Bioinspired Hybrid Polymeric Microspheres with Fractionated Lignin: Advanced Sorbents for Tetracycline Removal from Aqueous Media

This article focuses on the development of bioinspired hybrid polymeric microspheres for the efficient removal of tetracycline hydrochloride (TC) from aqueous solutions, leveraging the renewable and abundant nature of lignin as a sustainable component. The microspheres are synthesized via suspension polymerization, incorporating ethylene glycol dimethacrylate (EGDMA), vinyl acetate (VA), 1-vinyl-2-pyrrolidone (VP), various acrylate monomers, silane compounds, and fractionated lignin to enhance functionality and ecofriendliness. The objective is to create thermally stable, morphologically defined sorbents with high adsorption capacity. Thermogravimetric analysis revealed excellent thermal resistance up to 305-335 °C, while scanning electron microscopy confirmed uniform spherical morphology. Sorption studies demonstrated that microspheres with low-molecular-weight lignin (KS-6) exhibited a twofold increase in adsorption capacity (q_m up to 7.84 mg g^-1) compared to nonlignin counterparts, attributed to enhanced hydrogen bonding, π-π stacking, and electrostatic interactions. Kinetic data best fit the pseudo-second-order model (R² > 0.9999), indicating chemisorption as the dominant mechanism, with Freundlich isotherms suggesting multilayer adsorption on heterogeneous surfaces. These findings highlight the potential of lignin-based microspheres as cost-effective, sustainable sorbents for pharmaceutical pollutant removal, contributing to the valorization of lignin and advancing green water treatment technologies.