Enhanced Vitamin D3 Adsorption Through Novel Hydrophobic Halloysite–Alginate Biopolymer Composites

Abstract

This study presents a sustainable strategy to enhance polymer encapsulation, adsorption, and functional properties by chemically modifying sodium alginate with hydrophobic groups. Hydrophobic alginate derivatives were synthesized via a solvent-free method using hexadecyl trimethylammonium bromide, resulting in nanoparticles capable of effectively capturing non-polar compounds. To further improve compatibility within alginate-based biocomposites, halloysite nanotubes were modified through ball milling and surfactant-assisted treatments. The resulting nanocomposites (MBHA and MHHA) exhibited significantly enhanced adsorption and controlled release behavior, as confirmed by FTIR analysis of hexadecyl alginate ester conjugation. Vitamin D3 adsorption followed the Langmuir isotherm, with high correlation coefficients (R2 = 0.998 for MBHA and R2 = 0.991 for MHHA), indicating monolayer adsorption on a homogenous surface. Kinetic modeling revealed that the adsorption process adhered to a pseudo-second-order model (R2 = 0.9969 for MBHA and R2 = 0.999 for MHHA), suggesting that chemisorption was the dominant rate-controlling mechanism. These results demonstrate the critical role of surface modification in designing nano-engineered biopolymers with superior adsorption, stability, and release profiles, offering sustainable applications in medicine, agriculture, and environmental remediation.