• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.139-151
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• 2009

Mineralogical characteristics of secondary precipitate formed at some mineral water springs in Gyeongbuk Province, Korea were studied in relation to water chemistry. The chemical water types of mineral water springs are mostly classified as $Ca-HCO_3$ type, but $Na(Ca)-HCO_3$ and $Ca-SO_4$ types are also recognized. Ca, Fe, and $HCO_3\;^-$ are the most abundant components in the water. The pH values of most springs lie in 5.76${\sim}$6.81, except Hwangsu spring having pH 2.8. Saturation indices show that all springs are supersaturated with respect to iron minerals and oxyhydroxides such as hematite and goethite. The result of particle size analysis shows that the precipitate is composed of the composite with various sizes, indicating the presence of iron minerals susceptible to a phase transition at varying water chemistry or the mixtures consisting of various mineral species. The particle size of the reddish precipitate is larger than that of the yellow brown precipitate. Based on XRD and SEM analyses, the precipitate is mostly composed of ferrihydrite (two-line type), goethite, schwertmannite, and calcite, with lesser silicates and manganese minerals. The most abundant mineral fanned at springs is ferrihydrite whose crystals are $0.1{\sim}2\;{\mu}m$ with an average of $0.5\;{\mu}m$ in size, characterized by a spherical form. It should be interestingly noted that schwertmannite forms at Hwangsu spring whose pH is very low. At Shinchon spring, Gallionella ferruginea, one of the iron bacteria, is commonly found as an indicator of the important microbial activity ascribed to the formation of iron minerals because very fine iron oxides with a spherical form are closely distributed on surfaces of the bacteria. A genetic relationship between the water chemistry and the formation of the secondary precipitate from mineral water springs was discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.110-114
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• 2004

Formation behavior of aragonite precipitated calcium carbonate was investigated with changed the concentration of $Na_2CO_3$ solution and addition method which added in the $Ca(OH)_2$ slurry at $75^{\circ}C$. In this reaction, we found that $Na^+$ ions were substituted into $Ca^{2+}$ion site then disturb the growth of calcite, and while proceed the crystal growth in a certain direction and promote the formation of aragonite. Also, a decrease of reaction rate by control the concentration of $CO_3^{2-}$ ion, induce the homogeneous precipitate reaction and increase substitution ability of $Na^+$ ions, consequently it was promote the formation and growth of aragonite.

• Restorative Dentistry and Endodontics
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• v.37 no.4
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• pp.188-193
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• 2012

Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyapatite (CDHA). These mineral precipitate were reported to form the MTA-dentin interfacial layer which enhances the sealing ability of MTA. Clinically, the use of zinc oxide euginol (ZOE) based materials may retard the setting of MTA. Also, the use of acids or contact with excessive blood should be avoided before complete set of MTA, because these conditions could adversely affect the hydration reaction of MTA. Further studies on the chemical nature of MTA hydration reaction are needed.

• Resources Recycling
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• v.29 no.5
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• pp.28-37
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• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.39-45
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• 2015

We produced magnetite nanoparticles (MNPs) and a Mg-rich solution as a nano-adsorbent and a coagulant for water treatment, respectively, using a low-grade iron ore. The ore was leached with aqueous hydrochloric acid and its impurities were removed by solvent extraction of the leachate using tri-n-butyl phosphate as an extractant. The content of Si and Mg, which inhibit the formation of MNPs, was reduced from 10.3 wt% and 15.5 wt% to 28.1 mg/L and < 1.4 mg/L, respectively. Consequently, the Fe content increased from 68.6 wt% to 99.8 wt%. The high-purity $Fe^{3+}$ solution recovered was used to prepare 5-15-nm MNPs by coprecipitation. The wastewater produced contained a large amount of $Mg^{2+}$ and can be used to precipitate struvite in sewage treatment. This process helps reduce the cost of both sewage and iron-orewastewater treatments, as well as in the economic production of the nano-adsorbent.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.202-208
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• 2001

Aluminum dross should be recycled in consideration of characteristics of the dross and its reutilization after processing. In this study, aluminum dross generated in the domestic secondary aluminum industry was processed to use it as raw material for producing aluminum hydroxide. Sample dross was classified according to its size. The dross smaller than 1mm was leached with sodium hydroxide solution to extract the remaining aluminum from the dross into the solution, and then aluminum hydroxide precipitate was recovered from the leach liquor. Purity of the obtained aluminum hydroxide was above 98 percent, and particle size of the sample was in range of 3-39${\mu}{\textrm}{m}$. From the result, it was suggested that this process could be applicable to recycling of aluminum dross.

