Calcium Carbonate Suspensions Research Articles

Tribology test design for friction measurements with application to oral medicines

In recent years tribology tests have been used to measure friction properties of oral consumables such as semi-solid foods and medicines. The tests aim to simulate thin-film mastication conditions and are intended to correlate with mouth feel or food texture properties. In this paper a new approach is proposed to better simulate shear conditions, fluid supply and friction data capture associated with mastication and swallowing. Two primary changes are suggested: these are the reduction of the inlet influence on lubricant film properties and the ability to measure transient and time-dependent friction. The new test was used to measure friction for a range of oral medicines including a viscous solution (cough syrup) and particulate suspensions (paediatric, calcium carbonate) in combination with an artificial saliva (mucin solution), The tongue-palate was replicated by a PCX glass lens loaded and reciprocating against a textured silicone surface. A short stroke length, comparable to the Hertzian diameter of the contact, was used so the contact operated in a partially replenished lubrication condition. This ensured the film in the contact region has the same composition as the bulk fluid. Friction was measured continuously during reciprocation for up to 5 cycles (comparable to mastication time) and data was sampled at 100 Hz to capture transient friction. Tests were run with and without a mucin layer present. The results showed that tests performed after 20 min adsorption of an artificial saliva solution reduced the friction coefficient from μ = 1 to μ = 0.2–0.3. Tests with the paracetamol suspensions, which contain hard particles, recorded transient friction spikes which were not recorded for the softer calcium carbonate suspensions. Key conclusions for the design of pertinent simulation tests are that the film properties in the oral cavity are not determined by the inlet as for classical lubrication. The (bulk) oral sample is captured in the tongue-palate contact and not continually replenished. When sheared it will exhibit time (transient, longer-term) and speed dependent friction responses which contribute to sensory and texture perception.

Targeting oxidation sites on boreal acid sulfate soil macropore surfaces mitigates acid and metal release to recipient water streams

When reduced sulfidic parent sediments are oxidized, they become acid sulfate soils and discharge metal laden acidic solutions that can damage the environment, infrastructure, and human health. Consequently, methods to mitigate the effect of acid sulfate soils are a priority in affected areas. In this study, acid sulfate soil core samples, consisting of a natural network of preferential-flow soil macropores with defined macropore surfaces and inner cores of denser clay, were characterized and subjected to treatments with calcium carbonate and peat suspensions, or combinations thereof. The effects on the geochemistry and microbial communities were examined on both macropore surfaces and in inner cores. Although transport of treatment substances into the inner cores was demonstrated, no substantial effects were found on the geochemistry and microbial community that consisted of bacterial taxa commonly identified in acid mine drainage. In contrast, positive treatment effects were clearly detected on macropore surfaces and the most promising mitigation effects were detected for treatments combining calcium carbonate and peat suspensions. These treatments increased the pH of the macropore surfaces, added an electron donor in the form of peat, and significantly decreased the relative abundance of acidophilic bacterial populations while shifting the microbial community towards species typically growing at circumneutral pH values. These new environmental conditions were favorable for iron reduction that resulted in a positive effect on permeate quality. The study presents novel data regarding the important differences between acid sulfate soil macropore surfaces and inner cores, as well as their diverse biogeochemical characteristics. It further establishes that the major oxidation-reduction processes occur at the macropore surfaces, and that the combination treatment was the most effective at mitigating the negative environmental effects.

Shear thickening in presence of adhesive contact forces: The singularity of cornstarch

Hypothesis: A number of dense particle suspensions experience a dramatic increase in viscosity with the shear stress, up to a solid-like response. This shear-thickening process is understood as a transition under flow of the nature of the contacts – from lubricated to frictional – between initially repellent particles. Most systems are now assumed to fit in with this scenario, which is questionable.Experiment: Using an in-house pressure sensor array, we provide a spatio-temporal map of the normal stresses in the flows of two shear-thickening fluids: a stabilized calcium carbonate suspension, known to fit in with the standard scenario, and a cornstarch suspension, which spectacular thickening behavior remains poorly understood.Findings: We evidence in cornstarch a unique, stable heterogeneous structure, which moves in the velocity direction and does not appear in calcium carbonate. Its nature changes from a stress wave to a rolling solid jammed aggregate at high solid fraction and small gap width. The modeling of these heterogenities points to an adhesive force between cornstarch particles at high stress, also evidenced in microscopic measurements. Cornstarch being also attractive at low stress, it stands out of the classical shear-thickening frame, and might be part of a larger family of adhesive and attractive shear-thickening fluids.

