• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.523-528
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• 2015

In this study, we investigated the effects of sulfuric acid on the synthesis of calcium borate in the artificial boron-containing brine (bittern) saturated with calcium hydroxide. For the study, we attempted to synthesize calcium borate under various conditions such as reaction temperature, reaction time, and cooling temperature after heating, and then to examine the recovery and purity of the calcium borate according to the presence or absence of sulfuric acid at each condition. The XRD analysis confirmed that, regardless of the presence of sulfuric acid, the calcium borate ($Ca_2B_2O_5{\cdot}H_2O$) was synthesized, while, in the presence of sulfuric acid, the calcium sulfate ($CaSO_4{\cdot}0.5H_2O$) was produced as a by-product. In all the experiments performed by varying the reaction temperature and time, the recovery and purity of the calcium borate without sulfuric acid were observed higher than those with it. The results indicated that the addition of sulfuric acid increased the solubility of the calcium hydroxide, but the calcium sulfate produced as a by-product could decrease the recovery and purity of the calcium borate by preventing the synthesis. In this study, the artificial boron-containing brine (bittern) (500 mg-B/L) was saturated with calcium hydroxide in the absence of sulfuric acid, and then the solution was heated at $80-105^{\circ}C$ for less than 10 minutes to synthesize the calcium borate. The recovery and purity of calcium borate were measured as high as 80 % and 96 %, respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.2
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• pp.198-203
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• 1989

Field experiment was conducted to find out the effect of lime materials application on yield, and chemical composition of Burley 21 in 1986. Lime materials and application rate were CaSO$_4$ : Ca 35kg/l0a. CaCO$_3$ : Ca 35kg/l0a and Liming: pH6.5. Contents of Ca and Mg in fresh or cured leaves were increased, but AI, Fe and Mn were decreased by applying lime materials. Yield were increased by applying lime materials. Among lime materials treatment, yield of limed and CaCO$_3$ plot were higher than that of CaSO$_4$ plot. Value per kg of cured leaves was not affected by applying lime materials. Cured leaves of CaSO$_4$ plot contained higher NH$_3$-nitrogen and alkalinity number of water insoluble ash than those of unlimed plot. Cured leaves of CaCO$_3$, plot contained higher alkalinity number of water soluble ash, insoluble ash and volatile neutral constituent, but lower protein-nitrogen and petroleum ether extracts than those of unlimed plot. Cured leaves of limed plot contained higher alkalinity number of water soluble and insoluble ash, NO$_3$-nitrogen and volatile neutral constituents, but lower protein -nitrogen, nicotine and petroleum ether extracts than those unlimed plot. Yield was increased, however leaf Quality in respect to chemical and organoleptic characteristics were not affected considerably by applying lime materials. Therefore, it suggests that controlling the soil pH about 6.5 by liming might be necessary for tobacco cultivation.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.31-38
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• 2003

It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soils. Volume changes in lime-stabilized soils can take place due to sulphate compounds such as ettringite. Sulphate compounds caused a variety of serious geotechnical hazards such as swelling pressure and damages to light structures and pavements. This paper discusses the influence of sulphate on the soil specimens treated with quicklime and chemical additives. The physical and mechanical characteristics were studied by means of laboratory tests. The results showed that the presence of sulphate treated soil reduced the shear strength of the lime treated soils and increased the swelling properties. SEM and XRD results indicated that the presence of sulphate producted needle-like crystals such as ettringite. Moreover, the role of needle-like crystals in specimen was probably related to the swelling properties.

• Resources Recycling
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• v.15 no.3 s.71
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• pp.74-80
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• 2006

In this article, we would like to investigate a durability characterization of cement mortar with inert filler, which is ground calcium carbonate(GCC). The kinds of techniques to evaluate cement mortar are chloride ion ingress, carbonation and sulfate attack. For the experimental result of the resistance of chloride ion ingress, carbonation and sulfate attack, as the addition of GCC makes decreasing the permeability by micro-filler effect, the specimens of $5{\sim}15%$ ratio of replacement are superior to the GCC0 mortar specimen with respect to durability of cement matrix in this scope.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.7-16
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• 2023

