Sustainable polypyrrole@CoFe ₂ O ₄ nanocomposite for the enhanced removal of toxic mercury(II): kinetic modeling and mechanistic approach

Abstract The proficient elimination of heavy metals from contaminated water is a critical environmental challenge due to their toxicity and persistence. Mercury has an adverse impact on the immune system and kidneys and is linked to a number of diseases, such as Alzheimer’s and Parkinson’s. Herein, a composite of polypyrrole (PPy) with cobalt ferrite (CoFe 2 O 4 ) was synthesized and evaluated for its removal capacities towards Hg(II) ions. The composites were prepared via in situ polymerization, yielding material with advanced physicochemical properties. Characterization through XRD, FTIR, and SEM confirmed the successful nanocomposite formation, with a particle diameter of around 50 nm. Batch adsorption experiments demonstrated that PPy@CoFe 2 O 4 exhibits significant removal abilities (609.8 mg g −1 ), with equilibrium time achieved in 90 min. Adsorption equilibrium was perfectly characterized by the Langmuir isotherm model, indicating monolayer adsorption. Kinetic investigations revealed adherence to pseudo-second-order kinetics, suggesting chemisorption as the dominant mechanism, while thermodynamic examinations emphasized the spontaneity and exothermic character of the procedure. The prepared PPy@CoFe 2 O 4 can be utilized effectively up to five instances with negligible degradation in performance. Electrostatic interaction is a primary mechanism influencing Hg(II) adsorption onto the surface of PPy/CoFe 2 O 4 . The study contributes to developing affordable and sustainable hybrid material for water decontamination, addressing crucial environmental concerns.