Lead (Pb²⁺) and copper (Cu²⁺) remediation from water using superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles...

Superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles of controllable morphology were successfully synthesized using a flame spray pyrolysis (FSP) technique. Their physico-chemical properties, size, morphology, and surface chemistries were determined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), selected area electron diffraction patterns (SAED), SEM-EDX, scanning electron microscopy (SEM), and pH_ZPC(6.3). Elemental contents before and after adsorption were identified using energy dispersive X-ray fluorescence (ED-XRF), energy dispersive X-ray analysis (EDX) and elemental mapping. Surface area (S_BET 79.35m²/g) and size distribution analyses were conducted using a surface area analyzer and dynamic light scattering (DLS), respectively. The magnetic moment (44.5 at 300K and 50.16 at 2K) was determined using a physical properties measurement system (PPMS). The first adsorption study using γ-Fe₂O₃ nanoparticles synthesized by FSP to successfully remediate Pb²⁺ and Cu²⁺ from water is reported. Batch adsorption studies were carried out. An optimum pH of 5.0 was studied for Pb²⁺ and Cu²⁺ removal. Pb²⁺ and Cu²⁺ removal mechanisms by these maghemite nanoparticles were presented. The adsorption of Pb²⁺ and Cu²⁺ was highly pH-dependent. The metal ion uptake was mainly governed by electrostatic attractions. Sorption kinetic data followed the pseudo-second-order model. The Freundlich, Langmuir, Redlich-Peterson, Radke and Sips adsorption isotherm models were applied to interpret equilibrium data. The Freundlich and Langmuir isotherm equations best fit the respective equilibrium data for Pb²⁺ and Cu²⁺. The maximum Langmuir adsorption capacities of these maghemite nanoparticles were 68.9mg/g at 45°C for Pb²⁺ and 34.0mg/g at 25 °C for Cu²⁺. Thus, these maghemite nanoparticles made by FSP were readily prepared, characterized and showed promise for remediating heavy metal ions from aqueous solutions.