Calcium carbonate 680mg / Magnesium carbonate heavy 80mg chewable tablets

Amorphous calcium carbonate (ACC) is known as a precursor to crystalline calcium carbonate polymorphs (CaCO3) in various natural and synthetic systems. While ACC has been shown to form by heterogeneous nucleation in biological systems, it is less obvious whether it plays any role in inorganic settings where carbonate minerals grow on pre-existing surfaces. Tight assemblies of calcium carbonate (CaCO3) phases and clay minerals occur in rock-forming quantities in marlstones, are abundant in Earth’s critical zone, in the sediments of aqueous environments, and in the atmosphere as aerosol particles. Previous studies suggested that the co-occurrence of clay and carbonate minerals (especially smectite and calcite) results from the heterogeneous nucleation of CaCO3 on the surface of smectite. In order to understand the role of ACC in the heterogeneous nucleation of carbonate minerals and the effects of common silicate mineral surfaces on the stability of ACC, we synthesized ACC both in the presence and absence of smectite, kaolinite, and quartz, monitored the pH of the solution during the experiments, and studied the precipitated phases with various transmission electron microscopy techniques. Since Mg2+ and (PO43−) ions are known to prolong the lifetime of ACC and are important components in natural aqueous environments, we tested their effects on ACC transformation in both homogeneous and heterogeneous systems. In all studied systems ACC was the first condensed carbonate phase. The presence of smectite in the solution reduced the lifetime of ACC and led to the rapid formation of calcite. We suggest that the main factor driving the transition was the enhanced growth of ACC particles on the surfaces of smectite flakes. On the other hand, the presence of kaolinite and quartz slightly increased ACC stability; ACC typically rimmed the silicate particles and transformed slower than separated, individual ACC particles. When Mg2+ was present in the solution, ACC stability significantly increased and led to the formation of aragonite instead of calcite in both homogeneous and heterogeneous systems. The presence of (PO4)3− ions caused only a minor delay in ACC transformation and the crystalline product was calcite, irrespective of the presence of silicate minerals. These observations suggest that smectite minerals play important roles in the formation of carbonate minerals by providing a suitable surface for the rapid growth and coalescence of ACC particles, leading to larger particle sizes which, in turn, result in the conversion of ACC into calcite.

Abstract licence: CC BY-NC-ND

This study investigates the effects of inorganic flame retardants, zinc borate, and magnesium hydroxide, on the thermal, morphological, flame retardancy, and mechanical properties of polypropylene (PP)/calcium carbonate composites for potential construction industry applications. Polypropylene/calcium carbonate (50 wt.%) composites containing 5 and 10 wt.% flame retardants were prepared using a batch mixer, followed by compression moulding. The results demonstrated enhanced thermal stability, with the highest char residue reaching 47.2% for polypropylene/calcium carbonate/zinc borate (10 wt.%)/magnesium hydroxide (10 wt.%) composite, a notably strong outcome. Additionally, the composite exhibited an elevated limited oxygen index (LOI) of 29.4%, indicating a synergistic effect between zinc borate and magnesium hydroxide. The proposed flame retardancy mechanism suggests that the flammability performance is driven by the interaction between the flame retardants within the polypropylene/calcium carbonate matrix. Magnesium hydroxide contributes to smoke suppression by releasing water, while zinc borate forms a protective glassy foam that covers the burning surface, promoting char formation and acting as a physical barrier to heat transmission and fire spread. Scanning electron microscopy confirmed good dispersion of the additives alongside calcium carbonate within the polymer matrix. Despite the addition of up to 10 wt.% flame retardants, the composites maintained high-notched impact strength.

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) shift from Ca (-6.28 ± 0.05) to Mg (-4.54 ± 0.16) ACMC endmember, can be explained by the increasing water content and changes in short-range order, as Ca is substituted by Mg in the ACMC structure. The results of this study shed light on the factors controlling ACMC solubility and its temporal stability in aqueous solutions.

Abstract licence: CC BY-NC

• Biomimetic deposited calcium carbonate coating was treated by sodium stearate. • Corrosion current density dropped 3 orders after treatment, with improved resistance. • Cell viability increased by 20% after treatment, showing a better biocompatibility. Magnesium alloy is a promising biodegradable metal material for hard tissue engineering. However, its high corrosion rate limits its application. In our previous study, we biomimetically deposited a calcium carbonate coating on the surface of magnesium alloy using siloxane induction. This calcium carbonate coating demonstrated excellent in vitro biocompatibility and provided partial protection for the magnesium alloy substrate. In this study, we further enhanced the corrosion resistance of the calcium carbonate coating by treating it with stearic acid and its derivative, sodium stearate. Electrochemical corrosion tests revealed that the sodium stearate-treated calcium carbonate coating reduced the corrosion rate by two orders of magnitude. Additionally, in vitro biocompatibility assessments showed that while the biocompatibility of the sodium stearate-treated coating was slightly reduced, it remained acceptable compared to the magnesium substrate. This study builds on our previous work and offers a promising reinforcement strategy for degradable magnesium alloys in medical applications.

Abstract licence: CC BY-NC-ND

The discovery of cyanobacteria fossils in microbialite prompts the investigation of carbonate biomineralization using cyanobacteria. However, the impact of coexisting magnesium and iron in microbialite on carbonate biomineralization has been overlooked. Here, Synechocystis sp. PCC 6803 was used to induce calcium carbonate in the presence of coexisting magnesium and ferric ions. The findings demonstrate that cell concentration, pH, carbonic anhydrase activity, and carbonate and bicarbonate concentrations decreased with increasing concentrations of magnesium and calcium ions. Ferric ions yielded a contrasting effect. The levels of deoxyribonucleic acid, protein, polysaccharides, and humic substances in extracellular polymeric substances increased in the presence of separated or coexisting calcium, magnesium, and ferric ions. Magnesium ions inhibited calcium ion precipitation, whereas ferric ions exhibited the opposite effect. Protein secondary structures became more abundant and O-C=O and N-C=O contents increased with increasing ion concentrations by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. Scanning electron microscopy revealed that ferric ions lead to rougher surfaces and incomplete rhombohedral structures of calcite, whereas magnesium ions promoted greater diversity in morphology. Magnesium ions enhanced the incorporation of ferric ions. This work aims to further understand the effect of magnesium and ferric ions on calcium carbonate biomineralization induced by cyanobacteria.

Abstract licence: CC BY

Maintaining the concentration of magnesium in potable water above minimum levels has been suggested to have public health benefits. A twelve-month trial of attempting this goal by partial replacement of limestone with dolomite in eight out of twenty-six post-treatment contactors at the Ras al Khair seawater desalination plant, the largest such plant in Saudi Arabia with a daily production of over 1,000,000 m3 of desalinated water. Over the course of the trial increases in Mg concentration in the range 1 to 2 ppm were achieved without necessitating increases in carbon dioxide utilization or any reduction in production volume. Alkalinity, calcium, and total dissolved solids remained within acceptable parameters. Calculated supersaturation values suggest strongly that it will not be possible to increase concentrations significantly further at the pH and temperature conditions of the study. Thus, while use of dolomite to this extent is a very low-cost strategy for magnesium supplementation, its scope of application without additional carbon dioxide consumption and capital investment is limited. The ratio of magnesium to chloride in SWRO product water was estimated in the course of the study and was found to be approximately half of the ratio in Standard Seawater, suggesting that under operational conditions (giving 1500 mg/L from first pass reverse osmosis) rejection of magnesium was significantly greater than rejection of sodium.

Abstract licence: CC BY