Precipitated Calcium Research Articles

CBX7 Rejuvenates Late Passage Dental Pulp Stem Cells by Maintaining Stemness and Pro-angiogenic Ability.

Ever-growing tissue regeneration causes pressing need for large population of stem cells. However, extensive cell expansion eventually leads to impaired regenerative potentials. In this study, chromobox protein homolog 7 (CBX7) was overexpressed to rejuvenate late passage dental pulp stem cells (DPSCs-P9). The recruitment of copper ions (Cu2+)-activated hypoxia-inducible factor-1α (HIF-1α) to the CBX7 gene promoter was confirmed by chromatin immunoprecipitation assay. Functions subsequent to Cu2+-induced or recombinant overexpression of CBX7 on proliferation, multipotency, odontoblastic differentiation and angiogenesis were investigated in vitro, while murine subcutaneous transplantation model was used to further detect the effects of Cu2+-induced CBX7 overexpression in vivo. Our data displayed that CBX7 overexpression maintain proliferation and multipotency of DPSCs-P9 almost as strong as those of DPSCs-P3. Both gene level of odontoblast-lineage markers and calcium precipitation were nearly the same between CBX7 overexpressed DPSCs-P9 and normal DPSCs-P3. Moreover, we also found upregulated expression of vascular endothelial growth factor in DPSCs-P9 with CBX7 overexpression, which increased the number of capillary-like structures and migrating co-cultured human umbilical vein endothelial cells as well. These findings indicate CBX7 as an effective factor to rejuvenate late passage stem cells insusceptible to cell expansion. Cu2+ has been proved to achieve CBX7 overexpression in DPSCs through the initiation of HIF-1α-CBX7 cascade. Under Cu2+ stimulation since P3, DPSCs-P9 exhibited ameliorated regenerative potential both in vitro and in vivo. Long-term stimulation of Cu2+ to overexpress CBX7 could be a new strategy to manufacture large population of self-renewing stem cells.

Changes in fold cracking properties and mechanical properties of high-grammage paper as affected by additive and fillers

Fold cracking, which reduces the economic feasibility of paper-making, is a localized surface deformation caused by extreme bending stress. Most paper products, such as base paper and coated paper, generate fold cracking during folding processing. To control fold cracking, the mechanical properties of the base paper can be strengthened, and the flexibility of the structure can be increased by controlling the modification in pulp fibers and stock preparation conditions. This study analyzed the changes in the mechanical properties of high-grammage paper in response to the addition of precipitated calcium carbonate (PCC) and cationic starch (C-starch). The application of inorganic filler (PCC) drastically reduced the internal bond strength and tensile strength, causing fold cracking, whereas C-starch increased the bond strength between fibers, which improved the tensile strength, internal bond strength, and elongation. However, when applied independently, fold cracking occurred because of extreme increase or decrease in strength. Therefore, the combined application of C-starch and PCC made it possible to form a paper-based structure with high fold cracking resistance. Moreover, when the fold cracking resistance was excellent, the mechanical properties were balanced without being biased in one direction even under conditions of relatively low mechanical properties.

Flocculation of alkyl ketene dimer and calcium carbonate on paper sizing and filling performance

Abstract In order to solve the conflict between precipitated calcium carbonate (PCC) filling and alkyl ketene dimer (AKD) sizing for paper, this study explored two new flocculation methods: AKD and PCC were flocculated separately in the process ((A)(P)F), while the two pre-flocs from AKD and PCC were blended in the process ((AP)F). The result showed that increasing the dosage of the flocculant cationic starch (CS) resulted in a significant growth in the median size of PCC flocs and reduction in the specific surface area, turbidity, the negative charge of Zeta potential, as well as the adsorption capacity of PCC to AKD. Consequently the sizing degree and filler retention rate of the handsheets rose markedly. With 125 mg g−1 of CS, compared with the conventional process, the filler retention rate for (A)(P)F grew up to 86.16%; the Cobb60 values for both (AP)F and (A)(P)F declined, and the contact angle (CA) increased to 120.65° and 127.65° respectively. At the same time, the filler bondability factor (FBF) were increased due to the intensified bonding force between fibers, and resultantly the comparable mechanical properties of papersheets with a high level of filler retention was obtained from (AP)F and (A)(P)F flocculation processes.

