Lignosulfonate-functionalized alginate hybrids reinforced with Fe-MOG: synergistic adsorption mechanisms for enhanced tetracycline hydrochloride removal in livestock breeding wastewater systems

Abstract

The widespread occurrence of tetracycline hydrochloride (TCH) in livestock wastewater has created an urgent need for adsorbents with high adsorption capacity, excellent mechanical stability, and good reusability. Herein, a novel Fe-MOG-loaded composite microsphere (FSS) was fabricated by immobilizing Fe-beads metal-organic gel (Fe-MOG) within a sodium alginate/sodium lignosulfonate (SA/SLS) dual-matrix hydrogel. The dual-matrix strategy effectively overcame the poor recoverability and limited mechanical strength of powdered Fe-MOG while preserving its excellent adsorption performance. Batch adsorption experiments showed that FSS achieved a maximum adsorption capacity of 1684.13 mg g⁻¹ toward TCH and maintained excellent adsorption performance over a wide range of pH values and complex aqueous environments. Mechanistic investigations demonstrated that TCH adsorption was governed by the synergistic effects of pore filling, electrostatic attraction, hydrogen bonding, and π–π interactions, with hydrophobic interactions as a possible contributing factor. Furthermore, regeneration experiments confirmed the excellent reusability of FSS, while application in real livestock wastewater demonstrated its outstanding adsorption efficiency, mechanical robustness, and operational stability under practical conditions. This work presents an effective strategy for improving the engineering applicability of powdered metal-organic gel adsorbents and highlights the considerable potential of dual-matrix Fe-MOG composite microspheres for the sustainable treatment of antibiotic-contaminated livestock wastewater.