Microdroplets upcycle paper waste into chemical compound
A catalyst-free, room-temperature process converts lignin into a smaller molecule that can accept and donate electrons.
Researchers at the University of Illinois Urbana-Champaign, USA, have reported the method for converting Kraft lignin into a smaller, redox-active molecule using sonicated water microdroplets.
Kraft lignin is a complex polymer produced in large quantities by the pulp and paper industry, but its strong chemical bonds make it difficult to break down and turn into higher-value products.
The new approach uses ultrasonication to generate tiny water droplets in a mixture of oil, water, lignin and acid. These sonicated, emulsive, water microdroplets help cleave bonds in the lignin, converting around 56% of it within 20 minutes at room temperature, without added catalysts or high temperatures.
The resulting compound, named SEMILL-A, contains functional groups that make it redox-active and pH-sensitive. The researchers have confirmed its structure and behaviour using optical microscopy, infrared spectroscopy, 1D and 2D nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, chromatographic, and electrochemical analysis.
The team is now studying how the deconstruction and nitration reactions occur, and whether the approach can be extended to other biopolymers and plastics.
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