Sorption of selenium at micromolar levels onto hydrous titanium oxide from aqueous solutions using radiotracer technique

Titanium oxide (TiO₂·2H₂O) has been prepared and characterized by surface area, pore size and porosity measurements, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The sorption of selenium(IV) at micromolar levels (7 x 10^-8 - 7.09 x 10^-6 M) onto titanium oxide has been studied in detail. The sorption is dependent upon the nature and concentration of electrolyte, sorbent and sorbate and on the equilibration time between the two. Maximum sorption of selenium is achieved from 0.01 M nitric acid solution at a w/v ratio of 22.2 mg cm³ at 1.77 x 10^-8 M selenium concentration. Only thiosulphate ions inhibit the sorption significantly whereas acetate, citrate, iodide, sodium and zinc ions cause relative enhancement in the sorption. Ag(I), Mn(II) and Co(II) have shown low sorption under optimal conditions chosen for selenium sorption. Titanium oxide can be used for the preconcentration of selenium and other elements having large R(d) values and their separation from Ag(I), Mn(II), and Co(II). Sorption capacity (86.7 ± 7.3 mmol g^-1), sorption free energy (9.41 ± 0.67 kJ mol^-1) and B(- 0.00564 ± 0.00082 mol² kJ^-2) are evaluated for this system using linear regression analysis and D-R parameters.