Influence of Processing Conditions on the Colloidal Stability of CNCs from Coconut Fiber

Abstract

The production of cellulose nanocrystals (CNCs) from agro-industrial residues represents a sustainable and technically feasible alternative, promoting the reuse of low-cost materials with high cellulose content. This study evaluated the effect of two bleaching routes of coconut fiber — using buffered sodium hypochlorite (PC) and alkaline hydrogen peroxide (PP) — on the colloidal properties of CNC suspensions obtained by sulfuric acid hydrolysis. Four different reaction conditions were tested, combining acid concentration, time, and temperature, in the following configurations: 40_25_35, 60_25_35, 40_40_35, and 60_40_35. The samples were characterized by dynamic light scattering (DLS) and zeta potential analysis, assessing average particle size (Z-Average), polydispersity index (PdI), and colloidal stability. The results showed that sample PC60_40_35 had the best performance, with a reduced size (255.4 nm), a moderate PdI (0.412), and a high absolute zeta potential (−32.36 mV), indicating good electrostatic stability and a homogeneous particle size distribution. Samples such as PP40_25_35 and PP60_25_35 also exhibited intermediate particle sizes (≈530 nm), but with lower stability. Overall, the PC bleaching route, combined with higher acid concentration and longer reaction time, favored the production of CNCs with more suitable colloidal properties, demonstrating the combined impact of treatments on suspension quality. These data have practical relevance and can be used to optimize future industrial processes for producing nanocellulose.