• Transactions of the Korean hydrogen and new energy society
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• v.19 no.4
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• pp.340-347
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• 2008

Dissolution process of serpentine in distilled water was systematically investigated for study on pre-treatment of serpentine which was a candidate material for carbon dioxide sequestration. The metallic ions(Ca, Si, Mg etc.) were dissolved in distilled water at ambient condition and their concentrations were changed with dissolution time. The precise evaluation of dissolution process for serpentine dissolved solvent was performed by ion conductivity and pH measurement. Serpentine dissolution in distilled water was evaluated as a stable pre-treatment process without changes of crystallographic structure and chemical structure changes.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.74-81
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• 2005

The heat treatment of serpentines for mineral carbonation was studied systematically. Crystallographic, spectroscopic and thermochemical properties were investigated for serpentines before and after heat treatment. Drastic weight loss due to the removal of hydroxy groupe(-OH) occupied in serpentine crystalline was revealed after heat treatment. In XPS results, MgO was founded at heat treated serpentine powders while Mg(OH) was observed at untreated serpentine powders. Metallic oxides originated from serpentine ingredients were regenerated by heat treatment.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.301-308
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• 2007

Silicate mineral serpentine with magnesium and calcium was selected as a mineral carbonation mediators for carbon dioxide storage. Serpentine has various metallic elements as an oxides form of magnesium, iron, calcium, aluminium etc. Magnesium and calcium could be carbonation salt preferentially than other metal component within serpentine. Systemic thermochemical treatment for serpentine could change physicochemical properties like a surface area and pore dimensions. Due to the rapid chemical reaction rate depended on dimensional values, carbonation formation could determined by surface property change of thermochemical treated serpentine.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.11a
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• pp.475-476
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• 2004

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.526-532
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• 2008

The proposed $CO_2$ storage technology in the present study is a one-step sequestration process that stabilizes $CO_2$ in a reactor with Serpentine. The advantage of this technology is associated with its high stability of final product so that the entire system is recognized as permanent environment-friendly $CO_2$ removal method. Since the sequestration reaction mechanisms are generally understood that carbonation reaction proceeds with very slow rate, so that pretreatment method to increases reaction rate of $CO_2$ carbonation reaction should be developed. To increase the reactivity of Serpentine with $CO_2$, two different methods of pretreatment are carried out in the present investigation. One is heat-treatment, the other is chemical pretreatment. In this study, only chemical pretreatment is considered leaching method of magnesium from Serpentine using sulfuric acid at the various reaction temperatures, times, and acid concentrations. Experimental results illustrated that pretreatment by sulfuric acid increases surface area of serpentine from $11.1209m^2/g$ to $98.7903m^2/g$ and extracts magnesium compounds. Single variable experiment demonstrated the enhancements of magnesium extraction with increased reaction temperature and time. Amount of magnesium extraction is obtained by using the data of ICP-AES as maximum extraction condition of magnesium is 2 M acid solution, $75^{\circ}C$ and 1hr. After performing chemical pretreatment, carbonation yield increased from 23.24% to 46.30% of weight.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.13-22
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• 2016

The objectives of this study were to recover silica and iron oxides and $CO_2$ sequestration using serpentine via various acid dissolution and pH swing processes. Serpentine collected from Guhang-myeon in S. Korea were mainly composed of antigorite and magnetite consisting of $SiO_2$ (45.3 wt.%), MgO (41.3 wt.%), $Fe_2O_3$ (12.2 wt.%). Serpentine pulverized ($${\leq_-}75{\mu}m$$) and then dissolved in 3 different acids, HCl, $H_2SO_4$, $HNO_3$. Residues treated with acidic solution were recovered from the solution (step 1). And then the residual solution containing dissolved serpentine was titrated using $NH_4OH$. And pH of the solution increased up to pH=8.6 to obtain reddish precipitates (step 2). After recovery of the precipitates, the residual solution reacted with $CO_2$ and then pH increased up to pH=9.5 to precipitate white materials (step 3). The mineralogical characteristics of the original sample and harvested precipitates were examined by XRD, and TEM-EDS analyses. ICP-AES analysis was also used to investigate solution chemistry. The dissolved ions were Mg, Si, and Fe. The antigorite became noncrystralline silica after acid treatment (step 1). The precipitate at pH=8.6 was mainly amorphous iron oxide, of which size ranged from 2 to 10 nm and mainly consisting of Fe, O, and Si (step 2). At pH=9.5, nesquehonite [$Mg(HCO_3)(OH){\cdot}2(H_2O)$] and lasfordite [$MgCO_3{\cdot}H_2O$] were formed after reaction with $CO_2$ (step 3). The size of carbonated minerals was ranged from 1 to $6{\mu}m$. These results indicated that the acid treatment of serpentine and pH swing processes for the serpentine can be used for synthesis of other materials such as silica, iron oxides and magnesium carbonate. Also, This process may be useful for the precursor synthesis and $CO_2$ sequestration via mineral carbonation.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.24-28
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• 2010

