Melamine-based dendrimer amine-modified magnetic nanoparticles as an efficient Pb(II) adsorbent for wastewater treatment: Adsorption optimization by response surface methodology

Abstract

Magnetic Fe3O4 nanoparticles with an average diameter of 64 nm was synthesized solvothermically and subsequently modified with melamine-based dendrimer amine (MDA–Fe3O4) via grafting method. The synthesized materials were characterized using DLS, SEM, XRD, FTIR, VSM, TGA and elemental analysis techniques. The MDA–Fe3O4 was employed for the efficient removal of Pb(II) ions from an aqueous solution. The adsorption efficiency was investigated in relation to the independent variables of Pb(II) concentration (80–250 mg L−1), pH of the solution (3–7), adsorbent dosage (0.1–0.5 g L−1) and temperature (10–40 °C) via a central composite design (CCD) using response surface methodology (RSM). The significance of independent variables and their interactions was tested using ANOVA at a 95% confidence limit (α = 0.05). A second-order quadratic model was established to predict the adsorption efficiency. Under the optimum condition (initial Pb(II) concentration = 110 mg L−1, MDA-Fe3O4 dosage = 0.49 g L−1, pH = 5 and temperature = 30 °C) a removal percentage of 85.6% was obtained. The isotherm data fitted well to the Freundlich model within the concentration range of the experimental study. A maximum adsorption capacity of 333.3 mg g−1 was predicted by the Langmuir model. The adsorption rate of Pb(II) ions onto MDA–Fe3O4 was in good agreement with the pseudo-second-order model (R2 = 0.999; k2 = 4.7 × 10−4 g mg−1min−1). Thermodynamically, adsorption was spontaneous and endothermic. The MDA–Fe3O4 was successfully regenerated using 0.3 M HCl with little loss of adsorption capacity (≈7%) for five successive adsorption cycles.