Underestimation of Regenerated Cellulosic Microfibers in the Environment: Errors Introduced by Using Extraction Methods for Microplastics

Due to the rising concern about microplastic (MPs) pollution, production of regenerated cellulose fiber (RCFs), as a substitute for petrochemical-based synthetic fibers (SFs), has been increasing over the last decades. While RCFs are generally considered environmentally friendly, they are not necessarily biodegradable, and their occurrence and toxicity in the environment have previously been overlooked. The lack of suitable extraction methods for RCFs may be a crucial factor hindering research on their environmental effects as it remains largely unknown whether the extraction methods for MPs are applicable for RCFs. This study revealed that digestion reagents (such as Fenton’s and H2O2) and flotation salt solutions (such as NaCl, ZnCl2, etc.) commonly used for MPs separation cannot effectively recover RCFs. The digestion of RCFs in 30% H2O2 at 70 °C resulted in significant breakdown and dissolution. Moreover, the flotation efficiency of RCFs in various salt solutions was <30%. We propose using soybean oil as a flotation reagent, which can recover 99% of acetate cellulose and 69–85% of other RCFs. This study is the first to highlight the limitations of the current methods for separating RCFs from environmental media and to propose a feasible solution.