Calcium Carbonate Nanoparticles Research Articles

Combine Drug Delivery of Thymoquinone-Doxorubicin by Cockle Shellderived pH-sensitive Aragonite CaCO3 Nanoparticles

Background: Cockleshell-derived aragonite calcium carbonate nanoparticles were prepared by the top-down approach for combine delivery of two types of drugs. Objective: The aim of this study was to synthesize and characterize thymoquinone-doxorubicin loaded cockle shell-derived aragonite calcium carbonate nanoparticle. Aragonite calcium carbonate nanoparticles encapsulating thymoquinone and doxorubicin alone were also prepared. Methods: The blank and drug-loaded nanoparticles were characterized by field emission scanning electron microscopy, transmission electron microscopy, Zeta potential, Fourier transformed infrared and X-ray diffraction. Drug delivery properties, in vitro drug release study at pH 7.4, 6 and 4.8, and effect of blank nanoparticles on MCF10A, 3T3, MDA MB231 cells were also analyzed. Results: The blank and drug-loaded nanoparticles were pleomorphic and their sizes varying from 53.65 ± 10.29 nm to 60.49 ± 11.36 nm with an overall negative charge. The entrapment efficiency of thymoquinone and doxorubicin were 41.6 and 95.8, respectively. The FTIR showed little alteration after loading thymoquinone and doxorubicin while XRD patterns revealed no changes in the crystallizations of nanoparticles after drug loading. The drug release kinetics of doxorubicin and thymoquinone from the nanoparticles showed a continuous and gradual release after an initial burst release was observed. At pH 4.8, about 100% of drug release was noticed, 70% at pH 6 while only 50% at pH 7.4. The cell viability was 80% at a concentration of 1000 ug/ml of blank nanoparticle. Conclusion: The cockle shell-derived pH sensitive aragonite calcium carbonate nanoparticle provides an effective and simple means of multiple drug delivery and function as a platform for pH controlled release of loaded therapeutic agents.

Synergistic Effect of Calcium Carbonate and Biobased Particles for Rubber Reinforcement and Comparison to Silica Reinforced Rubber

Silica is a standard commercial filler to reduce rolling resistance of tires. The co-filler of nano-size calcium carbonate and bio-based particles also produce reinforced rubber with similar tensile properties and rolling resistance as silica reinforced rubber. A synergistic effect between calcium carbonate and soy protein nanoparticles was observed to produce reinforced rubber with good tensile properties and low rolling resistance. The protein increases the effective crosslink density and moduli of calcium carbonate reinforced rubber. Stearic acid coated calcium carbonate particles have a greater reinforcement effect than the uncoated calcium carbonate particles. Mechanical properties of the composites can be adjusted through the complimentary effect of these two fillers. The composite that contains 60% protein and 40% coated calcium carbonate has mechanical properties comparable to that of the silica reinforced rubber. The temperature and strain dependent dynamic mechanical properties, as well as the stress relaxation behaviors of these rubbers, reveal synergistic effect between the co-fillers. This development demonstrates an economical method to produce useful reinforced rubbers.

Experimental study of gas dehydration via PDMS/CaCO3 NP-coated PVC hollow fiber membrane contactor

In this study, diethylene glycol (DEG) as an absorbent was used for gas dehydration. For this purpose, hollow fiber membrane contactor was fabricated from polyvinyl chloride. The effect of surface modification with polydimethylsiloxane in the presence of calcium carbonate nanoparticles, relative humidity percentage of inlet air, variation in the gas and liquid flow rates in a dehydration process were investigated. The surface modification of the membranes increased the contact angle from 64° to 101° and a liquid entry pressure of as high as 7bar was achieved. Moreover, increasing the gas flow rate led to a significant enhancement in absorption performance. Conversely, it was observed that the liquid flow rate had marginal effect on the mass transfer efficiency and flux i.e. RM+L/RM+G=0.001–0.01. This revealed that the mass transfer resistance was not controlled by the liquid phase. Although higher fluxes were observed for the unmodified membrane contactor, the membrane modified with polydimethylsiloxane and calcium carbonate nanoparticles (i.e. M0.5-1) was more effective compared to the neat membrane (M0) in a 35-day long-term performance test i.e. ηM0.5-1≈0.12 versus ηM0=1.0. The results show that the applied technique for fabricating the hollow fiber membrane contactor can be a promising technique in gas conditioning.

