Preparation and Properties of Zr-Bearing Sorption Materials Based on Coal Fly Ash Microspheres

Abstract

The influence of hydrothermal conditions on synthesis of analcime and a composite material ZrO2- analcime as well as zirconomolybdate coverings with ion exchange properties was studied using narrow fractions of aluminosilicate microspheres with a high content of a glass phase (91-95 wt. %). The possibility to synthesize ZrO2-analcime composites of narrow particle size distributions with maximum of about 40 μm and 6 μm under hydrothermal treatment at 150 °С was demonstrated starting from microspheres with Si/Al=2.7 and applying different regimes of a reaction mixture agitation. A microsphere material of a “core-shell” type such as ZrMo2O7(OH)2(H2O)2@(SiO2-Al2O3)glass with the nanostructured covering was prepared. Sorption properties of the materials regarding Nd3+, Sr2+ and Cs+ were studied under equilibrium conditions by means of determination of sorption isotherms and their fitting by the Langmuir model. Sorption parameters were determined including distribution coefficients which reach the values of 104−105 mL/g

Hydrothermal synthesis and sorption performance to Cs(I) and Sr(II) of zirconia-analcime composites derived from coal fly ash cenospheres

“…Evaluation of sorption properties of the small-sized HZD-ANA particles with respect to Nd 3+ , taken as an imitator of actinides (III), demonstrated that the material traps Nd 3+ cations from diluted solutions with a distribution coefficient of about 10 5 mL/g and efficiency of up to 99.6% [22]. The Nd 3+ sorption parameters obtained for HZD-ANA are comparable with ones determined for pure analcime.…”

“…The size of pore entrances imparts a molecular/ion sieve property to zeolites. In particular, analcime (ANA) having the minimal pore entrances (d = 2.6 Å) compared to other zeolites displays an affinity towards well-proportioned cations of actinides, lanthanides, and heavy metals [20][21][22]. At the same time, due to the ion sieving effect, analcime has a poor Cs + and Sr 2+ sorption capacity at 25 °C [23] but is capable to trap these cations under hydrothermal conditions at 250-300 °C [24].…”

“…Recently, the analcime based composite materials with hydrous zirconium dioxide (HZD) species embedded in a zeolite analcime body (HZD-ANA) were synthesized hydrothermally in an alkaline media using coal fly ash cenospheres as a Si and Al source and zirconium citrate, ammonium complex, as a Zr source [22,32]. Variation of the synthesis conditions enables producing small-sized and large-sized ZrO2analcime crystals of narrow size distributions with maxima at about 6 μm [22] and 40 μm [32], respectively.…”