Protection of Historical Mortars through Treatment with Suspensions of Nanoparticles

Mortars, which are very important elements for the integrity of historic monuments, consist mainly of calcium carbonate and silicates in different proportions. Chemical dissolution due to exposure in open air is very important for the degradation of mortars. Inorganic nanoparticles with chemical and crystallographic affinity with mortar components are expected to be effective structure stabilizers and agents offering resistance to chemical dissolution. In the present work, we have developed and applied suspensions of amorphous calcium carbonate (ACC), silicon oxide (am-SiO2) and composite nanoparticles by the precipitation of ACC on am-SiO2 and vice versa. The application of suspensions of the synthesized nanoparticles on three different historical mortars of Roman times (1st century AD), retarded their dissolution rate in solutions undersaturated with respect to calcite, in acid pH (6.50, 25 °C). All three test historic mortars, treated with suspensions of the nanoparticles prepared, showed high resistance towards dissolution at pH 6.50. The ability of the nanoparticles’ suspension to consolidate the damaged mortar was the key factor in deciding the corresponding effectiveness in the retardation of the rate of dissolution. The combination of ACC with am-SiO2 nanoparticles showed high efficiency for protection from the dissolution of calcite rich mortars.

Novel Colloidal Dispersing Concept in Aqueous Media for Preparation by Wet-Jet Milling Dispersing Method

Dispersing particles in a liquid phase is significant for producing various functional nano/bio applications. The wet-jet milling method has been gaining attention as an attractive dispersing method in the preparation of soft material suspensions. This is because the main driving force of dispersion by the wet-jet milling method is the shear force, which is weaker than that it is in the ultrasonication dispersing method. In the wet-jet milling method, the pressure of the narrow channel which the liquid is passes through and the number of passes are used as the control parameters for dispersing the particles. However, the values of the pressure depend on the size (diameter and length) of the narrow channel, thus, it is not a commonly used dispersing parameter in dispersing by wet-jet milling to set the dispersing condition by various wet-jet milling instruments. In addition, wet-jet milling users must optimize the dispersing conditions such as the pressure and number of passes in the narrow channel, therefore, a simple prediction/optimization method of the dispersing size by the wet-jet milling method is desired. In this study, we established a novel colloidal dispersing concept, the dispersing energy input based on a calorimetric idea, for particle suspension preparation using the wet-jet milling method. The dispersing energy input by wet-jet milling was quantitatively calculated under various conditions during the dispersing by wet-jet milling, and then, the dispersing size of the particles was easily predicted/optimized. We demonstrated the usability of the concept by preparing aqueous suspensions of calcium carbonate (CaCO3) particles with various surfactants using the wet-jet milling method. Based on the established concept, in a case study on dispersing CaCO3, we found that changes in the micelle sizes of the surfactants played a role in wet-jet milling. The novel idea of the representation of energy input makes it possible to estimate the appropriate condition of the dispersing process by wet-jet milling to control the size of particles.

Jet instability of suspensions of different shaped particles exhibiting discontinuous shear thickening