Effect of nano C–A–S–H seeds on the early-stage hydration and pore structure of Portland cement pastes

Most previous studies have focused on the addition of nanoparticles of silicon dioxide, calcium carbonate, aluminium oxide, tin(IV) oxide or calcium silicate hydrate to speed up cement hydration. In this research, nano seeds of calcium aluminium silicate hydrate (C–A–S–H) were added to Portland cement systems. It was found that, with the addition of 1%, 3% and 5% C–A–S–H seeds, the hydration process was brought forward by about 2 h, 3 h and 7 h, the initial setting time was reduced by 16.4%, 25.5% and 34.5%, and the final setting time was reduced by 16.8%, 35.1% and 41.1%, respectively. However, the paste fluidity was reduced by 11.6%, 21.6% and 28.9%, respectively, resulting in decreased workability. X-ray diffraction analysis showed that adding C–A–S–H seeds accelerated the formation of calcium monosulfoaluminate hydrate (AFm). Compared with a control sample, the compressive strength of the mortar doped with 1% C–A–S–H seeds was increased by 4.6%, 3.4% and 5.2% at 3, 7 and 28 days, respectively. However, an increase in the content of C–A–S–H seeds to 3% and 5% led to decreases in compressive strength. The total porosity declined with the addition of 1% C–A–S–H seeds, whereas the total porosity with 3% and 5% C–A–S–H seeds was higher than that of the control sample.

Thermodynamics of antibiotics: natural cyclodextrin inclusion complex formation and covering of nano-metric calcite with these substances

Isothermal titration calorimetry (ITC) has been used to characterize inclusion complex formation of natural (α-, β-, γ-)cyclodextrins with antibiotics (ampicillin—sodium, penicillin G—sodium, streptomycin sulfate) in aqueous solutions. ITC measurements were taken at 298.15 K on Isothermal Titration Calorimeter Nano ITC. The experimental data were analyzed on the basis of the independent site model. Based on the experimental values of equilibrium constant (K) and enthalpy of complex formation (ΔH), the Gibbs energy of complex formation (ΔG) and the entropy of complex formation (ΔS) have been calculated. The analysis of the obtained inclusion complexes show that independently of the kind of cyclodextrin and antibiotics the obtained equilibrium constants are almost the same, but it is a difference between the changes in enthalpies of complex formation for the investigated systems. The stoichiometry of complexes formed both by ampicillin—sodium and by penicillin G—sodium with all the natural cyclodextrins is the same and equal to 1:1 and the complex formation is entropy driven. Three antibiotics (ampicillin—sodium, penicillin G—sodium and streptomycin sulfate) have been used further for covering of the monodisperse calcium carbonate nanoparticles obtained in the reactor (three-phase reaction) with rotating disks. Three series of experiments have been performed. First was connected with adsorption of the antibiotics on the surface on nano-calcite and two others with intercalation of the drugs into nano-metric CaCO3 structure (aggregates). An intercalation has been performed in two ways: one where the antibiotic was added to the reactor chamber at the beginning of the precipitation reaction and second where it was added just after the end of the reaction. Both pure CaCO3 nanoparticle and antibiotic-coated CaCO3 powders were deeply analyzed by the use of the thermogravimetric and the differential scanning calorimetry method. The performed investigations showed that all the antibiotics used can be both adsorbed and intercalated into the nano-metric CaCO3 obtained in the reactor with rotating disks. The different adsorption obtained by different antibiotics was caused by the different interaction between them and nano-calcite, caused by their different structure. The experimental data have allowed also for distinction between the antibiotics molecules present on calcite surface (adsorption) or antibiotics molecules intercalated into the nano-calcite structure. The conducted research shows that both approaches, i.e., formation of inclusion complexes with natural cyclodextrins and covering (adsorption and intercalation) of nano-metric CaCO3, can be successfully implemented for their pharmaceutical applications.

