Limestone Samples Research Articles

Complexity of Respirable Dust Found in Mining Operations as Characterized by X-ray Diffraction and FTIR Analysis

The mineralogical complexity of mine dust complicates exposure monitoring methods for occupational, respirable hazards. Improved understanding of the variability in respirable dust characteristics, e.g., mineral phase occurrence and composition, is required to advance on-site monitoring techniques that can be applied across diverse mining sectors. Principal components analysis (PCA) models were applied separately to XRD and FTIR datasets collected on 130 respirable dust samples from seven mining commodities to explore similarities and differences among the samples. Findings from both PCA models classified limestone, iron, and granite mine samples via their analytical responses. However, the results also cautioned that respirable samples from these commodities may not always fit patterns observed within the model. For example, one unique sample collected in a limestone mine contained no carbonate minerals. Future predictive quantification models should account for unique samples. Differences between gold and copper mine dust samples were difficult to observe. Further investigation suggested that the key to their differentiation by FTIR may lie in the characterization of clays. The results presented in this study provide foundational information for guiding the development of quantification models for respirable mineral hazards in the mining industry.

The effect of pressure on electrical rock typing, formation resistivity factor, and cementation factor

As a key parameter in the calculation of fluid saturation, cementation factor (m) is routinely approximated using the Archie's equation. Numerous correlations and several techniques have been proposed to determine cementation factor, one of which is electrical rock typing. Besides hydraulic rock typing, which plays a significant role in modeling and numerical simulation of reservoirs, electrical rock typing refers to categorizing rocks into distinct groups based on similarity in electrical properties of the rocks. The current study focuses on the effective pressure impact on electrical rock typing. In addition, the effect of change in effective pressure due to production on petrophysical properties, and consequently rock capacity for transmitting electricity was studied. In this paper, 39 limestone samples were studied to analyze the effect of pressure on porosity (ϕ), formation resistivity factor (F), and m. Performance of the Archie's equation under different effective pressures was further examined. Considering the fact that an increase in effective pressure causes pore and throat deformation, the pressure impact on the rock quality for transmitting electricity was scrutinized. Then, the influence of effective pressure on electrical rock typing was studied. It was discovered that due to an increase in effective pressure, F and m increase while ϕ decreases. The rock quality for transmitting electricity and the effective pressure were found to be correlated through a second-order polynomial equation. It was further concluded that the electrical rock typing was affected by the changes in electrical efficiency, and the number of electrical rock types and the presence of samples in them were influenced by variations of the effective pressure. This was a noticeable point because different rock types require the adoption of different correlations for determining the parameters of the Archie's equation; therefore, realizing that each sample belongs to which rock type is essential. The findings of this study contributed to a better understanding of the impact of the effective pressure on Archie's parameters and petrophysical properties, leading to a method for determining fluid saturation under different effective pressures during the reservoir lifespan.

The Influence of Size Effect on Strength and Deformation Characteristics of Different Types of Rock Samples

This paper presents the results of the experimental study of the influence of sizes effect on the strength and deformation characteristics of samples of hornfels, limestone, sandstone, siltstone and ore-bearing rocks. Tests were performed on cylindrical samples of three sizes of diameters - 10, 30 and 60 mm under uniaxial compression and tension loading. The results of the study demonstrated that the values of ultimate strength decrease when the size of samples increases for the samples of cornea, limestone, sandstone and siltstone. The ultimate strength increases with increasing of sample size for ore-bearing rocks containing viscous inclusions. The samples of smaller size of ore-bearing rocks exhibit a brittle character of the fracture for all types of rocks, and the viscosity of fracture increases with increasing size of samples. the obtained regularities were analysed from the positions of otwo types of size effect (volume and surface).

