Tag Archives: Inventwood

Desalination with nanowood

A new treatment for wood could make renewable salt-separating membranes. Courtesy: University of Maryland

An August 6, 2019 article by Adele Peters for Fast Company describes a ‘wooden’approach to water desalinization (also known as desalination),

“We are trying to develop a new type of membrane material that is nature-based,” says Z. Jason Ren, an engineering professor at Princeton University and one of the coauthors of a new paper in Science Advances about that material, which is made from wood. It’s designed for use in a process called membrane distillation, which heats up saltwater and uses pressure to force the water vapor through a membrane, leaving the salt behind and creating pure water. The membranes are usually made from a type of plastic. Using “nanowood” membranes instead can both improve the energy efficiency of the process and avoid the environmental problems of plastic.

An August 2, 2019 University of Maryland (UMD) news release provides more detail about the research,

A membrane made of a sliver of wood could be the answer to renewably sourced water cleaning. Most membranes that are currently used to distill fresh water from salty are made of polymers based on fossil fuels.

Inspired by the intricate system of water circulating in a tree, a research team from the University of Maryland, Princeton University, and the University of Colorado Boulder have figured out how to use a thin slice of wood as a membrane through which water vapor can evaporate, leaving behind salt or other contaminants.

“This work demonstrates another exciting energy/water application of nanostructured wood, as a high-performance membrane material,” said Liangbing Hu, a professor of materials science and engineering at UMD’s A. James Clark School of Engineering, who co-led the study.

The team chemically treated the wood to become hydrophobic, so that it more efficiently allows water vapor through, driven by a heat source like solar energy.

“This study discovered a new way of using wood materials’ unique properties as both an excellent insulator and water vapor transporter,” said Z. Jason Ren, a professor in environmental engineering who recently moved from CU Boulder to Princeton, and the other co-leader of the team that performed the study.

The researchers treat the wood so that it loses its lignin, the part of the wood that makes it brown and rigid, and its hemicellulose, which weaves in and out between cellulose to hold it in place. The resulting “nanowood” is treated with silane, a compound used to make silicon for computer chips. The semiconducting nature of the compound maintains the wood’s natural nanostructures of cellulose, and clings less to water vapor molecules as they pass through. Silane is also used in solar cell manufacturing.

The membrane looks like a thin piece of wood, seemingly bleached white, that is suspended above a source of water vapor. As the water heats and passes into the gas phase, the molecules are small enough to fit through the tiny channels lining the walls of the leftover cell structure. Water collected on the other side is now free of large contaminants like salt.
To test it, the researchers distilled water through it and found that it performed 1.2 times better than a conventional membrane.

“The wood membrane has very high porosity, which promotes water vapor transport and prevents heat loss,” said first author Dianxun Hou, who was a student at CU Boulder.
Inventwood, a UMD spinoff company of Hu’s research group, is working on commercializing wood based nanotechnologies.

Here’s a link to and a citation for the paper,

Hydrophobic nanostructured wood membrane for thermally efficient distillation by Dianxun Hou, Tian Li, Xi Chen, Shuaiming He, Jiaqi Dai, Sohrab A. Mofid, Deyin Hou, Arpita Iddya, David Jassby, Ronggui Yang, Liangbing Hu, and Zhiyong Jason Ren. Science Advances 02 Aug 2019: Vol. 5, no. 8, eaaw3203 DOI: 10.1126/sciadv.aaw3203

This paper appears to be open access.

In my brief survey of the paper, I noticed that the researchers were working with cellulose nanofibrils (CNF), a term which should be familiar for anyone following the nanocellulose story, such as it.

Wood’s natural nanotechnology

“Wood’s natural nanotechnology: is an unusual term and it comes at the end of this February 7, 2018 University of Maryland (US) news release about a technique which will make wood stronger than titanium alloy,

Engineers at the University of Maryland in College Park have found a way to make wood more than ten times times stronger and tougher than before, creating a natural substance that is stronger than titanium alloy.

“This new way to treat wood makes it twelve times stronger than natural wood and ten times tougher,” said Liangbing Hu, the leader of the team that did the research, to be published on Thursday [February 7, 2018] in the journal Nature. “This could be a competitor to steel or even titanium alloys, it is so strong and durable. It’s also comparable to carbon fiber, but much less expensive.” Hu is an associate professor of materials science and engineering and a member of the Maryland Energy Innovation Institute.

