Presence Of CaCO3 Research Articles

Enhanced arsenic removal from water and easy handling of the precipitate sludge by using FeSO4 with CaCO3 to Ca(OH)2

In this work, the removal of arsenic from aqueous solution by using FeSO4 with CaCO3 was investigated. Arsenic removal was significantly improved in the presence of CaCO3, compared with Ca(OH)2, giving an arsenic removal rate of 99.64% with the Fe/As molar ratio of 2:1 and Ca/Fe molar ratio of 1.5:1. With both FeSO4+Ca(OH)2 (FSCH) and FeSO4+CaCO3 (FSCC), several analytical methods including SEM-EDS, XRD, FTIR, and TG-DSC etc. were performed to characterize the sediments. The sediment from FSCC has much larger particle size, six time faster filtration speed and only one-third volume compared with that from traditional FSCH, allowing a very easy handling of the precipitate sludge, another clear advantage of using CaCO3. Moreover, much less fine and sticky CaSO4 was generated in the FSCC sludge than that from FSCH.

Formation of active Fe(OH)3 in situ for enhancing arsenic removal from water by the oxidation of Fe(II) in air with the presence of CaCO3

The wide-spread arsenic contamination is considered one of the most global serious environmental issues in the world. In this work, enhanced arsenic removal from water by the oxidation of FeSO4 with CaCO3 in air was investigated and the mechanisms were discussed. Oxidation of Fe(II) into Fe(OH)3 in air became possible in the presence of CaCO3, of which the hydrolyzed OH− from CaCO3 changed the conversion route of Fe(II) to Fe(OH)3. Freshly generated Fe(OH)3 in situ presented high activity for arsenic removal, with Fe/As molar ratio at 2 giving the removal rate of 99.93% and low remaining concentration of 0.035 mg/L from 50 mg/L initial concentration. Precipitation products were characterized by a set of analytical methods including XRD, XPS and Raman analyses to confirm the existence of ferric arsenate phase. Different from using Ca(OH)2 with enough OH− group, the slow hydrolysis of CaCO3 resulted in a continuous generation of fresh Fe(OH)3 for arsenate precipitation and could avoid its rapid transformation into stable FeOOH of large particle size to lose the activity. Aging the ferric compositions by prolonged agitation of Fe(II) and CaCO3 before with arsenate solution confirmed the growth of FeOOH and resulted in a rapid decrease in the capacity for arsenic removal. The observed phenomena were interpreted based on the difference between the precipitation by fresh Fe(OH)3 and the adsorption by large crystalline particles of FeOOH. Controlling the forming speed of ferric composition from Fe(II) with the addition of solid CaCO3 to maintain a fresh state as an easy operation could enhance tremendously its efficiency for As removal, with the ever highest capacity of 248 mg/g among iron absorbents.

Prediction of Lime Tolerance in Rhododendron Based on Herbarium Specimen and Geochemical Data.

Rhododendrons are typically known to be calcifuges that cannot grow well in lime soils. Data on lime tolerance of different taxa in Rhododendron are scarce. Habitats of naturally distributed specimens of genus Rhododendron were compiled as Chinese text-based locations from the Chinese Virtual Herbarium. The locations were then geocoded into latitude/longitude pairs and subsequently connected to soil characteristics including pH and CaCO3 from the Harmonized World Soil Database (HWSD). Using the upper quartile values of pH > 7.2 and CaCO3 > 2% weight in topsoil as threshold, we predicted the lime tolerant taxa. A dataset of 31,146 Rhododendron specimens including the information on taxonomy, GPS locations and soil parameters for both top- and subsoil was built. The majority of the specimens were distributed in soils with moderately acidic pH and without presence of CaCO3. 76 taxa with potential lime tolerance were predicted out of 525 taxa. The large scale data analysis based on combined data of geocoded herbarium specimens and HWSD allows identification of valuable Rhododendron species, subspecies or botanical varieties with potential tolerance to lime soils with higher pH. The predicted tolerant taxa are valuable resources for an in-depth evaluation of lime tolerance or for further use in horticulture and breeding.

