Electromagnetic-field-sensitive bridges based on urchin-like La/Cu-Fe3O4 nanocapsules for ultra-efficient phosphate recovery and water disinfection

Abstract

Efficient phosphate recovery and water disinfection are critical for addressing environmental sustainability challenges. However, conventional nanomaterials have exhibited unsatisfactory performance and limited controllability, complicating their application in wastewater treatment. Here, we propose urchin-like La/Cu-Fe₃O₄ nanocapsules (NCs) featuring perpendicular La/Cu nanosheets surrounding an Fe₃O₄ nanosphere core. These NCs were synthesized using high-density adsorption and a controlled crystallization strategy, yielding a hydrotalcite-like structure that enhances phosphate adsorption and disinfection through osmotic pressure-mediated mechanisms. The La/Cu-Fe₃O₄ NCs exhibited an exceptional phosphate adsorption capacity of up to 1085.56 mg PO₄³⁻ g^–1, with rapid adsorption kinetics achieving equilibrium within 5 min. Coexisting ions facilitated the penetration of phosphate ions into the NCs, promoting stable binding with La and achieving 100% recovery efficiency at an initial concentration of up to 10 mg PO₄³⁻ L^–1. Additionally, the NCs demonstrated superior disinfection activity, achieving ~ 100% inactivation of total coliform bacteria through Cu-induced contact toxicity. The electromagnetic-field-induced self-assembly of the NCs into bridges enables controlled deployment in aqueous systems to prevent secondary pollution and fouling. This control mechanism facilitates efficient phosphate recovery and water disinfection in continuous flow systems, achieving ~ 100% phosphate recovery efficiency with consistent performance for over 10 consecutive adsorption–desorption cycles with less than 4% efficiency loss. Our study introduces a multifunctional nanomaterial that integrates high-performance phosphate recovery, rapid disinfection, and electromagnetic control, offering a scalable solution for wastewater treatment and resource recovery.