• Geomechanics and Engineering
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• 제29권1호
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• pp.79-90
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• 2022

Soybean-urease induced carbonate precipitation (EICP), as an alternative to microbially induced carbonate precipitation (MICP), was employed for soil improvement. Meanwhile, soluble calcium produced from industrial waste carbide slag powder (CSP) via the acid dissolution method was used for the EICP process. The ratio of CSP to the acetic acid solution was optimized to obtain a desirable calcium concentration with an appropriate pH. The calcium solution was then used for the sand columns test, and the engineering properties of the EICP-treated sand, including unconfined compressive strength, permeability, and calcium carbonate content, were evaluated. Results showed that the properties of the biocemented sand using the CSP derived calcium solution were comparable to those using the reagent grade CaCl₂. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that spherical vaterite crystals were mainly formed when the CSP-derived calcium solution was used. In contrast, spherical calcite crystals were primarily formed as the reagent grade CaCl₂ was used. This study highlighted that it was effective and sustainable to use soluble calcium produced from CSP for the EICP process.

• Journal of Microbiology and Biotechnology
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• 제23권5호
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• pp.707-714
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• 2013

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process that has various applications in remediation and restoration of a range of building materials. In the present investigation, five ureolytic bacterial isolates capable of inducing calcium carbonate precipitation were isolated from calcareous soils on the basis of production of urease, carbonic anhydrase, extrapolymeric substances, and biofilm. Bacterial isolates were identified as Bacillus megaterium, B. cereus, B. thuringiensis, B. subtilis, and Lysinibacillus fusiformis based on 16S rRNA analysis. The calcium carbonate polymorphs produced by various bacterial isolates were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X ray diffraction, and Fourier transmission infra red spectroscopy. A strain-specific precipitation of calcium carbonate forms was observed from different bacterial isolates. Based on the type of polymorph precipitated, the technology of MICCP can be applied for remediation of various building materials.

• 한국지반환경공학회 논문집
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• 제13권5호
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• pp.51-57
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• 2012

본 연구에서는 친환경적인 그라우트재의 개발을 위하여 연약지반에 대한 바이오그라우트 가능성을 확인하고, Bacillus Pasteurii 균을 이용하여 탄산칼슘 침전 효과를 분석하였다. 연약지반에 미생물의 탄산칼슘 침전을 이용하여 바이오그라우트에 미치는 영향을 알아보기 위해 4가지 시료의 조건(멸균 시료, 비멸균 시료, 반응용액과 미생물용액의 선처리 혼합시료, 반응용액과 미생물용액의 후처리 혼합시료)으로 실험되었다. 전자현미경(SEM), EDX와 X선 분석 회절기(XRD)를 이용하여 연약지반 시료의 분석을 수행하였고, 이러한 연구결과를 바탕으로 탄산칼슘 침전을 이용한 미생물 처리 공법은 바이오그라우트의 특성을 개선하였다.

• Geomechanics and Engineering
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• 제7권6호
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• pp.649-663
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• 2014

In past few years, the use of bacterial calcium carbonate precipitation (biocementation) has become popular as a ground improvement technique for sandy soil. However, this technique was not applied to organic soil. This study focused on bacterial calcium carbonate precipitation and its effect on permeability in organic soil. A special injection system was prepared for inducing bacterial solution to the samples. The bacterial solution supplied to the samples by gravity for 4 days in specific molds designed for this work. Calcite precipitation was observed by monitoring pH value and measuring amount of calcium carbonate. Change in the permeability was measured before and after biocementation. The test results showed that the pH values indicates that the treatment medium is appropriate for calcite precipitation, and amount of precipitated calcium carbonate in organic soil increased about 20% from untreated one. It was also found that the biocementation can be considered as an effective method for reducing permeability of organic soil. The results were supported by Scanning electron microscopy (SEM) analysis and energy-dispersive x-ray (EDX) analysis.

• 한국지반공학회논문집
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• 제37권4호
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• pp.39-47
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• 2021

최근 효소 기반 탄산칼슘 침전(EICP) 기법은 시멘트 기반 지반보강공법의 대안 중 하나로 간주되어 왔다. 하지만 EICP 기법에서 발생하는 환경 유해 부산물인 암모늄 이온의 배출에 대한 문제는 해결되지 않고 있다. 따라서 본 연구에서는 칼슘 치환 제올라이트를 사용하여 환경 유해 부산물이 없는 EICP(Ze-EICP)의 실험적 연구를 수행하고자 한다. 실험결과는 칼슘 치환 제올라이트를 사용하는 Ze-EICP가 염화칼슘을 사용하는 EICP와 비교하여 암모늄 이온은 96.96%가 제거되었으며, 거의 동일한 양의 탄산칼슘이 침전되었음을 보여주었다. 또한 Ze-EICP는 제올라이트의 조밀화와 탄산칼슘의 고결화로 인해 EICP 대비 높은 강도증진 효과를 보여주었다.

