Fabrication of SiO2/CuFe2O4/polyaniline composite: A highly efficient adsorbent for heavy metals removal from aquatic environment

A novel multifunctional of SiO₂/CuFe₂O₄/polyaniline composite was synthesized through the interaction between silica (SiO₂), copper iron oxide (CuFe₂O₄), and polyaniline (PANI) as starting materials. SiO₂/CuFe₂O₄/polyaniline composite was characterized for morphology, crystallinity, textural properties, and utilised for the removal of Fe(II), Mn(II), and Cu(II) from synthetic wastewater solutions. The roles of solution pH (2.0–6.0), interaction time (15–420 min), initial ion concentration (50–700 mg/L), and solution temperature (30–50 °C) in the adsorption process were investigated. The adsorption capacities of SiO₂/CuFe₂O₄/PANI for the tested metal ions were high compared to SiO₂, CuFe₂O_4, and polyaniline. Equilibrium studies indicated that Fe(II) and Mn(II) adsorption were compliant with the Langmuir model, while the Freundlich equation described the removal of Cu(II) ions. The maximum Langmuir capacities were up to 285.71, 416.67, and 454.55 mg/g for Cu(II), Fe(II), and Mn(II), respectively. The pseudo-first-order kinetic model fitted well the metal ions removal data. The rate-controlling step reflected the involvement of surface and inner pore diffusion (intraparticle) processes. Electrostatic attractions and chelation were mainly responsible for the binding of metals ions onto SiO₂/CuFe₂O₄/PANI. The selectivity of the studied ions was governed mainly by the hydrated ionic radii and the composite adsorption active sites. SiO₂/CuFe₂O₄/PANI can be easily reused with a slight decrease (around 2–3%) in metal removal efficiency after four successive regeneration cycles.