This work is devoted to the detailed study of jet instability occurring in concentrated aqueous mixtures of calcium carbonate (CC) isotropic-shaped particles and rigid polyamide (PA) fibers. These mixtures exhibit very sharp discontinuous shear thickening (DST). The jets were subjected to a free fall under gravitational stretching at a constant flow rate. In the absence of PA fibers, we observed relatively strong lateral oscillations occurring for jet lengths L≳6cm and accompanied by small periodic undulations of the jet diameter. Two-dimensional Direct Fourier Transform analysis reveals approximately linear dispersion relations for propagation of lateral oscillations and diameter undulations with similar wave speeds ∼1m/s. This instability is ascribed to complex rheological behavior in an extensional flow above the DST transition. Theoretical modeling reveals abrupt jumps of the tensile stress along the jet likely leading to fluctuation of longitudinal and transverse velocity fields within the jet perceived through jet diameter and centerline undulations. The addition of PA fibers to CC suspension damps lateral oscillations but favors ruptures along the jet. This is tentatively explained by the interplay between growing lower and decreasing upper DST threshold stresses with increasing fiber volume fraction φf along with the thinning of the jet diameter down to the size of fiber flocs. Quantitatively, the stabilizing effect of PA fibers is manifested through an abrupt decrease in the lateral drift amplitude at φf≳0.75vol%.

Influence of polymers on the grinding and rheology of ultrafine Egyptian calcium carbonate suspension

Influence of polymers on the grinding and rheology of ultrafine Egyptian calcium carbonate suspension

Calcium Carbonate of Blood Cockle (Anadara granosa) Shells induced VEGF-A Expression in Dentin Pulp Complex An In Vivo Study

Introduction: Mild or moderate-intensity injury will respond with a brief inflammatory response followed by reactionary dentinogenesis. Calcium hydroxide has been considered the gold standard for pulp capping materials for decades to stimulate the formation of tertiary dentin. Blood clamshells (Anadara granosa) contained a high content of calcium carbonate (CaCO3) in the blood clamshells. It is a source of calcium and it has good biocompatibility to be used as a bone repair material. This study is aimed to reveal the expression VEGF-A in odontoblast pulp cells on days 1, 3, and 7 after administration of blood clam shells derived calcium carbonate in dentin pulp complex. Methods: Thirty Wistar rats (Rattus norvegicus) were divided into 6 groups consist of 5 random samples each. The experimental group’s cavity was prepared on the occlusal side of the right upper molar, and they were treated with blood clamshell calcium carbonate suspension and sealed with RMGIC. For decalcification, the solution was replaced with ethylene-diamine tetra acetic acid (EDTA) after 24 hours and was refreshed every day. Anti-VEGF-A monoclonal antibodies were used for HE and immunohistochemical staining. Result: In this study, the results were obtained consecutively on the 1st, 3rd, and 7th day with p> 0.05 for VEGF-A in all groups. Conclusion: The application of calcium carbonate is expected to be an innovative treatment in opening up new pathways for the regenerative dentin process through upregulation of VEGF-A

Effect of Neutralization of the Grinding Aid in the Production of Fine CaCO3 Slurries

AbstractThe most commonly used additive in wet grinding of calcium carbonate is a low‐polydispersity‐index sodium polyacrylate with an optimized molecular weight. A similar polyacrylate was tested under different Na‐Ca and Na‐Mg neutralization states. Results of the grinding experiments revealed logarithmic relations between the weight percentage of fine particles and specific energy consumption (SEC). Power‐law functions were established between the median size and SEC. A steady increase of SEC occurred with r = M2+/CO2−. This energy increment with r is greater when the grinding aid is a Na‐Ca‐neutralized polyacrylate. Moreover, the quantities of non‐adsorbed dispersant in the ground calcium carbonate suspensions after grinding decline with r and are not dependent on the nature of M2+.

A resource efficient and environmentally safe charge structure for mining in an open-pit

Purpose. The purpose is to reduce mineral losses during the explosive destruction of rocks and environmental pollution by harmful gases and fine particulate matter. Methods. To achieve the objectives of the study, methods of physicochemical analysis and mechanics of continuous media have been used. The method of physico-chemical analysis has been used to determine the quantitative and qualitative characteristics of the composition of the well stemming depending on the parameters of the well, the type of explosive, the amount and type of harmful gases formed during the explosion. Methods of solid medium mechanics have been used to establish the patterns of pressure waves during an explosion depending on the characteristics of the gap filler between the charge and the well wall. To solve the problem of the behavior of a two-layer medium during the loading of a cylindrical cavity by a nonstationary load, a numerical method based on the finite-difference McCormack predictor-corrector scheme has been used. Findings. A resource-saving and environmentally friendly charge structure for rock mining by explosion was developed. The design of the charge involves the formation of a gap between the charge and the wall of the borehole, and filling it with a suspension of calcium hydroxide or a suspension of calcium carbonate. Originality. SThe dependences of the volume of harmful gases (NO2, CO2, CO) formed during the explosive destruction of rocks and the magnitude of the pressure peak in the area close to the charge on the chemical composition of the filler of the radial gap between the charge and the well wall have been set. Practical implications. Developed charge design allows to neutralize the harmful gases formed during the explosion, to reduce the pressure peak in the area of the rock massif close to the charge, and can be widely used in non-metallic quarries that extract minerals for the production of crushed stone.

