Addition Of CaCO3 Research Articles

Effect of CaCO3, SrCO3 and BaCO3 additions on the microstructure and electrical characteristics of SnO2-based varistor ceramics

The ceramic varistors SnO2–Co3O4–Nb2O5–Cr2O3 with the addition of CaCO3, SrCO3 or BaCO3 were sintered at temperatures 1250 and 1350°C, then their structures and electrical properties were studied. In all samples, the SnO2 cassiterite phase with a rutile-type structure and the Co2SnO4 phase with a spinel-type structure were observed. All materials exhibited a highly nonlinear dependence of the current density on the electric field with the nonlinearity coefficient 24–50. When alkaline earth metal carbonates were added, the grain size of all samples decreased and the electric field E1 increased. The addition of CaCO3 lead to the decrease of the low-field electrical conductivity of varistors. The lowest low-field conductivities 4·10-13 and 6·10-13 Ω-1 cm-1 were found in the samples with CaCO3 addition baked at 1250 and 1350°C, respectively. The observed effect is due to the increase of the potential barrier height at the SnO2 grain boundaries by 7 and 13%, respectively, and the decrease of the grain size by 26 and 28% compared to SnO2-based varistor ceramics without CaCO3 addition.

Achieving high-strength, high-porosity and relatively low-shrinkage in extrusion-based 3D printed ZrO2 ceramics by adjusting CaCO3 addition and sintering temperature

High-strength, high-porosity and relatively low-shrinkage ZrO2 ceramics were successfully fabricated by material extrusion 3D printing technology via optimizing CaCO3 addition and sintering temperature. The effects of different CaCO3 additions on the performance, phase formation, and microstructure of porous ZrO2 ceramics sintered at different temperatures were systematically investigated and discussed. The results showed that flexural strength, porosity and shrinkage of the ZrO2 ceramics were significantly affected by CaCO3 addition and sintering temperature. The appropriate addition of CaCO3 could promote sintering and phase transformation of m-ZrO2, increase the number and size of pores in the matrix. The corresponding flexural strength and porosity of the sintered samples increased, while the shrinkage rate decreased. The raised sintering temperature appropriately facilitated the formation of CaZrO3. Microstructural analysis indicated that CaZrO3 exhibited a larger polyhedral bulk morphology, mainly distributed at the edges of pores, which could stabilize the pore structure and thicken the sintering necks, and thereby exhibiting well-balanced comprehensive performance. The ZrO2 ceramics with high flexural strength, high porosity and relatively low shrinkage rate were achieved by adding 15 wt% CaCO3 and sintering at 1450 ℃. The resulting flexural strength and porosity were 27.33 MPa and 67.62 %, respectively, presenting an improvement of 563.35 % and 13.69 % compared to ZrO2 ceramics without CaCO3. Moreover, the shrinkage rates in the X-direction (9.98 %), Y-direction (9.62 %), and Z-direction (9.94 %) significantly reduced, decreasing by 38.28 %, 38.10 %, and 41.46 %, respectively.

РОЛЬ САСО3 У ФОРМУВАННІ МІЦНІСНИХ І ДЕКОРАТИВНИХ ВЛАСТИВОСТЕЙ ПОРОШКОВОГО ЛУЖНО-АКТИВОВАНОГО ШЛАКОПОРТЛАНДЦЕМЕНТНОГО БЕТОНУ

The article discusses approaches to the formation of compositions of alkali-activated decorative Portland slag cements containing Portland cement type CEM1 5...45% with high performance and decorative properties. The optimization of the compositions of decorative alkali-activated Portland slag cements was carried out using statistical methods for designing experiments. Finely dispersed TiO2 and CaCO3 additives with a whiteness of 90% were used as bleaching components. The alkaline component is sodium metasilicate in the form of a non-hygroscopic powder. The research carried out made it possible to obtain decorative Portland slag cements with a whiteness of 45...77%, which allows them to be used to produce colored cements with a wide range of colors from white to black. It has been established that alkali-active decorative Portland slag cements have an activity of 37...59 MPa at the age of 28 days. All compositions have good hardening dynamics and, based on the strength at the age of 2 days  22...36.6 MPa, they can be classified as fast-hardening. Based on them, it is possible to produce dry construction mixtures. All mortar compositions based on alkali-active decorative Portland slag cements demonstrate fairly high frost resistance  F200. This allows them to be used for the manufacture of products and solutions both for indoor use and when exposed to atmospheric influences without loss of design characteristics and decorative appeal. The inherent shrinkage strains of decorative alkali-activated Portland slag cements are 0.51...0.61 mm/m, which eliminates cracking and premature destruction of products. The use of the CaCO3 additive is especially effective for controlling the shrinkage deformations. Thus, the CaCO3 additive performs the functions of not only a decorative component, but also a structure-forming component. Concrete and mortar mixtures can be used to produce decorative products using the traditional method, extrusion, 3D printing on construction printers, etc. And not too long setting times and a rapid increase in strength make it possible to produce products without thermal treatment or with minimal consumption of thermal energy.

