Optimization of Cellulose Isolation from Nypa Fruticans Fronds Assisted by Hydrolysis and Re-bleaching

Abstract

Converting Nypa fruticans fronds (NFF) into valuable microcrystalline cellulose (MCC) is a sustainable solution with many benefits. This study aimed to isolate microcrystalline cellulose from NFF by a sequential process from alkalization with varying concentrations of NaOH, first bleaching with 10% wt H2O2, hydrolysis with acid, and re-bleaching with NaOCl. The treatment results were evaluated based on percent yield and cellulose content, physicochemical properties, functional group analysis, crystallinity index, and surface morphology. The optimal NaOH concentration parameter was obtained at 10% wt NaOH with 57.10% cellulose, 10.73% hemicellulose, and 8.87% lignin. After the first bleaching, hydrolysis, and re-bleaching processes, the cellulose content increased sequentially from 62.13% to 71.26%, while hemicellulose decreased from 8.76% to 7.56%, and lignin decreased from 7.33% to 4.23%. Sequential treatments also caused a decrease in the swelling index from 1.441% to 1.224% and water binding capacity from 4.30% to 2.29%, indicating a decrease in hydrophilicity. XRD analysis showed that hydrolysis and re-bleaching treatments increased the crystallinity index of cellulose to 72.49%, which is close to the crystallinity of commercial cellulose (C-MCC) of 79.63%. SEM analysis showed that the surface morphology of cellulose was rod-like with a heterogeneous size. FTIR analysis revealed changes in the functional groups of NFF after sequential treatment from alkalization to re-bleaching, indicating the reduction of lignin and hemicellulose. The characterization results showed that the hydrolysis and re-bleaching assisted isolation process was sufficient to produce microcrystalline cellulose from Nypa fruticans fronds for various applications.