Adsorption performance of barium from industrial wastewater using nano calcium alginate-manganese (IV) oxide beads

Barium contamination in industrial wastewater, particularly from refractory, ceramic, and oil-gas related industries, poses serious environmental and health risks due to its toxicity and persistence. In this study, a novel and cost-effective calcium alginate/manganese dioxide (CaAlg/MnO₂) nanosorbent was synthesized and applied for the selective removal of Ba²⁺ ions from aqueous solutions and real industrial wastewater. MnO₂ nanoparticles were successfully immobilized within the calcium alginate hydrogel matrix through Ca²⁺‑induced crosslinking, forming stable composite beads. The synthesized nanosorbent was characterized using FTIR, XRD, FESEM-EDS, BET, and TGA analyses. Batch adsorption experiments demonstrated that Ba²⁺ removal was strongly influenced by solution pH, contact time, adsorbent dosage, and ionic strength. Under optimal conditions (pH 8, 25 °C, 100 min), a maximum adsorption capacity of 52 mg g⁻¹ and a removal efficiency of 91% were achieved. Despite the relatively low BET surface area (2.18 m² g⁻¹), the high adsorption performance was attributed to ion-exchange mechanisms and strong chemical interactions between Ba²⁺ ions and functional groups of alginate and MnO₂. Regeneration experiments confirmed good reusability, with more than 85% removal efficiency retained after five cycles. The results indicate that CaAlg/MnO₂ nanosorbent is an environmentally friendly and efficient material for barium removal from complex wastewater systems.