Structure–Property Relationship of Citric Acid-Crosslinked Sericin/PVA Electrospun Nanofibers for Sustainable Dye Adsorption

Abstract In this study, eco-friendly, water stable sericin/poly(vinyl alcohol) (PVA) nanofibrous mats were successfully fabricated via aqueous electrospinning, utilizing citric acid (CA) as a green crosslinking agent. The electrospinning performance was optimized by systematically evaluating the shear viscosity of PVA/sericin spinning solutions, achieving the optimal solution viscosity and molecular chain entanglement required for uniform, defect free fiber formation. Subsequent thermal curing with 10 wt% CA established a robust three-dimensional polymer network primarily through esterification between the carboxyl groups of CA and the hydroxyl groups of PVA and sericin, which effectively stabilized the highly porous, interconnected fibrous architecture against dissolution in aqueous environments. Comparative studies using control films supported that sericin intrinsically possesses a high affinity for cationic dyes, while CA serves a crucial dual role: reinforcing the structural matrix and providing abundant unreacted carboxylic acid groups as key adsorption sites. The optimized crosslinked nanofibrous mat exhibited a remarkable maximum methylene blue adsorption capacity of 75.86 mg/g. The adsorption equilibrium and kinetic data were better described by the Langmuir and pseudo-second-order models, respectively, while pH dependent adsorption and pH pzc measurements supported an important contribution of electrostatic interactions. Furthermore, the adsorbent demonstrated outstanding structural stability and reusability, maintaining over 81% of its original dye removal efficiency across ten consecutive adsorption–desorption cycles. By leveraging biodegradable and nontoxic materials, these highly recyclable electrospun nanofibers provide a sustainable, resource efficient platform for advanced wastewater remediation, contributing significantly to the advancement of material reuse and regeneration.