• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.39-47
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• 2021

Recently, the enzyme-induced carbonate precipitation (EICP) technique has been considered as one of the alternatives to the cement-based soil reinforcing method. However, the problem with the emission of ammonium ion has not been solved. In this study, an experimental study on the EICP without releasing an environmental contaminant (Ze-EICP) is performed using calcium-exchanged zeolite. The results show that the Ze-EICP using calcium-exchanged zeolite reduced the amount of ammonium ions by 96.96% and precipitated almost the same amount of calcium carbonate, compared to the EICP using calcium chloride. In addition, the Ze-EICP shows higher strength improvement rate than the EICP due to densification of zeolite and cementation of calcium carbonate.

• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.51-57
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• 2012

The purpose of study is to understand the possibility of biogrout of soil induced by bacteria. Microbial Calcium Carbonate Precipitation(MCP) has been analysed using the microorganism Bacillus Pasteurii. In order to understand the biogrout of soft ground treated with microbial calcium carbonate precipitation, four types of specimens(sterilization soil, non-sterilization soil, reaction solution and microorganism solution with pre-treatment mix and reaction solution and microorganism solution with post-treatment mix) were made. Scanning Electron Microscope(SEM), EDX and X-ray diffraction(XRD) analyses were performed on the soft ground specimens. On the basis of the preliminary results, it appears that microbial treatment methods using calcium carbonate precipitation may be possible to improve property of biogrout.

• Journal of the Korean Geotechnical Society
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• v.33 no.9
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• pp.61-69
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• 2017

This study presents the experimental results of $CaCO_3$ formation in sand by the Enzyme Induced Carbonate Precipitation (EICP) method. Concentration of $CaCO_3$ with elapsed reaction time is calibrated by standardized procedure by measuring $CO_2$ pressure, and it increases with time towards asymptotic value. Jumunjin sand saturated with EICP solution shows that both shear wave velocity and electrical conductivity sharply increase as the reaction starts to approach to the constant values after 50 hours of reaction time. Urease concentration of 0.5 g/L exhibits 224% higher final shear wave velocity than that of 0.1 g/L. The nucleation models hint that carbonate tends to precipitate not only at grain contacts but also at grain surfaces. Regardless of urease concentration, electrical conductivity and shear wave velocity follow the unique path. The scanning electron microscopic images and X-ray computed tomographic images validate the spatial configuration of produced $CaCO_3$ in soils.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.166-170
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• 2000

Amorphous calcium carbonate was prepared by wet chemical method and performed the control of their shape using crystalline calcium carbonate that prepared from oyster shell by the $CO_2$ gas blowing method. As a result, amorphous calcium carbonate was obtained by the dissolution process of crystalline calcium carbonate in the dil-HC1 solution, mixing of sodium carbonate solution, precipitation and filtering with high speed. And using the amorphous calcium carbonate of mud type, crystalline calcium carbonates with cubic, needle, spindle, spherical and plate shape were obtained in the temperature rang of 2~$85^{\circ}C$ and reaction time range of 5~60 minute.

• Journal of the Korean Geotechnical Society
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• v.36 no.1
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• pp.17-28
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• 2020

This study presents the experimental results of ground improvement efficiency induced by enzyme-induced carbonate precipitation (EICP) in soils. First, the optimal mixture ratio of EICP solution was determined by comparing the amount of induced carbonate depending on the different ratio among urea, CaCl₂, and urease. Next, we evaluated the shear stiffness and strength of EICP-treated sandy soil by performing shear wave velocity measurement and triaxial shear test. Furthermore, induced carbonate in treated soil was visually investigated by X-ray CT and SEM analysis. The results showed that the maximum shear stiffness evolved 19~30 times after 6 hours of reaction time compared with non-treated sands. Also, the cohesion and the friction angle tended to increase and decrease, respectively, as the amount of induced carbonate increased.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.59-64
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• 2011

Clogging in drainage pipe is one of the important problems, so it needs a remedy urgently. Recently, scale in drainage pipe is removed by water jet cleaning and other treatment. But these treatments need much cost and regular management. The principal component of scale in drainage pipe is $CaCO_{3}$. It was observed the setting of $CaCO_{3}$ by some kind of analysis such as SEM, XRD, visual and weight measuring analysis to solve these problems and prevent setting formation in drainage pipe. As a result, in case of magnetic, particle shape of $CaCO_{3}$ is changed Aragonite from Calcite. Also in case of Quantum Stick, the amount of scale is reduced by expert inspector's result. As a whole, Magnetic treatment and Quantum Stick have the effect for protecting of scale precipitation.

• 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.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.75-84
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• 2011

There are some kinds of microorganisms within soils which can precipitate some minerals such as calcite under suitable conditions. Such precipitated calcites within pores of soil may reduce permeability and also cement soil particles. In this study, whether such microorganisms can fill pores within soil and increase the strength is investigated. Basillus pasteurii was repeatedly injected into weakly cemented sand with 3% cement ratio up to 10 times for 20 days. Then, cemented sand injected with microorganisms was tested for an unconfined compressive strength and evaluated for filling voids between soil particles. The unconfined compressive strength of one time injected specimen showed a 5% increase compared to untreated specimen. However, for more than two times the strength of injected specimens gradually decreased up to 50% of the untreated specimen by microorganisms. As the number of microorganism injection increased, the amount of calcite precipitation slightly increased within voids. However, over-precipitated calcites may result in strength decrease of slightly cemented soils.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.174-178
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• 2008

Nano-crystalline slaked lime was synthesized using design of experiment. In order to synthesize slaked lime, calcium chloride $(CaCl_2)$ and urea were used as starting materials. Calcium chloride solution and urea solution were mixed and heated in vessel that calcium carbonate was precipitated during heating. Precipitates were filtered, washed several times using D.I.water and ethanol and finally dried in oven. Slaked lime $(Ca(OH)_2)$ has been fabricated by the hydration of calcined $CaCO_3$. Design of experiment (Taguchi method) was used to optimize parameter, to minimize noise factors of experiment and to statistically analyze the results. Slaked lime having about 50 nm in optimized crystallite size could be obtained by calcination of $CaCO_3$ at $1000^{\circ}C$ for 0.5 h and hydration with D.I water containing ethanol and oxalic acid.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.273-284
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• 2005

Coagulation and precipitation process by using lime$(Ca(OH)_2)$ and calcium carbonate $(CaCO_3)$ were applied to remove heavy metals from groundwater in laboratory scale. From results of batch tests, by the addition of $0.3\;wt.\%$ lime, more than $90\%$ of As and Mn were removed and $70-80\%$ of Cd and Zn were removed by using $0.5\;wt.\%$ of lime. Removal efficiency of Pb almost reached $100\%$ with only $0.1\;wt.\%$ of calcium carbonate and more than $93\%$ of Cd were removed by the addition of $0.1\;wt.\%$of calcium carbonate. Pilot scale column experiments were performed to remove heavy metals in the separation process of precipitated Hoc to supernatant after the coagulation/ precipitation. For lime as a coagulant, more than $99\%$of As were removed from artificial groundwater and removal efficiencies of Cd, Mn, and Zn were over $80\%$. By using calcium carbonate, more than $95\%$ of Cd and Pb were removed in column experiment. Fe and Mn contaminated groundwater taken from a real landfill site, Ulsan was used for the column experiment and more than $99\%$ of Fe and Mn were removed by the addition of $1\;wt.\%$ lime in column experiment, suggesting that the coagulation/precipitation process by using lime and calcium carbonate have a great possibility to remove heavy metals from contaminated groundwater.