Chemistry for Sustainable Development 22 (2014) 155–160
155
UDC 661.849
Ñhemical Mercury Carbonization
in Industrial Wastes
YU. V. OSTROVSKIY1, G. M. ZABORTSEV1, I. M. BELOZEROV2, A. V. BABUSHKIN3, D. YU. OSTROVSKIY3 and V. A. MININ4
1
Research and Production Center Eidos Ltd.,
Ul. B. Khmelnitskogo 2, Novosibirsk 630075 (Russia)
E-mail: ost@vni piet-nsk.ru
2
State Specialized Design Institute JSC, Novosibirsk VNIPIET,
Ul. B. Khmelnitskogo 2, Novosibirsk 630075 (Russia)
3
Novosibirsk Chemical Concentrates Plant (NCCP) OJSC,
Ul. B. Khmelnitskogo 94, Novosibirsk 630110 (Russia)
4
Siberian Geotechnology Ltd.,
Vesenniy proezd 6, Novosibirsk 630090 (Russia)
(Received December 3, 2013)
Abstract
The method of gas-chemical carbonization of mercury in industrial mercury containing wastes (construction
waste and soils) of companies of SC Rosatom with the use of carbon dioxide has been examined. The thermodynamic analysis of the reaction of the formation of divalent mercury basic carbonate (HgCO3 ⋅ 2HgO) at the
interaction of mercury oxide with carbon dioxide was performed. The influence of the pressure of carbon
dioxide, temperature and treatment time on the effect of gas-chemical carbonization of mercury oxide
was studied. The technological scheme of the two-stage gas chemical recycling of mercury-containing
wastes has been proposed. Biotesting of samples of construction waste and soils subjected to gas-chemical
carbonization of mercury has been held.
Key words: mercury-containing wastes, carbon dioxide, basic carbon ate of divalent mercury, hydrogen
peroxide, carbonization, biotesting
INTRODUCTION
Prolonged using the mercury in the production cycles at the enterprises of the SC Rosatom leads to the fact that this metal and the
products of its interaction with the atmosphere
are accumulated on the walls of industrial premises and in the ground [1].
Currently, technologies of solid mercury
waste demercurization are divided into two
groups. Technologies of the first group provide
decreasing the concentrations of mercury in the
wastes (thermal and hydrometallurgical technologies); the second group consists of the technologies aimed at reducing the mobility and
overall toxicity of mercury wastes by means
of changing the species thereof in the wastes
(solidification technology) [2].
In case of processing large amounts of mercury wastes the technologies of the second
group are more preferable.
We have earlier proposed a method for the
neutralization of the metallic mercury via its
immobilization in different materials (soils,
brick, concrete etc.) [3]. The method involves
the oxidation of the mercury by an aqueous
solution of hydrogen peroxide followed by the
treatment with a solution of a reagent-preci pitator, in the course of which the metallic mercury is converted to an insoluble or hardly wa-
 Ostrovskiy Yu. V., Zabortsev G. M., Belozerov I. M., Babushkin A. V., Ostrovskiy D. Yu. and Minin V. A., 2014
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YU. V. OSTROVSKIY et al.
ter-soluble compound. As the reagents one uses
aqueous solutions of alkali or alkaline earth
metals such as sulphates, phosphates or carbon ates. The disadvantage of this method consists in the formation of secondary wastes.
This work is devoted to developing the technology of carbonization of mercury in solid
wastes that excludes the secondary pollution and
reduces their toxicity, in particular, to the gaschemical carbonization of mercury in the form
of water-insoluble basic two-valent mercuric
carbon ate (HgÑO3 ⋅ 2HgÎ), obtained by the interaction of oxidized mercury forms with carbon dioxide under pressure [4].
EXPERIMENTAL
In the studies on the gas-chemical carbonization of mercury we used mercury oxide HgO
and industrial mercury-containing wastes.
The experimental installation for the investigation of the gas chemical immobilization of
mercury included a stainless steel reactor placed
in an oven with electric heating, supply system and carbon dioxide discharge.
Watered waste samples were placed into the
reactor that was covered tightly with a lid, then
carbon dioxide was delivered under pressure,
electrical heating was turned on and kept for a
certain time. Then, the pressure was dropped
and the samples were taken out. To conduct
experiments hydrogen peroxide of ch. d. a. reagent grade (pro analysi) (State Standard GOST
10929–76) and mercuric oxide HgO of ch. reagent grade (purum) (State Standard GOST
5230–74) were used.
The measurement of the pH of the solutions
was performed using the I-120 ionometer. Colorimetric measurements were performed using the
KFK-2 colorimeter, and HACH DR/2010 spectrophotometer (the USA). The determination of
mercury in solutions was performed using a titration by potassium thiocyanate according to a
technique described by the authors of [5].