Application of hydraulic flow unit for prediction of flow zone in carbonate reservoir

The feasibility of oil production in any reservoir depends on the porosity and the permeability of that reservoir. Particularly, the permeability in the reservoir allows the ease of flow of fluid through it. High permeability is always desirable for the successful production of oil in any reservoir. The porosity and permeability depend on the reservoir rock. In general, the higher value of porosity and permeability makes limestone a suitable reservoir. Therefore, it is very important to characterize the reservoir in terms of porosity and permeability for the feasibility of oil production. In this investigation, reservoir characterization was carried out to determine the porosity and permeability of limestone reservoirs obtained from four different basins of Oilmax Mumbai. A total of 32 core samples of NX size were tested for characterization and determined porosity and permeability values. The variation in porosity and permeability was observed from 0.3 to 20.5% and 0.002 to 1.484 mD at the burial depth from 1618.86 to 1634.14 m, respectively. The normalized porosity and reservoir quality index were determined using the experimentally obtained porosity and permeability values. Normalized porosity values were used to calculate the flow zone indicator (FZI), which varied from 0.071971 to 6.024804. The least-square regression method was used to determine the hydraulic flow units (HFU) for different limestone samples. The porosity range indicates the highly porous reservoir, while the lower permeability was observed due to the non-linearity between porosity and permeability correlations. The results showed the consistent flow regime in five different hydraulic flow units in wellbore A. The consistent fluid regime in the other wellbore is only possible by increasing the reservoir’s permeability. Hence, hydraulic fracturing is highly recommended before the establishment of a production well.

ASSESSMENT OF DETERIORATION PROCESS IN EXPOSED CARVED LIMESTONE FALSE DOOR OF ABUSIR ARCHAEOLOGICAL AREA

Carved limestone false door dating back to the late Sixth Dynasty or the First Intermediate Period in Abusir archaeological area suffers from many physiochemical and mechanical deterioration factors, which lead to various deterioration phenomena, such as distort the carvings, decorations, the disappearance of paint, cracks in different depths, and salt calcification. It was found in the fill of Shaft 5 in the tomb AS 79 at Abusir South, Excav. No. 9/AS79/2015 and located in the storeroom of Czech Excavation in Abusir area. The current work aims to study the type of limestone which the false door is made of, and to know if there were colors on the false door or not, also to know if there were deterioration mechanisms that affect the carved limestone false doors of Abusir to evaluate the deterioration ratio in stone structure and the effects of surrounding environmental factors on stone. The investigation and characterization processes of archaeological limestone samples were carried out by polarizing microscopy (PLM), optical microscopy (OM), scanning electron microscopy (SEM-EDX) micro-analysis system, X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). The results revealed that the limestone material of the false door belongs to micrite limestone with very fine grains and needs to be conserved.

Organic petrological characterisation and facies interpretation of the Upper Triassic (Carnian – Julian) black limestone in the Lesno Brdo area (External Dinarides, Central Slovenia)

Upper Triassic (Carnian - Julian) bedded dark limestone in the Lesno Brdo area, more precisely in the Drenov Grič quarry (Central Slovenia), was investigated in this study to describe its carbonate facies, its geochemical characteristics of the inorganic and organic matter, and to estimate its hydrocarbons generative potential. The site was chosen as a well referenced location of previous lithological and paleontological studies with the aim to fill a gap in the up-to-date knowledge on organic petrology of the investigated rocks termed as the Julian “Carbonate Member” within the Lesno Brdo stratigraphic sequence. The study represents the first multi-analytical organic petrological investigation of Mesozoic carbonate rocks in Slovenia. In the Drenov Grič (DRG) section, 7 microfacies were defined. A total of 38 DRG samples of micritic limestones, marlstones, and a coaly sample were collected from the section. The average total organic carbon (TOC) content of the samples is 0.70 wt% with one outstanding sample DRG-28 with a TOC content of 15.56 wt.%. According to the TOC content, DRG samples are considered as a fair to good source rock for hydrocarbons generation. In addition, the samples with TOC >0.5 wt.% were characterised by the Rock-Eval S1, S2 and S3 peaks, hydrogen and oxygen indices (HI, OI), Tmax and production index (PI) values. According to these data, typical “black” Julian carbonate beds from the Drenov Grič locality are poor source rocks. Based on pyrolysis data (HI versus OI), the type of the organic matter could not be determined, so a micropetrographic examination was performed. . The predominant and the only clearly visible maceral in the DRG samples is vitrinite within the amorphous organic matter. Given the low S2 peaks, thermal maturity was determined by vitrinite reflectance. Vitrinite reflectance results (between 2.71 ± 0.19 %Ro and 3.89 ± 0.17 %Ro) indicate that the organic matter in the DRG samples is in a thermally mature to overmature stage, which is also consistent with the Thermal Alteration Index (TAI) (4- - 4). All 38 samples were also analysed on main and trace elements, focusing on the redox sensitive trace elements (Ni, Mo, Th, U, V and Zn) to supplementary interpret depositional conditions. Overall, the “black” carbonate rocks of the Drenov Grič section show a negligible potential for the generation of hydrocarbons. Their original dispersed organic matter was thermally strongly transformed. Therefore, the investigated carbonate rocks almost completely exhausted their ability to generate a considerable quantity of hydrocarbons. They can therefore be classified as “spent source rocks”, which could conditionally generate some dry gas.

