Fabrication of Silica Microspheres (HB/A@SI-MNS) for Hafnium and Zirconium Recovery from Zirconyl Leach Liquor

This work describes the synthesis of silica microspheres using sodium silicate obtained as a byproduct in the production of Egyptian Rosetta zircon concentrate. The obtained mesoporous silica microspheres were further modified with aminopropyltriethoxy silane and 2,4-Dihydroxybenzaldehyde to produce Schiff's base silica sorbent (HB/A@Si-MNS). HB/A@Si-MNS was used for the selective extraction of hafnium from zircon mineral leach liqueur. The fabrication process and surface properties of HB/A@Si-MNS were confirmed by the means of X-ray Fluorescence (XRF), scanning electron microscop (SEM), energy depressive X-ray (EDX), Fourier-transform infrared spectroscopy (FT-IR), and elemental analysis. The uptake behavior of HB/A@Si-MNS towards Zr(IV) and Hf(IV) ions were studied under different experimental conditions. Adsorption curves indicate that the uptake of Zr(IV) and Hf(IV) on HB/A@Si-MNS is a spontaneous, endothermic monolayer system controlled by intraparticle diffusion. Elution efficiencies were found to be 94% and 98% for Zr(IV) and Hf(IV), respectively. The regenerated HB/A@SI-MNS showed uptake capacity comparable to that of fresh ones over 3 cycles. The results of the extraction of Hf(IV) than Zr(IV) from Rosetta zircon concentrate show that HB/A@SI-MNS has a preferential selectivity towards Hf(IV) than Zr(IV). Therefore, the studied material may be promising for the selective separation of Hf(IV) from Zr(IV).