Advanced Materials Research
ISSN: 1662-8985, Vols. 726-731, pp 2881-2884
doi:10.4028/www.scientific.net/AMR.726-731.2881
© 2013 Trans Tech Publications, Switzerland
Online: 2013-08-16
Composition analysis and recovery of Boron slurry in Liaoning Province
Yonghong Wua, Bing Zhangb, Guoliang Shen, Hongyu Liu
School of Petrochemical Engineering, Shenyang University of Technology, Liaoning 111003, China
a
[email protected], b [email protected]
Keywords: Boron slurry; magnesium; calcinations; Recovery
Abstract. Boron slurry is the waste of borax manufacture. Here, the property and compositions in
Boron slurry were analyzed by FTIR, TGA and XRD, which is derived from a borax factory in
Dashiqiao of Liaoning Province, China. Some valuable inorganic elemental compositions in Boron
slurry, such as Mg, Si, Ca, Fe and Mn were recovered by the processes of calcination, precipitation
and filtration. Results have shown that the recovery of MgCO3 can be reached at 90% when the
calcinations temperature is 750℃.
Introduction
Boron slurry is a kind of solid waste originated from the production of Borax, in which comprises
of many valuable elements, such as major magnesium oxide, silicon dioxide, and some ferric oxide,
alumina, as well as minor boron oxide, calcium oxide and manganese oxide, etc. [1]. Humid Boron
slurry contents about 30% moisture, with the form of pasty and good plasticity. After the humid
Boron slurry turning into dry form, it is easy to be crashed and grinded to powder. It is evaluated that
the manufacture of one ton Boron usually comes out four tons Boron slurry, which is alkalinity and
prone to permeable into underground, resulting into reduction of farmland output and pollution of
drink water [2]. In addition, it is required much space to land those waste [3]. Therefore, it is
imperatively needed to dispose the problems raised by the successive expansion of Boron production
[4].
There is much residue of magnesium in Boron slurry, especially in Dashiqiao of Liaoning Province,
China. If the Boron slurry were properly treated, magnesium oxide about 60-80% and B2O3 with
8-15% should be recovered to use as fertilizer, refractory, building materials, flocculant, etc. It is
significant to study the elemental composition and recover the valuable constitutes in Boron slurry.
Experimental
Raw materials and treatment. The raw material, Boron slurry, was supplied by a Boron factory
in Dashiqiao of Liaoning Province, China. Reagents, hydrochloric acid (36-38%), sodium hydrogen
carbonate (99.8%) and sodium hydroxide (96%), were procured commercially.
The first treatment step is calcinations for 30 min to trigger the reaction, MgCO3 → MgO + CO2 ↑.
The second step is acid treatment at 85℃ for 2h, followed by neutralizing with the titration of
0.5mol/L NaOH till the pH value reaching to 9.0. Last important step is washing and filtration.
According to the solubility products Ksp of every components, Mg2+, Ca2+, Fe2+ and Fe3+ were
separated from liquor in sequence by controlling the pH value of sediment (Fe(OH)2=7.6-9.6,
Fe(OH)3=2.3-3.7, Mn(OH)2=7.8-9.8, Al(OH)3=9.3-10.8, and Mg(OH)2=3.7-4.7). The Mg2+ was
collected from liquor by titration of 1.0mol/L NaHCO3 and the steps of calcinations and filtration.
Characterization. The thermal stability of samples was characterized by a HCT-1
thermogravimetric analyzer in air from room temperature to 900 ℃ at a heating rate of 10℃/min. The
structure of samples was recorded by a XRD-7000 X-ray diffraction analyzer in the 2theta range of
5-60o. The surface functional group was tested by Nexus 470 type ATR-FTIR.
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Advances in Environmental Technologies
Results and discussion
Elemental analysis in raw material. The elemental composition in raw material is listed in Table
1, by chemical analysis method. It is noticed that MgO and SiO2 are the major component, followed
with Fe2O3, Al2O3, and CaO, Na2O.
To further testify this, TG-DTA test was performed as shown in Fig.1. We can see that an
exothermic peak position appears around 510℃ on the DTA curve together with a weight loss stage
in TG curve, suggesting the degradation reaction of MgCO3.
Besides, on the FTIR spectrum (Fig.2), some strong reflectance peaks at 1440 cm-1, 890 cm-1 and
750 cm-1 is due to the MgCO3. Other peaks at 980 cm-1, 890 cm-1 and 610 cm-1 are ascribed to the
magnesium olivine in sample.
Advanced Materials Research Vols. 726-731
2883
From the XRD patterns (Fig.3), typical sharp diffraction peaks at 26o, 32o, 36o, 37o and 53o are
respectively ascribed to the large amount of magnesium olivine, MgCO3, Fe3O4, serpentine and
CaCO3, and so on. It means that the major form of Mg in sample is magnesium olivine, MgCO3 and
serpentine.
Recovery of MgCO3. Calcination temperature is an important factor in the determination of
product recovery. From Table 2, it can be found that the weight loss rapidly boost from 17.51% to
20.86% with the temperature elevating from 700 to 750 oC. Then the weight loss slightly climbs to
about 20.93% till at 850 oC. Considering the operation cost, the optimum calcinations temperature is
set at 750oC for 0.5h.
Fig.4 shows the effects of HCl amount usage on the recovery of Mg. It can be found that the
recovery quickly increases from 80% to 88% with the increment of HCl amount from 6.0mL to
7.0mL. Then, the increase trend slows when the HCl amount further increases from 7.0 mL to 8.0mL.
A phenomenon is also noticed during the experiment that is the color of amorphous SiO2 turning into
dark due to the incomplete degradation of olivine. Therefore, the optimum amount of HCl is adopted
at 7.0 mL (350mL/100g Boron sludge).
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Advances in Environmental Technologies
In order to measure the grade of recovered MgCO3, TGA was also used to characterize the
collected sample, as shown in Fig. 5. We can see that the two curves of MgCO3 sample in present
work is well agreement with pure MgCO3 in literature report. It implies the high purity of present
sample. It can concluded that highly purified MgO or high degrade MgCO3 would be further easily
obtained from the present sample.
Summary
In the present work, all the solid compositions in Boron slurry have been completely recovered
without discharge of spent reagents and secondary pollution. The optimum operation condition is:
calcinations temperature 750 oC, HCl immersing amount of 350mL/100g at 85 oC for 2 h, and the pH
value being at 9.0 during the purification of MgCl2, resulting into the purity being greater than 90%,
recovery being 30%, for basic magnesium carbonate.
Acknowledgement.
This work was financially supported by Liaoning Natural Science Foundation of China (No.
20102170), the Program for Liaoning Excellent Talents in University (LJQ2012010), and the State
Key Laboratory of Fine Chemicals (KF1107).
References
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[3] D. Wu, S. Wang, Y. Wang and R. Wang. The study of treating the beer wastewater with boron
sludge composite coagulant. Technology of Water Treatment 26(2000): 293-296.
[4] B. Recep, M.M. Kocakerim and H. Ersahan. Technical note upgrading of the reactor waste
obtained during borax production from tincal. Minerals Engineering 12(1999): 1275-1280.