Adsorptive removal of Pb(II) ions from aqueous solutions by multi-walled carbon nanotubes functionalised by selenophosphoryl groups: Kinetic, mechanism, and thermodynamic studies

Mull-walled carbon nanotubes functionalised by di-t-butyl selenophosphoryl groups were used to remove Pb(II) ions from synthetic and real aqueous solutions. The effects of the initial Pb(II) ion concentrations, pH, and volume of the synthetic aqueous solution, adsorbent dosage, and temperature on the efficiency of the adsorption process were investigated in batch experiments. The highest Pb(II) removal efficiency was observed at pH 5.0 and 313 K. The results of reusability tests showed that the investigated adsorbent could be successfully reused four times without significant losses of its adsorption properties towards Pb(II) ions. Kinetic and mechanism studies of Pb(II) adsorption were carried out, and the experimental data fitted well to the pseudo-second-order kinetic, and Langmuir and Temkin isotherm models. The thermodynamic parameters Delta G(0), Delta H-0, and Delta S-0 indicated the spontaneous and endothermic physisorption of Pb(II) on the used carbon nanotubes. The selectivity of Pb(II) removal from the solution containing Pb(II), Zn(II), Cd(II), Cu(II), Ni(II), and Co(II) ions was high.