This study aimed to evaluate the sulfate removal capacity of the enzyme-induced carbonate precipitation (EICP) technique through the chemical precipitation of sulfate with calcium ions. The optimal EICP recipe was obtained to retain the excess calcium cations in the solution for the generation of a sufficient amount of calcium carbonate (CaCO₃) mineral. The effect of gypsum precipitation on the EICP-treated sand specimen was investigated by measuring the shear wave velocity and by visual inspection via scanning electron microscopy. The EICP solution using soybean crude urease, as an alternative to laboratory-grade purified urease, exhibited a lower sulfate removal efficiency at a similar CaCO₃ production rate compared with the optimal EICP recipe because of soybean impurities.

• Clean Technology
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• v.24 no.4
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• pp.315-322
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• 2018

Industrial use of waste oyster shells is limited because of requiring excessive energy for converting natural oyster shells in the form of calcium carbonate ($CaCO_3$) into calcium oxide (CaO) for this purpose. This study aimed to develop energy-saving process for producing solidifying agent using waste oyster shells for backfill materials. It was suggested that oyster shells were converted to calcium sulfates which were mixed with sodium hydroxide solution and red clay, forming solid specimen. The optimal concentrations of sulfuric acid for sulfation of oyster shell and sodium hydroxide to generate calcium hydroxide ($Ca(OH)_2$), were determined. Unconfined compressive strength of solid specimen increased with increasing the content of solidifying agent while it increased also with increasing ratio of natural oyster shells to coal ash. The result clearly demonstrates that solidifying agent consisting of sulfuric acid-treated oyster shell, coal ash, and sodium hydroxide solution, can be effectively utilized for preparing backfill materials using natural oyster shell and coal ash. Sulfuric acid-treated oyster shell-based solidifying agent has not been previously developed and will contribute to broaden industrial application of waste oyster shells.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.770-772
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• 2010

기존의 연구는 열화에 의한 물리적 평가 및 열화에 영향을 미치는 수화생성물의 존재여부에 대한 연구는 활발하게 이루어지고 있으나, 그에 따른 수화생성물의 정량화에 대한 연구는 미흡한 실정이다. 본 논문은 XRD 분석 기법을 이용하여 원전 콘크리트 구조물에 대해 열화요인 중 탄산화와 황산염에 대한 상대적 정량화에 대한 연구를 실시하였다. 두 열화인자는 콘크리트 내의 수산화칼슘과 반응하여 에트린가이트와 탄산칼슘을 생성하게 되는데, 본 연구에서 열화인자에 대한 노출기간이 증가할수록 열화에 영향을 미치는 수화 생성물이 증가하는 것을 확인 할 수 있었다. 그에 따른 수산화칼슘의 양이 감소하는 것도 확인 할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.756-765
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• 2004

We present extraction process and reaction mechanism of boric acid from one of calcium borate ores, colemanite by reaction with sulfuric acid. Colemanite has been fully decomposed under pH 5 with sufficiency amount of sulfuric acid, more than the amount stoichiometrically required. Calcium sulfate was separated out, leaving boron in the liquid phase after sulfuric acid addition. The extraction process of boric acid was affected by dissolution temperature and time, amount of sulfuric acid and ammonium sulfate, pH and a degree of concentration before recrystallization. The $SiO_2$ of the impurities which colemanite contains was insoluble so that it was separated out with calcium sulfate from liquid phase. The species of $CaO,\;Al_2O_3,\;Fe_2O_3,\;MgO$ were remained in a liquid phase after reaction with sulfuric acid. These impurities were separated out by addition of ammonia to the liquid phase, funhermore, boric acid was produced by process of pH adjustments and acidification, concentration, and recrystallization.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.804-811
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• 2004

We have studied microwave extraction process of boric acid from one of calcium borate ores, colemanite. Calcium and boron have separated by addition of sulfuric acid, and calcium has been separated out as calcium sulfate. It was possible to extract boron with the smaller amount of sulfuric acid and with short heating time in microwave heating compared to conventional heating process. The products of boric acid was the same purity and thermal characteristic, but smaller in particle size.

• 대한치과보철학회:학술대회논문집
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• 1997.11a
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• pp.59-59
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• 1997