Hybrid Technology Seawater Desalination Based on Reverse Osmosis and Membrane Distillation Methods

The article presents the results of a computational and analytical study of hybrid RO–MD (Reverse Osmosis–Membrane Distillation) technologies for desalination of the Caspian Sea, providing for the production of an additional amount of desalinated water by the MD method from RO concentrates heated to 50–80°C due to waste heat of fuel combustion products in steam boilers. Two options for solving the problem of the formation of CaCO3 and CaSO4 precipitates on membranes were studied: with preliminary nanofiltration (NF) or Na-cationation (Na) of sea water, as an alternative to the use of antiscalants (AS) and acid. The negative environmental effect of most plants (eutrophication of water bodies) and their low efficiency at high concentrations of desalinated water are taken into account. The Langelier index (СаСО3) and the degree of concentrate saturation (СаSO4) were used as criteria for precipitation of deposits on the membranes. The NF and RO processes were studied using the ROSA computer program, and the MD and Na processes were studied by computer simulation of the corresponding calculation models. It was found that at a 70% permeate yield at the NF and RO stages, the possibility of calcium precipitation on the RO and MD membranes is prevented, but their precipitation on the NF membranes is predicted, which makes the use of AS forced. At the same time, additional permeate production at the MD stage from RO concentrates reaches 40% of the amount of permeate from RO stadium, and the electricity consumption in general according to the scheme is 1.88 kWh/m3. Reducing the calcium hardness of sea water to 50 µg-eq/dm3 by the Na-cationization method makes it possible to refuse both the use of AS and acidification with sulfuric acid with additional production of MD permeate – 27% relative to RO permeate. Electricity consumption rises to 2.5 kWh/m3. To use the known advantages of NF without the use of AS, a hybrid Na–NF–RO–MD scheme is proposed. It has been established that at 80% yields of NF and RO permeates, to prevent the formation of CaSO4 precipitates at all stages of treatment, it is sufficient to reduce the hardness of sea water from 16 to 5.5 m-eq/dm3, and by acidifying the softened water to exclude the formation of CaCO3 precipitates.

Chemical Defense against Herbivory in the Brown Marine Macroalga Padina gymnospora Could Be Attributed to a New Hydrocarbon Compound.

Brown marine macroalga Padina gymnospora (Phaeophyceae, Ochrophyta) produces both secondary metabolites (phlorotannins) and precipitate calcium carbonate (CaCO3-aragonite) on its surface as potential defensive strategies against herbivory. Here, we have evaluated the effect of natural concentrations of organic extracts (dichloromethane-DI; ethyl acetate-EA and methanol-ME, and three isolated fractions) and mineralized tissues of P. gymnospora as chemical and physical resistance, respectively, against the sea urchin Lytechinus variegatus through experimental laboratory feeding bioassays. Fatty acids (FA), glycolipids (GLY), phlorotannins (PH) and hydrocarbons (HC) were also characterized and/or quantified in extracts and fractions from P. gymnospora using nuclear magnetic resonance (NMR) and gas chromatography (GC) coupled to mass spectrometry (CG/MS) or GC coupled to flame ionization detector (FID) and chemical analysis. Our results showed that chemicals from the EA extract of P. gymnospora were significantly important in reducing consumption by L. variegatus, but the CaCO3 did not act as a physical protection against consumption by this sea urchin. An enriched fraction containing 76% of the new hydrocarbon 5Z,8Z,11Z,14Z-heneicosatetraene exhibited a significant defensive property, while other chemicals found in minor amounts, such as GLY, PH, saturated and monounsaturated FAs and CaCO3 did not interfere with the susceptibility of P. gymnospora to L. variegatus consumption. We suggest that the unsaturation of the 5Z,8Z,11Z,14Z-heneicosatetraene from P. gymnospora is probably an important structural characteristic responsible for the defensive property verified against the sea urchin.