Experimental evidence that poor soil phosphorus (P) solubility typical of drylands due to calcium co-precipitation favors autonomous plant P acquisition over collaboration with mycorrhizal fungi

Calcareous dryland soils are rich in precipitated phosphate and represent >30% of Earth's land, yet the relative importance of phosphorus-acquisition strategies (PAS) among plant species in these systems is not well known. No experiment has investigated potential interactions between varying amounts of added calcium carbonate (CaCO3) and arbuscular mycorrhizal fungi (AMF) on plant performance and PAS which could test for potential mechanisms without the limitations of in-situ comparisons along natural gradients. To fill this knowledge gap, we conducted an experiment with CaCO3 addition, AMF inoculation, and three invasive and five native grassland plants. We expected an increase in soil [CaCO3] of an alkaline subsoil to 1) reduce soil-available phosphorus (P), 2) reduce plant biomass and P uptake, and 3) shift PAS toward increased root mining as Ca-bound P increases. The largest CaCO3 addition reduced available P by as much as 57%. On average, the largest addition of CaCO3 reduced total biomass of plants by 19% and plant uptake of P by 15%. The PAS seemed to have changed, and CaCO3 additions tended to increase an indicator of root exudation (shoot [Mn]) to mobilize Ca-bound P, suggesting plasticity for some inducible root mining, especially Artemisia frigida and Poa secunda. However, CaCO3 and plant species interacted to affect shoot [Mn]. The invasive grass Bromus tectorum was superior at acquiring P (> P uptake, > shoot [Mn]) and thus tolerating low soluble P conditions. Rarely did AMF and CaCO3 interact to affect plant biomass. When they did, mycorrhizal responsiveness did not increase where P was less available, suggesting AMF become less beneficial upon P and Ca coprecipitation. In dryland soils with less soluble P, plants are thus likely to rely more on root mining PAS than mycorrhizal scavenging, except for the invasive forb Euphorbia esula that always benefitted from AMF inoculation.

Enhancing strength and irradiation tolerance of Mg alloy via co-addition of Mn and Ca elements

The Mg alloys with combination of high strength and excellent irradiation resistance are currently required for research reactors. In this work, the novel Mg-3Mn-0.5Ca alloy with a high strength of over 300 MPa has been fabricated via co-addition of Mn and Ca elements. Moreover, the Xe ion implantation (300 °C/4.5 × 1015 ions/cm2) is conducted for pure Mg, Mg-3Mn and Mg-3Mn-0.5Ca alloys. Microstructure characterization shows that the number density of dislocation loops is comparable between Mg-3Mn and pure Mg, while the phase boundary of nano-Mn particles could act as the sink to absorb more Xe atoms, resulting in the abundant formation of Xe bubbles in the matrix of irradiated Mg-3Mn alloy. With further minor addition of Ca element, the formation of Xe bubbles and dislocation loops in Mg-3Mn-0.5Ca alloy has been obviously suppressed, and the abundant grain boundaries (GBs) due to grain refinement then act as the sink region for Xe precipitation. The limited number density of Xe bubbles leads to the extremely low swelling ratio in Mg-3Mn-0.5Ca alloy, ∼0.08 %. The result above suggests that the Mn and Ca co-addition could enhance the mechanical properties and irradiation tolerance of Mg alloys, simultaneously. The present low-alloying strategy would provide a new design reference for novel nuclear materials.

