By Cameron Chai
Scientists from the Savannah River National Laboratory (SRNL) of the U.S. Department of Energy have demonstrated novel ways to substitute monosodium titanate (MST)’s micron-sized particles with nano-sized particles, thus improving the efficacy of the ion exchange material.
Sandia National Laboratories and SRNL developed MST and its peroxide-modified form called mMST in a fine power form comprising spherically-shaped particles with a diameter of 1-10 µm. In this project, the researchers wanted to make titanate materials with particles of nano-scale sizes of 1-200 nm.
According to SRNL’s Dr. David Hobbs, who leads the project, by replacing with smaller particles, the amount of MST’s surface area is increased when compared to its total volume, which in turn increases its working area. The researchers studied three techniques for making nanoparticles, resulting in particles that have three different shapes. They employed a sol-gel technique similar to the method used for producing typical MST micron-sized particles. However, here they used surfactants and mild concentrations of reactive chemicals for controlling the size of the particles, resulting in spherical particles with a diameter of 100-150 nm.
In the second method, they started with standard micron-sized particles, which were then delaminated and unzipped to form fibrous particles with a length of 100-150 nm and a diameter of 10 nm. The third process is a hydrothermal technique, which created nanotubes with a length of 100-500 nm and a diameter of 10 nm. All of these nano-sized titanates demonstrated good ion exchange properties. The researchers were also able to convert these titanates into the peroxide-modified form. However, the peroxide-modified form of the nano-sized titanates demonstrates a yellow color as with the micron-sized titanates. The color intensity is low for hydrothermally made titanates due to the restriction caused by their chemically resistant surface to mMST conversion.