Optical‐physical and inkjet printing properties of created hybrid CaCO3 coated papers

AbstractThe aim of this study is to examine the role of different formulations of calcium carbonates on the inkjet printing quality, with the use of cationic carboxymethyl cellulose (CMC)‐starch as a binder in the formation of the coating structure of paper to use for inkjet printing. For this, GCC (ground calcium carbonate), PCC (precipitated calcium carbonate) and ECC (eggshell calcium carbonate), which have been tried as new coating materials in recent years, are mixed in different proportions to form a different coated formulation and plastered on the newly produced paper surface. Then, optical and physical tests of the obtained samples are carried out. Then, printing properties of the papers on which drop‐on‐demand system inkjet printing is made are examined. According to the obtained data, it is determined that the optical properties of coated paper with GCC + PCC blends outperformed papers coated with other blends. According to the physical test results, GCC + PCC blended coated papers showed the best performance in breaking length and tear indices. ECC + PCC blended coated papers however showed the best performance in burst indices. It is determined that as the particle size of the calcium carbonates in the coating materials decreased, the burst indices value also decreased. This situation is the opposite for breaking length and tear indices values. When the inkjet printing features are examined, it is seen that the best results are obtained from GCC + ECC coated papers in general. The most optimal metamerism indices results, measured under three different light sources, are obtained on GCC + PCC coated papers.

The effects of various operational- and materials-oriented parameters on the carbonation performance of low-quality recycled concrete aggregate

This study focuses on the examination of the parameters affecting the carbonation performance of low-quality recycled concrete aggregates (RCA) obtained from end-of-life buildings and having low mechanical and chemical properties. The accelerated carbonation process was implemented by using a lab-scale carbonation reactor, providing a dynamic carbonation process. In the scope of this study, as the main operational parameters, relative humidity (RH) (50-70-90%), medium pressure (1-2-3 bar), and temperature (50–90 °C) were determined. Carbonation processes were implemented on the low-quality RCAs with 5 different particle size ranges, including <0.85, 0.85–2.00, 2.00–4.75, 4.75–9.50, and 9.50–14.00 mm. Effects of carbonation durations (2-4-6-12-24-48-72-96-120 h) on the carbonation performance of RCAs were also investigated. Thermogravimetry was the test method used to quantify the CO2 uptake rate of low-quality RCAs. In addition, the water absorption capacity of RCAs was determined to gain insight into precipitated calcium carbonate. To evaluate the microstructure of carbonation products, scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were used. Mortar specimens were prepared using uncarbonated and carbonated RCAs to assess the effects of the carbonation on the workability and mechanical properties of the RCAs-incorporated cementitious system. Results showed that all parameters tested were effective on the carbonation performance of the RCAs. Implementing carbonation with an optimal condition (70% RH, 1 bar, 90 °C, 48 h) resulted in an increase in the quality of low-quality RCAs in favor of increasing the compressive strength of the cement-based systems. Therefore, valuable upcycling of low-quality RCAs for the construction industry is possible in high-tech applications with accelerated carbonation under optimum conditions.

Risk Evaluation of Chemical Clogging of Irrigation Emitters via Geostatistics and Multivariate Analysis in the Northern Region of Minas Gerais, Brazil

In this study, we analyzed the hydrogeochemistry of 350 underground wells in the northern region of the state of Minas Gerais, Brazil, for water-chemical parameters that may contribute to the chemical clogging of emitters in drip irrigation systems. Risk class maps were generated for each parameter, and the area was classified based on the water characteristics, considering the degree of water-use restriction in micro-irrigation (i.e., no, moderate, and severe restriction). Inverse distance-weighted, random forest, and ordinary kriging methods were used as interpolation methods. Moreover, a multivariate analysis was conducted to analyze the results. Pearson’s correlation coefficient showed a strong and significant correlation between pH and carbonates, hardness, total dissolved solids (TDS), and electrical conductivity (EC) and between TDS and EC. Principal component analysis revealed that most of the variations in the water quality of the wells could be explained by water–rock interactions with the consequent dissolution of minerals. The principal components were natural sources of ionic salt groups, dissolution of minerals rich in alkaline cations, chemical weathering of iron–magnesium minerals, and increased pH with the conversion of bicarbonates into carbonates. In the parameter cluster analysis, three possible mechanisms that contribute to emitter clogging in the study area were identified: precipitation of calcium and magnesium salts; oxidation of iron and manganese ions forming oxides and insoluble hydroxides; an increase in pH, which converts bicarbonates into carbonates. Clustering analysis revealed the wells that are susceptible to clogging with the exact cause.

