Adsorption of barium and zinc ions by mesoporous TiO2 with chemosorbed carbonate groups

<p>In the present paper the mesoporous TiO₂ with chemosorbed carbonate groups was investigated as an adsorbent for the removal of Zn²⁺ and Ba²⁺ cations from aqueous solutions.</p> <p>The dependence of the adsorption values of Zn²⁺ and Ba²⁺ on the agitation time, solution’s acidity, and modification of surface of TiO₂ was determined. The process of Zn²⁺ and Ba²⁺adsorption fit well by Lagergren’s pseudo-second-order kinetic model. The equilibrium adsorption was investigated in the concentration of heavy metal’s ranges 27.46 mg/L – 7809 mg/L. The experimental data was approximated by Langmuir and Dubinin-Radushcevich adsorption theories. The energy of adsorption Zn²⁺ and Ba²⁺ onto modified TiO₂and unmodified TiO₂ was calculated using Dubinin-Radushkevich equations, and was found to be 15.82 - 9.399 kJ/mol, which corresponds to the mechanism of physical adsorption. The application of Langmuir theory to experimental adsorption data gives high R², close to unit. Separation factor <em>R_L</em> indicates, that adsorption Zn²⁺ and Ba²⁺ onto modified TiO₂ is very favorable.</p> <p>The mechanism of adsorption of bivalent cations by the modified sample is approximately the same. The difference in the adsorption of Zn²⁺ compared with Ba²⁺ is that cations of Zn²⁺ (with small size) can diffuse into the micro pores of modified TiO₂. The adsorption of Zn²⁺is not so strongly influenced by the presence of Ba²⁺, as in the adsorption of Ba²⁺ the presence of Zn²⁺in the solution. This fact can be used for the separation of the Zn²⁺ - Ba²⁺ pair.</p> <p>Modified mesoporous ТіО₂is very efficient adsorbent toward Zn²⁺ and Ba²⁺ cations from their individual solutions as well as from their mixture, and able to compete with the best world analogues.</p>