Inhibited and Retarded Behavior by Ca2+ and Ca2+/OD Loading Rate on Ureolytic Bacteria in MICP Process

Fukue, Masaharu; Lechowicz, Zbigniew; Fujimori, Yuichi; Emori, Kentaro; Mulligan, Catherine N.

doi:10.3390/ma16093357

Cited by 1 publication

(1 citation statement)

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“…Murungan et al [44] demonstrated that the completion of urea hydrolysis required a longer time in cementation solutions inoculated with a low amount of bacterial cells due to the insufficiency of bacterial cells, which reduced the level of urease. Nonetheless, Fukue et al [62] stated that a high initial ratio of Ca 2+ /OD and a high concentration of calcium ions may inhibit the processes of ureolytic MICP. A high concentration of calcium ions may cause an electrochemical gradient leading to outflow of protons from the cell [63].…”

Section: Discussionmentioning

confidence: 99%

Assessment of the Composition Effect of a Bio-Cementation Solution on the Efficiency of Microbially Induced Calcite Precipitation Processes in Loose Sandy Soil

Fronczyk,

Marchelina,

Pyzik

et al. 2023

Materials

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Soil properties are the most important factors determining the safety of civil engineering structures. One of the soil improvement methods studied, mainly under laboratory conditions, is the use of microbially induced calcite precipitation (MICP). Many factors influencing the successful application of the MICP method can be distinguished; however, one of the most important factors is the composition of the bio-cementation solution. This study aimed to propose an optimal combination of a bio-cementation solution based on carbonate precipitation, crystal types, and the comprehensive strength of fine sand after treatment. A series of laboratory tests were conducted with the urease-producing environmental strain of bacteria B. subtilis, using various combinations of cementation solutions containing precipitation precursors (H2NCONH2, C6H10CaO6, CaCl2, MgCl2). To decrease the environmental impact and increase the efficiency of MICP processed, the addition of calcium lactate (CaL) and Mg ions was evaluated. This study was conducted in Petri dishes, assuming a 14-day soil treatment period. The content of water-soluble carbonate precipitates and their mineralogical characterization, as well as their mechanical properties, were determined using a pocket penetrometer test. The studies revealed that a higher concentration of CaL and Mg in the cementation solution led to the formation of a higher amount of precipitates during the cementation process. However, the crystal forms were not limited to stable forms, such as calcite, aragonite, (Ca, Mg)-calcite, and dolomite, but also included water-soluble components such as nitrocalcite, chloro-magnesite, and nitromagnesite. The presence of bacteria allowed for the increasing of the carbonate content by values ranging from 15% to 42%. The highest comprehensive strength was achieved for the bio-cementation solution containing urea (0.25 M), CaL (0.1 M), and an Mg/Ca molar ratio of 0.4. In the end, this research helped to achieve higher amounts of precipitates with the optimum combination of bio-cementation solutions for the soil improvement process. However, the numerical analysis of the precipitation processes and the methods reducing the environmental impact of the technology should be further investigated.

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Section: Discussionmentioning

confidence: 99%