A Novel One Step Method to Prepare Carboxycellulose Nanofibers from Raw Biomass and their Applications to Remediation for Heavy Metal Ions

摘要

A sustainable one-step method has been developed to prepare carboxycellulose nanofibers, directly from raw biomass by using only nitric acid or nitric acid-sodium nitrite. The direct use of raw biomass to produce carboxycellulose nanofibers, has successfully overcome multi-step processes to convert raw biomass into nanocelluloses. This new approach has been able to effectively reduce about 94.8% consumption of toxic chemicals and 66.6% water consumption along with 98.7% decrease in consumption of electrical energy during the conversion process. In addition, the effluent can be efficaciously neutralized with base to produce nitrogen rich salts that can be used as a plant fertilizer. The versatility of this process has been proven on different sources such as raw jute fiber, spinifex grass and bamboo cellulose. TEM measurement of produced carboxycellulose nanofibers were in the range of 250-400 nm and width 4-5 nm, having PDI ratio of 0.286-0.382. Interestingly, these nanofibers were prominently non-crystalline as determined by TEM diffraction pattern, WAXD and 13C CPMAS NMR analysis. For example, the crystallinity index (CI) measured by WAXD for jute-derived nanofibers was only 35%, when compared with 62% in raw jute. Carboxycellulose nanofibers with low degree of crystallinity can be used as low cost, sustainable and effective media to remove common water pathogens (including toxic heavy metal ions such as uranium, lead and cadmium) from drinking water purification and beyond.