“It is both strong and tough, which is a combination not usually found in nature,” said Teng Li, the co-leader of the team and the Samuel P. Langley associate professor of mechanical engineering at the University of Maryland. His team measured the dense wood’s mechanical properties.  “It is as strong as steel, but six times lighter. It takes 10 times more energy to fracture than natural wood. It can even be bent and molded at the beginning of the process.”

The team’s process begins by removing the wood’s lignin, the part of the wood that makes it both rigid and brown in color. Then it is compressed under mild heat, at about 150 F. This causes the cellulose fibers to become very tightly packed. Any defects like holes or knots are crushed together.  The treatment process was extended a little further with a coat of paint.

The scientists found that the wood’s fibers are pressed together so tightly that they can form strong hydrogen bonds, like a crowd of people who can’t budge – who are also holding hands. The compression makes the wood five times thinner than its original size.

The team also tested the material by shooting a bullet-like projectile at it. Unlike natural wood, which was blown straight through, the fully treated wood actually stopped the projectile partway through.

“Soft woods like pine or balsa, which grow fast and are more environmentally friendly, could replace slower-growing but denser woods like teak, in furniture or buildings,” Hu said.

“The paper provides a highly promising route to the design of light weight high performance structural materials, with tremendous potential for a broad range of applications where high strength, large toughness and superior ballistic resistance are desired, “ said Dr. Huajian Gao, a professor at Brown University, who was not involved in the study. “It is particularly exciting to note that the method is versatile for various species of wood and fairly easy to implement.”

“This kind of wood could be used in cars, airplanes, buildings – any application where steel is used,” Hu said.

“The two-step process reported in this paper achieves exceptionally high strength, much beyond what [is] reported in the literature,” said Dr. Zhigang Suo, a professor of mechanics and materials at Harvard University, also not involved with the study. “Given the abundance of wood, as well as other cellulose-rich plants, this paper inspires imagination.”

“The most outstanding observation, in my view, is the existence of a limiting concentration of lignin, the glue between wood cells, to maximize the mechanical performance of the densified wood. Too little or too much removal lower the strength compared to a maximum value achieved at intermediate or partial lignin removal. This reveals the subtle balance between hydrogen bonding and the adhesion imparted by such polyphenolic compound. Moreover, of outstanding interest, is the fact that that wood densification leads to both, increased strength and toughness, two properties that usually offset each other,” said Orlando J. Rojas, a professor at Aalto University in Finland.

Hu’s research has explored the capacities of wood’s natural nanotechnology [emphasis mine]. They previously made a range of emerging technologies out of nanocellulose related materials: (1) super clear paper for replacing plastic; (2) photonic paper for improving solar cell efficiency by 30%; (3) a battery and a supercapacitor out of wood; (4) a battery from a leaf; (5) transparent wood for energy efficient buildings; (6) solar water desalination for drinking and specifically filtering out toxic dyes. These wood-based emerging technologies are being commercialized through a UMD spinoff company, Inventwood LLC.

At a guess, “wood’s natural nanotechnology” refers to the properties of wood and other forms of cellulose at the nanoscale.

Here’s a link to and a citation for the paper,

Processing bulk natural wood into a high-performance structural material by Jianwei Song, Chaoji Chen, Shuze Zhu, Mingwei Zhu, Jiaqi Dai, Upamanyu Ray, Yiju Li, Yudi Kuang, Yongfeng Li, Nelson Quispe, Yonggang Yao, Amy Gong, Ulrich H. Leiste, Hugh A. Bruck, J. Y. Zhu, Azhar Vellore, Heng Li, Marilyn L. Minus, Zheng Jia, Ashlie Martini, Teng Li, & Liangbing Hu. Nature volume 554, pages 224–228 (08 February 2018) doi:10.1038/nature25476 Published online: 07 February 2018

This paper is behind a paywall.

h/t Feb. 7, 2018 news item on Nanowerk and, finally, you can find out more about the wood-based emerging technologies being commcercialized by the University of Maryland here on the Inventwood website.