The Protection of Building Materials of Historical Monuments with Nanoparticle Suspensions

Marble and limestone have been extensively used as building materials in historical monuments. Environmental, physical, chemical and biological factors contribute to stone deterioration. The rehabilitation of stone damage and the delay of further deterioration is of utmost importance. Inorganic nanoparticles having chemical and crystallographic affinity with building materials is very important for the formation of protective coatings or overlayers. In the present work, we have tested the possibility of treating calcitic materials with suspensions of amorphous calcium carbonate (am-CaCO3, ACC) and amorphous silica (AmSiO2). Pentelic marble (PM) was selected as the test material to validate the efficiency of the nanoparticle suspension treatment towards dissolution in undersaturated solutions and slightly acidic pH (6.50). Suspensions of ACC and AnSiO2 nanoparticles were prepared by spontaneous precipitation from supersaturated solutions and by tetraethyl orthosilicate (TEOS) hydrolysis, respectively. The suspensions were quite stable (nine days for ACC and months for AmSiO2). ACC and Am SiO2 particles were deposited on the surface of powdered PM. The rates of dissolution of PM were measured in solutions undersaturated with respect to calcite at a constant pH of 6.50. For specimens treated with ACC and AmSiO2 suspensions, the measured dissolution rates were significantly lower. The extent of the rate of dissolution reduction was higher for AmSiO2 particles on PM. Moreover, application of the nanoparticles on the substrate during their precipitation was most efficient method.

Effect of polyacrylic acid molar mass as a surface modifier on rheological properties of calcium carbonate suspensions

Effect of polyacrylic acid molar mass as a surface modifier on rheological properties of calcium carbonate suspensions

Influence of particle shape and sample preparation on shear thickening behavior of precipitated calcium carbonate suspensions

To more closely bridge the technological advent of shear thickening fluids with material applications, a well-defined sample preparation protocol is needed. In this work, preparation conditions have been studied for suspensions of precipitated calcium carbonate (PCC) particles by means of a 2k Factorial Experimental Design (DOE), with three center points, and as a function of PCC particle shape. Shear thickening maximum viscosity was the response variable and the corresponding analyzed factors were: particle concentration, stirring time, stirring speed and sonication time. Samples with rosette PCC particles exhibited a stronger shear thickening behavior in view of stronger frictional interactions and they also shear thicken at lower shear rates compared to samples with acicular PCC particles. In the case of acicular PCC particles, the shear thickening fluid that provided the highest maximum viscosity ηm was obtained with higher particle concentration, lower stirring speed and shorter sonication time, as acicular PCC particles align more easily in the flow direction. In the case of rosette PCC particles, ηm was achieved with higher particle concentration, longer stirring time and shorter sonication time. Finding optimal sample preparation conditions and particle shapes that take the most advantage of shear thickening behavior is very important for final applications.

