Favored surface-limited oxidation of cellulose with Oxone® in water

Abstract

A novel method for favored primary alcohol oxidation of cellulose was developed. Cellulose pulp and Cladophora nanocellulose were oxidized in a one-pot procedure by Oxone® (2KHSO₅·KHSO₄·K₂SO₄) and efficient reaction conditions were identified. The effects of the reaction on the morphology, viscosity and chemical structure of the products obtained were studied. The primary alcohol groups were oxidized to carboxyl groups and the content of carboxyl groups was determined by conductometric titration. SEM, capillary-type viscometry and XRD were applied to characterize the products and to investigate the influence of oxidation. For the first time, low-cost and stable Oxone® was used as a single oxidant to oxidize cellulose into carboxyl cellulose. The oxidation is an inexpensive and convenient process to produce carboxylic groups on the surface of the cellulose fibers and to make the cellulose fibers charged. Particularly, this method can avoid the use of halogens and potentially toxic radicals and constitute a green route to access carboxylated cellulose. Further, sodium bromide could be used as a co-oxidant to the Oxone® and increase the carboxylic acid content by 10–20%. The Oxone® oxidation is a promising method for oxidation of cellulose and might facilitate the production of CNC.