The Zug El Bohar hydrothermal uranium-base metal deposits, southwest El Quseir, Red Sea Coast, Egypt

The Zug El Bohar area belongs to the Red Sea coastal plain of Egypt. Lithostratigraphically, this area is represented by a section of Late Cretaceous-Late Miocene sedimentary rocks and it is affected by both a WNW-ESE sinistral strike-slip fault and a NNW-SSE shear zone. The deposits in the NNW-SSE shear zone were subjected to mineralogical and geochemical studies in order to elucidate the importance of these sediments for hosting valuable minerals. The geochemical study indicated that the shear zone has an abnormal concentration of U as well as high concentrations of Mo, Pb, and Zn and As. Whereas the mineralogical study has not been detected any uranium minerals, whereas minerals such as wulfenite (PbMoO4), zaccagnaite [Zn4Al2(CO3)(OH)12.3H2O] and baileychlore [(Zn,Fe2+,Al,Mg)6(Si, Al)4O10(OH)8)], mimetite [Pb5(AsO4)3Cl], calcian mimetite, arsenatian vanadinite [Pb5(V,As)O4Cl], Galena (PbS) and zinnwaldite [KLiFeAl(AlSi3)O10(OH,F)2], celestite (SrSO4) were identified. The deposits of the shear zone were formed due to a moderately oxidized saline fluid that led to precipitate minerals with a change in pH and temperature. The presence of CaCO3 and sulfate in the shear were played an important role in a decreasing adsorption of U on ferrihydrite and the disequilibrium with its daughters as well as the precipitation of Mo, Pb, Zn , As and REE from the mixed solution.

Synthesis of magnetic 3D graphene decorated with CaCO3 for anionic azo dye removal from aqueous solution: Kinetic and RSM modeling approach

In this work, a new magnetic 3D graphene aerogel/CaCO3 nanocomposite was synthesized successfully using a one-step in situ self-assembly of graphene oxide in the presence of CaCO3 and Fe3O4 nanoparticles. The product was characterized using various techniques such as Field Emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR), energy dispersive X-ray (EDX), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). The prepared nanocomposite was used as a novel absorbent to remove Acid Red 88 (AR88) dye from aqueous solutions as an anionic azo dye model. The effects of operational parameters such as absorbent dosage, dye concentration, pH and contact time on AR88 removal were investigated by using response surface methodology (RSM). From RSM results, the optimized values in the range of quantities used in this work for 100% removal of AR88 dye were found to be 87mg nanocomposite, 14mg/L dye (AR88) concentration, pH 6 and contact time 18min. Absorption of AR88 obeyed intra-particle diffusion kinetic model. These results suggest that the magnetic 3D graphene aerogel/CaCO3 nanocomposite is a good candidate for the rapid removal of AR88 from aqueous solutions.

Compositional modification of products from Co-Pyrolysis of chicken manure and biomass by shifting carbon distribution from pyrolytic oil to syngas using CO2

Co-pyrolysis of chicken manure and biomass was investigated in this study. The pyrolysis of individual samples was characterized by thermogravimetric analysis (TGA) under N2 and CO2 atmospheres. This demonstrated that the impact of CO2 content on the physical aspects of pyrolysis such as onset and end temperatures, and residual mass was negligible. However, a high CaCO3 content (17 wt%) in chicken manure catalyzed the Boudouard reaction. Despite its negligible physical influence, CO2 evidently affected the co-pyrolysis of chicken manure and biomass chemically. It expedited the thermal cracking of hydrocarbons from the co-pyrolysis of chicken manure and biomass. Moreover, between 550 and 660 °C, CO2 reacted with condensable hydrocarbons, effectively improving CO generation. This observation suggested that CO2 acted as both carbon scavenger and oxygen donor in the co-pyrolysis of chicken manure and biomass, a driving force for shifting carbon distribution between pyrogenic products. For example, pyrolytic oil was transformed into syngas, especially CO, offering an innovative means to modify compositions of pyrolytic products. These effects were not observed in the presence of CaCO3 and/or CaO.