Raman spectroscopy provides insight into carbonate rock fabric based on calcite and dolomite crystal orientation.

Carbonate rocks record the oldest forms of life on Earth, and their geologic reconstruction requires multiple methods to determine physical and chemical processes before conclusions of ancient biosignatures are made. Since crystal orientation within rock fabric may be used to infer geologic settings, we present here a complementary Raman method to study the orientation of calcite (CaCO3) and dolomite [CaMg (CO3)2] minerals. The relative peak intensity ratio of the carbonate lattice Eg modes T and L reveals the crystallographic orientation of calcite and dolomite with respect to the incident light polarization. Our results for calcite show that when the incident laser light propagates down the crystallographic a/b axis: (1) the L mode is always greater in intensity than the T mode (I T < I L), and (2) the spectra are most intense at 45° and least intense at 90° polarization angles measured from around the c axis. Our results for dolomite show that (1) I T > I L when the incident light propagation is down the crystallographic c axis and (2) I T < I L when the incident light propagation is down the crystallographic a/b axis. This study reveals mineral orientation variation related to deposition and paragenesis within limestone and dolostone samples. The method presented yields information related to growth and deformation during diagenetic and metamorphic alteration and may be used in research seeking to identify the fabric parameters of any calcite or dolomite containing rock. The compositional and structural data obtained from Raman mapping is useful in structural geology, materials science, and biosignature research.

Experimental study of thermomechanical effects in water-saturated limestones during their deformation

Stability control of elements of stone constructions of various structures is a prerequisite for their safe operation. The use of modern methods of non-destructive diagnostics of the stress-strain state of such constructions is an effective, and in many cases the only way to control it. Studies of thermal radiation accompanying the processes of solid bodies deformation allowed to justify and develop a method that allows to obtain non-contact information about changes in the stress-strain state in various types of geomaterials, including limestones. However, studies of the water saturation influence of rocks on the thermal radiation parameters recorded in this way are currently superficial. Taking into account the water saturation degree of rocks is necessary when monitoring the mechanical condition of stone structures that are in direct contact with water. The main purpose of this work is to study the dependences of changes in the intensity of thermal radiation from the surface of limestone samples with different humidity under conditions of uniaxial compression. The obtained results showed the expected significant decrease in the mechanical properties (uniaxial compressive strength and elastic modulus) of water-saturated samples in comparison with dry ones. At the same time, a significant increase in the intensity of thermal radiation of limestone samples subjected to compression with an increase in their water saturation was recorded, which makes it necessary to take into account the revealed regularity when identifying changes in the stress state of stone structures established according to non-contact IR diagnostics in real conditions.

A Laboratory Forced-Oscillation Apparatus for Measurements of Elastic and Anelastic Properties of Rocks at Seismic Frequencies

