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[HRE13-P11] Effect of organic acids on calcium carbonate formed by biomineralization
Keywords:Biomineralization, Calcium carbonate, Organic acids, Biocementation
Biocementation is a novel and unique technique to produce cementing materials such as CaCO3 by biological actions. This technique includes biomineralization and can be applied to solidify a soil or to strengthen constructions. We have developed enzymatically- or microbially-induced carbonate precipitation (EICP/MICP) to produce CaCO3, where urea-degrading enzyme (urease) hydrolyzes urea to bicarbonate and ammonium ion, resulting in CaCO3 formation in the presence of Ca2+ ion. This method does not need high temperature or strong chemicals and thus is considered as a green cementation technique in place of conventional cementation methods.
Here, biominerals are usually composed of organic and inorganic materials to exhibit versatile and desirable physical and chemical properties as industrial materials. Interestingly, the morphology of biomineral is correctly controlled by organic compounds such as proteins and polysaccharides as shown in seashells and skeleton of living things. Control of morphology of biominerals could possibly expand the application of biominerals or biocementation for next generation industrial materials.
It was reported that organic acids have effects on crystal form and morphology of CaCO3 formed by chemical method. In the present work, we investigated the effect of organic acids on crystal form and morphology of CaCO3 produced in EICP. Calcium carbonate precipitates formed by urease in the presence of acetic acid, propionic acid, pyruvic acid phosphoenolpyruvic acid and citric acid, which are kinds of metabolites in bacteria, at pH 7.5 and 25℃ was analyzed by SEM-EDS and XRD.
We found calcite was mainly formed in EICP method in our previous study. In the presence of acetic acid, propionic acid and pyruvic acid, rhombohedral calcite and spherical vaterite were formed. These organic acids may adsorb on the surface of calcium carbonate crystal, inhibiting the crystal growth of calcite, resulting in the formation of vaterite. Unlike these three organic acids, citric acid and phosphoenolpyruvic acid gave significantly different results. Spherical crystals composed of small rhombohedral calcite was observed in the presence of citric acid, indicating that citric acid would contribute to the formation of aggregation of calcite crystals. Phosphoenolpyruvic acid totally gave amorphous CaCO3. We demonstrated that organic acids affected the crystal form and morphology of CaCO3 formed in EICP.
Here, biominerals are usually composed of organic and inorganic materials to exhibit versatile and desirable physical and chemical properties as industrial materials. Interestingly, the morphology of biomineral is correctly controlled by organic compounds such as proteins and polysaccharides as shown in seashells and skeleton of living things. Control of morphology of biominerals could possibly expand the application of biominerals or biocementation for next generation industrial materials.
It was reported that organic acids have effects on crystal form and morphology of CaCO3 formed by chemical method. In the present work, we investigated the effect of organic acids on crystal form and morphology of CaCO3 produced in EICP. Calcium carbonate precipitates formed by urease in the presence of acetic acid, propionic acid, pyruvic acid phosphoenolpyruvic acid and citric acid, which are kinds of metabolites in bacteria, at pH 7.5 and 25℃ was analyzed by SEM-EDS and XRD.
We found calcite was mainly formed in EICP method in our previous study. In the presence of acetic acid, propionic acid and pyruvic acid, rhombohedral calcite and spherical vaterite were formed. These organic acids may adsorb on the surface of calcium carbonate crystal, inhibiting the crystal growth of calcite, resulting in the formation of vaterite. Unlike these three organic acids, citric acid and phosphoenolpyruvic acid gave significantly different results. Spherical crystals composed of small rhombohedral calcite was observed in the presence of citric acid, indicating that citric acid would contribute to the formation of aggregation of calcite crystals. Phosphoenolpyruvic acid totally gave amorphous CaCO3. We demonstrated that organic acids affected the crystal form and morphology of CaCO3 formed in EICP.