Phase stability and kinetics of methane hydrate formation in presence of calcium and magnesium carbonate

ABSTRACTThe huge amount of methane hydrate deposits identified in deep marine sediments is considered as the new resource for future energy. Since carbonates are one of the major components of marine sediments, in the present study, an investigation has been made to study methane hydrate stability and kinetics in the presence of CaCO3 and MgCO3. Effect of the presence of carbonates on the solubility of methane in the system has also been examined as it directly affects the hydrate formation process. It has been observed that in presence of CaCO3 and MgCO3, the hydrate formation is inhibited. Comparative studies have also been done in the presence of artificial seawater to consider the effect of presence of different salts. Mole consumption of methane gas during hydrate formation in different carbonate samples was measured using real gas equation and found to be minimum in CaCO3 in seawater sample due to the combined effect of the presence of CaCO3 and different salts of seawater. An increase in nucleation and induction time was also observed demonstrating the inhibition of hydrate formation in the presence of these components. Further, the decrease in hydrate formation rate also confirmed the inhibition effect of CaCO3 and MgCO3 on hydrate formation.

Influence of inorganic additives on the photocatalytic removal of nitric oxide and on the charge carrier dynamics of TiO2 powders

Building materials employing TiO2 as photocatalyst usually contain several additives. The interplay of the additives and the photocatalytic NO degradation has been rarely investigated, although it is of utmost importance for the design of new highly active materials. Hence, in the present study the effects of such additives (BaSO4, CaCO3, and Na2CO3) on the photocatalytic activity and on the charge carrier dynamics have been evaluated. The degradation of nitric oxide (NO) was studied employing a standardized photocatalytic activity test (ISO 22197-1) and the charge carrier kinetics were observed by transient absorption spectroscopy. TiO2-additive powder samples were obtained by grinding pure anatase TiO2 with a single additive with varying volume composition. Overall, the obtained apparent quantum yields of the samples correlated well with the charge carrier concentration. Moreover, BaSO4 has proven its chemically inert character. However, the optical properties of the powder samples containing BaSO4 lead to relatively high photonic efficiencies even with low TiO2 content. TiO2-BaSO4 samples with only 25% TiO2 showed nearly the same quantum yield for the NO degradation as the pure photocatalyst. The reason for the high photocatalytic activity is the strong absorption of UV-light caused by the scattering inside the powder samples. The charge carrier kinetics of TiO2 after the addition of Na2CO3 and CaCO3 revealed two different chemical effects of the additives. Na2CO3 reduced the apparent quantum yield of the TiO2 samples due to the fast recombination of charge carriers (identified by a fractal kinetics fit). On the other hand, the presence of CaCO3 had a beneficial influence on the stabilization of trapped charge carriers in TiO2.

Isolation of Rare-Earth Elements from Mixtures of Calcium and Lanthanide Oxalates

The temperature regions for separate crystallization of rare-earth element (REE) oxides of the cerium group in the presence of CaCO3 have been determined using X-ray diffraction, differential thermogravimetric analysis, inductively coupled plasma mass spectroscopy, and X-ray fluorescence. The possibility to separate REE oxides from CaCO3 in H2SO4 solutions after heat treatment (450–600°C) has been studied. The solid phase of the precipitate is represented by slightly soluble calcium sulfate, whereas the REE oxides pass into the liquid phase in the form of highly soluble sulfates. After heat treatment of the test mixture of REE oxalates and calcium oxalate at a temperature higher than 750°C, calcium compounds pass into 1–2% HNO3 liquid phase in the form of nitrates, whereas lanthanide oxides remain in the insoluble phase of REE oxide solid solution having CeO2 structure.

STUDY ON SOME PROPERTIES AND MORPHOLOGY OF COMPOSITES BASED ON POLYETHYLENE GRAFTED ACRYLIC ACID/ETHYLENE-VINYL ACETATE COPOLYMER/CALCIUM CARBONATE

Composites based on polyethylene grafted acrylic acid (PE-g-AAc)/ethylene-co-vinylacetate copolymer (EVA)/calcium carbonate (CaCO3) were prepared by melt mixing. Relative melt viscosity, morphology, mechanical properties and thermostability of the composites were studied. The experimental results show that the presence of (CaCO3) activated by stearic acid (10-20 wt.%) changes lightly stable torque of polymer blend of PE-g-AAc/EVA. Use of modified PE improves compatibility of PE and EVA as well as makes the components disperse into each other better than in blends using unmodified PE. Tensile strength and elongation at break of both polymer blends decrease with presence of CaCO3. However, tensile strength of the composites of PE-g-AAc/EVA/CaCO3 is higher than that of composites of PE/EVA/CaCO3. Beside that, the composites of PE-g-AAc/EVA/CaCO3 have thermostability higher than the composites of PE/EVA/CaCO3.

