Isolation of Microcrystalline Cellulose (MCC) from Rice Husk: A Review

Rice husk (RH) is a by-product of the rice milling process and is regarded as agricultural waste if not utilized properly. RHs are recognized to contain significant nutritional benefits, including cellulose, hemicellulose, lignin, hydrated silica, organic carbons, and potassium. One of the most often used cellulose derivatives in the food and pharmaceutical business is microcrystalline cellulose (MCC). MCC's isolation process consists of four stages, which are delignification, bleaching, hydrolysis, and drying. These steps are linked to various crucial reactions, including cellulose yield (%wt/wt), MCC yield (%wt/wt), and crystallinity index (%CrI). This review aims to identify the ideal parameters for the delignification, bleaching, hydrolysis, and drying processes involved in the extraction of MCC from RH. The effects of these parameters on the yield of cellulose, MCC, and CrI are also discussed. The result shows that alkaline pulping is usually utilized to treat 100% of the delignification process. MCC yield is negatively correlated with the number of delignification processes, with one step being the ideal amount. The cost-effective reagent for the bleaching process is NaClO, which also reduces CrI compared to samples that have not been bleached. For hydrolysis, HNO3 is utilized to provide higher yields of MCC. There is no association between the drying process and the three dependent variables, which is at odds with the current theory. Further investigation is required to ascertain the impact of the drying process's time, temperature, and technique in addition to the previously listed factors.