certain chemicals.”
The duo’s research has great potential for well-gas purification, an important technology that can meet the increased global demand for high-purity natural gas.
“Well gas must be purified to remove dangerous contaminants, such as explosive condensable hydrocarbons, water, and corrosive sulfurous compounds,” explains Durning. “Advanced membranes have been identified as a strategic new technology that can enable more effective gas purification than current methods.”
The researchers have filed for a patent and are talking to others in the technology field about commercializing their solution.
“This underscores what scientific investigation is all about,” says Kumar. “You adapt an idea to a new application, and new physics emerge,” he says. “But I would never have thought to apply this to membranes, until I had that conversation with Chris.”
—by Amy Biemiller