RNAi Silencing of the Biomineralization Gene Perlucin Impairs Oyster Ability to Cope with Ocean Acidification

Calcifying marine organisms, including the eastern oyster (Crassostrea virginica), are vulnerable to ocean acidification (OA) because it is more difficult to precipitate calcium carbonate (CaCO3). Previous investigations of the molecular mechanisms associated with resilience to OA in C. virginica demonstrated significant differences in single nucleotide polymorphism and gene expression profiles among oysters reared under ambient and OA conditions. Converged evidence generated by both of these approaches highlighted the role of genes related to biomineralization, including perlucins. Here, gene silencing via RNA interference (RNAi) was used to evaluate the protective role of a perlucin gene under OA stress. Larvae were exposed to short dicer-substrate small interfering RNA (DsiRNA-perlucin) to silence the target gene or to one of two control treatments (control DsiRNA or seawater) before cultivation under OA (pH ~7.3) or ambient (pH ~8.2) conditions. Two transfection experiments were performed in parallel, one during fertilization and one during early larval development (6 h post-fertilization), before larval viability, size, development, and shell mineralization were monitored. Silenced oysters under acidification stress were the smallest, had shell abnormalities, and had significantly reduced shell mineralization, thereby suggesting that perlucin significantly helps larvae mitigate the effects of OA.

Investigation of self-healing properties in concrete with Bacillus licheniformis isolated from agricultural soil

One of the best methods to enhance the strength and durability of concrete and repair the cracks is to use a self-healing mechanism, based on bacterial-induced calcite precipitation. The main goal of this study includes the isolation and identification of wild-type calcium carbonate precipitation bacteria compatible with concrete from agricultural soil as a bacterial self-healing agent. These bacteria were recognized as Bacillus licheniformis by molecular identification.The bacteria were immobilized inside lightweight expanded clay aggregate (LECA) to be protected bacteria against harsh concrete conditions. Five different bacterial concentrations (104, 105, 106, 107, and 108 cells/ml) were studied in the mixtures to evaluate the optimum concentration of bacteria.The mechanical properties and durability were tested to estimate the effectiveness of bacteria on the performance of concrete specimens at 7, 28, and 90 days. Furthermore, the physicochemical properties of precipitated calcium carbonate were characterized using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD).Test results showed that in the specimen containing 107 cells/ml Bacillus licheniformis, the compressive and tensile strength was 21% and 32% more than ordinary concrete, respectively. Also, the maximum decrease in water and chloride ion permeability was 45% and 55%, respectively. These results suggest that the wild-type strain can survive in the cement matrix and by producing calcium carbonate deposits, it has the potential to improve the mechanical properties and durability.

Sand Consolidation Using Enforced Calcium and Magnesium Fluoride Precipitation

Abstract Sand production is a common problem that interrupts hydrocarbon production from unconsolidated formations. Different chemical and mechanical methods are used to prevent solid production either by consolidating the sand particles or installing downhole screens. This study presents a novel approach for sand consolidation using enforced calcium and magnesium precipitation. The used chemicals are ammonium hydrogen fluoride, calcium oxide, and magnesium oxide solutions. In this work, different measurements were carried out to assess the performance of the new consolidation method. Also, the impact of soaking the consolidated sand in freshwater, toluene, and HCl was examined. The rock mineralogy was determined before and after each soaking treatment using X-ray diffraction (XRD) analysis. The nuclear magnetic resonance (NMR) technique was used to evaluate the pore system at different stages. In addition, scanning electron microscope (SEM) technique was used to examine the morphology and chemistry changes after each chemical treatment. Finally, the rock strength was measured before and after the treatment using a scratch test. Results indicate that the proposed chemical method can significantly improve the sand consolidation and increase the rock strength to 34 MPa (4931 psi). Soaking the consolidated sand sample in water and toluene showed minor alterations in the rock properties. However, using HCl lead to increasing rock permeability due to mineral dissolution. The strength measurements showed that the consolidated sand can withstand the water and toluene treatment, and the rock strength was reduced by less than 10%. Overall, a new chemical treatment is presented to improve the sand consolidated utilizing enforced calcium and magnesium precipitation. The consolidated sand sample showed very reasonable rock strength which can prevent sand migration.