Effects of calcium carbonate nanoparticles on water quality, growth and metabolic activity of Macrobrachium nipponense in zero-water exchange biofloc system

Effects of calcium carbonate nanoparticles on water quality, growth and metabolic activity of Macrobrachium nipponense in zero-water exchange biofloc system

Structural analysis of CaCO3 nanoparticle/pulp fiber composites by tube flow fractionation

Two slurries that consisted of precipitated calcium carbonate (CaCO3) nanoparticles and unbeaten hardwood bleached kraft pulp (HBKP) were prepared via ultrafine bubble and mixing methods. In the ultrafine bubble method, a CO2 gas flow was bubbled into a HBKP slurry that contained Ca(OH)2 to prepare a precipitated CaCO3/HBKP composite slurry. The HBKP/water and precipitated CaCO3/water slurries were prepared separately and mixed to prepare a precipitated CaCO3/HBKP mixture slurry. Each of the two CaCO3/HBKP slurries was separated into five fractions using a tube flow fractionation (TFF) system. The first and second fractions consisted of long HBKP fibers and fiber aggregates. The third fraction had the highest mass ratio of the components in the five fractions, and it had approximately 1-mm-long HBKP fibers. The fourth fraction contained primarily HBKP short fibers and CaCO3 aggregates. Thus, the CaCO3/HBKP components in the slurry were separated adequately by TFF, depending on their hydrodynamic sizes. The average width of each fraction in the CaCO3/HBKP composite slurry was always larger than that of the corresponding fraction from the CaCO3/HBKP mixture slurry, which indicated that precipitated CaCO3 nanoparticles and their aggregates attached stably to long and short pulp fiber surfaces in the composite slurry.

Influence of poly(butylene succinate) and calcium carbonate nanoparticles on the biodegradability of high density-polyethylene nanocomposites

The biodegradation is becoming one of the most imperative properties of plastic products nowadays to promote the sustainable development and the conservation of the environment. In this framework, the main objectives of this study are to prepare an environmental friendly high density polyethylene (HDPE) nanocomposite and investigate the effect of the incorporation of nanoparticles of calcium carbonate (NPCC) and poly butylene succinate (PBS) on the prepared nanocomposites. The nanocomposites of HDPE/PBS/NPCC samples were prepared by the addition of PBS and NPCC at (1, 2 and 4 wt%) to HDPE matrix using the injection molding technique. Morphological, mechanical, thermal, physical and biodegradation analysis were conducted on the nanocomposite samples. The mechanical properties of the samples were improved (the elongation at break by 35%, and the impact strength by 26%) compared to the neat HDPE. Moreover, the thermal and physical properties were enhanced by reinforcement NPCC to the nanocomposites. The biodegradation occurrence in the HDPE nanocomposite samples was proved by the Scanning Electron Microscope (SEM) observations and the weight loss percentage (0.265 wt% after 8 weeks).

Preparation and characterization of phosphate-stabilized amorphous calcium carbonate nanoparticles and their application in curcumin delivery

