Removal of Pb2+ and Zn2+ using modified Chocolate B clay: a study using statistical analysis, equilibrium isotherms, and adsorption kinetics

Abstract

In this work, natural and thermally modified Chocolate B clays were used for batch adsorption of Pb 2+ and Zn 2+ from an aqueous solution. The materials were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, nitrogen adsorption, and cation exchange capacity. The tests were performed in a finite bath following a 2 2 factorial design, with the variables: pH and initial concentrations of metal. Results revealed that the thermal treatment caused alterations on the Chocolate B clay structure and decreased the specific surface area. Affinities between Pb 2+ or Zn 2+ and Chocolate B clay were found with adsorption capacities up to 3.36 and 3.72 mg.g -1 , respectively. The maximum adsorption capacities were 6.79 mg.g -1 for Pb 2+ and 3.35 mg.g -1 for Zn 2+ using thermally activated clay. The Langmuir and Freundlich models were used for the adsorption equilibrium analysis, and the Langmuir model provided the best fit for sorption isotherms. The adsorption kinetics was evaluated by two models: pseudo-first-order and pseudo-second-order. The pseudo-first-order kinetic model represented well the mechanism of interaction involved during Pb 2+ adsorption into the pores of the clay. However, the two models represented well the mechanism of interaction of Zn 2+ adsorption into the pores of the clay.

New Urea Controlled-Release Fertilizers Based on Bentonite and Carnauba Wax

“…The 20.6% fire loss for Bent-R is probably related to moisture, coordinated and adsorbed water losses, organic matter burning, carbonate decomposition, and structural destruction of clay minerals. In general, it was observed that Bent-R has a typical chemical composition of bentonite clays [23,24]. Bent-Na presented all constituents detected in natural clay; the sodium present resulted from sodium functionalization.…”