Contents lists available at ScienceDirect
Journal of Environmental Chemical Engineering
journal homepage: www.elsevier.com/locate/jece
ZrMo
2
O
7
(OH)
2
(H
2
O)
2
coated microsphere glass supports derived from coal
fly ash cenospheres as a novel sorbent for radionuclide trapping
Tatiana A. Vereshchagina
a,
⁎
, Ekaterina A. Kutikhina
a
, Elena V. Fomenko
a
, Leonid A. Solovyov
a
,
Sergei N. Vereshchagin
a
, Alexander G. Anshits
a,b
a
Institute of Chemistry and Chemical Technology SB RAS, Federal Research Center “Krasnoyarsk Science Center SB RAS”, 50/24 Akademgorodok, Krasnoyarsk, 660036,
Russia
b
Department of Chemistry, Siberian Federal University, Svobodny pr. 79, Krasnoyarsk, 660041, Russia
ARTICLE INFO
Keywords:
Zirconium molybdate
Cenospheres
Coating
Sorbent
Radioactive wastewater
ABSTRACT
The nanostructured polycrystalline ZrMo
2
O
7
(OH)
2
(H
2
O)
2
coating was synthesized on coal fly ash cenosphere
derived microsphere glass supports via a two-step mild hydrothermal procedure resulting in a microsphere
composite of a hollow core-shell structure. Sorption properties of the microsphere composite with respect to
Cs
+
, Sr
2+
and Nd
3+
as non-radioactive imitators of
137
Cs,
90
Sr and actinides (III) were estimated. The nanos-
tructured design of the coating was shown to enhance the Nd
3+
, Sr
2+
,Cs
+
sorption in comparison with pure
microsized ZrMo
2
O
7
(OH)
2
(H
2
O)
2
. Nd
3+
, Sr
2+
, Cs
+
sorption distribution coefficients were determined (0.52∙10
4
,
0.40∙10
3
and 0.92∙10
2
mL/g, respectively) and preferential Nd
3+
sorption was explained on the basis of
ZrMo
2
O
7
(OH)
2
(H
2
O)
2
structure.
1. Introduction
The synthesis of layers of predetermined composition and structure
on a solid surface (“core-shell” design [1]) is a generally accepted
strategy to modify physicochemical parameters of solid materials,
specifically, sorption properties [2,3]. Silicate glasses of different
compositions and geometric forms including solid and hollow micro/
nanospheres are reported as substrates for fabrication of composite
materials displaying a solid/hollow core-shell structure [4–6]. Surface
functionalization of glass cores are being realized by means of vapor
deposition [5], sol-gel synthesis [6], hydrothermal synthesis [7,8], etc.
Recently, coal fly ash cenosphere supported micromesoporous zir-
conomolybdate films were synthesized via a hydrothermal technique
[9]. As reported, the composite displayed enhanced parameters of
Nd
3+
sorption in comparison with bulk zirconomolybdate. The un-
dertaken method resulted in a product with a low level of Mo inclusion
in zirconomolybdate (Mo/Zr ≤0.4) and heterogeneity of the covering.
Additionally, crystalline zirconium molybdates with stoichiometric
compositions are known, such as Zr(MoO
4
)
2
(M
2
O)H
2
O (M = Na
+
,
NH
4
+
)[10] and ZrMo
2
O
7
(OH)
2
(H
2
O)
2
[11], but core-shell composites
with Zr(MoO
4
)
2
(M
2
O)H
2
O or ZrMo
2
O
7
(OH)
2
(H
2
O)
2
surface depositions
displaying ion-exchange properties have not been synthesized yet.
However, the basic zirconium molybdate ZrMo
2
O
7
(OH)
2
(H
2
O)
2
possesses protolytic hydroxo- and aqua-groups providing the ion-ex-
change function of the compound. But ZrMo
2
O
7
(OH)
2
(H
2
O)
2
crystals
have a compact structure prohibiting the bulk cation diffusion [11]. It is
of interest to facilitate the ion-exchange/sorption properties of
ZrMo
2
O
7
(OH)
2
(H
2
O)
2
by creating the composite with the nanos-
tructured design of the surface phase. The enhancement of its sorption
ability is expected to be due to the increase of a surface area and,
consequently, a contact surface with a sorbate.
The objective of this paper is to demonstrate the possibility to
synthesize the nanostructured ZrMo
2
O
7
(OH)
2
(H
2
O)
2
coating on mi-
crosphere glass supports derived from coal fly ash cenospheres with
enhanced sorption properties regarding to Cs
+
, Sr
2+
and Nd
3+
as non-
radioactive imitators of radionuclides
137
Cs
+
,
90
Sr
2+
and actinides (III).
2. Materials and methods
2.1. Microsphere glass supports
The cenosphere fraction −125 + 160 μm (SiO
2
67.5 wt.%, Al
2
O
3
21.3 wt.%; glass phase 91.5 wt.%; mullite 1.5 wt.%, quartz 6.7 wt.%)
separated from a Kuznetsk coal fly ash cenosphere concentrate [12] was
a precursor of microsphere glass supports (MGS).The cenospheres were
treated with 1 M NH
4
F in 1.2 M HCl [13] followed by etching with
https://doi.org/10.1016/j.jece.2019.102887
Received 21 August 2018; Received in revised form 9 December 2018; Accepted 3 January 2019
⁎
Corresponding author.
E-mail address: tatiana@icct.ru (T.A. Vereshchagina).
Journal of Environmental Chemical Engineering 7 (2019) 102887
Available online 04 January 2019
2213-3437/ © 2019 Elsevier Ltd. All rights reserved.
T