Comparative adsorption study of As³⁺ and Se⁴⁺ by different crystalline phases of copper ferrite with experiments and DFT calculation

Magnetic solid phase extraction (MSPE) has gained attention as an effective method for removing hazardous ions from aqueous solutions. However, its broader application remains constrained due to relatively low adsorption capacities, largely stemming from a limited understanding of the underlying mechanisms. This study uses a co-precipitation method to investigate the adsorption performance of arsenic and selenium ions on spinel copper ferrite (CuFe₂O₄) nanoparticles synthesized in cubic and tetragonal crystalline phases. X-ray diffraction (XRD) analysis confirms the formation of distinct crystalline phases, while density functional theory (DFT) simulations reveal the adsorption mechanisms at the atomic level. The results show that adsorption on both phases is driven by chemisorption, mediated by electron exchange between CuFe₂O₄ and the adsorbates. The crystalline structure plays a crucial role, with tetragonal CuFe₂O₄ demonstrating significantly enhanced adsorption capacity compared to the cubic phase. DFT calculations attribute this improvement to the looser surface structure and higher-energy d-bands of the tetragonal phase, while XRD data validate the material's phase purity and surface characteristics. These findings provide valuable insights into the phase-dependent mechanisms that enhance MSPE technology for water purification.