Nano-sized amorphous calcium carbonate (ACC) have a great potential for drug transport and drug delivery because of their high drug loading capacity, excellent biocompatibility and biodegradability. However, ACC is the thermodynamically least stable phase of calcium carbonate, and such thermal metastability often transforms it into more stable vaterite or calcite phases, so the inhibition of the phase transformation of ACC is of great significance for its application in drug delivery systems. Herein, phosphate as a morphology controlling additive was introduced to stabilize the metastable ACC. The results showed that the composite nanoparticles (named here the ACCP) with narrow size distribution located at approximately 128 nm (measured by dynamic light scattering) were obtained, when Ca2+ concentration and C/P were 10 mM and 7/3 respectively, prepared at 30 °C for 10 min. The powdered X-ray diffraction (XRD) results showed that phosphate has an excellent ability to stabilize ACC, and even after storage for 60 days at room temperature, the structure of ACCP remains amorphous. The in vitro drug release tests showed that ACCP nanoparticles had a high curcumin (Cur) loading capacity and a sustained drug release property. Moreover, the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) radical scavenging activity assay showed that ACCP-encapsulating strategy could effectively prevent the decomposition of Cur. In vitro cytotoxicity tests demonstrated that the resultants have excellent biocompatibility. Therefore, the as-prepared ACCP nanoparticles are promising for drug delivery applications.

Adsorption of natural CaCO3 nanoparticles on the reservoir rock surfaces in the enhanced oil recovery process: equilibrium, thermodynamics, and kinetics study

The major challenges in using nanoparticles in oil and gas industry projects are high investment costs and environmental problems. Bio-nanoparticles provide a solution to environmental and economic challenges in the nano-assisted EOR processes. In this work, the potential of natural calcium carbonate nanoparticles containing chitin for wettability alteration in enhanced oil recovery was studied. The adsorption behavior of bio-nanoparticles onto calcite-dolomite rock surface was distinguished through kinetics, equilibrium, and thermodynamics assessments. Besides, oil recovery is measured through forced imbibition experiments. The Taguchi experimental design was conducted to optimize the parameters influencing oil recovery factor in forced imbibition experiments, including nanofluid concentration, temperature, and oil type. Results of the adsorption experiment showed that adsorption kinetics of bio-Ca nanoparticles onto calcite-dolomite surface follows the pseudo-second-order model and monolayer, Langmuir adsorption of bio-nanoparticles. The endothermic heat of physical adsorption (physisorption) was found 3.32 kJ/mol. Based on the experimental design, the optimum parameters that can rise to additional oil displacement are a nanofluid concentration of 0.05 wt.%, normal heptane as liquid phase, minimum salinity (Milli-Q-water), and ambient temperature. The oil recovery factor increased by 17.52% at an optimum nanofluid concentration of 0.05 wt.% in comparison to a base fluid without nanoparticle. The results indicate that synthesized bio-Ca nanoparticles have proper EOR potential in both light oil and heavy oil reservoirs at certain conditions.

Utilization of Nano and Micro Particles to Enhance Drilling Mud Rheology

Nanoparticles have been used to overcome the limitations of drilling oil and gas wellbores under harsh conditions of high pressure and high temperature (HPHT). In the present work, calcium carbonate (CaCO3: 5 µm particles), graphene (powder and platelets) and carbon nano sphere nanoparticles were used as rheology enhancer and fluid loss agent for HTHP drilling fluid technology. The results revealed that by adding only 0.1 wt% of nanoparticles to ester-based drilling mud improved the stability for drilling deep and ultra-deep wells up to 230°C. Furthermore, adding graphene powder gave more effective results comparing to graphene platelets and carbon nano sphere. The mud can plug 10 µm of formation size with 8 ml of filtration and 775 mD of permeability using (21/2 × 1/4 ) inch of ceramic disc. The nanoparticle enhanced ester-based drilling fluid also showed superior rheology, fluid loss amount and mud cake thickness. The application of nano ester based drilling fluid is in oil and gas drilling industry.

