by Laura Buenning
A common problem plagues membrane filtration systems.
Deposits of suspended or dissolved substances clinging to the filter can obstruct the pores, fouling the membrane with material that can only be removed by expensive, time-consuming chemical cleansing.
In the bioenergy arena, where harsh conditions typify pretreatment of lignocellulosic biomass, LDRD team leader Ramesh Bhave (ORNL Materials Science and Technology Division), JDRD team leader Gajanan Bhat, and PhD student Vincent Kandagor have an idea for a durable, nanoporous membrane that would make biomass more immediately available to biochemical conversion and in the bargain increase the yield of sugars and other chemicals of value.
Bhave’s team is making the filtration membrane from ceramic and porous metal materials. Bhat and Kandagor are developing a coating for the new membrane—one that will not only protect it from the elevated temperatures and dilute acids or bases found in biomass pretreatments but also prevent fouling.
“The challenge,” Bhat says, “is to develop a coating and an application method that keeps the filter’s surface free of debris and the nanopores open.”
So, they’ve chosen a coating material known for its ability to resist fouling. “Like the TEFLON in a skillet, it prevents things from attaching themselves to the filter. The key is to lay down a monolayer inside and out, without closing the pores.”
During year one of the project, Bhat and Kandagor studied membranes provided by the LDRD team, testing to see if coatings would stick properly to the filter fabric and calculating its pore size. Then, Kandagor tested airbrush and dipping techniques on a similarly spaced stainless steel mesh fabric with varying low concentrations of an amber-translucent resin called Ulterm®. The team examined scanning electron microscopic images of the coated material to see if the pores remained open. They also tested this resin against two additional materials to see which of the three performed the best filtration and remained intact under inhospitable conditions, concluding that the original Ultem® resin outperformed the other two.
An expert in developing nonwoven fabrics, for filters in air and water purifiers and the like, Bhat says this project uses his skills in an entirely new way. It is also his first opportunity to work with ORNL scientists.
Monolayer Polymeric Coatings to Enhance the Performance and Service Life of Membranes for High Temperature Biomass Pretreatment
Gajanan Bhat, UT Cepartment of Materials Science and Engineering
Nanoporous Inorganic Membranes for Selective Separations in High Temperature Flow-through Recycle Pretreatment of Lignocellulosic Biomass
Ramesh Bhave, ORNL Materials Science and Technology Division