Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 9, pp. 1366−1370.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © O.I. Zakutevskyy, T.S. Psareva, V.V. Strelko, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 9, pp. 1451−1455.
Sorption of U(VI) Ions on Sol-Gel-Synthesized Amorphous
Spherically Granulated Titanium Phosphates
O. I. Zakutevskyy, T. S. Psareva, and V. V. Strelko
Institute for Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
Received November 1, 2011
Abstract—The ion-exchange–precipitation mechanism of sorption was established for amorphous spherically
granulated titanium phosphates. Under optimal conditions (pH 5.0–6.0) uranium undergoes sorptive accumulation
in amounts substantially exceeding the ion-exchange capacity of the sorbents. Under acidic and alkaline conditions,
where ion exchange cannot proceed, uranium sorption follows the precipitation mechanism, which allows treatment
of real uranium-containing solutions without optimized conditions. The ion-exchange–precipitation mechanism
also operates in sorption of some heavy metals on amorphous spherically granulated titanium phosphates.
Uranium compounds combine radiological and
chemical toxicity with high migration mobility, which
makes them extremely hazardous to humans and animals
. In Ukraine, the main sources of environmental
pollution with uranium compounds are liquid radioactive
waste and wastewaters from currently operating nuclear
power plants (NPPs) and the now-inoperative Chernobyl
NPP [2, 3], as well as uranium-extracting mines and
tailings ponds .
Treatment of contaminated water sources traditionally
employs sorption technologies whose efficiency is
determined by the properties of the sorbents used. The
Institute for Sorption and Problems of Endoecology,
National Academy of Sciences of Ukraine, developed
original sol-gel synthesis techniques which have been
implemented in continuous production of amorphous
spherically granulated sorbents based on Group IV metal
phosphates and hydroxides [5, 6]. This procedure allows
preparation of sorbents in the form of spherical granules
with controllable porosity and surface chemistry.
The drawback suffered by this procedure of synthesis
of sorbents consists in the need for prolonged rinsing of
granules to remove phosphate ions loosely bound to the
sorbent matrix due to the presence of occluded Н
poor hydrolytic stability of the Ti–O–P bonds. Published
studies [7–11] showed that, during treatment of aque-
ous solutions, an individual phase of U(VI) phosphate
compounds is formed on the surface of a number of
phosphate-containing inorganic sorbents. In this connec-
tion, it was of interest to examine the sorption properties
with respect to U(VI), displayed by sol-gel-synthesized
amorphous spherically granulated titanium phosphates
from which the phosphate ions trapped during synthesis
were not completely removed by a rinsing step.
A sample of amorphous spherically granulated
titanium phosphate (TiP-3) was synthesized by the sol-
gel procedure [5, 6] from a mixture of TiCl
solutions taken in the molar ratio P : Ti = 0.8 : 1. The
sol-gel procedure can give titanium phosphates with
different ratios of elements , but it was preliminarily
estimated that the optimal sorption of uranium(VI) is
achieved speciﬁ cally at P : Ti = 0.8 : 1. The phosphate
ions were partially removed from the resulting sorbent
by rinsing until pH of the rinsate was ~4.0.
The acidity of the surface groups was estimated
by pH-metric titration of the sorbent using the known