Investigating the influence of synthesis parameters on chitosan microparticle characteristics and Cr(VI) adsorption potential

Chitosan, a biopolymer derived from chitin, is a promising sustainable material for environmental remediation due to its biocompatibility and non-toxicity. Chitosan microparticles (ChMPs) offer enhanced functionality over bulk chitosan, yet their properties are highly sensitive to synthesis conditions. This study systematically evaluates the effects of bulk chitosan concentration (3, 6, and 9% w/v), degree of deacetylation (DD; 79.9%, 81.1%, and 82.6%), and stirring time (2, 4, and 6 h) on the morphology, size, and adsorption performance of ChMPs produced via ionic gelation followed by spray drying. SEM and FTIR analyses confirmed successful ionic cross-linking and revealed that longer stirring times and lower chitosan concentrations yielded smaller particles with more porous and irregular morphologies. Higher DD increased charge density and cross-linking intensity, resulting in structurally stable particles with enhanced surface accessibility. ChMPs synthesized under optimized conditions exhibited significantly improved Cr(VI) adsorption compared to bulk chitosan. These findings provide a reproducible framework for tailoring ChMP properties and demonstrate their potential as efficient, scalable, and sustainable adsorbents for heavy-metal removal.