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Extraction of magnesium from calcined dolomite ore using hydrochloric acid
leaching
Conference Paper in AIP Conference Proceedings · May 2018
DOI: 10.1063/1.5038299
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Extraction of magnesium from calcined
dolomite ore using hydrochloric acid
leaching
Cite as: AIP Conference Proceedings 1964, 020017 (2018); https://doi.org/10.1063/1.5038299
Published Online: 15 May 2018
Ahmad Royani, Eko Sulistiyono, Agus Budi Prasetiyo, and Rudi Subagja
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Preface: Proceedings of the International Seminar on Metallurgy and Materials (ISMM 2017)
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AIP Conference Proceedings 1964, 020017 (2018); https://doi.org/10.1063/1.5038299
© 2018 Author(s).
1964, 020017
Extraction of Magnesium from Calcined Dolomite Ore
Using Hydrochloric Acid Leaching
Ahmad Royania), Eko Sulistiyonob), Agus Budi Prasetiyoc) and Rudi Subagjad)
Research Center for Metallarugy and Materials - Indonesian Institute of Sciences, Kawasan Puspiptek 470 –
Tangerang Selatan 15314, Indonesia.
a)
Corresponding author: ahmad.royani@lipi.go.id
b)
eko22168@gmail.com
c)
aguschencen@gmail.com
d)
rudibagja@yahoo.com
Abstract. Magnesium is widely used in varieties industrial sector. Dolomite is one source of magnesium besides
seawater. The extraction of magnesium from dolomite ores can be done by leaching process. In this work, the dolomite
leaching to extract magnesium by hydrochloric acid was investigated. The leaching experiments were performed in a
spherical glass batch reactor having a capacity of 1000 ml. The effects of the stirring speed, acid concentration, reaction
temperature and liquid-solid ratio for each reaction time of 1; 2; and 3 h on the Mg leaching have been evaluated. 5 ml of
solution sample were collected from the leached solutions, then it was filtered prior to analysis by ICP OES. The
experimental results show that the magnesium extraction increases along with the increase of acid concentration, liquidsolid ratio and temperature. The optimum conditions for magnesium extraction were achieved at temperature 75 °C,
extraction time 3 h, the HCl concentration of 2 M, the liquid-solid ratio 20 ml/g and stirring speed of 400 rpm. At this
condition 98,82 % of magnesium were extracted from dolomite. The conclusion obtained from this leaching process is
that the magnesium can be extracted from dolomite by using hydrochloric acid solutions.
INTRODUCTION
Magnesium and its compounds have been used in many applications such as insulation, alloy formation,
desulfurization of molten iron, agriculture, fertilizers, pyrotechnics, aerospace, flares, refractory materials,
construction, in chemical and other industries [1]. After aluminum and iron, magnesium is considered the third most
commonly used structural metal. Magnesium is found in minerals such as magnesite, dolomite, brucite, serpentinite,
etc. and is mostly recovered from seawater, brines and bitterns [2].
Dolomite ore is considered one of the most suitable ores for obtaining magnesium and its various compounds.
Dolomite ore (CaCO3.MgCO3) is best considered as combining one layer of CaCO3 from calcite and one layer of
MgCO3 from magnesite. Dolomite occurs in metamorphic rocks chiefly in contact or regionally metamorphosed
with magnesia or dolomitic limestones where it may recrystallize to form a dolomite marble [2,3]. However,
dolomite is different from limestone and may contain minimum 45% of MgCO 3. The crystal structure of dolomite is
hexagonal-rhombohedral. Dolomite is naturally white but due to impurities it can be creamy gray, pink, green or
black [4,5]. The resources of dolomite in Indonesia are very abundant. The biggest deposit of dolomite can be found
at North Sumatra, West Sumatera, Central Java, East Java, Madura and Papua. The utilization of dolomite in
Indonesia is limited to fertilizer and bricks for the purpose of building materials [6,7].
