• Resources Recycling
• /
• v.26 no.1
• /
• pp.37-42
• /
• 2017

It has been reported that aqueous indirect carbonation process of calcium silicate mineral could be one of the most promising methods for $CO_2$ sequestration. The process consists of two main steps, extraction of Ca from calcium silicate and carbonation of the extracted solution by $CO_2$. Many types of acids such as HCl and $HNO_3$ can be used in the extraction step of the process. In the case of using aqueous acetic acid solution as the extraction solvent, acetic acid can be reproduced at the carbonation step of the extracted solution by $CO_2$ and recycled to extraction step for reuse it. Industrial by-products such as iron and steel slags are potential raw materials of the indirect carbonation process due to their high contents of calcium silicate. In this study, in order to examine the extraction efficiency of domestic electric arc furnace steel slag by aqueous acetic acid solution, extraction experiments of the slag were performed by using the aqueous acetic acid solutions of varying extraction conditions ; acetic acid concentrations, extraction temperatures and times.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.21-33
• /
• 2021

The purpose of this study is to determine the order of priority for the use of amendments, matching the optimal amendment to the specific site in Korea. This decision-making process must prioritize the stabilization and economic efficiency of amendment for heavy metals and metalloid based on domestic site contamination scenarios. For this study, total 5 domestic heavy metal contaminated sites were selected based on different pollution scenarios and 13 amendments, which were previously studied as the soil stabilizer. Batch extraction experiments were performed to quantify the stabilization efficiency for 8 heavy metals (including As and Hg) for 5 soil samples, representing 5 different pollution scenarios. For each amendment, the analyses using XRD and XRF to identify their properties, the toxicity characteristics leaching procedure (TCLP) test, and the synthetic precipitation leaching procedure (SPLP) test were also conducted to evaluate the leaching safety in applied site. From results of batch experiments, the amendments showing > 20% extraction lowering efficiency for each heavy metal (metalloid) was selected and the top 5 ranked amendments were determined at different amount of amendment and on different extraction time conditions. For each amendment, the total number of times ranked in the top 5 was counted, prioritizing the feasible amendment for specific domestic contaminated sites in Korea. Mine drainage treatment sludge, iron oxide, calcium oxide, calcium hydroxide, calcite, iron sulfide, biochar showed high extraction decreasing efficiency for heavy metals in descending order. When the economic efficiency for these amendments was analyzed, mine drainage treatment sludge, limestone, steel making slag, calcium oxide, calcium hydroxide were determined as the priority amendment for the Korean field application in descending order.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.2
• /
• pp.126-132
• /
• 2001

This research is carried out to investigate the formation and preservative effectiveness of inorganic substance, calcium carbonate($CaCO_3$), in wood. The specimens were prepared by the impregnation with saturated solutions of potassium carbonate($K_2CO_3$) into the wood followed by precipitation in saturated solutions of calcium chloride($CaCl_2$) for 24h, 72h and 120h, and then they were leached in instrument flowing with water for 24h. The weight percent gains of $K_2CO_3$ solution impregnated specimens reached approximately a maximum value (108.1%) by 72h precipitation in $CaCl_2$ solutions. Inorganic substances were observed to he produced in the lumina of tracheids of specimens. From these inorganic substances filling in the tracheids, characteristic X-rays of calcium(Ca-$K_{\alpha}$) were detected by energy dispersive X-ray analyzer. Moreover, it was shown from a leaching treatment that these substances could not he leached easily from the specimens. Therefore, they were could he considered to be insoluble calcium carbonates. The weight losses of the prepared specimens were hardly occurred by test fungi attacks. Thus inorganic substances in specimens can be said to have preservative effectiveness.

