Presence Of Calcium Carbonate Research Articles

Sustainable concrete construction by microorganism and monitoring using EMI technique: A review

Construction of concrete infrastructures is developing worldwide from the ancient period therefore; sustainable concrete is required for clean environment reason. The formation of cracks/fissures creates problems to the concrete which reduces durability of concrete structures. These cracks/fissures in concrete originate due to the natural forces viz., weathering and landslide, seismic, flooding and human interventions which affect the service life of structures. The application of microorganisms in concrete is the innovative technology for sustainable construction and self-healing of cracks. These microorganisms' bacterium produces calcium carbonate in presence of moisture and carbon dioxide. The use of bacteria in concrete consumes carbon dioxide available in the atmosphere and produces solid substances like calcium carbonate for self-healing of the cracks and develop sustainable infrastructure. Electro-Mechanical Impedance (EMI) technique is based on smart materials and used for monitoring of crack/fissures present in structures. The impedance and admittance signatures can be used for determination of the presence of damage. Admittance signature consists of conductance (real part) and susceptance (imaginary part) signature, respectively. The changes in the signature from the healthy state baseline signature indicate presence of damage in structures. The research review article is focused on microbial-based concrete and its importance related to the clean environment and sustainable construction development. Furthermore, the types of bacteria used in concrete and its optimal concentration have been covered. Moreover, the EMI technique and its application on concrete industry for monitoring the health of structures have been taken into consideration. The use of EMI technique to monitor the performance of bacterial concrete will be helpful for sustainable buildings. The review article will suggest new research directions in the field of sustainable construction industry.

Photolysis mechanisms of tetracycline under UV irradiation in simulated aquatic environment surrounding limestone.

As the most typical geological environment, limestone landforms are widespreading in the world and affect the waters that flow around them, which may also change the fate of organic contaminants in these waters. In this study, aquatic environment surrounding limestone was simulated with calcium carbonate, and the photolysis of tetracycline was evaluated under UV irradiation (30μW/cm2). More tetracycline (up to 98%) was removed in 4h in the presence of calcium carbonate while only 50% of tetracycline was eliminated in control experiment. The removal of tetracycline was greatly enhanced due to the major roles of alkaline pH and minor roles of Ca2+ and HCO3-/CO32-. In alkaline pH, tetracycline existed as TCs- with higher electronic density in the ring structures, which was more easily attacked by OH. Besides, it could also change the bond orbital energy to facilitate tetracycline absorbing more photon. Moreover, alkaline pH was beneficial to generate more OH and thus promote the indirect photolysis. In addition, alkaline pH also changed the degradation path of tetracycline and rapidly convert tetracycline to the byproducts with m/z 457 via hydroxylation and hydrogen abstraction. This work provides not only better understanding about the fate of tetracycline in aquatic environments but also new insights into the treatment of antibiotic-contaminated water.

Mine Waste: Consolidation Behaviour of Precious Metal Tailings

All mine processing plants generate waste. These byproducts include waste rock and a fine-grained slurry referred to as ‘tailings’ (Beier, 2015). The primary objective of treating tailings is to remove water, to enhance strength and stiffness (Sobkowicz and Morgenstern, 2009). Studying the geotechnical properties of tailings is essential to understand consolidation behaviour and facilitate land reclamation. Moreover, the geochemical characteristics of tailings should be examined to examine the potential onset of acid rock drainage (ARD). Acid rock drainage occurs when pH falls below 4, which can cause metal heavy leaching as they become present in solution. This study investigates both the geotechnical and geochemical behaviour of precious metal tailings in atmospheric conditions. The geochemical parameters of interest are pH, redox potential (Eh) and electric conductivity (Ec). The Large Strain Consolidation test (LSC) was implemented to characterize the compressibility behaviour of the sample. Accordingly, the amount of deformation that the tailings underwent was measured as they were loaded to different effective stresses. In addition, the hydraulic conductivity or the velocity of water flow was measured at the end of each consolidation step. Furthermore, the chemical parameters were evaluated using standardized probes. The tailings exhibit high compressibility during self-weight consolidation due to a combination of high initial void ratio and a high initial saturated hydraulic conductivity. In addition, hydraulic conductivity decreases nonlinearly as the samples are loaded because loading reduces the pore volume. The permeability decreased two orders of magnitude during loading, from 2.14E-05 m/s to 1.60E-7 m/s. From the geochemical point of view, there is no significant change in pH as the tailings consolidate. In this scenario, the presence of calcium carbonate has an acid-neutralizing capacity. Moreover, there is a slight increase in both redox potential and electric conductivity due to exposure to the atmosphere. The increasing trend of redox potential had a slope of 10 mV per day. While the slope of electric conductivity was 9 mS/cm per day.

A study of the early hydration processes and properties of fly ash-slag binders

The results of a study on the early hydration process of pastes composed of ground granulated blast furnace slag and fly ash from fluidized bed combustion of brown coal are presented here. The results of the tests concerning setting time, hydration processes (spectroscopy, calorimetry and thermogravimetry) and mechanical strength confirm that the hydration process occurs and solid microstructures and hydration products (hydrated calcium silicates and aluminosilicates, sulphoaluminates and calcium hydroxide) are formed. The presence of calcium carbonate was confirmed. Increasing the amount of fly ash in pastes intensifies the process of early hydration, thereby accelerating the initial setting time and increasing the amount of water bound in hydration products. The early compressive strength is also improved. For example, the specimen containing the highest amount of fly ash showed a decrease in the initial setting time by about 20% and an increase in the 2-day compressive strength by 22%, compared to the specimen containing the lowest amount of fly ash.