The Crystal Structure of Calcium Sebacate by X-ray Powder Diffraction Data

Sodium sebacate salts have several industrial applications as additives, lubricants, and a metal self-healing promoter in general industry, and some derivatives also have wide applications in cosmetics and pharmaceutical fields. Calcium sebacate formation and precipitation can be detrimental for the systems where sodium sebacate is used. It is thus important to investigate their crystallization features. Sodium and calcium sebacate were prepared, purified, and crystallized with different approaches to carry out a full X-ray diffraction powder diffraction structural analysis since suitable single crystals cannot be obtained. The calcium sebacate crystal structure was solved by simulated annealing. Calcium ions form layers connected by straight “all trans” sebacate molecules, a conformation that is also suggested by Fourier-transform infrared spectroscopy FTIR data. Water molecules are caged within calcium layers. The crystal structure is characterized by the calcium layers bent by 10.65° with respect to the plane where sebacate chains lie, different from other dicarboxilic salts, such as cesium suberate, where the layers are perpendicular to the cation planes. The sodium sebacate crystal structure resulted in being impossible to be solved, despite several crystallization attempts and the different data collection approaches. FTIR spectroscopy indicates marked differences between the structures of calcium and sodium sebacate, suggesting a different type of metal coordination by carboxyls. Calcium sebacate shows a bis-bidentate chelating and bridging configuration ((κ2)−(κ1−κ1)−μ3−Carb), while for sodium sebacate, FTIR spectroscopy indicates an ionic interaction between sodium and the carboxyls. A thermogravimetric analysis TGA was carried out to assess the hydration states of the two salts. Calcium sebacate shows, as expected, a total weight loss of ca. 7%, corresponding to the single water molecule located in the crystal structure, while sodium sebacate shows no weight loss before total combustion, indicating that its structure is not hydrated. Scanning electron microscopy SEM images show different morphologies for calcium and sodium salts, probably a consequence of the different interactions at the molecular lever suggested by FTIR and TGA. The used approach can be extended to fatty acid salt in general, a still under-explored field because of the difficulty of growing suitable single crystals.

Batchwise Leaching of Calcium from Demolition Concrete Fines in an Aqueous Ammonium Nitrate Solution: Part 2 Modeling

This article addresses the application of the indirect mineral carbonation process to recycled concrete aggregates (RCA). In such a process, calcium is first leached from the RCA feedstock into an aqueous ammonium nitrate solution and then it is carbonated to precipitate calcium carbonate. The calcium leaching step is modeled in this contribution, whereas it was investigated experimentally in part 1 of this series, where the focus was more on thermodynamic aspects than on kinetics. In this part 2 paper, kinetics aspects are also included by modeling them using two different approaches. In the first approach, the reaction–diffusion model is implemented, accounting for the congruent dissolution of the calcium hydroxide phase and the incongruent dissolution of the calcium silicate hydrate components of concrete fines. In the second approach, a double-shrinking-core model is used, which for the sake of simplicity assumes congruent dissolution of calcium silicate hydrates as well, infinitely fast reaction/dissolution kinetics, and pseudo-steady-state diffusion. The model parameters have been either determined through targeted experiments or estimated by fitting measurements obtained in experiments with two different materials, both in the size range of up to a diameter of 4 mm. Both models exhibit satisfactory accuracy in describing the experimental data; particularly for particles larger than about 0.1 mm in diameter, the two models calculate a nearly identical evolution of the calcium concentration in solution. The simplifications of the double-shrinking-core model lead to a loss of resolution in characterizing the evolution of leaching inside the particles, whereas they enable faster computations. The latter feature makes such a model a convenient tool for studying process performance, namely, productivity, calcium recovery, and solvent efficiency, through parametric analysis; this has been demonstrated as reported in the last part of the article.