• Geomechanics and Engineering
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• 제17권5호
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• pp.465-473
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• 2019

Biocementation due to the microbially induced calcium carbonate precipitation (MICP) process is a potential technique that can be used for soil improvement. However, the effect of biocementation may be affected by many factors, including nutrient concentration, bacterial strains, injection strategy, temperature, pH, and soil type. This study investigates mainly the effect of chemical concentration on the formation of calcium carbonate (e.g., quantity, size, and crystalline structure) and unconfined compressive strength (UCS) using different treatment time and chemical concentration in the biotreatment. Two chemical concentrations (0.5 and 1.0 M) and three different treatment times (2, 4, and 8 cycles) were studied. The effect of chemical concentrations on the treatment was also examined by making the total amount of chemicals injected to be the same, but using different times of treatment and chemical concentrations (8 cycles for 0.50 M and 4 cycles for 1.00 M). The UCS and CCC were measured and scanning electron microscopy (SEM) analysis was carried out. The SEM images revealed that the sizes of calcium carbonate crystals increased with an increase in chemical concentrations. The UCS values resulting from the treatments using low concentration were slightly greater than those from the treatments using high concentration, given the CCC to be more or less the same. This trend can be attributed to the size of the precipitated crystals, in which the cementation efficiency increases as the crystal size decreases, for a given CCC. Furthermore, in the high concentration treatment, two mineral types of calcium carbonate were precipitated, namely, calcite and amorphous calcium carbonate (ACC). As the crystal shape and morphology of ACC differ from those of calcite, the bonding provided by ACC can be weaker than that provided by calcite. As a result, the conditions of calcium carbonate were affected by test key factors and eventually, contributed to the UCS values.

• 한국지반공학회논문집
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• 제39권8호
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• pp.7-16
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• 2023

본 연구는 매립지 침출수 내 황산염 농도를 저감하기 위해 친환경 지반개량 공법인 Enzyme Induced Carbonate Precipitation(EICP) 공법을 활용하였다. 황산염의 화학적 침전을 유도하기 위해 충분한 탄산칼슘을 생성함과 동시에 여분의 칼슘 이온을 남길 수 있는 최적의 EICP 혼합비가 계산되었다. 최적 혼합비로 처리된 사질토 시편에서 황산염 침전이 전단 강성도에 미치는 영향을 확인하고자 전단파 속도를 측정하였고 전단파 속도 측정은 EICP 반응 및 황산염 반응 시간동안 수행되었다. 실험 결과, 생성된 침전물에 따른 전단 강성도의 발달을 확인하였고 주사전자현미경(SEM)으로 침전물의 유형 및 패턴을 시각적으로 관찰하였다. 고순도 우레아제의 대체제로서 백태가루를 효소로 사용한 EICP 용액의 경우 고순도 EICP 용액과 동일한 탄산칼슘 생성 효율에서 보다 낮은 황산염 제거 효율을 보였는데 이는 백태가루에 포함된 불순물이 석고의 침전을 방해하기 때문이다.

• 한국결정성장학회지
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• 제10권2호
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• pp.166-170
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• 2000

굴 패각으로부터 탄산가스 화합법에 의해 제조된 결정질의 침강성 탄산칼슘을 출발원료로 하여, 습식법으로 비정질 탄산칼슘을 제조하였으며 그리고 형상제어를 행하였다. 그 결과 비정질 탄산칼슘은 결정질의 침강성 탄산칼슘을 묽은 염산용액으로 용해시킨 뒤 여기에 묽은 소다회 용액의 급속한 혼합, 침전 및 비속적인 여과과정에 따라 제조할 수 있었다. 그리고 니상 상태의 비정질 탄산칼슘을 이용하여 반응온도; 2~$85^{\circ}C$, 반응시간;5~60분의 범위에서 각각 결정화시켜 입방형, 침상형, 방추형, 구형, 판상형의 결정질 탄산칼슘을 선택적으로 제조하였다.

• Journal of Microbiology and Biotechnology
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• 제26권3호
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• pp.540-548
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• 2016

Microbially induced calcium carbonate precipitation (CCP) is a long-standing but re-emerging environmental engineering process for production of self-healing concrete, bioremediation, and long-term storage of CO₂. CCP-capable bacteria, two Bacillus strains (JH3 and JH7) and one Sporosarcina strain (HYO08), were isolated from two samples of concrete and characterized phylogenetically. Calcium carbonate crystals precipitated by the three strains were morphologically distinct according to field emission scanning electron microscopy. Energy dispersive X-ray spectrometry mapping confirmed biomineralization via extracellular calcium carbonate production. The three strains differed in their physiological characteristics: growth at alkali pH and high NaCl concentrations, and urease activity. Sporosarcina sp. HYO08 and Bacillus sp. JH7 were more alkali- and halotolerant, respectively. Analysis of the community from the same concrete samples using barcoded pyrosequencing revealed that the relative abundance of Bacillus and Sporosarcina species was low, which indicated low culturability of other dominant bacteria. This study suggests that calcium carbonate crystals with different properties can be produced by various CCP-capable strains, and other novel isolates await discovery.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.219-222
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• 2004

Removal characteristics of Mn and Co was studied from the contaminated solutions via surface reaction with various calcium carbonate (calcite). Synthetic calcium carbonates which has different surface morphology as well as surface areas were prepared by a spontaneous precipitation method and used. Mn and Co removal behavior by the different solid surface demonstrate characteristic sorption behaviors depend on the type of calcite used, such as surface area or surface morphology. Calcium carbonate crystals (mostly calcite) which exhibit complicated surface morphology (c-type) shows strong sorption affinity for Mn and Co removal via sorption than on the a-type or b-type calcite crystals of less complicated surfaces. The applicability of two kinetic models, the pseudo-first-order kinetic equation and the Elovich kinetic model was examined on these sorption behavior. Elovich kinetic model was found more suitable to explain the very early stage adsorption kinetics, while the pseudo-first-order kinetic equation was successfully fitted for the adsorption kinetics after 50 hours.