Hydration induced morphological change on proppant surfaces employing a calcium-silicate cement system

Commercial aluminosilicate proppant particles have been coated with Ca-Si oxides, with the aim to provide an in-situ increase in the angularity (decrease in Krumbein roundness value) to facilitate their immobilization. Ca-Si oxide systems have been synthesized via sol-gel, cured, and sintered at 1200°C using (a) CaCO3, (b) CaCO3+orthosilicic acid (Si(OH)4, SA), and (c) CaCO3+fused silica (SiO2, FS). When the proppant is cured in the presence of CaCO3 and silicic acid the coatings undergo a significant compositional change, while sintering results in the conversion of the cured samples to ceramic agglomerates with the desired “popcorn” shapes. The best results are obtained in the presence of Si reagents, and hydration of these sintered proppants allows for a distinct increase in the angularity, which is the desired transformation to allow the proppant to be locked-in-place once located in the reservoir. The samples have been characterized at each stages of preparation by scanning electron microscopy (SEM) with associated energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and infrared (IR) spectroscopy.

Pt y Pd soportado en carbón activado para la oxidación de 5-hidroximetilfurfural a ácido 2,5-furanodicarboxílico


 En este trabajo se estudió la transformación en fase líquida de 5 hidroximetilfurfural (5-HMF) a ácido 2,5-furandicarboxilico con el uso de catalizadores de Pt y Pd soportados en carbón activado con la presencia de NaOH ó CaCO3. Los catalizadores fueron caracterizados por quimisorción de H2 a temperatura ambiente, espectroscopia de rayos X (XPS) y análisis termogravimétrico (TGA). Los resultados indican que el tamaño de partícula de los catalizadores sigue el orden PtCl/C < PdCl/C < PdN/C el cual esta estrechamente relacionado con la actividad catalítica. Se encontró que las partículas metálicas están presentes como especies de Pd0 and Pt0. Siendo el catalizador de Pt-Cl/C con el uso de CaCO3 como aditivo.

Molybdenite–limestone oxidizing roasting followed by calcine leaching with ammonium carbonate solution

Oxidizing roasting of molybdenite with lime can significantly reduce SO2 pollution compared with the traditional roasting without lime. However, the calcine is subsequently leached by sulfuric acid, resulting in serious equipment corrosion and abundant non-recyclable CaSO4 slag. In this work, a novel process, in which the molybdenite was roasted with CaCO3 followed by (NH4)2CO3 solution leaching, was proposed to improve the art of lime roasting–sulfuric acid leaching. Oxidizing roasting of molybdenite with CaCO3 was investigated through thermodynamic calculation, thermogravimetric analysis and roasting experiments. The results show that the products of the oxidizing reaction of MoS2 in the presence of CaCO3 and O2 are CaSO4, CaMoO4 and CO2 at 573–1000 K. The MoS2 conversion rate achieves approximately 99% and the sulfur-retained rate attains approximately 95% with a CaCO3-to-MoS2 molar ratio of 3.6 at 500 °C for 1 h by adding 5% mineralizer A (mass fraction). The leaching results show that the leaching rate of Mo reaches 98.2% at 85 °C for 7 h with a (NH4)2CO3 concentration of 600 g/L and a liquid–solid ratio of 10 mL/g. The results presented are potential to develop a novel cleaner technique for ammonium molybdate production.

Microstructures and Mechanical Study of Mg Alloy Foam Based on Mg-Zn-Ca-CaCO3 System