Evaluation of Calcium Binding Capacity of Chelating Agents in Calcium Carbonate Suspension and Effects on Calcium Distribution of Calcium Chelating Agents

In this study, the binding capacity of calcium ions of sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), trisodium citrate (TSC), and potassium oxalate (PO) were evaluated, and the calcium distribution in the presence of STPP and TSPP in CaCl2 solutions (50 mmol L−1) were investigated. Under conditions simulating industrial toothpaste, the concentration of fluoride in calcium carbonate suspensions (30 g/50 g) was measured by ion chromatography to investigate the effects of chelating agents on calcium ions. Among all the chelating agents, STPP and TSPP have the highest retention rate of fluoride, indicating better calcium binding capacity. Preliminary studies were carried out in CaCl2 solutions to investigate the influence of concentration and pH on the chelating performance of STPP and TSPP. The distribution of free calcium, chelated calcium, and precipitated calcium in CaCl2 solution in the presence of STPP and TSPP were investigated to reveal two different calcium-chelation mechanisms and laws for STPP and TSPP. This work has a positive guiding significance for the stabilisation of calcium and fluoride in toothpaste formula.

Encapsulated calcium carbonate suspensions: A drug delivery vehicle sensitive to ultrasound disruption

A calcium carbonate suspension, encapsulated within particles of calcium alginate hydrogel, is proposed as a drug delivery device susceptible to ultrasound disruption. Spheres approximately 1mm in diameter were prepared by the coaxial airflow method from mixtures of 1% sodium alginate (m/v) and each of 50%, 75% and 100% calcium carbonate (m/v) in distilled water. This product was subjected to cycles of 85 Watt ultrasound in 1 second on/off bursts via a lab sonication system until fully disintegrated, a process requiring between 8 and 20 minutes depending upon initial calcium carbonate concentrations. The spheres subjected to vortex did not demonstrate any signs of mechanical degeneration after 30 minutes. Before use as a model implant, further work is required to develop a method of drying the particles to make them impermeable to drug diffusion before the time of their disruption with ultrasound.

An Electrochemical Simulation and Treatment Study for the Carbonate and Chloride Based Corrosion of Heritage Silver–Copper Alloys

ABSTRACT This study aimed to investigate the corrosion of a group of historic silver–copper alloy coins and their conservation treatment on defined parameters by potentiostatic methods. Basic copper carbonates and silver chloride were identified on the surface of the coins by a combination of scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction (XRD) analyses. The carbonate and chloride-based corrosion mechanisms were synthetically simulated on modern silver–copper alloy samples (Ag72/Cu28) by anodic polarisation measured by linear sweep voltammetry (LSV) in sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) solutions. Cathodic polarisation curves, measured by LSV, were used to identify the working conditions to reduce the corrosion products on the corroded samples and to treat the actual coins. The reduction process was then monitored by chronoamperometry. Following the potentiostatic reduction process, the metallic copper spots on the treated samples were wiped with cotton swabs moistened with a diluted solution of silver nitrate (AgNO3) to obtain a silvery appearance, and the treatment was completed by a gentle rubbing of the redeposited silver with a cotton swab moistened with a calcium carbonate (CaCO3) suspension followed by rinsing and drying. The corrosion products identified on the synthetically corroded samples indicated that the deterioration mechanisms were dominated by selective attack on the copper-rich phases of the (Ag72/Cu28) alloy, which is consistent with an internal galvanic corrosion phenomenon. The potentiostatic methods showed excellent effectiveness in determining treatment parameters and monitoring the reduction process of the corrosion products on the coins, which helped to preserve surface details in the cleaning process and to prevent over-treatment.

Fish-hook effect in granulometric efficiency curves of hydrocyclones: A misuse of laser diffraction particle size analysers

Numerous studies have reported the so-called fish-hook effect on granulometric efficiency curves of hydrocyclones. This effect has been reported since laser diffraction particle size analysers started to be used. In this work a 15-mm-diameter Bradley hydrocyclone has been used to separate a suspension of calcium carbonate 1,2% in volume to analyse the fish-hook effect. The Malvern Mastersizer 2000 particle size analyser has been used and both Fraunhofer's and Mie's light scattering theories have been assessed. It has been concluded that the fish-hook effect is a result of using Fraunhofer's correlation to determine the size of particles which are knowingly out of its range of validity (diameters smaller than 50 μm) or using Mie's correlation with inappropriate particles' imaginary refraction indexes (IRI). A method to determine the appropriate IRI in the Malvern Mastersizer 2000 is also presented. The fish-hook effect is therefore a misuse of laser diffraction particle size analysers.