There are several methods to extract metals and their compounds from ores, however the hydrometallurgical
methods are generally used to extract magnesium from their minerals [8-12]. Dolomite leaching has rarely been
studied in the past [7,13], but two major prominent industrial processes for treating dolomite for metal production
are: (a) thermal reduction of magnesium oxide, mainly from dolomite with ferrosilicon, known as silicothermic
process; and (b) recovery of magnesium chloride from raw material prior to its conversion to the metal through
Proceedings of the International Seminar on Metallurgy and Materials (ISMM2017)
AIP Conf. Proc. 1964, 020017-1–020017-6; https://doi.org/10.1063/1.5038299
Published by AIP Publishing. 978-0-7354-1669-7/$30.00
020017-1
molten salt electrolysis [13]. The study on the leaching of a Nigerian dolomite ore in organic acids showed that the
kinetically leaching is controlled by surface chemical reaction [13]. The value of the activation energy for the
reaction was obtained to be 42.08 kJ/mol. The leaching kinetics of natural magnesite ore involving dilute organic
acids such as succinic acid and gluconic acid was carried out [14-15], and it was investigated that the leaching
process was chemically controlled.
A A. Baba et al (2014) studied the kinetics and optimization of the dissolution of dolomite ore in hydrochloric
acid solutions. They investigated the kinetics of the reaction between water and MgO powders at 9, 18, 28 and 38 oC
in a stirred batch reactor. They studied six commercial samples of MgO prepared from Mg(OH)2 plus two of
unknown origin with specific surface areas of 12 to 80 m2/g, and after correcting for particle size distribution, they
found that the rate of reaction was found to be directly proportional to the surface area. The use of hydrochloric acid
has been used in the research of dolomite-talk ore dissolution to obtain a solution of MgCl2-CaCl2 in a purification
process of powder. The experimental results show that the dissolution process is one of the feasible approaches to
efficiently utilize low grade carbonate ore sources. The dissolution process also has the advantage of clean
production that is a friendly and green route for production of MgO and CaCO 3 from dolomite-talk ore [16].
The aim of this study is to investigate the effect of some leaching parameters such as: stirring speed, acid
concentration, reaction temperature and liquid-solid ratio on the magnesium extraction from dolomite.
MATERIALS AND METHODS
Materials
In this study, the dolomite is obtained from East Java. The result of dolomite analysis by using XRF at table 1
shows that the obtained dolomite from East Java contains CaO, MgO, Na 2O, SiO2, Al2O3, P2O5, SO3, K2O and
Fe2O3. This table also shows that CaO and MgO become the dominant compound in dolomite, and another
compound such as Na2O, SiO2, Al2O3, P2O5, SO3, K2O and Fe2O3becomes minor compounds.
Figure 1 shows the result of dolomite analysis by using X-ray diffraction (XRD). The figure shows that most of
XRD peaks are belong to dolomite, and the the XRD could not detect the peaks of minor compounds.
TABLE 1.Quantitative analysis results of the dolomite ore by XRF.
Element
CaO MgO Na2O
Composition (wt. %) 61.38 25.73 7.93
SiO2
1.19
Al2O3 P2O5
0.84 0.54
SO3
0.41
K2O
0.40
Fe2O3
0.37
FIGURE 1. XRD pattern of the raw dolomite ore.
Methods
Before leaching process, dolomite ores were heated at 900 oC for 5 h in furnace. The calcined dolomite sample
was analyzed by inductively couple plasma (ICP OES). The leaching experiments were performed in a spherical
glass batch reactor having a capacity of 1000 mL. The leaching parameters were covering HCl concentration
ranging from 0.5 M to 2.0 M, temperatures from 30 to 75 oC, and leaching time from 1 hrs to 3 hrs. During the
leaching experiment, 600 ml of leaching solution were used for every leaching parameter, and at pre-determined
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time intervals, a certainty amount of solutions sample were collected from the leached solutions. Those solutions
samples were then filtered prior to magnesium analysis by Inductively Couple Plasma (ICP).
