Chemical isolation and characterization of different cellulose nanofibers from cotton stalks

Authors: SONI, BHAWNA - Mississippi State University; HASSAN, EL BARBARY - Mississippi State University; MAHMOUD, BARAKAT - Mississippi State University

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2015
Publication Date: 8/1/2015
Citation: Soni, B., Hassan, E., Mahmoud, B. 2015. Chemical isolation and characterization of different cellulose nanofibers from cotton stalks. Carbohydrate Polymers. 134:581-589.

Interpretive Summary: This study revealed that isolation of cellulose from abundantly available agricultural post-harvesting residues is a proficient utilization for production of CNFs. It is an environmentally sound method that serves as valuable renewable resources to produce biodegradable nano-scale reinforcement materials that are relatively cheap. In this study, various cellulose nanofibers were prepared by different chemical-ultrasonic treatments and compared by many chemical and physical properties. FE-SEM and AFM analysis clearly explained the difference in dimensions and surface morphology between nanofibers. Untreated CNFs showed incomplete individualization and broader size distribution (100–500 nm width and 20 nm length and). Sulfuric acid dialyzed and neutralized CNFs showed also incomplete individualization and no significant differences in their dimensions (10–50 nm width and 200–500 nm length). TEMPO-mediated oxidation produced uniform and very small CNFs (3–5 nm width and 10–100 nm length) with 90% yield. FTIR spectrum of TEMPO oxidized CNFs showed prominent peak at 1610 cm-1 corresponds to carbonyl groups that make it different from other CNFs. Thermographs of DTG-TGA analysis showed that the thermal decomposition of TEMPO oxidized and H2SO4 dialyzed CNFs was completely different from both H2SO4 neutralized and untreated bleached CNFs. Production of very small and uniform CNFS from TEMPO-mediated oxidation and Introducing various appropriate functional moieties make the produced fibers are much more effective for use in a wide range of industrial applications.

Technical Abstract: Recently, cellulose nanofibers (CNFs) have received wide attention in green nanomaterial technologies. Production of CNFs from agricultural residues has many economic and environmental advantages. In this study, four different CNFs were prepared from cotton stalks by different chemical treatments followed by ultrasonication. CNFs were prepared from untreated bleached pulp, sulfuric acid hydrolysis, and TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl) oxy radical]-mediated oxidation process. Physical and chemical properties of the prepared CNFs such as morphological (FE-SEM, AFM), structural (FTIR), and thermal gravimetric analysis (TGA) were investigated. Characterization results clearly showed that the method of preparation results in a significant difference in the structure, thermal stability, shape and dimensions of the produced CNFs. TEMPO-mediated oxidation produced brighter and higher yields ('90%) of CNFs compared to other methods. FE-SEM and AFM analysis clearly indicated that, TEMPO-mediated oxidation produced uniform nano-sized fibers with a very small diameter (3-15 nm width) and very small length (10-100 nm). This was the first time uniform and very small nanofibers were produced.