Products Cited in Publications Worldwide The Role of Transition Metal Oxidants in the Nitro-Oxidation of Cellulose and Applications of the Resulting Cellulose Fibers

The Role of Transition Metal Oxidants in the Nitro-Oxidation of Cellulose and Applications of the Resulting Cellulose Fibers

Khan, Madani A

Abstract

Cellulose is a highly ordered and linear polymer where D-glucopyranose units are linked via b-1,4- linkages. Lignocellulose biomass can contain up to 30-50 wt% cellulose, 19-45 wt% hemicellulose, and 15-35 wt% lignin, depending on the source. Traditional methods of extracting cellulose from lignocellulosic biomass include physical, chemical, or biological treatment, or a combination of these. Nitro-oxidation is a process developed by the Hsiao group that produces cellulose nanofibers and nitrogen-rich effluent from various agricultural wastes. The primary reagents used for this method are 14 mL of nitric acid and 0.96 grams of sodium nitrite per gram of biomass. While this method is highly efficient in producing cellulose nanofibers with a carboxylate group, the excess amount of sodium in the effluent may impede plant growth if used as liquid fertilizer. Our current study explores the use of different transition metal salts as oxidizing agents for the nitro-oxidation process without using sodium nitrite. The results suggested that the iron salts can remove lignin and oxidizing jute biomass like potassium nitrite with a degree of oxidation exceeding 1 mmol/g. Furthermore, the degree of oxidation changes with the source of cellulose and the valency of the transition metals. The newly oxidized cellulose fibers have numerous carboxylate groups, and these negatively charged polymers can be used in various applications. For one of the applications, we demonstrated that we could combine these fibers with gelatin to create a new type of hydrogel that can potentially be used for water treatment. We also found that these fibers can remove positively charged malachite green (a dye) from water with a removal efficiency greater than 90%. In another study, a new glucose-based saccharide derivative was synthesized that can be used as a simple model compound to study cellulose modification reactions and processes. The synthesized compound will be subjected to cellulose modification reactions, and the resulting products will be isolated and fully characterized. These studies will identify conditions for oxidation to a carboxyl group at carbon six, conditions under which cleavage of glycosidic linkages occurs in the resulting products, and any other reaction products.

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