BENGALURU: With industries and chemical labs synthesizing a wide variety of organic molecules every day and most of them done in water, they often undergo side reactions, yielding unwanted toxic products. To address this problem, chemists use toxic organic solvents, and more than 80% of the waste generated in chemical processes from such solvents is not disposed of properly.
Scientists revealed that waste produced by cashews can be a good substitute. India is the second largest producer of cashew nuts in the world, hence the raw material is easy and inexpensive to source.
The Department of Inorganic and Physical Chemistry (IPC), Indian Institute of Science (IISc), has come up with a solution and has synthesised a surfactant derived from cashew nut shell liquid (CNSL) -- an agricultural waste product generated during the roasting of cashews to separate the kernels. This process is called micellar catalysis.
“Since we were aiming to replace organic solvents, we felt that the substitute must be bio-based,” said Pritesh Keshari, first author and PhD student at IPC. The study published in ACS Sustainable Chemistry and Engineering explained that surfactants are molecules that have a water-loving (hydrophilic) as well as a water-repelling (hydrophobic) component. The researchers combined cardanol, a hydrophobic compound found in CNSL, with m-PEG, a hydrophilic polymer, to create their surfactant.
“Suppose you dip a football in a pond or sea. As long as the football doesn’t leak, it remains floating with no water entering inside the ball. We use the same analogy for micellar catalysis. When the substrate goes inside the micelle, it separates itself and the reaction product from the bulk water – and that’s where the chemistry happens,” said Susanta Hazra, Assistant Professor at IPC and corresponding author of the study. She added that the micellar catalysis mimics biological systems – many natural enzymes have a hydrophobic pocket much like the one in micelles.
“CNSL-1000-M led to 80% higher product yields in water compared to reactions carried out in organic solvents. Compared to existing surfactants, the new surfactant also gave 30% higher yields for reactions carried out in water,” read the IISc release.
Using the surfactant can also help replace expensive catalysts like palladium with inexpensive nickel complexes, and facilitate reactions at lower temperatures.
The researchers are keen to work with industries to enable the transition from using toxic organic solvents to micellar technology as a sustainable and green alternative.