• The Korean Journal of Ecology
• /
• v.15 no.4
• /
• pp.387-394
• /
• 1992

Decomposition in the litteras of platanus orientalis was studied by month in the dam of seoul national university. total amounts of the litter had the tendency to decrease with the laps of the time. Those of crude protein and phosphate contents, however, increased much more than initial amounts. It was throught that the growth of aquatic microbes gave rise to increase them. Dry weight, organic matter and holocellulose tended to decreased gradually. But, the amount of calcium loss increased rapidly since march and then the amoung of potassium and sodium decreased slowly. It was thought that this changing pattern was ascribed to water temperature, the growth of aquaqtic microbes and the leaching of soluble parts by stream current.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.09a
• /
• pp.73-77
• /
• 2003

Red mud is a waste material formed during the production of alumina when the bauxite ore is subjected to caustic leaching. It is a brick-red colored highly alkaline (pH 10-12) sludge containing mostly oxides of iron, aluminum, titanium, and silica. Red mud, due to its high aluminum, iron, and calcium contents, has been suggested as a cheap adsorbent for removal of toxic metals (e.g., As, Cr, Pb, Cd) as well as for water or wastewater treatment. The basic advantage of red mud is its versatility in application. This study was conducted to evaluate the effect of red mud on stabilization and fixation of heavy metals (such as Pb, Cu, C $r^{6+}$, Cd, Zn) contained in the Al-coating sludge and soil. The results showed that the concentration of heavy metals leached from the treated sludge and soil was low, meeting the regulatory permit level.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.1
• /
• pp.17-30
• /
• 2014

Waste cement generated from recycling processes of waste concrete is a potential raw material for mineral carbonation. For the $CO_2$ sequestration utilizing waste cement, this study was conducted to obtain basic information on the aqueous carbonation methods and the characteristics of carbonate mineral formation. Cement paste was made with W:C= 6:4 and stored for 28 days in water bath. Leaching tests using two additives (NaCl and $MgCl_2$) and two aqueous carbonation experiments (direct and indirect aqueous carbonation) were conducted. The maximum leaching of $Ca^{2+}$ ion was occurred at 1.0 M NaCl and 0.5 M $MgCl_2$ solution rather than higher tested concentration. The concentration of extracted $Ca^{2+}$ ion in $MgCl_2$ solution was more than 10 times greater than in NaCl solution. Portlandite ($Ca(OH)_2$) was completely changed to carbonate minerals in the fine cement paste (< 0.15 mm) within one hour and the carbonation of CSH (calcium silicate hydrate) was also progressed by direct aqueous carbonation method. The both additives, however, were not highly effective in direct aqueous carbonation method. 100% pure calcite minerals were formed by indirect carbonation method with NaCl and $MgCl_2$ additives. pH control using alkaline solution was important for the carbonation in the leaching solution produced from $MgCl_2$ additive and carbonation rate was slow due to the effect of $Mg^{2+}$ ions in solution. The type and crystallinity of calcium carbonate mineral were affected by aqueous carbonation method and additive type.

• Korean Journal of Soil Science and Fertilizer
• /
• v.23 no.2
• /
• pp.107-113
• /
• 1990

In comparision with calcium sulphate, the effect of calcium-carbonate, -silicate and -hydroxide on desalinization of tidal saline soil was investigated in a continuous leaching column experiments after mixing with an equivalent amount of Ca to sodium plus magnessium in the saline soil. One half of liming materials was mixed to the top one-tenth of column soil and the remainder was spread on the surface. Results obtained are as follows ; 1. Gypsum made easy to percolate and desaline (Na) tidal marine soil but accumulated magnessium in subsoil. 2. $Ca(OH)_2$, $CaCO_3$, and $CaSO_3$ precipitated Mg in the soil which limes were mixed, but they washed down magnessium more severely from the immediate bellow the limed soil and less from the subsequent soil layers. This leaching was more severer at the treatment of $Ca(OH)_2$and lowest at the treatment of $CaSiO_3$. 3. The alkalinity of lime in addition to the dissociation of exchangeable Na raised pH of limed leached tidal soil and slowed down the percolation rate which retarded desalining Na from limed saline soils. This effect was most severe in the $Ca(OH)_2$ treated soil. 4. pH of leached soils was correlated possitively with exchangeable Na and negatively with exchangeable Mg giving follwing relationship pH= 7.77+0.489 Na/Mg r = 0.845.