In presented paper, we describe the technical and physical aspects of the application of a low-frequency (LF) apparatus based on a longitudinal type of forced oscillations. In particular, we investigate the influence of the strain gauge position on a tested sample on measurement results, we also examine the creep effect associated with the mineralogy of rocks, as well as the dispersion and attenuation in a liquid-saturated rock sample caused by the presence of the volume of pore fluid exterior to the sample (dead volume). The effect of the position of the strain gauges is investigated using a cylindrical acrylic sample and two pairs of strain gauges fixed in the middle and at one of the sample ends under a uniaxial pressure of 15 MPa. The obtained results demonstrate that elastic and anelastic parameters of the tested sample are independent from the location of the strain gauges. The impact of the creep phenomenon on elastic moduli was studied using three room-dry samples of Savonnieres limestone, Berea sandstone and Eagle Ford shale. The measurements were conducted for 120 h at a frequency of 2 Hz under a uniaxial pressure of 10 MPa and demonstrated that the LF moduli of all rocks were noticeably reduced with time. The effect of dead volume was investigated at seismic frequencies using limestone saturated with n-decane. It was found that the Young’s and bulk moduli exhibit strong dispersion at frequencies above 10 Hz if the dead volume is close to or greater than the pore volume of the sample. We also found that the characteristic frequency of dispersion corresponding to the attenuation peak is independent of the size of the dead volume and determined only by the physical parameters of the sample and pore fluid. We present also the results of the Young’s modulus and attenuation measurements conducted at seismic frequencies on vertical and horizontal shale samples saturated with water. It was shown that the relationship between the extensional attenuation and the Young’s modulus dispersion observed in the samples saturated at a relative humidity of 97.5% is consistent with the Kramers–Kronig relation.

Local geochemical features of Lower Paleozoic rocks in the area of Duderhof dislocations (North-West of the Russian plate)

Research subject. A geochemical study of Cambrian-Ordovician deposits was carried out within the area of the Duderhof dislocations of the platform cover of the southern frame of the Baltic shield. Materials and methods. The ICP-MS method was used to study 14 samples of sandstones, limestone, phosphorites and black shales, which comprise both weakly dislocated stratified formations (stratified horizons) and strongly deformed formations, as well as secant dome-like and dike-like bodies. Results. Geochemical studies showed that, in the zones of tectonic disturbances, lower Paleozoic deposits are characterized by high concentrations of a number of trace elements, significantly exceeding the Clark values for sedimentary rocks. This applies to such chemical elements, as Be, Sc, V, Co, Ni, Cu, Mo, Pb, Th and U. At the same time, the concentrations of V and U are higher than those in the developed fields of Estonia and Sweden. An analysis of the cambriansands of the sablin formation showed that the eastern (Archean) part of the Baltic shield could not have been the source of food for their formation. The presence of leucoxene in the sands of the Sablinsky formation, a mineral formed by ilmenite under the influence of high temperatures, and the presence of mechanically unstable minerals in dike-like formations, indicate the influence of deep fluids on the sedimentary cover, whose flows moved along fault zones and carried the above-mentioned chemical elements to the near-surface layers of the earth’s crust. All this points to the endogenous rather than exogenous (glacial) nature of secondary structural-material transformations in the area of the Duderhof dislocations, as well as their genetic relationship with deformations in the Baltic-Mezen shear zone.

Lithological characteristics and formation conditions of lower jurassic limestones occuring in the Patil mountain (south-western Crimea)

Background. In this article, we investigate an outcrop of the Lower Jurassic limestones of the Eskiorda suite located on the northern slope of the Bodrak River basin in the south-western Crimea.Aim. The outcrop under study is mentioned in the majority of monographs devoted to the geology of the Crimean Mountains. Although the palaeontology of this assemblage has been sufficiently studied, its lithological aspects require elucidation. We carried out a series of lithological studies to identify the composition, structure and formation conditions of this limestone assemblage.Materials and methods. A macroscopic study of the outcrop was conducted followed by a detailed lithological study of collected limestone samples using a polarising microscope.Results. The conducted microscopic analysis revealed three structural types: organogenic-detrital, detrital and oolitic-organogenic-detrital limestones. The dominant component in the composition was fragments of echinoderms, mainly crinoids. Among other components were — in descending order — brachiopods, gastropods, foraminifera, remains of green algae, sponges, ostracods, ammonites and radiolarians, whose total content did not exceed 10%. Cinoid fragments were round to a various degree. The limestone fragments (intraclasts) were characterised by organogenic-clastic and pelitomorphic structures with an organogenic sludge, occasionally containing fine-sandy and silty quartz admixtures. Oolitic-organogenic-detrital limestones were almost entirely composed of crinoid fragments, some of which represented oolith cores. A specific feature of the limestones under study is their significant hardness resulting from the cementation of the structural components predominantly with crustification cement of several generations.Conclusions. The obtained results allowed us to draw conclusions about the formation conditions of the studied rocks. The limestones were formed in shallow water under the action of waves on the sediment in zones of constant currents. The hydrodynamic action on the sediment led to the formation of intraclasts. The early lithification of the sediment contributed to the formation of a hard seabed, on which subsequent generations of echinoderms settled, lived and died, forming an accumulative carbonate body.

