Assessing Commonly Used Methods in Measuring Yield of Cellulose Nanocrystals

Cellulose is a ubiquitous, renewable biopolymer found in plants that can be broken down to isolate cellulose nanocrystals (CNCs). CNCs have been utilized in various applications that include biomedical technology, structural composites, and barrier films because of their unique mechanical, optical, and physicochemical properties. CNCs can be produced by a variety of approaches from cellulosic materials; however, strong acid hydrolysis is the most common and effective technique as it results in stable colloidal suspensions. Existing literature reveals a wide range of CNC yields, depending on the production process, raw material used, and the method of yield estimation. The yields of CNCs are typically determined by one of four methods: air-drying films, oven-drying films, freeze-drying, chemical oxygen demand (COD) of organic materials in solution. Discrepancies exist in the methods to determine CNC yield, making it difficult to compare yields from different studies, even those using the exact same process and starting material; therefore, it is crucial that a standard method of calculating yield is utilized. This study used acid hydrolysis conditions that were optimized in the University of Arkansas Bio/Nano Technology Laboratory to deconstruct cellulose into its crystalline nanostructures. Because different materials have varying levels of purity and cellulose content, three raw materials, i.e. microcrystalline cellulose (MCC), pulp from sweetgum (a hardwood) and pulp from pine (a softwood), were chosen to produce CNCs, to capture the entire range of commonly-used starting materials. CNC yields from each of these raw materials were determined using each of the four methods mentioned above and statistical analysis was conducted using one-way ANOVA to find differences in means. The goal of this study was to compare the different commonly used methods of calculating yield of CNCs to determine the most suitable method that should be used by the research community for determining CNC yields