The Color Formation Mechanism of the Blue Karst Lakes in Jiuzhaigou Nature Reserve, Sichuan, China

The karst lakes in Jiuzhaigou Nature Reserve are an integral part of the karst lake landscape, yet research on the formation mechanism for the color of the blue-green lakes in Jiuzhaigou is insufficient. With the help of hyperspectral instruments, coupled with hydro-chemical analysis, this paper elaborates on the unique color characteristics of the Jiuzhaigou karst lakes, delves into the color formation mechanism of the lakes, establishes a regression equation for the color of the lakes as well as the water quality parameters, and sheds light upon the causes for the color distinction between the karst lakes in Jiuzhaigou and the plateau freshwater lakes. The experiment shows that the Jiuzhaigou karst lakes are primarily blue and green, while the proportion of short-wavelength light in the normalized water-leaving radiance and the total incident irradiance of lake water is higher. Based on the redundancy analysis and the correlation analysis, travertine deposition is the core link in the color formation of the blue karst lakes in Jiuzhaigou, while the selective reflection and scattering of the suspended calcium carbonate particulate matters towards visible light represents the optical foundation for the formation. In addition, physical factors such as depth and transparency, changes to the water quality parameters that affect the travertine deposition rate, and the eutrophication process will all exert significant influence over the formation. By building on water-leaving radiance, this paper quantifies the lake color with the tristimulus values (R, G, B) via colorimetrical methods, which features solid goodness of fit with the linear regression equation established based on the water quality parameters. The principal component analysis and colorimetrical analysis show that the color of the karst lakes in Jiuzhaigou varies substantially from that of the plateau freshwater lakes, which mainly results from the difference in the water quality. Research conducted in this paper on the color formation mechanism of the distinct blue karst lakes in Jiuzhaigou illuminates the formation and maintenance mechanism of the plateau karst lakes, which is conducive to better understanding towards the relationship between the water quality and colors of the karst lakes, and provides scientific proof for the establishment of the water quality assessment indicator system based on the colors of the karst lakes.

Inhibitory substances contained in calcium carbonate wettable powder on the oviposition of the peach fruit moth, Carposina sasakii.

Spraying a calcium carbonate suspension “White Coat” on the fruit of apples significantly suppresses the oviposition of the peach fruit moth, Carposina sasakii. In gas chromatography (GC) with an electroantennographic detector analysis, adult female antennae showed responses to three compounds that were identified as 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) and its two mono-hydrolyzed analogs, texanols (1- and 3-isobutyrates), all added as a plasticizer to the agents. An oviposition-choice test using adult moths revealed that TXIB has clear deterrent properties when applied to young apple fruits. Video recording analysis showed that female moths spent longer on self-grooming and searching around TXIB-treated fruits. In the same assay, pure calcium carbonate treatment prevented the moths from climbing up or landing on the fruits, while such was not the case with White Coat-treated fruits. TXIB, an adjuvant aimed to provide rain/wind resistance, weakened the slipperiness of the calcium carbonate coating but, coincidentally, maintained the oviposition inhibitory activity of the White Coat by its deterrent odorant.

Structurally controlled synthesis of calcium sulphate dihydrate from industrial wastes of spent sulphuric acid and limestone

Abstract All types of gypsum binders are obtained mainly from the natural gypsum and man-made products. As a sustainable analogue of these materials, synthetic gypsum as a product of spent dilute sulphuric acid and calcium carbonate was proposed. We investigated the effect of various technological parameters on the production of calcium sulphate dihydrate particles with a given morphology. The sizes of calcium sulphate dihydrate crystals with optimal values of technological parameters and exposure time up to 4.5 h increased from 18 to 28 μ m and combined into agglomerates with sizes that mostly lie in the range from 200 to 600 μ m. Synthesized calcium sulphate crystals acquiring a prismatic shape instead of a needle shape which simplified and accelerated the industrial filtration process. Our study shows that a promising sustainable and cheap source of gypsum-containing raw materials is synthetic gypsum, obtained by reacting a suspension of calcium carbonate and spent sulphuric acid.