Magnesium alloy, a material that has potential to use some applications such as aerospace components, computer parts, and mobile phones. Magnesium alloy can also be a popular candidate as an orthopedic implant material for biodegradability, non-toxicity, and mechanical and physical properties that are excellent. Magnesium, one of the main macro elements required for the proper functioning of the human organism, is used to test the materials for biodegradable implants. The main objective of this study was to find out the microstructure, and mechanical characteristics of the Mg-Ca-Zn-CaCO3 alloy as porous implant materials are biodegradable. The presence of CaCO3 on the alloy functions as a foaming agent expected to produce gas bubbles during manufacturing process taken place that will form pores in the alloy. Mg-Ca-Zn-CaCO3 alloy was made by powder metallurgy method with three variations of composition (96Mg-Ca-3Zn-CaCO3, 91Mg-Ca-3Zn-5CaCO3, and 86Mg-Ca-3Zn-10CaCO3 wt%). Milling process was by using a shaker mill for 2 hours to produce a powder size distribution which was more homogeneous. The mixed powder was uniaxially pressed at a pressure of 100 MPa for 2 minutes and 200 MPa for 3 minutes into green compacts with dimensions of 10 mm in diameter and 10 mm in length. The sintering process was carried out at 650°C with a variation of holding time of 10 and 15 hours, and then the specimens were cooled down at room temperature. Microstructural analysis was performed by using X-Ray diffraction technique and Scanning electron microscopy equipped with an energy disperse spectrometry (EDS). The mechanical characteristics were analyzed by using Universal Testing Machine. The density and porosity of specimen were further measured by using Archimedes method. The results show that the optimum microstructure and mechanical characteristics are the holding time of 10 hours. The value of compression was 208.398 N/mm2, the density was 1.63 g/cc and a porosity was 18% on the composition of 86Mg-Ca-3Zn-10CaCO3 wt%.

Treatment additives reduced arsenic and cadmium bioavailability and increased 1,2-dichloroethane biodegradation and microbial enzyme activities in co-contaminated soil

Bioremediation of co-contaminated environments is difficult because of the mixed nature of the contaminants and the fact that the two components often must be treated differently. This study investigated the use of inorganic treatment additives, namely calcium carbonate (CaCO3), gypsum (CaSO4·2H2O), and disodium phosphate (Na2HPO4) to improve remediation of soil co-contaminated with 1,2-dichloroethane (1,2-DCA) and arsenic or cadmium. The soil samples were collected from a specific site in the Westville area in Durban, KwaZulu-Natal, South Africa. Microcosms were set up by artificially co-contaminating the soil sample (100 g mixed with 75 ml of synthetic groundwater in sterile screw-capped 250-ml serum bottles) with 1,2-DCA + risk elements; As3+ (150 mg/kg); or Cd2+ (170 mg/kg). Thereafter, each microcosm was amended with either 5 g CaCO3, 2 g CaSO4·2H2O, or 1.12 g Na2HPO4 + 0.046 g NaCl, separately. The samples were analyzed for the degradation of 1,2-DCA using GC–MS, while total 1,2-DCA degrading bacterial populations were determined at different sampling times using a standard spread plate technique. Soil dehydrogenase and urease activities were also monitored during the experimental period using standard enzyme assays. Addition of CaCO3 resulted in an approximately 2-fold increase in 1,2-DCA degradation in both the As3+ and the Cd2+ co-contaminated soil as compared to the co-contaminated soil without CaCO3. All the treatment additives were more effective in the As3+ co-contaminated soil resulting in 11.19, 9.25, and 5.63% increase in 1,2-DCA degradation in the presence of CaCO3, Na2HPO4 + NaCl, and CaSO4·2H2O, respectively, compared to the Cd2+ co-contaminated soil. The total 1,2-DCA degrading bacterial population increased in treated soils over time. Overall, soil dehydrogenase and urease activities were lower in the heavy metal co-contaminated samples compared to the treated soil. The inhibitory effect of heavy metal was less in As3+ co-contaminated soil for both CaCO3- and Na2HPO4 + NaCl-treated soil, with up to 7.92% increase in dehydrogenase activity obtained compared to soil co-contaminated with Cd2+. Results from this study indicate that treatment additives can be used to reduce bioavailable fractions of risk elements in the soil matrices, thereby limiting the toxicity of these risk elements to 1,2-DCA degrading microorganisms. Thus, this approach can be applied to enhance organic compound degradation in co-contaminated soil environments.

Co-expression of two heterologous lactate dehydrogenases genes in Kluyveromyces marxianus for l-lactic acid production