Effect of particle size on in-situ desulfurization for oxy-fuel CFBC

Oxy-fuel circulating fluidized bed combustion (Oxy-CFBC) has been widely recognized as an economically promising way to capture carbon dioxide by injecting pure O2 and recycling CO2 from the flue gas because Oxy-CFBC has the advantages of fuel flexibility, in-situ desulfurization and NOx emission reduction. In this study, domestic limestone samples with a particle size range of 0–1 mm (0–75 μm, 75–106 μm, 106–212 μm, 212–300 μm and 500–1000 μm) were reacted in a thermogravimetric analyzer (TGA) under 60% CO2/40% O2 and 80% CO2/20% O2 at 1073 K and 1123 K for a direct desulfurization reaction. The surface and cross-section of limestone and CaSO4 samples with different conversion ratios were analyzed using a field emission scanning electron microscope (FE-SEM) and an energy dispersive spectrometry (EDS). FE-SEM images and EDS analysis of limestone and CaSO4 showed that direct desulfurization reaction starts from surface and progresses to center of particles, and the layer of CaSO4 expands into the whole particle. Since the experimental conditions of all particles were the same, the difference in CaSO4 conversion ratio by particle size confirmed through the TGA results depends only on the specific surface area. Also, the CaSO4 layer was formed at a uniform thickness regardless of the particle size.

Application of the Theory of Critical Distances for the Fracture Assessment of a Notched Limestone Subjected to Different Temperatures and Mixed Mode with Predominant Mode I Loading Conditions

This work aims to assess the fracture of U-notched limestone samples subjected to mixed mode I + II loading conditions with a predominant mode I influence, both at room temperature and at 250 °C. This analysis is based on the use of the Theory of the Critical Distances, and more specifically on the use of the Line Method, considering both an analytical and a numerical approach for the definition of the stress fields. An experimental campaign of almost 400 three-point bending tests has been performed as a basis for the fracture assessment of the limestone, using Single Edge Notched Bend (SENB) specimens with notch radii varying from 0.15 mm up to 15 mm, different temperature conditions and variable loading positions. The Theory of Critical Distances has successfully been applied to study the experimental results. The analytical and numerical stress fields for pure mode I fracture assessments provide similar accurate results both at 23 °C and 250 °C. Similarly, the mixed mode (I + II) fracture assessments allow the critical distance ( $$L$$ ) to be characterised for different mode mixities ( $${M}_{\mathrm{e}}$$ ), using the stress field around the notch tip obtained from the numerical models. Comparing the values of the critical distance against the mode mixity in isolation, a slight decrease of $$L$$ is observed as it approaches pure mode I conditions ( $${M}_{\mathrm{e}}$$ = 1). However, if the results are analysed separately for each notch radius, $$L$$ seems to be relatively constant with $${M}_{\mathrm{e}}$$ . In parallel, a certain influence of the notch radius on the critical distance is appreciated, which shows an increment both at 23 °C and 250 °C.

In Situ Investigation of Fluid‐Rock Interactions at Ångstrom Resolution

AbstractThe flow of aqueous phases through porous media shapes the world. It changes the courses of rivers, erodes mountainsides, dissolves historical monuments, builds caves, regulates the carbon cycle, and changes porosity in aquifers and hydrocarbon reservoirs. Despite the significance of this process both to natural phenomena and human endeavors, fundamental insight into the mechanisms that drive it at the Ångstrom scale is scarce. Here, we employ environmental transmission electron microscopy (ETEM) to visualize interactions between water and various types of porous media, including sandstone, limestone, and dolostone samples, at Ångstrom resolution in real time. Unlike other techniques presented in the literature, ETEM allows for direct visualization of both the aqueous phase and the porous media. As expected, dissolution and recrystallization were observed to significantly impact the shapes, sizes, and interconnectivities of the pores in the rocks. However, for the first time, we provide direct in situ experimental evidence that adsorption‐induced strain can also significantly impact the above‐mentioned parameters, especially in micropores. In some cases, adsorption was observed to reduce effective pore size by more than 60%. The magnitude of the change in pore size was found to vary with pore wall mineralogy and pore geometry. This work presents the first direct Ångstrom‐resolution observations of liquid adsorption films and adsorption‐induced strain.

