Sustainable valorization of rice husk: thermal behavior and kinetics after chemical treatments

This study explores the potential of utilizing lignocellulosic agricultural residues as sustainable alternative materials to traditional ones by reinforcing them with polymers. Rice husk, a lignocellulosic biomass obtained during the rice milling process, is investigated for this purpose. However, its poor interaction with polymer matrices, primarily due to the presence of hemicellulose and lignin alongside cellulose, poses a challenge. Various surface treatments are evaluated to enhance the surface properties of rice husk and improve its interaction with polymers. Specifically, pretreatment with 5% w/w alkali solutions of KOH in water and 0.05% concentrated KMnO solution with water is studied. Fourier-transform infrared (FTIR) analysis assesses the changes in functional groups in rice husk resulting from these chemical treatments. The thermal potential and pyrolysis reaction kinetics of treated rice husks are examined through thermogravimetric analysis (TGA) at three different heating rates. Model-free methods are applied to the TGA data To determine the activation energies. The average activation energy of KOH-treated rice husk ranges from 111.91 to 186.69 kJ/mol, while that of KMnO-treated rice husk falls between 134.26 and 188.42 kJ/mol. These results highlight the effectiveness of chemical treatments in improving the suitability of rice husk as a reinforcement filler in polymer matrices. Notably, KOH treatment exhibits more potential for removing hemicellulose from rice husk than KMnO treatment. As treatment duration is very short comparatively in the case of using KMnO so treatment with KMnO may be preferred for fast action over alkali treatment. These findings underscore the importance of pretreatment processes to enhance the compatibility and performance of lignocellulosic agricultural residues in sustainable materials development. Graphical Abstract: [Figure not available: see fulltext.].