Lactic acid (LA) is a versatile compound used in the food, pharmaceutical, textile, leather, and chemical industries. Biological production of LA is possible by yeast strains expressing a bacterial gene encoding l-lactate dehydrogenase (LDH). Kluyveromyces marxianus is an emerging non-conventional yeast with various phenotypes of industrial interest. However, it has not been extensively studied for LA production. In this study, K. marxianus was engineered to express and co-express various heterologous LDH enzymes that were reported to have different pH optimums. Specifically, three LDH enzymes originating from Staphylococcus epidermidis (SeLDH; optimal at pH 5.6), Lactobacillus acidophilus (LaLDH; optimal at pH 5.3), and Bos taurus (BtLDH; optimal at pH 9.8) were functionally expressed individually and in combination in K. marxianus, and the resulting strains were compared in terms of LA production. A strain co-expressing SeLDH and LaLDH (KM5 La+SeLDH) produced 16.0g/L LA, whereas the strains expressing those enzymes individually produced only 8.4 and 6.8g/L, respectively. This co-expressing strain produced 24.0g/L LA with a yield of 0.48g/g glucose in the presence of CaCO3. Our results suggest that co-expression of LDH enzymes with different pH optimums provides sufficient LDH activity under dynamic intracellular pH conditions, leading to enhanced production of LA compared to individual expression of the LDH enzymes.

Role of CaCO3 in the physicochemical properties of crustacean-sourced structural polysaccharides

Crustacean shells are rigid and comprise mainly calcium carbonate (CaCO3), chitin and protein. These principal minerals vary with specie and full elimination could influence the physicochemical properties of chitin. In this study α-chitin sourced from crab and shrimp shells was extracted via chemical means using 0.4 M hydrochloric acid (HCl) and sodium hydroxide (NaOH) for demineralization and deproteinization processes respectively. Results from Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA) showed that CaCO3 is more predominant in the crab shell than that of the shrimp. Average hydrogen bond energy (EH) in shrimp chitin was calculated to be 5.25 kCal while that obtained from crab measured 4.71 kCal. Presence of CaCO3 in each exoskeleton is responsible for low thermal stability of embedded chitin, which improves after treatment with both chemicals.

Effects of Fe deficiency on the protein profiles and lignin composition of stem tissues from Medicago truncatula in absence or presence of calcium carbonate

Iron deficiency is a yield-limiting factor with major implications for crop production, especially in soils with high CaCO3. Because stems are essential for the delivery of nutrients to the shoots, the aim of this work was to study the effects of Fe deficiency on the stem proteome of Medicago truncatula. Two-dimensional electrophoresis separation of stem protein extracts resolved 276 consistent spots in the whole experiment. Iron deficiency in absence or presence of CaCO3 caused significant changes in relative abundance in 10 and 31 spots, respectively, and 80% of them were identified by mass spectrometry. Overall results indicate that Fe deficiency by itself has a mild effect on the stem proteome, whereas Fe deficiency in the presence of CaCO3 has a stronger impact and causes changes in a larger number of proteins, including increases in stress and protein metabolism related proteins not observed in the absence of CaCO3. Both treatments resulted in increases in cell wall related proteins, which were more intense in the presence of CaCO3. The increases induced by Fe-deficiency in the lignin per protein ratio and changes in the lignin monomer composition, assessed by pyrolysis-gas chromatography–mass spectrometry and microscopy, respectively, further support the existence of cell wall alterations. Biological significanceIn spite of being essential for the delivery of nutrients to the shoots, our knowledge of stem responses to nutrient deficiencies is very limited. The present work applies 2-DE techniques to unravel the response of this understudied tissue to Fe deficiency. Proteomics data, complemented with mineral, lignin and microscopy analyses, indicate that stems respond to Fe deficiency by increasing stress and defense related proteins, probably in response of mineral and osmotic unbalances, and eliciting significant changes in cell wall composition. The changes observed are likely to ultimately affect solute transport and distribution to the leaves.

Development of formulations based on TEOS-dicarboxylic acids for consolidation of carbonate stones

Dicarboxylic acids (DAs) act differently in the presence of CaCO3, becoming interesting additives in the consolidation of carbonate stones.

Ignition characteristics of metal dusts generated during machining operations in the presence of calcium carbonate

Metal dust explosions in machining industries have caused large losses in recent years. In order to evaluate and control the ignition likelihood of metal dusts generated during machining operations, it is necessary to determine the ignition characteristics such as minimum ignition energy (MIE) and minimum ignition temperature (MIT). The aim of this paper is to investigate the inerting effect of calcium carbonate (CaCO3) on these ignition characteristics. Six kinds of typical metal dusts and two kinds of pure atomized metal powders were used to determine the MIE and MIT of dust cloud in the presence of CaCO3. To provide a practical guidance for metal dust explosion prevention, the recommended percentage of CaCO3 were discussed based on the inerting effect.