The X-ray study of the samples was performed using the Bruker D8 Advance diffractometer (Germany, database JCPDS, PDF-4,
2011). The dispersion composition of the samples was determined using a Microsizer-201A
laser-based particle dispersiveness analyzer (the
interval of dispersiveness of particles 2–
300 µm). The hazard class of the wastes was
determined at the “Center of Laboratory Analysis and Technical Measurements of the Siberian Federal District” (Novosibirsk).
RESULTS AND DISCUSSION
Features of mercury-containing industrial wastes
The mercury-containing wastes were obtained by us after the extraction of the main
portion of metallic mercury therefrom by
means of the gravitation al technology in the
concentrator ITOMAK-CG 5.0.
The features of the mercury-containing
wastes are presented in Table 1.
The concentration of mercury in the decantate
of the construction wastes after the treatment
thereof in the concentrator ITOMAK CG-5.0 was
0.09 mg/L that of ground was almost 0.02 mg/L.
According to the results of bioassay testing
the initial samples of mercury-containing
wastes, the construction wastes belong to the
3rd class of hazard, and the mercury-containing soil belongs to the 4th class of hazard.
The particle size of mercury-containing
waste (soils and construction materials) is varied within the range from 1 to 300 µm.
When oxidizing metallic mercury by hydrogen peroxide mercury oxide HgO prevails [3] in
TABLE 1
Composition of the mercury-containing wastes, %
Components
Content, %
Construction wastes
Soils
Hgox
0.0048
0.00455
Hgmet
0.0032
0.00045
Fetotal
5.50
7.70
Al
0.18
0.14
Cu
0.091
0.046
Utotal
0.017
0.012
Itotal
3.70
5.27
F–
0.18
0.20
Cl–
n/d
n/d
SO2–
4
n/d
n/d
Notes. 1. The humidity of construction wastes is 32 %,
of grounds is 29.5 %. 2. n/d – non detected.
ÑHEMICAL MERCURY CARBONIZATION IN INDUSTRIAL WASTES
157
Fig. 1. Appearance of HgO samples immobilized by carbonic gas (the dispersion medium is water). Treatment time, h: 0 (a),
1 (b), 2 (c), 3 (d), 5 (e), 24 (f).
the composition of the mercury-containing
wastes, therefore, we performed thermodynamic
calculations of the reaction of the formation of
basic two-valent mercuric carbon ate
(HgCO3 ⋅ 2HgO) when interacting HgO and CO2.
It has been found that within the temperature range of 273–373 K the reaction equilibrium is irreversibly shifted towards the formation of basic two-valent mercuric carbon ate.
The dispersed an alysis of the sample of
mercury oxide HgO demonstrated that distribution of particles by sizes in HgO sample has
the bimodal character: alongside with a coarse
fraction with the average size of about 50 µm
there is a fine one with the maximum at
5–6 µm.
Effect of the treatment time of mercury oxide
The samples of mercury oxide HgO (0.5 g)
in distilled water (25 mL) were treated with
carbon dioxide at a temperature of 20 °Ñ and
pressure P = 25 atm. The processing time ranged
from 0 to 24 h.
According to the X-ray phase analysis (XPA)
results, the samples represent a mixture of the
two phases of mercury oxide HgO and basic mercuric carbonate HgCO3 ⋅ 2HgO (Fig. 1). It can be seen
that the colour of samples changes from orange
(the colour of original HgO) to red-brown (the colour of HgCO3 ⋅ 2HgO) in the treated samples with
increasing the treatment time. In addition, the solubility of mercuric oxide is reduced (down to 5 mg/L).
Fig. 2. XRD patterns of HgO samples immobilized by carbon dioxide with a different treatment time (the dispersion
medium is water).
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YU. V. OSTROVSKIY et al.
Fig. 3. Changing the concentration of HgO in the course
treating thereof with carbon dioxide (the dispersion
medium is water).
Fig. 5. Residual concentration of HgO depending on the
treatment temperature.
According to [6], the solubility of mercuric oxide in
water at 25 °Ñ is equal to 51 mg/L.
At the gas-chemical treatment of mercuric
oxide by carbon dioxide for 5 h, the residual
content of HgO decreases abruptly because of
the fact that HgCO3 ⋅ 2HgO is formed on the
surface of particles of mercury oxide HgO
(Figs. 2 and 3).
Temperature effect on the processing
of mercury oxide
Effect of carbon dioxide pressure
on the treatment of mercuric oxide
Samples of mercury oxide with the mass
of 2.0 g were treated with 20 mL of distilled
water at different carbon dioxide pressure values (exposure time τ = 24 h, temperature 20 °Ñ).
Experimental results are presented in Fig. 4.
