Canadian researchers are separating solvents in polluted water with hydroxystearic acid (HSA), essentially reengineering the water’s structure for purity, according to a new study that suggests the work may have important implications for water treatment and preservation.
The University of Guelph (U of G) and scientists from the Canadian Light Source (CLS) at the University of Saskatchewan used Mid-IR and Brockhouse beamlines to investigate the efficacy of their technique and visualize the ways molecules interact when removing industrial runoff often found in wastewater.
The beamlines allow for a wide range of complementary diffraction and scattering techniques to characterize the structure of materials.
Erica Pensini, associate professor in the School of Engineering at U of G, said she hopes that the separation, or isolation process, for industrial wastewater contaminants may eventually help to minimize water withdrawals while addressing water scarcity, particularly when coupled with other treatment techniques.
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Pensini described the process her team used as essentially creating a membrane around the solvents within the water.
The new study looked at industrial runoff acetonitrile (AN), tetrahydrofuran (THF), and hexavalent chromium, or Cr (VI). AN is commonly used as a solvent, for spinning fibres, and in lithium batteries, while THF can be used as a solvent for PVC and varnishes. It is also used to clean clogged 3D printer parts. Cr (VI) can be used as pigments in dyes, paints, inks and plastics, for leather tanning, and is also used as an anticorrosive agent added to paints, primers and other surface coatings.
Pensini and Alejandro Gregorio Marangoni, a U of G professor and Tier I Canada Research Chair in Food, Health and Aging, led the research published as “Mechanisms of separation between tetrahydrofuran and water using hydroxystearic acid.”
They utilized the expertise of beamline scientist Jarvis Stobbs, as well as Thamara Laredo, an associate professor of chemistry at Lakehead University. Students Tatianna Marshall and Laura Earnden also assisted on the study.
The researchers discovered that the fatty acid hydroxystearic acid can separate THF, via hydrogen, from water. They previously established this separation mechanism using sugars and surfactants and other water miscible solvents. The bond increases the proportion of single hydrogen-bond donors relative to double hydrogen-bond donors.
“We’ve been looking at the purification of surface water, groundwater and wastewater,” explained Pensini in a statement from the Canadian Light Source. “We found that it was possible to use molecules that are both water-loving and oil-loving to separate solvents from water.”
Pensini said they could see droplets separating from the water and understand how those molecules can “self-assemble” and “interact with each other.”
She added that the beamlines allowed the researchers to see the purity of the droplets without the need for dye.