This presentation describes our approach for making chemically reactive forms of lignin and lignin-containing materials and applying these materials to fabricate growing media for hydroponics. Lignin is an abundant, under-utilized, and cheap bio-resource. Our strategy is to couple lignin with a bifunctional linker molecule containing an aromatic amine and a protected vinyl sulfone. The chemical process starts with converting the aniline nitrogen of this linker to an electrophilic diazonium salt, which then reacts with the electron-rich naphthalene rings of the lignin to form the chemically reactive lignin. The other functional end of the linker is deprotected under basic conditions and slightly elevated temperatures (pH~8 and 60 °C) to yield the vinyl sulfone for forming covalent bonds to the hydroxyl groups of substrates via the Michael reaction. The process is eco-friendly because it is performed in water without organic solvents and harmless inorganic salts are the only major byproducts.<br/><br/>Our chemical approach was demonstrated to activate lignin within hemp materials in the fabrication of hemp fiber composites. The recent increase in the cultivation of hemp in the U.S. has led to a large supply of hemp fibers. The lignin of hemp fibers was functionalized using the diazonium bifunctional linkers to make chemically reactive hemp. The anchored vinyl sulfonate groups were applied to crosslink hemp fibers with polyvinyl alcohol to yield hemp fiber composites. The hemp composites did not easily crumble under compressive mechanical tests. However, they became soft upon soaking in water. Properties of this hemp composite such as carbon/nitrogen ratio, water retention capacity values, and salinity were investigated to determine their suitability for hydroponics applications. The hemp fiber composites were evaluated as hydroponic growing media for model plant systems. Our results showed that the hemp composite can be successfully applied as other organic growing media such as peat moss for hydroponics.

Diazonium-based chemical approach to fabricate hemp fiber composites for hydroponic application

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.