Kinetic and thermodynamic evaluation of adsorptive removal of lead(II) from aqueous solutions using Polypyrrole@CoFe2O4 nano-adsorbent

Water contaminants represent a significant global challenge that impacts the environment. Research shows that lead exposure may result in urinary, cardiovascular, digestive, respiratory, and neurological disorders. By in-situ polymerizing pyrrole on CoFe2O4 nanoparticles, a polypyrrole-coated cobalt ferrite (PPy@CoFe2O4) magnetic nanosorbent is synthesized to achieve efficient removal of Pb(II). XRD data corroborated the findings of the SEM examination, which showed spherical nanoparticles with diameters of about 50 nm. The investigation of zeta potential revealed that the polypyrrole-coated cobalt ferrite nanoparticles have a positive surface charge in an acidic medium and a negative surface charge in alkaline media. The equilibrium time was found to be 70 min, and the adsorption behavior aligned with a pseudo-second-order kinetic model. The adsorption isotherms were accurately represented by the Langmuir model. PPy/CoFe2O4 demonstrates a maximal monolayer adsorption capacity of 357.14 mg·g−1 under optimum conditions (330 K temperature, 0.16 g·L−1 adsorbent dose, and pH 8.0). The removal efficiency was still higher than 94% following the five adsorption-desorption cycles. Electrostatic interaction is a primary mechanism influencing Pb(II) adsorption onto the surface of PPy/CoFe2O4. A negative ΔG° indicates that Pb(II) adsorption onto PPy/CoFe2O4 proceeds spontaneously. The results indicate that the PPy/CoFe2O4 composite functions as a highly efficient adsorbent, showcasing extensive applicability in the treatment of wastewater contaminated with heavy metal ions.