Selective Microcrystalline Cellulose Extraction from Chinese Medicine Residues via Direct PMS Oxidation

Abstract

The valorization of Chinese medicine residues (CMRs) into high-value-added products, such as microcrystalline cellulose (MCC), has garnered significant interest in the current post-pandemic era, particularly in regions where Chinese medicine (CM) is widely utilized (i.e., Southeast Asia). In this study, we propose a facile and economical protocol for selectively extracting MCC from CMRs via one-step direct peroxymonosulfate (PMS) oxidation without the need for intricate steps. Importantly, our proposed protocol has been verified to be versatile and can be applied to various solid waste sources rich in cellulose, with an average extraction rate of 75%. Analysis using the Fukui index revealed that the β-O-4 bond, the aromatic ring in lignin, specific O sites in hemicellulose, and the amorphous region of cellulose are more susceptible to electrophilic attack by PMS than to reactions involving HO•, SO4•−, or 1O2. Leveraging this distinct mechanism, the extracted MCC demonstrated ultrahigh purity (∼95%) and crystallinity (∼85.36%). Overall, our work involves transforming solid waste into high-value products through the provision of a technical solution, with the potential for onsite application. This represents a significant advancement to the valorization of CMRs, particularly in providing theoretical guidance for accelerating the recycling of waste materials.