Amino-containing polymer-coated magnetite nanoparticles as nano-adsorbents for bisphenol A: Synthesis, kinetic and thermodynamic study

Abstract

Magnetite nanoparticles coated with poly(dimethyl aminoethyl methacrylate) (PDMAEMA@MNPs) and their quarternized form (PQDMAEMA@MNPs) were successfully synthesized and used as nano-adsorbents for bisphenol A (BPA). The particles were spherical with the average particle size between 10 and 20 nm in diameter with a moderate degree of nanoclustering (ca.150-200 particles/cluster). In terms of adsorption properties, the PDMAEMA@MNPs exhibited a higher BPA adsorption capacity (1.05 mg/g MNP at pH 9) than the quaternized form (0.50 mg/g MNP at pH 9). Equilibrium isotherm, kinetic, and thermodynamic characteristics of BPA adsorption on the PDMAEMA@MNPs were investigated. It was found that the BPA adsorption on the MNPs reached an equilibrium within 5 min and the maximum adsorption capacity (qe) was 9.88 mg/g. The adsorption isotherm study results indicated that the BPA adsorption process on PDMAEMA@MNPs exhibited the best fit with the Freundlich model, and the adsorption kinetics followed the pseudo-second order model with the R2 value of 1.00. The thermodynamic data exhibited a negative enthalpy change (ΔH◦ = -2585.571 J/mol), indicating exothermic BPA adsorption, and a negative Gibbs free energy (ΔG◦), implying a spontaneous BPA adsorption process.