Optimization of Milling Procedures for Synthesizing Nano-CaCO3 from Achatina fulica Shell through Mechanochemical Techniques

The possibility of obtaining calcium carbonate nanoparticles from Achatina fulica shell through mechanochemical synthesis to be used as a modifying filler for polymer materials has been studied. The process of obtaining calcium carbonate nanopowders includes two stages: dry and wet milling processes. At the first stage, the collected shell was dry milled and undergone mechanical sieving to ≤50 μm. The shell particles were wet milled afterward with four different solvents (water, methanol, ethylene glycol, and ethanol) and washed using the decantation method. The particle size and shape were investigated on transmission electron microscopy, and twenty-three particle counts were examined using an iTEM image analyzer. Significantly, nanoparticle sizes ranging from 11.56 to 180.06 nm of calcium carbonate was achieved after the dry and wet milling processes. The size particles collected vary with the different solvents used, and calcium carbonate synthesis with ethanol offered the smallest organic particle size with the average size ranging within 13.48-42.90 nm. The effect of the solvent on the chemical characteristics such as the functional group, elemental composition, and carbonate ion of calcium carbonate nanopowders obtained from Achatina fulica shell was investigated. The chemical characterization was analyzed using Fourier transform infrared (FTIR) and a scanning electron microscope (SEM) equipped with an energy-dispersive spectroscope (EDX). The effect of milling procedures on the mechanical properties such as tensile strength, stiffness, and hardness of prepared nanocomposites was also determined. This technique has shown that calcium carbonate nanoparticles can be produced at low cost, with low agglomeration, uniformity of crystal morphology, and structure from Achatina fulica shell. It also proved that the solvents used for milling have no adverse effect on the chemical properties of the nano-CaCO3 produced. The loading of calcium carbonate nanoparticles, wet milled with different solvents, exhibited different mechanical properties, and nanocomposites filled with methanol-milled nano-CaCO3 offered superior mechanical properties.

Zein coated calcium carbonate nanoparticles for the targeted controlled release of model antibiotic and nutrient across the intestine

In this study, a novel bio-inspired method was used to synthesize calcium carbonate nanoparticles (CaCO3 NPs) using gelatin as a template for the co-delivery of vitamin D and amoxicillin. The synthesized CaCO3 NPs were characterized using Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET). XRD and TEM confirmed nanocrystalline nature of CaCO3 in size range of 10−15 nm. Further, CaCO3 NPs encapsulated with vitamin D, coated with zein and finally loaded with amoxicillin as a model drug. The release study of vitamin D and amoxicillin was performed in the simulated gastric fluid (SGF) (pH 1.2) and simulated intestinal fluid (SIF) (pH 6.8) and (pH 7.4) at 37 °C temperature. The encapsulation of hydrophobic vitamin D in CaCO3 NPs with an external zein coating approach enhances their controlled and sustained release property at the target site. The role of gelatin molecule in the synthesis of nano-sized CaCO3 was demonstrated using CD spectroscopy. MTT assay was performed on zein coated CaCO3 NPs at varying concentrations on kidney (HEK) and liver (Hep G2) cell lines after 24 h exposure to ensure its biocompatibility.

Solid-State Phase Transformation and Self-Assembly of Amorphous Nanoparticles into Higher-Order Mineral Structures

Materials science has been informed by nonclassical pathways to crystallization, based on biological processes, about the fabrication of damage-tolerant composite materials. Various biomineralizing taxa, such as stony corals, deposit metastable, magnesium-rich, amorphous calcium carbonate nanoparticles that further assemble and transform into higher-order mineral structures. Here, we examine a similar process in abiogenic conditions using synthetic, amorphous calcium magnesium carbonate nanoparticles. Applying a combination of high-resolution imaging and in situ solid-state nuclear magnetic resonance spectroscopy, we reveal the underlying mechanism of the solid-state phase transformation of these amorphous nanoparticles into crystals under aqueous conditions. These amorphous nanoparticles are covered by a hydration shell of bound water molecules. Fast chemical exchanges occur: the hydrogens present within the nanoparticles exchange with the hydrogens from the surface-bound H2O molecules which, in turn, exchange with the hydrogens of the free H2O molecule of the surrounding aqueous medium. This cascade of chemical exchanges is associated with an enhanced mobility of the ions/molecules that compose the nanoparticles which, in turn, allow for their rearrangement into crystalline domains via solid-state transformation. Concurrently, the starting amorphous nanoparticles aggregate and form ordered mineral structures through crystal growth by particle attachment. Sphere-like aggregates and spindle-shaped structures were, respectively, formed from relatively high or low weights per volume of the same starting amorphous nanoparticles. These results offer promising prospects for exerting control over such a nonclassical pathway to crystallization to design mineral structures that could not be achieved through classical ion-by-ion growth.