Variations in ultrasonic wave velocities of Miocene carbonate and clastic sedimentary rocks under dry and fully water saturated conditions

This study investigates the variations in P and S wave velocities (Vp, Vs) under dry and saturated conditions and attempts to develop empirical equations estimating Vs based on Vp. In this context, 48 intact core specimens extracted from the Miocene sedimentary rocks were examined. A significant decrease was observed in Vp under saturated conditions (Vp-sat) for several specimens. Thus, selected samples were further examined by thin section, X-ray diffraction, and scanning electron microscopy equipped with an energy dispersive spectrometer. Correlation analyses were performed to reveal the causes of reduction in Vp-sat in terms of porosity, microcrack density, and mineralogical content. Vs was also observed to have a decreasing trend under saturated conditions. Strength and elasticity loss after saturation were not well correlated with the reduction in Vp-sat. The measured velocity values were also compared with the ones derived from Gassmann’s theory. Despite the discrepancy in the literature, a new parameter explaining the negative difference between the values of saturated and dry Vp was suggested. The mudstone texture and the abundant microporosity were firstly declared to be indicative of a negative velocity difference among the same rock group having similar mineralogy. Afterward, two empirical equations estimating Vs were derived from the ultrasonic wave velocities measured in this study and the data compiled from published literature. These equations were applied to a different dataset and compared with the ones suggested by various researchers. Proposed equations were determined to be more widely applicable and valid for limestone, mudstone, and sandstone samples according to several accuracy metrics.

Studying the Effect of some Factors on the Stress-Strain Behavior of the Rostov Region Limestones in the Course of their Production and Use

The paper considers the current state of the mineral raw material base and the construction material market of the Rostov Region. The effect of various factors on the strain-stress behavior of local limestones has been investigated. The scientific and technical literary sources devoted to the processes of rock failure under various loads have been analyzed. The experimental studies have shown that the tested samples of limestone with a high content of cuboidal grains have characteristics comparable to those of the crushed granite stone. It has been concluded that the use of the Rostov Region limestones in the construction industry is competitive and feasible, provided the proper implementation of the engineering measures proposed in their production.

Influence of application method and number of applications of nanolime on the effectiveness of the Doulting limestone treatments

Over the last two decades, nanolime has been recognized as a promising consolidation approach to consolidate historic calcareous substrates due to its compatibility, durability and fast carbonation. The effectiveness of nanolime products has been widely proven for superficial consolidation treatments, especially in historic wall-paintings. However, its consolidation mechanism in highly porous substrates, such as in the case of limestones or lime mortars, still needs to be fully understood. This paper aims to study the influence of application method and number of applications on the effectiveness of nanolime treatments, which has never been targeted until now. In this experimental work, the Ca(OH)2 nanoparticles were freshly synthetized by anion exchange resins and applied in historic Doulting limestone samples, extracted from a capital from the Cathedral of Wells (Somerset, UK). In order to study the influence of application method on the effectiveness of treatments, samples were treated by: (1) brush; (2) spray; and (3) capillary absorption. Additionally, to study the influence of the number of applications on the consolidation effectiveness, these three application methods were applied by: (1) 1 application; (2) 5 applications; (3) 10 applications. The consolidation effectiveness of the resulting nanolime treatments was studied by assessing changes in porosity, superficial and internal stone’s density, superficial cohesion, water absorption by capillarity and aesthetic properties. Results showed that repeated applications (i.e. 10 applications) of a low concentrated nanolime (i.e. 5 g/L) by spray and brush can increase the superficial cohesion, mechanical properties and density of the stone at the surface. Additionally, results suggest that the application method does not significantly affect the consolidation effectiveness of nanolime treatment, contrary to what was commonly believed. Results also show that a single application treatment of low concentrated nanolime (i.e. 5 g/L) does not significantly provide noticeable consolidation effectiveness regardless of the application method, also contrary to what was commonly believed. These results suggest that for a noticeable consolidation treatment with low concentrated nanolime the application must consist of several applications (> 10). This could have a high impact on the Built Heritage conservation community that commonly use nanolime in conservation activities.