Low-Temperature Water Electrolysis Under a Sustained pH-Gradient for Electrochemically-Induced Decarbonation of Limestone into Hydrated Lime

Lime holds considerable potential in diverse environmental applications. However, its current production remains highly carbon-intensive, emitting more than one ton of CO2 per ton of lime. To address this issue, recent studies have explored the concept of electrifying the decarbonation of limestone to produce hydrated lime. In this work, a two-compartment electrolysis cell capable of producing Ca(OH)2 has been tested at different currents. Precise pH and Ca2+ concentration measurements demonstrate that the electrolysis setup is able to dissolve CaCO3 and precipitate Ca(OH)2 with near-perfect efficiencies. Notably, it highlights that Faraday’s law and the concept of transport number can be applied to predict both the equilibrium and kinetic behavior of each step of the process in each of the two cell compartments. Moreover, the use of controlled batch additions of CaCO3 in the system, as opposed to one-time excess addition, was assessed to mitigate the fouling of the cationic exchange membrane used to separate the compartments. Finally, based on the experimental findings, key guidelines are proposed to achieve a perfect reaction stoichiometry for each step. These findings pave the way for a more sustainable and environmentally friendly approach to lime production.

Influence of Nano-Activated CaCO3-Metakaolin on Early Strength and Microstructure of Cement

The early strength, microstructure, and structure of cement mortar under low-temperature curing conditions were investigated through compressive strength tests, scanning electron microscopy, x-ray diffraction, synchronous thermal analysis (thermogravimetric analysis coupled with differential scanning calorimetry), and nuclear magnetic resonance tests. The study focused on the impact of the single addition of nano-activated CaCO3 (NAC) and the simultaneous addition of metakaolin (MK) on cement mortar. The results indicate that the addition of NAC accelerated the early hydration of cement. At a 1% dosage, the compressive strength increased by 6.84%, 14.77%, and 18.58% at 1 day, 3 days, and 7 days, respectively. When 5% MK was co-added, the compressive strength increased by 15.16%, 27.85%, and 21.66% at 1 day, 3 days, and 7 days, respectively. The combination of NAC and MK accelerated the hydration of cement, refined the products, reduced the porosity, improved the microstructure, and enhanced the early compressive strength of cement-based materials.

Influence of additive nano calcium carbonate (CaCO3) on SAE 10W-30 engine oil: A study on thermophysical, rheological and performance

Researchers have used nanomaterials as additives in base oil to improve its specifications, especially to minimize wear and friction during its applications. In this study, calcium carbonate (CaCO3) nanoparticles were selected as an additive to serve as a protective layer between components and anti-wear properties. In this study, calcium carbonate (CaCO3) nanoparticles were selected as an additive to serve as a protective layer between components and anti-wear properties. Nano lubricant samples were prepared using mass variations of CaCO3 and SAE 10W-30 base oil with concentrations of 0.05, 0.1, 0.15, and 0.2%, then homogenized. The nanolubricant samples obtained were analyzed for thermophysical, rheological properties and lubricant performance with the addition of nano CaCO3 in improving the wear resistance of FC25 cast iron. The results of thermophysical and rheological properties analysis suggest that the nanolubricant has better tribological properties compared to base lubricants. The highest values of thermal conductivity, density, and viscosity (40 oC) are 0.139 W/m.K, 812.203 kg/m3, and 106 mPa.s (40 oC). Meanwhile, the highest CoF, disc mass loss, and surface roughness of nanolubricant are 0.0706, 0.0037 grams, and 0.50 µm, respectively. These results indicate that the greatest wear-reducing agent is from the nanolubricant with the addition of CaCO3 nanopowder additives at 0.1 wt% concentration. These results are expected to give significant insights into the advancement of nano technology-based lubricants in the future.

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

Influence of CaCO3 on Density and Compressive Strength of Calcium Aluminate Cement-Based Cementitious Materials in Binder Jetting.

We investigated the impact of CaCO3 addition on the density and compressive strength of calcium aluminate cement (CAC)-based cementitious materials in binder jetting additive manufacturing (BJAM). To confirm the formation of a uniform powder bed, we examined the powder flowability and powder bed density for CaCO3 contents ranging from 0 to 20 wt.%. Specifically, powders with avalanche angles between 40.1-45.6° formed a uniform powder bed density with a standard deviation within 1%. Thus, a 3D printing specimen (green body) fabricated via BJAM exhibited dimensional accuracy of less than 1% across the entire plane. Additionally, we measured the hydration characteristics of CAC and the changes in compressive strength over 30 days with the addition of CaCO3. The results indicate that the addition of CaCO3 to CAC-based cementitious materials forms multimodal powders that enhance the density of both the powder bed and the green body. Furthermore, CaCO3 promotes the formation of highly crystalline monocarbonate (C4AcH11) and stable hydrate (C3AH6), effectively inhibiting the conversion of CAC and showing compressive strengths of up to 5.2 MPa. These findings suggest a strong potential for expanding the use of BJAM across various applications, including complex casting molds, cores, catalyst supports, and functional architectural interiors.

