Synthesis of Na-, Fe-, and Mg-containing titanate nanocomposites starting from ilmenite and NaOH and adsorption kinetics, isotherms, and thermodynamics of Cu(II), Cd(II), and Pb(II) cations

Highlights: • Titanate nanocomposite Na_xFe_yMg_iTiO_z was prepared using ilmenite as a raw material. • Titanate nanoparticulates were converted to nanorods upon increasing temperature. • Titanate nanorods were synthesized with NaOH/TiO₂ ratios of 1.1:1–1.6:1 at 900 °C. • Adsorption of Cu(II), Cd(II), and Pb(II) ions on titanate nanorods was spontaneous. -- Abstract: Nanosized titanate composites (Na_xFe_yMg_iTiO_z) were synthesized using ilmenite and NaOH as the starting materials with the NaOH/TiO₂ molar ratios of 1.1–1.6 by solid state route. When the calcination temperature was raised to 800 °C, sodium iron titanate phase was completely evolved with the formula of Na_0.61-0.70Fe_0.97Mg_0.07-0.08TiO_3.76-3.81. Further increasing the calcination temperature to 900 °C, titanate nanorods with the formula of Na_0.79-0.82Fe_0.96-0.98Mg_0.07-0.08TiO_3.85-3.88 were formed. The adsorption of Cu(II), Cd(II), and Pb(II) ions on titanate nanocomposite was well fitted by the pseudo-second-order adsorption kinetic and Langmuir adsorption models. At 20 °C, the maximum adsorption capacities of the titanate nanocomposite for Cu(II), Cd(II), and Pb(II) ions were 13.8, 8.8, and 20.3 mg g⁻¹, respectively. The thermodynamic parameters revealed that the adsorption of these ions was spontaneous and endothermic.