Isolation and characterization of cellulose nanocrystals from pineapple crown waste and their potential uses.

Pineapple crown is an important source of cellulose that is still going to waste because of the lack of knowledge about their economic uses. The isolation of cellulose nanocrystals (CNC) from pineapple crown leaf (PCL) wastes arises as an important alternative to use PCL wastes in high value-added applications, and has not been reported yet. In this study, CNC were successfully extracted from PCL wastes using chemical treatments followed by acid hydrolysis using sulfuric acid. FTIR results confirmed the removal of the non-cellulosic compounds of PCL through the mercerization and bleaching treatments. SEM and AFM showed that the diameter of PCL fibers was reduced from 18 μm to 39 nm after the hydrolysis reaction, resulting in CNC with rod-like shape. The obtained CNC showed cellulose I crystalline structure with high crystallinity index (73%). The thermal degradation of CNC started at 124 °C, what was attributed to the presence of surface sulfate groups identified by elemental analysis. The high hydrophilicity of CNC was verified by its high moisture content and absorption. The results showed that the CNC isolated from PCL have interesting properties to be used in many liquid media applications, besides their use as reinforcement in nanocomposites.