Atomic-molecular perspectives on local high-temperature structure and transport properties of CaCO3-foamed glass

Significant gaps remain in understanding of gas-melt interfaces in foamed glass systems. We attempt to address these gaps by reporting on the transition of local structure, ionic (molecular) diffusion, and melt viscosity of CaCO3-foamed soda-lime-silica glass using molecular dynamics calculations and experimental analyses. Our calculations show that despite the continual increase in network modifying CaO, the melt network experiences an abnormal polymerization process in the initial stage because of Na ion penetration from the melt skeleton to the interface. The percolation probability decays from the surface to the center of melt because of the gradual polymerized network structure, boosting nonmonotonic changes in the [SiO4] species, equilibrium constants, and average residual charge per O atom. Furthermore, the diffusion capacities of melt ions and CO2 molecules peak at 6 wt% CaCO3 addition, attributed to the combined effects of melt depolymerization and interface constraint. The viscosity jump occurring at 1 wt% CaCO3 addition results in the optimal sample with an even cellular glass framework and strong matrix. These findings contribute to the precise control of foamed glass with optimal performance.

Application of calcium carbonate (CaCo3) at different time intervals on the growth of freshwater lobster (Cherax quadricarinatus)

Freshwater lobsters are one of the crustacean commodities that have started to be developed through cultivation. Besides having high nutritional value, freshwater lobsters have a stable sales value or price throughout the year. Freshwater lobster is a crustacean commodity that is not easily stressed or easily attacked by disease. The availability of calcium is essential for lobster growth, especially the formation of its shell. This research aims to determine the effectiveness of adding calcium carbonate at different time intervals by adding 150 mg/L CaCO3 lime. The study was conducted from June to July 2020 at the Aquaculture Environmental Laboratory, Bogor Agricultural Institute. The research used a Completely Randomized Design (CRD) with five treatments and three replications. The treatment used was K+ and K-, and the time interval for adding CaCO3 was once every five days, once every ten days, and once every 15 days. The aquarium measures 100 x 50 x 51 cm with a water height of 21 cm. The lobster used measures 1.5 cm. The research results after statistical testing showed that aquarium A1 (addition of CaCO3 every five days) experienced an increase in length of 0.67 cm. Weight of 0.67 g, B1 (addition of CaCO3 every ten days) experienced an increase in length of 0.87 cm and weight of 0.78 g, C1 (addition of CaCO3 every 15 days) experienced an increase in length of 0.97 cm and weight of 0.98 g, K+1 experienced an increase in length of 1.05 cm and weight of 1.06 gr, K-1 experienced an increase in length of 0.46 cm and weight of 0.45 g.

Mechanical and environmental evaluation of ground calcium carbonate (CaCO3) filled polypropylene composites as a sustainable alternative to virgin polypropylene

Polypropylene (PP) has raised environmental concerns particularly for its depletion of fossil-fuels and contribution to climate change. To lower environmental impacts, PP can be combined with biobased fillers such as calcium carbonate (CaCO3). The mechanical and environmental properties of CaCO3 filled PP have not yet been explored in depth. Therefore, this study examines the aesthetic, tensile, flexural, impact, and environmental (via life cycle assessment) properties of injection moulded CaCO3 filled PP with filler content ranging from 0% to 40% at 5% increments. As filler percentage increased, yield strength decreased (0% CaCO3: 17.68 MPa, 40% CaCO3: 12.73 MPa), but young's modulus, flexural modulus, and impact strength increased (respectively 69%, 51%, and 35% greater than pure PP). Flexural strength increased initially at 5% CaCO3 but then declined as more filler was added. A yellowish hue was observed within all blends which growed stronger with more filler. The addition of CaCO3 reduced the environmental impact for all 11 impact categories. For every 5% of CaCO3 added, the material's global warming potential (GWP) decreased by 100g CO2 eq. per functional unit (1000 cm3) of composite. Abiotic depletion of fossil fuels declined by 32% when 40% CaCO3 was added. In addition to this study, it would be beneficial to explore other factors that affect the properties of CaCO3 filled PP such as particle size, particle distribution, and binding additives.