• Resources Recycling
• /
• v.11 no.1
• /
• pp.3-8
• /
• 2002

In order to make the high purity Mn$_3$O$_4$powder for the raw material of soft ferrite, Mn is extracted from the dust and the extracted solution is refined. The dust is generated in producing a medium-low carbon ferromanganese and contains 90% Mn$_3$O$_4$. Mn$_3$O$_4$in the dust was reduced into MnO by roasting with charcoal. Injection of the 180g/L of the reduced dust into 4N HCI solution increased pH of the leaching solution higher than 5 and then a ferric hydroxide was precipitated. Because the ferric hydroxide co-precipitates with Si ion etc, Fe and Si ion was removed from the solution and the about 10% Mn solution was obtained. The solution was diluted with water to Mn-15000 ppm and $NH_4$F was injected into the diluted solution at $70^{\circ}C$ to the F-3000 ppm. As a result, Ca ion is precipitated as $CaF_2$and the residual concentration of Ca was 14 ppm. Injection of the equivalent (NH$1.5M_4$)$_2$$CO_3$solution as 2 L/min at $25^{\circ}C$ into the above solution precipitated a fine and high purity $MnCO_3$powder. The deposition was filtrated and roasted at $1000^{\circ}C$ for 2 hours. As a result, $MnCO_3$powder is converted into $Mn_3$$O_4$powder and it had $8.2\mu$m of median size. The final production is above 99% $Mn_3$$O_4$powder and it satisfied the requirement of high purity $Mn_3$$O_4$powder for a raw material of soft ferrite.

• Journal of Korea Society of Waste Management
• /
• v.35 no.7
• /
• pp.670-682
• /
• 2018

Engineered nanomaterials (ENMs) can be released to humans and the environment through the generation of waste containing engineered nanomaterials (WCNMs) and the use and disposal of nano-products. Nanoparticles can also be introduced intentionally or unintentionally into waste streams. This study examined WCNMs in domestic industries, and target nanomaterials, such as silicon dioxide, titanium oxide, zinc oxide, nano silver, and carbon nanotubes (CNTs), were selected. We tested 48 samples, such as dust, sludge, ash, and by-products from manufacturing facilities and waste treatment facilities. We analyzed leaching and content concentrations for heavy metals and hazardous constituents of the waste. Chemical compositions were also measured by XRD and XRF, and the unique properties of nano-waste were identified by using a particle size distribution analyzer and TEM. The dust and sludge generated from manufacturing facilities and the use of nanomaterials showed higher concentrations of metals such as lead, arsenic, chromium, barium, and zinc. Oiled cloths from facilities using nano silver revealed high concentrations of copper, and the leaching concentrations of copper and lead in fly ash were higher than those in bottom ash. In XRF measurements at the facilities, we detected compounds such as silicon dioxide, sulfur trioxide, calcium oxide, titanium dioxide, and zinc oxide. We found several chemicals such as calcium oxide and silicon dioxide in the bottom ash of waste incinerators.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.5
• /
• pp.342-351
• /
• 2014

The present paper investigates the performance of direct wet mineral carbonation technology to fix carbon dioxide ($CO_2$) from relatively high $CO_2$ concentration feeding gas using wollastonite ($CaSiO_3$)-water (and 0.46 M acetic acid) suspension solution. To minimize the energy consumed on the process, the carbonation in this work is carried out at atmospheric pressure and slightly higher room temperature. As a result, carbon fixation is confirmed on the surface of $CaSiO_3$ after carbonation with wollastonite-water suspension solution and its amount is increased according to the $CO_2$ composition in the feeding gas. The leaching and carbonation ratio of wollastonite-water suspension system obtained from the carbonation with 50% of $CO_2$ composition feeding gas is 13.2% and 10.4%, respectively. On the other hand, the performance of wollastonite-acetic acid in the same condition is 63% for leaching and 1.39% for carbonation.