Production of TEMPO-oxidized cellulose nanofibers from cotton stalks and its utilization in different industrial applications

Cellulose nanofibers (CNFs) have established widespread attention in various industries with their potential applications. Production of CNFs from agricultural post harvesting wastes has several cost-effective and eco-friendly benefits. The objective of this research was to prepare four different types of CNFs from cotton stalks by different chemical treatments followed by ultra-sonication. CNFs via untreated bleached pulp, sulfuric acid hydrolysis, and TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl) oxy radical]-mediated oxidation process were produced. Physical and chemical properties of these CNFs were investigated by morphological (FE-SEM, AFM), structural (FTIR), and thermal gravimetric analysis (TGA). Developed TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs) were brighter and higher in yields (>90%). It was the first time uniform and very small sized (3-15 nm diameter and 10-100 nm length) nanofibers were produced. In application purpose, TEMPO-CNFs were introduced into chitosan matrix (prepared from shrimp exoskeletons) for the development of bionanocomposite food packaging films and into chitin for hydrogels preparation in order to eliminate heavy metals from water bodies. Development of bionanocomposite films (chitosan/TEMPO-CNFs compositions) was an effective and complete green approach with enhanced mechanical and barrier properties. Also use of TEMPO-CNFs in this method makes it possible to produce flexible, transparent, and low cost food packaging films with good antimicrobial activity against Salmonella enterica, E. coli O157:H7, and Listeria monocytogenes. In a similar way, generation of recyclable biobased adsorbents (chitin/TEMPO-CNFs compositions) with superior adsorption capacity and high surface area were effectively used in lead (Pb2+) removal from aqueous solutions, thus provide new opportunities as economical and environmentally friendly green remediation.