How does calcium carbonate enhance pollutants degradation under light illumination? Enhanced scattering and hydroxyl radical

Some trace pollutants exist extensively in the water, soil and other environment, as a result of unorganized emissions. The natural mineral CaCO3 is also widely found in these environments. In this study, we studied the effect of CaCO3 on the transformation of pollutants in water under light and the inactivation of bacteria in different environments. The photolysis of tetracycline (TC) under sunlight in the presence of CaCO3 can be as high as about 77%, which was improved comparing with the pure photolysis under sunlight (15%) and adsorption (32%). The same trend was found when the natural minerals containing CaCO3 (e.g. shell, oyster shell, limestone and marble) were adopted. It was determined that 1.10×10−5 mmol L−1 of ∙OH can be produced under Xenon lamp light source (HID) illumination after 2 h of reaction, which was increased to 4.28×10−5 mmol L−1 in the HID system with addition of CaCO3. According to the calculation by projector-enhanced wave (PAW) method, it was found that the O-H bond length was increased after H2O adsorption on CaCO3. The O-H bond cleavage was easier for more ∙OH generation under light illumination. Based on ZEMAX software simulations, CaCO3 can act as light scatterer and increase the residence time of light in solution.

Optimization of avocado oil solvent extraction assisted by CaCO3 as coadjuvant using Response Surface Methodology

Coadjuvants, such as CaCO3, are essential to improve the effectiveness of the extraction process. This study aimed to assess how the addition of CaCO3 as a coadjuvant impacts the yield of avocado oil through the process of solvent extraction using hexane. Response surface methodology was employed to optimize parameters influencing oil yield during solvent extraction. A Box-Behnken design with three factors and three levels was utilized for the optimization process. Factors involved are, concentration of CaCO3 (1, 1.5, 2%), extraction time (30, 60, 90 min), and temperature of extraction (25, 35, 45 °C). The linear model provided the most accurate fit to the experimental data, substantiated by the highest determination coefficient (R2) value. The experiment showed that the highest yield of avocado oil, reaching 48.06%, was obtained by extracting it under the specified conditions: a CaCO3 concentration of 1.92%, an extraction time of 89.85 minutes, and a temperature of 43 °C. The extraction yield of 48.77±0.14% obtained from the experiments using optimized conditions.

Eksperimentalna procena biomaziva sa dodatkom nanočestica kalcijum karbonata (CaCO₃) iz otpada ljuske kapice kao tečnosti za sečenje korišćenjem minimalne količine podmazivanja (MKL) u CNC procesu glodanja

Nano-cutting fluid sprayed using the minimum quantity lubricant (MQL) method is one example of a green manufacturing process. Meanwhile, vegetable oil is an appropriate lubricating base oil as it offers very high lubricating performance and environmental friendliness. Further, CaCO₃ nanoparticles are popular for their capacity to improve lubrication properties and performance. However, the optimum impact of utilizing different types of vegetable oil remains inadequately investigated. Therefore, this study aims to analyze the effect of CaCO₃ nanoparticles on the performance of cutting fluid, specifically on the thermophysical, rheological, and tribological properties in the CNC milling process of AISI 1045 Steel material. The nano-cutting fluid was prepared using different vegetable oils (canola, corn, soybean) added with CaCO₃ nanoparticles with a mass concentration of 0.15%. The results showed that the thermophysical properties, including density and viscosity, were highest when using canola oil, and the addition of CaCO₃ to all samples did not significantly affect thermal conductivity. Meanwhile, for the rheological properties, we observed Newtonian for all cutting fluid samples. For tribological properties, canola, and corn oil were better for obtaining a minimum Ra value, while soyabean oil was more effective in reducing cutting temperature. Based on the results of tool wear calculations, each oil presents the best performance in reducing wear, especially with the addition of CaCO₃. For chip formation, on average, the samples produce irregular tooth morphology with C-type, comma, and elongation shapes. Meanwhile, the resulting chip color was dark purple, which changed to dark brown and light brown, then turned silvery white due to wear and tear on the different sides of the chisel.

Facile Strategy for Boosting of Inorganic Fillers Retention in Paper.

Achieving the desired properties of paper such as strength, durability, and printability remains challenging. Paper mills employ calcium carbonate (CaCO3) as a filler to boost paper's brightness, opacity, and printability. However, weak interaction between cellulose fibers and CaCO3 particles creates different issues in the papermaking industry. Therefore, this study explores the influence of various inorganic additives as crosslinkers such as mesoporous SiO2 nanospheres, TiO2 nanoparticles, h-BN nanoflakes, and hydroxylated h-BN nanoflakes (h-BN-OH) on inorganic fillers content in the paper. They were introduced to the paper pulp in the form of a polyethylene glycol (PEG) suspension to enable bonding between the inorganic particles and the paper pulp. Our findings have been revealed based on detailed microscopic and structural analyses, e.g., transmission and scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and N2 adsorption/desorption isotherms. Finally, the inorganic fillers (CaCO3 and respective inorganic additives) content was evaluated following ISO 1762:2001 guidelines. Conducted evaluations allowed us to identify the most efficient crosslinker (SiO2 nanoparticles) in terms of inorganic filler retention. Paper sheets modified with SiO2 enhance the retention of the fillers by ~12.1%. Therefore, we believe these findings offer valuable insights for enhancing the papermaking process toward boosting the quality of the resulting paper.

