Removal of Pb(II) from Aqueous Solutions by Periclase/Calcite Nanocomposites

Abstract

Periclase/calcite nanocomposites (PCN) were synthesized via calcination and carbonation treatment of dolomite. The surface and structural properties of PCN were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption isotherm, thermogravimetry (TG), and transmission electron microscopy (TEM). The potential of PCN to remove Pb(II) from aqueous solutions was examined by batch experiments. The effects of solid-liquid ratio (0.1–1 g L−1), initial solution pH (2–7), reaction time (0–60 min), temperature (303–323 K), and initial Pb(II) concentration (100–500 mg·L−1) on lead removal were investigated. The results showed that the removal rate of Pb(II) firstly increased and then kept stable with the increasing initial pH from 2 to 7, and the optimal solid-liquid ratio was determined as 0.2 g L−1. The adsorption kinetics of Pb(II) on PCN was well fitted to pseudo-second-order model. The adsorption equilibrium isotherm of Pb(II) over PCN could be well fitted by Langmuir model, and the maximum removal capacity was 1150.06 mg g−1 at 323 K. The thermodynamic parameters indicated that the adsorption of Pb(II) was an endothermic and spontaneous process. According to the mechanism study, the gradual release of OH− and CO32− from the dissociation of periclase and calcite can react with Pb(II) to form hydrocerussite (Pb3(CO3)2(OH)2) on PCN surface.