Uptake Equilibria and Mechanisms of Heavy Metal Ions on Microporous Titanosilicate ETS-10

In this study, the uptake equilibria and mechanisms of heavy metal ions Pb(II), Cu(II), Cd(II), and Zn(II) on microporous titanosilicate ETS-10 were attempted in the absence and presence of background electrolyte NaNO 3 of different concentrations in batch systems. The uptake properties of the metals were found to be related to the zeta (ζ) potential profile of ETS-10 and the characteristics of the heavy metals in terms of their hydrolysis, hydrated ionic radii, and hydration energies. The ionic strength of NaNO 3 and the pH were observed to have a significant impact on the equilibrium uptake capacity due to the competition of Na + and proton and the variation of surface electrochemical properties of ETS-10 adsorbent. The desorption data of counterions indicated that ion exchange is mainly responsible for the uptake of heavy metals Cu(II), Cd(II), and Zn(II), while other mechanisms such as adsorption and complexation may be cooperative in addition to ion exchange in the case of Pb(II) uptake on ETS-10 solid.