Effect of different calcium salts on phosphorus availability and immobilization of heavy metals in municipal sludge derived biochar

Transforming municipal sludge (MS) into biochar via co-pyrolysis with calcium salts enhances phosphorus (P) recovery and reduces the risk of heavy metal contamination. In this study, the performance and mechanism of bioavailable P conversion and heavy metal stabilization were systematically compared under co-pyrolysis of MS with CaCO3, CaO, and CaCl2 at mass ratios of 2.5–10 % at 700 °C. The results showed that CaCl2 had the best ability to convert P from non-apatite inorganic P to apatite P, followed by CaO and then CaCO3. CaO and CaCO3 addition induced more Ca5(PO4)3OH formation, while CaCl2 induced more Ca2PO4Cl and Ca5(PO4)3Cl formation. The degree of stabilization of heavy metals (e.g., Cd, Cr, Cu, Ni, Pd, and Zn) was significantly improved after co-pyrolysis of MS with these salts, thus reducing the potential environmental risk. In particular, because of the dual action mechanism of chloride ions and calcium ions, co-pyrolysis with CaCl2 exhibited the lowest risk of heavy metal contamination compared with CaCO3 and CaO. These findings suggest that addition of 2.5 % CaCl2 can optimize the production of bioavailable P and the stabilization of heavy metals in biochar. This treatment is recommended for the safe utilization of P resources derived via MS pyrolysis.

Utilizing ultrapure magnetite concentrate for environmentally friendly and low-cost synthesis of high-performance strontium ferrite

The presence of Al and Si impurities from ultrapure magnetite concentrate (UMC) entering the lattice during the preparation of M-type strontium ferrite (SrM) has been a significant issue limiting the enhancement of magnetic properties in UMC- prepared SrM. In this article, the impact of CaCO3 on the phase formation mechanism of synthesizing SrM using UMC is investigated. It is found that the formation of intermediate SrFeO3−x phase and SrFe12O19 phase shifts to the lower temperatures upon CaCO3 addition. Lower calcination temperatures can inhibit excessive grain growth, thereby improving coercivity. At a calcination temperature of 1050 °C with the addition of 0.6 wt% CaCO3, the highest coercivity of 4672.29 Oe was achieved. Lattice parameters, magnetic properties, and micro-area composition analysis demonstrate that the addition of CaCO3 reacts with Al impurities, preventing the incorporation of Al ions into the SrM lattice and promoting an increase in saturation magnetization. The highest saturation magnetization of 71.45 emu/g was obtained at the calcination temperature of 1200 °C. It has reached the level of magnetic properties of SrM prepared from Fe2O3. CaCO3, being low-cost and environmentally friendly, can serves as an effective additive for improving the magnetic properties of UMC-prepared SrM without compromising its cost-effective and eco-friendly advantages.

Influence of micro‐sized CaCO3 on hydrates formation of residual calcium aluminate cement in castables during drying

AbstractThe addition of CaCO3 powder in calcium aluminate cement (CAC) is reported to accelerate the hydration of CAC and generate mono‐carbonate C4AC̅H11, which is conducive to shortening the curing time of CAC‐bonded castables at ambient temperatures. Although the hydration of CAC is relatively fast, there is still residual un‐hydrated CAC in castables after curing. The residual CAC would continue to hydrate to produce C3AH6 and AH3 during the subsequent drying procedures in the absence of CaCO3. But it is worth pondering which type of hydrate would be generated in the presence of CaCO3 during the drying at around 110°C. In this study, the effect of micro‐sized CaCO3 addition on the hydrate formation of CAC‐bonded castables during drying at 110°C was investigated. The results indicate that the C4AC̅H11 formed at the curing temperature of 30°C is not decomposed or converted during drying. The CaCO3 remained after curing does not participate in the hydration of residual CAC during drying at 110°C, and thus the residual CAC continues to hydrate to generate C3AH6 rather than C4AC̅H11.