Added Value of Limestone Batumilmil and Its Application in Industry

This study explains the added value of the North Sumatra Langkat limestone and its derivative products. Limestone is classified as high calcium, characterized by its high calcium oxide (CaO) content of 38.39% -55.84%, its physical characteristics show dark gray color, dominant calcite, smooth, hard and fossilized texture. So far, the use is in the form of chunks, especially as a raw material for building which gives a low value to the limestone. The 3 limestone samples SK5, SK7 and SK8 were calcined to obtain quicklime and hydrated lime products with different temperatures of 900°C-1100°C. Limestone SK7 and SK8 CaO content increased 59.7% and 66.08% respectively and were light white compared to SK5 55.8% and colored brownish gray. To produce hydrated lime, it is done by adding / soaking with water (H2O) to the quicklime to produce a heat rate of hydration (slaked). SK8 limestone shows an optimum temperature increase of 74.6°C for 75 seconds compared to SK7 and SK5 limestone 50.2°C and 48°C respectively at 900°C combustion temperature. The heat transper occurs on the outer side of the limestone, then spreads to the limestone body. The difference in hydrated heat in the limestone is due to the presence of mineral impurities and non-uniform grain size so that the heat obtained is not perfectly distributed. The impurities such as SiO2, Fe2O3, Al2O3 and MgO contribute to the product quicklime and reactivity of these samples. Besides the quicklime and hydrated lime products, the added value of Batumilmil limestone is derived by making ground calcium carbonate (GCC). The GCC product is fine mesh size of 60 mesh - 400 mesh ultrafine, with high calcium quality and bright / bright color. The increase in added value added from limestone products contributes to the selling value and various applications in the industrial sector.

Interaction of Ca2+ and soil humic acid characterized by a joint experimental platform of potentiometric titration, UV–visible spectroscopy, and fluorescence spectroscopy

Rocky desertification has become a major environmental issue in the karst region of southwestern China. Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils, despite the relatively higher soil organic matter (SOM) content in limestone soil. The underlying mechanism remains ambiguous. We speculated that the geochemical characteristics of limestone soils in the karst region plays an essential role, especially the high calcium content of limestone soil. To test this hypothesis, we collected limestone soil samples from a limestone soil profile in the southwestern China karst region and extracted humic acid (HA) from these limestone soil samples. We investigated the interaction of Ca2+ and three HA samples on a joint experimental platform, which consists of an automatic potentiometric titrator, a UV–visible spectrometer, and a Fluorescence spectrometer. HA solutions were titrated by Ca2+ and optical spectra of the HA solutions were monitored during the titration experiments. The results indicated that: (1) the interaction of Ca2+ and HA is a combined process of adsorption and complexation. Adsorption dominated the overall distribution behavior of Ca2+, which could be fit by Langmuir and Freundlich isotherm models. Complexation was distinguished only when the concentration of Ca2+ is low; (2) the changes of UV–visible spectroscopy and excitation–emission matrix fluorescence spectroscopy spectra of HA samples when they were binding with Ca2+ implied the apparent molecular size and structure of HA became larger and more complex; (3) the combination of Ca2+ and HA plays an important role in the SOM preservation of limestone soils but the stability of the Ca–HA association was relatively weak. The present study draws attention to maintaining the relatively higher Ca2+ concentration in limestone soils in ecologic restoration attempts in karst regions.

Comparison of the Properties of Natural Sorbents for the Calcium Looping Process.

Capturing CO2 from industrial processes may be one of the main ways to control global temperature increases. One of the proposed methods is the calcium looping technology (CaL). The aim of this research was to assess the sequestration capacity of selected carbonate rocks, serpentinite, and basalt using a TGA-DSC analysis, thus simulating the CaL process. The highest degrees of conversion were obtained for limestones, lower degrees were obtained for magnesite and serpentinite, and the lowest were obtained for basalt. The decrease in the conversion rate, along with the subsequent CaL cycles, was most intense for the sorbents with the highest values. Thermally pretreated limestone samples demonstrated different degrees of conversion, which were the highest for the calcium-carbonate-rich limestones. The cumulative carbonation of the pretreated samples was more than twice as low as that of the raw ones. The thermal pretreatment was effective for the examined rocks.