According to the XPA, the samples treated
represent a mixture of two phases, viz., mercury (II) oxide and basic two-valent mercuric
carbon ate. It has been found that with increasing the pressure of carbon dioxide an increase
of the HgCO3 ⋅ 2HgO yield is observed.
The samples of mercury oxide with the mass
of 2.0 g were treated at different temperature
values (the treatment time τ = 5 , the pressure
of carbon dioxide P = 25 atm) in 40 mL of distilled water. According to the XPA results, the
samples represent a mixture of mercury oxide
(II) and basic mercury carbon ate (II). The results of processing the HgO with carbon dioxide are demonstrated in Fig. 5.
It has been found that when increasing the
treatment temperature the yield of
HgCO3 ⋅ 2HgO increases abruptly. To all appearance, this could be caused by an increase in the
acidity of the solution of carbonic acid due to
increasing the processing temperature (Table 2).
Estimation of the rate of oxidation of metallic
mercury by hydrogen peroxide solution
A process of metallic mercury gas-chemical
treatment by 2.5 % hydrogen peroxide solution was studied at a pressure of carbon dioxide P = 25 atm and an the temperature equal
TABLE 2
Acidity of carbonic acid solution depending
on temperature at P = 25 atm
Fig. 4. Residual concentration of HgO depending on the
pressure of carbon dioxide.
Temperature, °Ñ
ðÍ
ÑÍ+, mmol/L
20
3.93
0.117
41
3.87
0.135
51
3.86
0.138
60
3.74
0.182
ÑHEMICAL MERCURY CARBONIZATION IN INDUSTRIAL WASTES
159
Fig. 6. Technological scheme of two-stage gas-chemical mercury carbonization in industrial wastes.
to 60 °C. The linear rate of mercury dissolution
under these conditions amounted to 0.02 mm/h.
It has been found that the minimum diameter
of a mercury particle that can be dissolved for
1 h under these conditions is equal to 40 µm.
The mercury particles of such diameter are
extracted in a centrifugal concentrator with the
efficiency of more than 70–80 %. The remaining particles of metallic mercury can be completely carbonized for 1 h.
Gas-chemical carbonization of mercury
in wastes
For gas-chemical carbonization of mercury
in industrial wastes using carbon dioxide a twolevel flowchart was offered (Fig. 6). It provides
the treatment of mercury-containing soils in a
heated autoclave at a temperature of 20 °Ñ
using simultaneously the two reagents: 2.5 %
hydrogen peroxide solution (reagent No. 1) and
carbon dioxide (reagent No. 2) at a pressure
P = 20–25 atm for 1 h (the of time hydrogen
peroxide decomposition in soils).
Further, the pulp was heated up to the temperature of 50–60 °Ñ and withstand for 4 h. After the separation of the suspension via thickening and filtration, the solid phase is directed
to disposal, whereas reagent No. 1 is supplied to
an intermediate tank for additionally concentrating the hydrogen peroxide, and further to the
treatment of a new batch of soil containing
mercury. The spent carbon dioxide is repeatedly
used or discharged to the atmosphere.
Using the chemical an alysis we determined
the mercury content in the solid and liquid phases, as well as the concentration of hydrogen
peroxide. Further, addition al concentrating reagent is performed.
This scheme allows using repeatedly the reagent No. 1, with correcting the composition
thereof in the course of the consumption of
hydrogen peroxide.
According to the test reports on the toxicity of the samples of construction wastes and
soils (Center of Laboratory An alysis and Technical Measurements of the Siberian Federal
District”, 2012), the technology of the gaschemical mercury-containing waste carbonization allows reducing the hazard class of construction wastes from the 3rd class of hazard
(moderately hazardous wastes) to 4th class of
hazard (low hazardous wastes), whereas that
for soil from the 4th class of hazard (low hazardous wastes) to 5th class of hazard (almost
non-hazard wastes).
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YU. V. OSTROVSKIY et al.
CONCLUSION
The carbonization of mercury in industrial
wastes containing oxidized and metallic mercury, using carbon dioxide under pressure alongside with oxidizing the metallic mercury by
hydrogen peroxide allows reducing the hazard
class of mercury-containing wastes via the formation of water insoluble basic two-valent
mercuric carbon ate. HgCO3 ⋅ 2HgO in the interaction HgO and ÑÎ2. The formation of this
compound is confirmed by the results of XRD
investigation and by changing the colour of the
samples from orange (HgO) to reddish brown
(HgCO3 ⋅ 2HgO). Under increasing the pressure
of carbon dioxide and the temperature, this
process can be intensified.
In case of the implementation of the proposed scheme of the two-staged gas-chemical
mercury carbonization, a number of environmental problems associated with the recycling
of mercury-containing wastes would be solved.
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