Effects of precipitated and ground calcium carbonate coating on mechanical properties of fluting paper

PurposeThe purpose of this study is to investigate the effects of a pigment coating on the mechanical properties of fluting paper.Design/methodology/approachTwo different calcium carbonate pigments were used in the preparation of the coated color, precipitated calcium carbonate (PCC) and ground calcium carbonate (GCC). Fluting paper produced by recycling waste paper was used as base paper. The effects of PCC and GCC pigments on mechanical properties were compared. Ring crush test (RCT), corrugating medium test (CMT), corrugating crush test (CCT), tensile and burst strength tests were applied to the coated papers, and the results were compared to the mechanical properties of base paper.FindingsThe tensile and burst indices of the coated papers were found to be higher than base papers about 13.9% and 6.05%, respectively. While the coating process positively affected the RCT and CCT values, it did not show a significant impact on the CMT values. GCC, one of the pigments used in coating colors, had a more effective effect on the mechanical properties of fluting papers compared to PCC.Originality/valueThese results suggest that coating of fluting papers has a positive effect on mechanical properties and the use of GCC as a pigment is more effective than PCC.

Methoxol's Impact on the Hepatic Microsomal Mixed Function Oxidase System Induced by Phenobarbital and Pyrene in Rats

Insecticides like methomyl (Lannate) are commonly used to keep pests at bay in vineyards. The mixed-function oxidase system undergoes dramatic change after being exposed to methomyl. This research set out to determine if methomyl inhibits phenobarbital-induced CYP 2B1, 2B2, and 3A, as well as benzo[a]pyrene-induced CYP 2D6 (CYP 1A1). There were a total of eight groups, each including six adult male rats. Calcium precipitation was used to separate the microsomes. Extinction coefficients were used to quantify the amounts of the electron transport components cytochrome P450, cytochrome B5, and cytochrome c-reductase. Drug metabolizing enzymes were tested for their efficacy. Mixed function oxidase was significantly elevated in rats when exposed to inducers like phenobarbital and benzo[a]pyrene. Inducer-(Phenobarbital, benzop [a] pyrene) pretreated rats given 4mg/kg methomyl had significantly lower levels of electron transport components and drug-metabolizing enzyme activity compared to inducer treatment alone. The enzymes involved in mixed-function oxidation were likewise affected by methomyl's influence on the induction of phenobarbital. The levels of electron transport components and drug metabolizing enzymes in methomyl-pretreated rats treated with benzo[a]pyrene were much lower than in rats treated with benzo[a]pyrene alone. These findings show that phenobarbital and benzo[a]pyrene increased cytochrome P450 isoform susceptibility to methomyl (CYP 2B1, 2B2, 3A; and CYP 1A1) and the induction pattern of some inducers with respect to CYP 450 isoforms are both modified by methomyl

Microbial mediated synthesis of lanthanum-modified seed crystals and their application for removal of phosphorus and calcium from domestic wastewater

In this study, lanthanum was introduced into the microbially induced calcium precipitation by bio-mediated action of Pseudomonas aeruginosa to synthesize modified seed crystals for the removal of calcium and phosphorus from domestic wastewater. The calcium and phosphorus removal efficiency reached to 60% and 94%, respectively, under the condition of 30 times repeated use. Meanwhile, chemisorption and intra-particle diffusion were identified as the main rate-limiting steps and electrostatic interaction, ligand exchange, and induced crystallization as the primary phosphorus removal mechanisms. This modified seed crystal exhibited better phosphorus removal performance in simulated reactors with different water quality parameters (phosphorus removal efficiency of 95%). This safe, stable, and efficient bio-material has a promising future in the current socio-economic condition of energy shortage and environmental pollution.

BIOFILM FORMATION AND CALCIUM PRECIPITATION IN BACILLUS LICHENIFORMIS AND ALCALIGENES FAECALIS FOR SOIL IMPROVEMEN

&#x0D; &#x0D; &#x0D; Calcium precipitation and biofilm formation in halophilic bacteria were investigated in the current study. The strain SMK (Bacillus licheniformis) was isolated from plant rhizosphere and and AQ-1 (Alcaligenes faecalis) from marble crushing soil in Lahore. Bacterial growth, biofilm formation and CaCO3 precipitation of both strains was determined under varying stress (pH, temperature, agitation and salinity). Soil aggregation was investigated under salt stress (NaCl and MgSO4). Results showed that pH 8.0, temperature 42°C, 1.5 M salt (NaCl and MgSO4) stress without agitation was favorable for biofilm formation. Both strains were able to precipitate CaCO3 in media specially at margins of colonies in AQ-1. Effervescence of crystals with addition of concentrated HCl showed confirmatory results. Stereomicroscopic analysis of aggregates in inoculated soil and sand showed precipitation under salt stress. SMK (Bacillus licheniformis) showed high aggregation in soil. From the results, it was concluded that these indigenous strains have potential for sustainable agriculture by improving disturbed soil.&#x0D; &#x0D; &#x0D;