Size-Controlled Preparation and Behavior Study of Phospholipid-Calcium Carbonate Hybrid Nanoparticles.

BackgroundCalcium carbonate (CC) nanoparticles have broad biomedical utilizations, owing to their multiple intrinsic merits. However, bare CC nanoparticles do not allow for the development of multifunctional devices suitable for advanced drug delivery in cancer therapy.MethodsPhospholipid-modified phospholipid–CC hybrid nanoparticles were prepared in our study using a combination of vapor-diffusion and solvent-diffusion methods to offer optimized pharmaceutical capabilities.ResultsConsidering that particle size is a critical parameter that plays an important role in both in vitro and in vivo behaviors of nanoparticles, we here for the first time a present detailed protocol for the size-controlled preparation of hybrid nanoparticles, as well as analysis of the in vitro/in vivo behaviors of differently sized hybrid nanoparticles.ConclusionOur results might significantly advance the application of this promising material in more varied fields.

Smart responsive-calcium carbonate nanoparticles for dual-model cancer imaging and treatment

Contrast-enhanced ultrasound (CEUS) is widely applied in cancer diagnosis clinically. However, the gas-filled contrast agents are unstable in the blood and exhibit shorter imaging time, which limit their clinical use. In this study, a diagnostic nanoparticle system was developed for dual-mode imaging (ultrasound and fluorescence), which after encapsulation with doxorubicin (DOX) demonstrated simultaneous therapeutic function towards cancer treatment. Thus, calcium carbonate (CaCO3) nanoparticles were encapsulated with doxorubicin (DOX) to obtain CaCO3-DOX. Under acidic conditions, it produced carbon dioxide (CO2) to enhance ultrasound imaging and increase the release of DOX. After intravenously injecting CaCO3-DOX to tumor-bearing mice, in the presence of an ultrasound field, CO2bubbles were sufficiently generated at the tumor tissues for echogenic reflectivity. Also, the indocyanine green (ICG) was encapsulated into CaCO3 nanoparticles, to further detect the tumor with fluorescence. The resultant theranostic nanoparticle system exhibited therapeutic efficacy towards tumour-bearing mice. Overall, this investigation provides an attractive strategy for dual-mode cancer diagnostics.

Colorimetric sensor and LDI-MS detection of biogenic amines in food spoilage based on porous PLA and graphene oxide

Biogenic amines are the important markers for food spoilage, thus, an on-package sensor for biogenic amine detection is crucial for food quality control. A dual detection platform including colorimetry and LDI-MS was developed for screening and quantitative determining of biogenic amines. Porous PLA film, was fabricated using calcium carbonate nanoparticles to enhance film porosity leading to increased surface area of colorimetric sensor. The color intensity significantly increases depending upon the enhanced analyte concentration with a linear range of 2.0–10.0 mg/mL for putrescine, and 0.1–6.0 mg/mL for cadaverine. On another layer, graphene oxide paper was applied as an LDI-MS substrate for sensitive quantification of biogenic amines. LOD values measured on graphene oxide coated side by LDI-MS were found to be 0.07 pM and 0.02 pM for putrescine and cadaverine, respectively. This platform was successfully applied for the detection of biogenic amines in pork samples with satisfactory results.

