Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations.

Abstract

CaTiO3 particles with different particle sizes and morphologies were synthesized starting from CaCl2 and titanium (IV) isopropoxide with or without the use of organic modifier by the hydrothermal synthesis method. Without the use of organic modifier, nanosized CaTiO3 particulates were mainly formed at the hydrothermal temperatures of 120 °C and 140 °C whereas CaTiO3 cuboids were predominantly formed at 180 °C. The utility of polyethylene glycol as an organic modifier favored the formation of small-sized CaTiO3 nanoparticulates. However, cetyltrimethyl ammonium bromide and trisodium citrate induced the formation of CaTiO3 cuboids. The adsorption of heavy metallic Cd(II), Pb(II), and Cu(II) cations on CaTiO3 powders was well illustrated by the pseudo-second-order adsorption kinetics. The Langmuir adsorption isotherm with the correlation coefficients (R2) of 0.9946-0.9967 well fitted their adsorption at equilibrium. The adsorption processes were spontaneous and endothermic. The CaTiO3 powders synthesized by the hydrothermal method had higher adsorption capacities for Cd(II) (82.6 mg g-1) and Pb(II) (261.8 mg g-1) cations than the porous CaTiO3 powders synthesized by the solid-state calcination method reported in literatures. The as-synthesized CaTiO3 powders by the hydrothermal method could have potential application in the removal of heavy metallic cations from waste water.