Co-doped LaFeO₃ perovskites for efficient Pb²⁺ removal from water

Abstract

The persistence of Pb²⁺ in aquatic systems necessitates efficient and recyclable adsorbents for sustainable remediation. In this work, pure LaFeO₃ (LFO) and Co-doped LaFeO₃ (LaFe₀.₉Co₀.₁O₃ and LaFe₀.₈Co₀.₂O₃) nanoparticles were synthesized via a sol-gel auto-combustion route and evaluated for lead removal from water. Structural analyses confirmed a single-phase orthorhombic perovskite structure with systematic reductions in lattice parameters and crystallite size upon cobalt substitution. Charge neutrality was maintained through the formation of tetravalent Fe⁴⁺ species, while XPS revealed the coexistence of oxygen vacancies and mixed Fe³⁺/Fe⁴⁺ valence states that collectively promote enhanced adsorption behavior. Optical measurements revealed a tunable bandgap, decreasing from 2.23 eV to 1.82 eV with increasing Co content, a trend further corroborated by DFT analysis. LaFe₀.₈Co₀.₂O₃ exhibited the highest Pb²⁺ adsorption efficiency, removing 2.49 ppm of Pb²⁺ from a 3.88 ppm solution, corresponding to a 64.2 % removal. The adsorption followed pseudo-second-order kinetics and the Freundlich isotherm. Enhanced magnetic properties with increasing Co content facilitate magnetic separation and indicate potential for future reusability. These results highlight that Co doping simultaneously improves adsorption performance and magnetic response, establishing Co-doped LFO nanoparticles as a promising perovskite-based platform for Pb²⁺ removal in water purification applications.