RESULTS AND DISCUSSION
Effect of stirring speed
The effect of stirring speed on the Mg extraction was investigated in the range of 200 to 500 rpm stirring speed.
Another leaching parameters such as temperature, solid/liquid ratio and HCl concentrations were kept constant at
temperature 30 0 C, solid/liquid ratio 10 gr/ml, and HCl concentration 1 M.
The results are plotted at Figure 2 which shows that the Mg extraction increases along with the increase of
agitation speed. When the agitation speed was increased from 200 rpm to 400 rpm, the Mg extraction increased from
13.84% to 21.77%. However, when the agitation speed exceeds 400 rpm, the agitation speed did not give any
significant effect on Mg extraction, and therefore the stirring speed of 400 rpm is adequate for the leaching process.
These experimental results were obtained from 2 hrs leaching experiment.
FIGURE 2.Effect of stirring speed on magnesium extraction concentration.
Effects of acid concentration
The effect of hydrochloric acid concentration on Mg extraction were carried out in leaching experiments at
temperature 30 oC, solid/liquid ratio 10 mL/gr and stirring speed 400 rpm. During the leaching experiments, the
hydrochloric acid concentrationswere varied from 0.5 M to 2 M. The results of experiment at figure 3 shows that the
Mg extraction increased along with the increase of hydrochloric acid concentration. For 3 hrs leaching experiment,
the increase of hydrochloric acid concentration from 0.5 M to 2 M lead to increase the Mg extraction from 2.56% to
59.84%.
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FIGURE3.Effect of hydrochloric acid concentration on magnesium extraction.
Effect of reaction temperature
The leaching experiments of calcined dolomite were carried out using aqueous hydrochloric acid solutions that
have HCl 2.0 M and 10 mL/gr liquid-solid ratio, at temperature range30-75 oCand 400 rpm stirring speed. The
result of experiment at Figure 4 shows that the Mg extraction increases along with the increase of temperatures. At
temperature 75 0 C and reaction time 3 hrs, 76,57 % of Mg was extracted from calcined dolomite. However the
temperatures higher than 75 oC are not favorable because of economic factors as well as possible acid loss [13].
FIGURE4.Effect of reaction temperature on magnesium extraction.
Effect of liquid-solid ratio
To optimize the effect of liquid-solid ratio on the Mg extraction, the leaching process was conducted with liquidsolid ratio between 5 mL/g and 20 mL/g by keeping other conditions constant (reaction temperature 75 oC;
hydrochloric acid concentration 2.0 M; stirring speed 400 rpm; leaching time 1 to 3 h). The results are summarized
in Figure 5. The lower liquid/solid ratio produces a higher concentration of magnesium in the leaching liquor, which
is beneficial to the subsequent precipitation process. As observed in Figure 5, the Mg extraction increases rapidly
with the rise in liquid/solid ratio. When liquid-solid ratio was decreased, the amount of dissolved solid per unit
liquid increase and hence the rate of leaching decrease. The Mg extraction reaches 98.82% with liquid-solid ratio of
20 mL/gr for 3 h.
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FIGURE5.Effect of liquid-solid ratio on magnesium extraction.
CONCLUSIONS
A leaching process to extract magnesium from calcined dolomite ore has been successfully demonstrated by
using aqueous hydrochloric acid solution. The results indicate that the Mg extraction increase along with the
increase of the HCl concentration, reaction temperature, stirring speed, liquid-solid ratio and reaction time. The
optimum conditions for the leaching process were 2.0 M HCl at 75 °C for 3 hours in a solid/liquid ratio of 20 mL/g
and stirring speed of 400 rpm. At this optimum conditions, 98,82 % of Mg was extracted from dolomite into the
aqueous hydrochloric acid solutions.
ACKNOWLEDGMENTS
This work was supported by a thematic research program of the Research centre for Metallurgy and Material
LIPI in 2017 from the research center for metallurgy and materials, Indonesian institute of sciences. The authors
would like to thank to research center for metallurgy and materials especially for the hydro-metallurgical laboratory
facilities for the support of this work.
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