Since the reaction of mineral fixation proceeds with a very slow rate, the pretreatment method to increases the rate of carbonation reaction should be required. To increase the reactivity of serpentine with $CO_{2}$, two pretreatment methods are performed in this study. The heat treatment is done at $630^{\circ}C$. A heat-treated serpentine shows that the strength of -OH has a lower peak in FT-IR spectrum. Chemical pretreatment is the method of leaching of magnesium from serpentine using sulfuric acid at $75^{\circ}C$ for 1 h. Because the protonation of the oxygen atoms polarizes and weakens the Mg-O-Si bond, the removal of magnesium atoms from the crystal lattice was facilitated. After performing the pre-treatment of serpentine, $CO_{2}$ fixation experiments are performed with treated serpentine in the batch reactor. Heat-treated serpentine is converted into 43% magnesite conversion, whereas untreated serpentine has 27% of magnesite conversion. Although the results of the heat-pretreatment are encouraging, this method is prohibited due to excessive energy consumption. Furthermore chemical pretreatment serpentine routes have been proposed in an effort to avoid the cost prohibitive heat pretreatment, in which the carbonation reaction was conducted at 45 atm and $25^{\circ}C$. Chemical-treated serpentine, in particularly is corresponded to a conversion of 42% of magnesite compared to 24% for the un-treated serpentine.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.1-9
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• 2020

Magnesium silicate minerals such as serpentine [Mg₃Si₂O₅(OH)₄] have a high potential for the sequestration of CO₂; thus, their reactivity toward dissolution under CO₂-free and CO₂-containing conditions in acidic solvents is a critical process with respect to their carbonation reactions. To examine the carbonation efficiency and dissolution mechanism of serpentine, hydrothermal treatment was performed to the starting material via a modified direct aqueous carbonation process at 100 and 150℃. The serpentine dissolution experiments were conducted in H₂SO₄ solution with concentration range of 0.3-1 M and at a CO₂ partial pressure of 3 MPa. The initial pH of the solution was adjusted to 13 for the carbonation process. Under CO₂-free and CO₂-containing conditions, the carbonation efficiency increased in proportion to the concentration of H₂SO₄ and the reaction temperature. The leaching rate under CO₂-containing conditions was higher than that under CO₂-free conditions. This suggests that shows the presence of CO₂ affects the carbonation reaction. The leaching and carbonation efficiencies at 150℃ in 1 M H₂SO₄ solution under CO₂-containing conditions were 85 and 84%, respectively. The dissolution rate of Mg was higher than that of Si, such that the Mg : Si ratio of the reacted serpentine decreased from the inner part (approximately 1.5) to the outer part (less than 0.1). The resultant silica-rich layer of the reaction product ultimately changed through the Mg-depleted skeletal phase and the pseudo-serpentine phase to the amorphous silica phase. A passivating silica layer was not observed on the outer surface of the reacted serpentine.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.101-111
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• 2017

Mineral carbonation is a technology in which carbonates are synthesized from minerals including serpentine and olivine, and industrial wastes such as slag and cement, of which all contain calcium or magnesium when reacted with carbon dioxide. This study aims to develop the mineral carbonation technology for commercialization, which can reduce environmental burden and process cost through the reduction of carbon dioxide using steel slag and the slag reuse after calcium extraction. Calcium extraction was conducted using NH4Cl solution for air-cooled slag and convert slag, and ${\geq}98%$ purity calcium carbonate was synthesized by reaction with calcium-extracted solution and carbon dioxide. And we conducted experimentally to minimize the quantity of by-product, the slag residue after calcium extraction, which has occupied large amount of weight ratio (about 80-90%) at the point of mineral carbonation process using slag. The slag residue was used to replace silica sand in the manufacture of cement panel, and physical properties including compressive strength and flexible strength of panel using the slag residue and normal cement panel, respectively, were analyzed. The calcium concentration in extraction solution was analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES). Field-emission scanning electron microscope (FE-SEM) was also used to identify the surface morphology of calcium carbonate, and XRD was used to analyze the crystallinity and the quantitative analysis of calcium carbonate. In addition, the cement panel evaluation was carried out according to KS L ISO 679, and the compressive strength and flexural strength of the panels were measured.