Nanoenabled Disruption of Multiple Barriers in Antigen Cross-Presentation of Dendritic Cells via Calcium Interference for Enhanced Chemo-Immunotherapy

Chemo-immunotherapy holds the advantage of specific antitumor effects by activating T cell immune response. However, the efficiency of chemo-immunotherapy is restricted to the insufficient antigen presentation of dendritic cells (DCs) in the tumor immunosuppression microenvironment. Here, we rationally designed a simple yet versatile calcium ion nanogenerator to disrupt the autophagy inhibition condition within DCs, enrich damage-associated molecular patterns (DAMPs), and attenuate acidity in the tumor microenvironment. After chemotherapy, honeycomb calcium carbonate (CaCO3) nanoparticles (OVA@CaCO3, denoted as HOCN, ovalbumin (OVA) acted as skeleton) could preferentially accumulate in the tumor and display a series of benefits for disrupting multiple barriers in antigen cross-presentation of DCs: (i) recovering cell viability of DCs by HOCN-induced tumor acidity attenuating; (ii) disrupting the autophagy inhibition condition in DCs by generating Ca2+ in cells; (iii) improving maturation of DCs by Ca2+ overloading-mediated enhanced DAMP release from tumor cells. In addition, HOCN can also disrupt the immunosuppressive microenvironment by reducing the infiltration of immunosuppressive cells and factors. We believe regulation of the intratumoral Ca2+ offers an alternative strategy for improving cancer chemo-immunotherapy.

Synthesis and Characterization of Calcium Carbonate Nanoparticles via Bacterial Mineralization in Steel Slag Comprising Cementitious Materials

Bacteria-induced mineralization is a new technique to produce calcium carbonate in steel slag for the preparation of building materials. Calcium carbonate nanoparticles were precipitated as a result of the enzymatic activity of Bacillus mucilaginous subtilis in steel slag. The crystal structure and morphology of the calcium carbonate precipitate were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic force microscopy (AFM), while thermal properties were studied by thermogravimetric-differential scanning calorimetry (TG-DSC) analysis. The experimental results showed that the microstructure of calcium carbonate precipitate induced by the reproductive enzymes of Bacillus mucilaginous differs from the chemical precipitation in simulated pore solution of steel slag. Powder XRD patterns confirmed the formation of Bacillus mucilaginous subtilis-induced calcium carbonate with an average particle size of 42.1 nm, while the average particle size of the chemically synthesized calcium carbonate was 59.3 nm. Compared with the chemical synthesis, we found that the decomposition temperature of calcite by bacterial precipitation was higher than that for the chemically-precipitated calcite. The compressive strength improved with the amount of bacterial content. Bacterial mineralization could accelerate the rate of carbon sequestration in the mineralization process. The content of calcium carbonate in microbial mineralized steel slag increased obviously. The compressive strength of steel slag mortar with 1.5% bacterial reached up to 51.5 MPa, the compressive strength increased over 50% compared with the carbonized steel slag mortar. The micron-size calcite by bacterial mineralization resulted in a more compact structure. Our study suggests that microbial mineralization technology is a good method to utilize steel slag for building materials.

Biogenic Nanoparticles of Calcium Carbonate - Preparation and Behaviour

Calcium carbonate is one of the most widespread natural material. Biogenic calcium carbonate nanoparticles are biocompatible. Currently, they are of great interest for their possible applications, especially in medicine. The aim of this introductory experimental study is to present a simple preparation of biogenic nanoparticles of calcium carbonate from natural resources with a subsequent specific behaviour of nanoparticles in aquatic environment. Different type of shells were used for the preparation of nanoparticles. All structures were burned at 850°C and then grounded to powder. The obtained powders were left in normal laboratory environment for 2 weeks and then placed in beakers with distilled water. Subsequently, two homogenization routes were used - stirring at 1000 rpm for 5 minutes and ultrasonic stirring for 5 minutes. One part of the particles was separated at the bottom of the beaker, but small formations started to create a fractal structure on the surface of water. These formations gradually increased. Crystalline interconnected structures built up with nanoparticles were confirmed by a subsequent analysis by a scanning electron microscope. EDX analysis confirmed the presence of calcium carbonate.