Development of a Semi-IPN xerogel composite from eggshell, hydroxyapatite, and chitosan for efficient dye removal in aqueous media

Abstract

Water pollution from the textile industry poses severe environmental and public health challenges due to the presence of toxic and persistent synthetic dyes. Effective wastewater treatment is crucial to mitigate these impacts. This study addresses the issue by developing a sustainable and cost-effective semi-interpenetrating polymer network (IPN) xerogel composite incorporating eggshell, hydroxyapatite (HAp), and chitosan for efficient dye removal. Ultrasonic-activated eggshell powder (UAESP), HAp, or their combination was integrated with chitosan-containing poly(methacrylic acid) (PMAA)-based xerogels to enhance adsorption capacities. Characterization using FTIR, SEM, EDS, XRF, BET, and tensile strength testing confirmed significant structural, textural, and mechanical enhancements. Adsorption experiments demonstrated high efficiency in removing dyes such as methylene blue, Congo red, crystal violet, and methyl orange, with the chitosan/UAESP + HAp composite achieving the highest adsorption capacity (98.4 mg/g) for Congo red. Kinetic studies revealed that adsorption follows a pseudo-second-order model, with chemisorption as the dominant mechanism. Furthermore, intraparticle diffusion analysis indicated that the adsorption process involved multiple stages, including boundary layer diffusion followed by intraparticle diffusion. Simulated textile wastewater tests confirmed the practical applicability of the xerogels, maintaining high dye removal capacities over multiple cycles. In conclusion, this study offers a sustainable and versatile solution for wastewater treatment, contributing to cleaner water resources and environmental sustainability.