Nanocrystalline cellulose from Calophyllum inophyllum shells waste by adjusting organic acid hydrolysis and optimization of reaction parameters using response surface methodology

Biodiesel production from Calophyllum inophyllum oil in Indonesia produces significant biomass waste, including seed shells. This study explores the conversion of the seed shell of Calophyllum inophyllum into nanocrystalline cellulose (NCC) via consecutive alkalization, bleaching and hydrolysis using various organic acids. Scanning electron microscopy (SEM) analysis showed a reduction in the diameter of cellulose fibers from 21.7 μm to 9.6 μm after alkalinization and bleaching. The hydrolysis process using several organic acids was optimized to produce thermally stable nanocellulose while maintaining its crystallinity. The diameter of the resulting nanofibrous cellulose was 20.53 nm for citric acid, 21.69 nm for maleic acid, and 22.06 nm for formic acid hydrolysis. In particular, lactic acid-derived NCC (NCC-LA) showed the highest crystallinity of 64.22 % with an average diameter of ~13.69 nm. Optimization of hydrolysis parameters using Response Surface Methodology (RSM) suggested 74.79 % crystallinity could be achieved with 6.01 M lactic acid following 3.46 h of hydrolysis at 91.12 °C.