Preparation of CaCO3/Al(OH)3 Composites via Heterogeneous Nucleation.

As one of the most widely used inorganic fine powder fillers, calcium carbonate is cheap. However, considering its poor light transmittance, it is not suitable to be added to resin matrix composites that require high light transmittance. Aluminum hydroxide has good light transmission and flame retardancy, but it is more expensive than calcium carbonate. CaCO3/Al(OH)3 composites with a core-shell structure that showed a trend toward the performance of aluminum hydroxide not only improved the surface properties of CaCO3, but also increased the added value of CaCO3. In the present paper, CaCO3/Al(OH)3 composites were successfully prepared in sodium aluminate solution via heterogeneous nucleation. Four types of calcium sources, including calcite-type precipitated calcium carbonate, vaterite-type precipitated calcium carbonate, ground calcium carbonate with two different particle sizes as the precursors and supersaturated sodium aluminate solution as the substrate, have been deeply investigated in terms of their influence on the preparation of CaCO3/Al(OH)3 composites. Results showed that the calcium carbonate precursor greatly affected the formation of CaCO3/Al(OH)3 composites. Both the precipitated calcium carbonate and the small particle ground calcium carbonate are likely to undergo anti-causticization and a complexation reaction with it to generate 3CaO·Al2O3·6H2O and 3CaO·Al2O3·CaCO3·11H2O, which go against the coating of calcium carbonate with aluminum hydroxide. Within the experimental range, the use of ground calcium carbonate with a particle size of 400-500 mesh is more suitable as a precursor for the preparation of core-shell CaCO3/Al(OH)3 composites.

Calcium carbonate precipitation by Paenibacillus fonticola and Sporosarcina luteola for its potential application in bio concrete

Concrete is one of the most widely used construction materials in various infrastructures. However, despite of several advantages, it has a high tendency to form cracks due to climatic effects and parameters like temperature fluctuations, exposure to corrosive and toxic chemicals, harmful gases, natural disasters, etc. These factors reduce the longevity of concrete which adds up to the cost of the maintenance and repair. Existing treatments have various limitations like weak resistance to weather, moisture sensitivity, heat and low sustainability. Hence, there is a need for alternative and sustainable treatment technologies. One such technology is bio concrete formation by the process of Microbially Induced Calcium Carbonate Precipitation (MICP). In nature, MICP occurs through different processes like urea hydrolysis, photosynthesis, denitrification, etc. Bio concrete is a combination of concrete and bacteria possessing the ability to precipitate calcium carbonate (CaCO3 ) that aids in sealing the cracks that appear in it. This self-healing property of bio concrete can be a potentially sustainable and economic technology. This study was aimed to enrich, isolate and screen bacteria capable of precipitating CaCO3 and their use in production of bio concrete. Total 11 samples predominantly containing speleothems and related materials were collected from different locations in Satara and Nashik districts of Maharashtra, India. The samples were further processed independently in B4 and Calcium Carbonate Precipitation (CCP) media for enrichment. A total of 94 isolates were obtained from the enriched samples. Subsequent screening and characterization of these isolates revealed that Paenibacillus fonticola and Sporosarcina luteola can substantially precipitate calcium carbonate.The Fourier Transform Infrared (FTIR) spectra, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) microanalysis of the CaCO3 precipitates formed by these bacteria renders both Paenibacillus fonticola and Sporosarcina luteola the potential candidature for bioconcrete formation.

Synthesis of precipitated calcium carbonate with the addition of aloe vera extract under different reaction temperatures

Synthesis of precipitated calcium carbonate with the addition of aloe vera extract under different reaction temperatures