Sorption studies of yttrium(III) ions on surfaces of nano-thorium(IV) oxide and nano-zirconium( IV) oxide

Abstract

Sorption of yttrium on nano-thorium oxide and zirconium oxide was carried out as a function of pH, contact time, concentration, temperature and co-ions. The effect of initial yttrium ion concentration has been investigated in the range of 0.5–50 ppm for 1.0 mg of sorbent dosages. Maximum sorption of 10.5 mg/g in case of nano-thorium oxide and 18.0 mg/g in case of nano-zirconium oxide was noticed from the solution of initial metal ion concentration 0.5 ppm, temperature of 298 K, pH 6.9, shaking time of 120 min (nano-thorium oxide) and contact time of 50 min (nano-zirconium oxide) for the yttrium ion sorption. Sorption followed both Dubinin–Radushkevich and Langmuir isotherms. The free energy of sorption was found to be 8.77 kJ/mol (yttrium(III) vs nano-thorium dioxide) and 18.4 kJ/mol (yttrium(III) vs nano-zirconium oxide) using Dubinin–Radushkevich isotherm. Sorption increased with increase in temperature in the studied temperature range. Sorption was endothermic. And the values of ∆H°, ∆S° and ∆G° were also evaluated. Pseudo-second-order equation fitted for the sorption kinetics. Reichenberg equation was used to explain the diffusion process. The effects of co-ions on sorptions were also investigated. BET surface areas of sorbent particles were 33 m2/g for nano-zirconium oxide and 25 m2/g for nano-thorium oxide. X-ray diffraction and high-resolution transmission electron microscopy data revealed that the size of the sorbent particles was 4.7 and 15.5 nm for nano-thorium dioxide and nano-zirconium dioxide, respectively.