Preparation and characterization of modified rice husks by biological delignification and acetylation for oil spill cleanup

Cellulose is widely used as an effective sorbent to treat wastewater. Cellulosic sorbents have the advantage of biodegradability, as they are natural plant-based materials, compared with the synthetic materials such as polypropylene (PP) or polyurethane (PU). Among the raw biomass materials used for cellulose production, rice husk is one of the most cost competitive and widely available. In this work, biological treatments are compared to find the most effective treatment method for cellulose fibre production from rice husk. Using biological delignification, cellulose was extracted from raw rice husk and acetylated to acquire hydrophobicity. Delignification was performed using both bacteria and fungi and their results were compared. The white-rot fungi strain using ‘Aspergillus flavus CICC 40258’ was found to be the most effective treatment method, achieving a modified product with up to 55% w/w cellulose concentration. Acetylation further facilitated the sorption process and the maximum oil uptake capacity using delignification and acetylation treatment was found to be 20 g/g. The as-prepared sorbents exhibited high oil uptake rates and saturation capacity was reached after 5 min of contact with oil. The kinetic study presents a good correlation with the pseudo-second order model. The isothermal studies demonstrated that the oil sorption capacity of rice husk follows the Langmuir model as compared with the Freundlich model.