• Journal of Dairy Science and Biotechnology
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• v.33 no.2
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• pp.153-157
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• 2015

Milk mineral, which is also called milk calcium, was recovered from concentrated skim milk ultrafiltration permeate (CUFP). Lactose, the major constituent of CUFP, was crystallized by the addition of ethanol; lactose precipitation was observed to increase as the ratio of CUFP to ethanol increased. The calcium content of CUFP remained constant at a CUFP to ethanol ratio of 1:2, while it significantly decreased at a CUFP to ethanol ratio of 1:4. When ethanol (95%, v/v) was reused to precipitate lactose out of CUFP, 85% of the initial lactose precipitated out, while 82% of calcium remained soluble in the CUFP after storage for 24 h.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.391-397
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• 2014

Acid mine drainage occurrence is a serious environmental problem by mining industry; it usually contain high levels of metal ions, such as iron, copper, zinc, aluminum, and manganese, as well as metalloids of which arsenic is generally of greatest concern. It causes mine impacted soil pollution with mining and smelting activities, fossil fuel combustion, and waste disposal. In the present study, three bacterial strains capable of producing urease were isolated by selective enrichment of heavy metal contaminated soils from a minei-mpacted area. All isolated bacterial strains were identified Sporosarcina pasteurii with more than 98% of similarity, therefore they were named Sporosarcina sp. KM-01, KM-07, and KM-12. The heavy metals detected from the collected mine soils containing bacterial isolates as Mn ($170.50mg\;kg^{-1}$), As ($114.05mg\;kg^{-1}$), Zn ($92.07mg\;kg^{-1}$), Cu ($62.44mg\;kg^{-1}$), and Pb ($40.29mg\;kg^{-1}$). The KM-01, KM-07, and KM-12 strains were shown to be able to precipitate calcium carbonate using urea as a energy source that was amended with calcium chloride. SEM-EDS analyses showed that calcium carbonate was successfully produced and increased with time. To confirm the calcium carbonate precipitation ability, urease activity and precipitate weight were also measured and compared. These results demonstrate that all isolated bacterial strains could potentially be used in the bioremediation of acidic soil contaminated by heavy metals by mining activity.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.233-240
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• 2008

The reductive precipitation of platinum and palladium in hydrochloric acid solution using hydrazine as a reducing agent was investigated. The reductive precipitation ratios of platinum and palladium increased when increasing the stoichiometric ratio for reducing agent, precipitation time, and pH. The precipitation ratio of platinum was much lower than that of palladium. This is the reason the reaction rate of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}$ at the reduction reaction step of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}{\rightarrow}Pt$ is very slow. The purity of platinum precipitated was very affected by metallic impurities, while it was possible to precipitate the high purity palladium since the precipitation rate of palladium was relatively fast. At the pH of 1.3, the precipitation temperature of $25^{\circ}C$, and the addition amounts of the hydrazine of 10 and 1.75 times the stoichiometric ratio, the reductive precipitation ratios of platinum and palladium from their hydrochloric acid solutions containing 2,000 ppm were 98.5% and 99.9% in 30 min, respectively.

• Journal of the Mineralogical Society of Korea
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• v.16 no.1
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• pp.107-123
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• 2003

The objective of this study was to investigate mineral precipitates, which derived from the zero valent iron (ZVI) corrosion during TCE dechlorination and to find the controlling factors in mineral precipitates. A series of column experiemnts were conducted to evaluate the location of ZVI and the effects of electrode arrangements in electro-enhanced permeable reactive barrier (E2PRB) systems. Based on mineralogical study, ZVI samples near the influent port had more lepidocrocite, ferrihydrite or Fe (oxy)hydroxide, and (phospho)siderite while backward samples had more akaganeite, magnetite/maghemite, and intermediate green rust (GR) I and GR II. A suite of mineral distribution was preferabley related to the dissolved oxygen and the increased pH. Controlling factors of mineral precipitates in an E2PRB system were found to be (1) pH, (2) dissolved oxygen, (3) the types of Fe intermediates, and (4) anionic species to form complex strongly.