Influence of the Amount of Ammonium Salts in Fly Ash on Concrete with Ternary Binders

The requirements for reducing nitrogen oxide emissions have led power and heating plants to installing reduction technologies such as the selective non-catalytic reduction (SNCR). The paper deals with the influence of the amount of ammonium salts in fly ash from power plants where SNCR method is used on the properties of mortars with ternary binders. Portland cement is the main component of this ternary binder system. As other components, fly ash and lime or finely ground recycled concrete dust were used. The synergic effect of all three components helps us to get a higher initial strength. This is caused by the presence of calcium carbonate and aluminate ions in the system. The chemical and physical-mechanical properties of fly ash are presented; especially, the amount of ammonium salts in accordance with ČSN ISO 7150-1 and the specific surface area. On mortars, the activity index of compressive strength and workability was examined.

Isosorbide‐based polysebacates as polymeric components for development of in situ forming implants

In situ forming implants (ISFIs) appear to be a convenient drug delivery system, alternative to conventional preformed implants and microparticles for parenteral drug delivery applications. It has been shown that they offer several advantages including easy and minimally invasive application, potential for local/site‐specific drug delivery that allows reduction of side effects associated with systemic administration of drug. A few ISFI formulations based on poly(α‐hydroxy acids), solidifying by solid phase separation, are currently commercially available. In this work, polyesters based on sebacic acid, isosorbide, and optionally 1,2‐propanediol were synthesized and characterized. Poly(isosorbide sebacate‐co‐1,2‐propylene sebacate) (PISEBPG) was chosen as an essential constituent of new ISFI formulations dedicated to controlled release of doxycycline hyclate (DOXY). Basic characteristics of new ISFI formulations were investigated. In particular, the influence of addition of a relatively hydrophobic cosolvent (triacetin, TA) to a more hydrophilic 1‐methyl‐2‐pyrrolidone (NMP) as well as the presence of calcium carbonate (CAC) on the morphology of resulted depots and DOXY release profile was evaluated. Scanning electron microscopy (SEM) analysis revealed that the presence of TA resulted in more porous morphology of the depots. DOXY has been releasing continuously from depots in vitro within 12 weeks depending on the composition. The release profile of the PISEBPG‐based formulation containing CAC indicates that it could be useful where short‐term (up to 14 d), rapid release of the antibiotic is required, while formulation without CAC, where after 21 days about 50% of the drug loaded may still be available for release, may be better for the long‐term delivery of DOXY.

Improvement of soil nutrient and biological properties and establishment of Lycium barbarum L. in an impermeable saline-sodic soil using drip irrigation

A sodicity-induced degraded wasteland, classified as takyric solonetz with low permeability (Ks <0.1mm d–1), is spread widely across the arid area of north-west China. A 3-year field experiment was conducted to evaluate the improvement of soil properties and growth performance of Lycium barbarum L. Drip irrigation of 5mm was triggered in each irrigation event by controlling the soil matric potential above –15 kPa, and urea, phosphoric acid and potassium nitrate were applied with irrigation water. Soils were sampled intensively in soil transects in different years. Results showed that the soil total nitrogen and organic carbon contents in the root zone increased by 63.9% and 16.3% after 3 years respectively, due to the addition of fertiliser and the return of more residue with plant growth. Similar increases occurred in soil nitrate contents, which showed obvious mobility with water flow. After reclamation, the reduced soil pH helped activate the original unavailable phosphorus caused by the presence of calcium carbonate in native soil, and increased the soil phosphorus availability. Soil urease, alkaline phosphatase and sucrase activities in the root zone were enhanced significantly by reclamation. Remarkable increases in soil respiration rates occurred within the horizontal 20-cm-distance from the drip line. Compared with the perpendicular direction to the drip line, more plant roots developed in the parallel direction, and their spatial distribution appeared in the range of 40-cm-width and 60-cm-depth beneath the drip line. An acceptable survival rate (>80%) and dry fruit yield (866kg ha–1) were obtained at 3 years. The findings provide an alternative for reclaiming the saline-sodic soil with low permeability.

Conformational polymorphic changes in the crystal structure of the chiral antiparasitic drug praziquantel and interactions with calcium carbonate

Praziquantel is an antiparasitic drug used for decades. Currently, the praziquantel commercial preparation is a racemic mixture, in which only the levo-enantiomer possesses anthelmintic activity. The knowledge of its properties in the solid state and other chemical-physical properties is necessary for improving its efficacy and applications. Drug solid dispersions were prepared with calcium carbonate at 1:5 drug to excipient weight ratio by solvent evaporation method. Then, the modification of the crystal structure of the racemic polymorph of praziquantel in presence of calcium carbonate has been studied by means of several analytical techniques (DSC, TGA, XRD, SEM, FTIR, Raman spectroscopy and chiral liquid chromatography). This study has been completed with atomistic calculations based on empirical interatomic force fields and quantum mechanics methods applied to the crystal structure of praziquantel and of intermolecular interactions. The results evidenced that calcium carbonate provoked a conformational change in the praziquantel molecule yielding the formation of different polymorphs of praziquantel crystal. These alterations were not observed replacing calcium carbonate with colloidal silica as excipient in the solid dispersion.

Study of hydration process of ternesite clinker

Currently ternesite, Ca5(SiO4)2SO4, is used in the cement production, is one of two key phases of calcium sulfoaluminate cement. Some investigators claim that this phase is nearly inert or very low reactive and it hydrates only after later age of hydration. In order to improve knowledge in this field, process of hydration of neat ternesite clinker under specific conditions of exposure was observed in this study. Ternesite was prepared by firing of raw meal consisting of high calcium limestone, microsilica and calcium sulfate hydrate. The resulting ternesite clinker was subsequently hydrated in four storage environments. Kinetics of hydration process was monitored in water and in environment of saturated carbonic acid, at two different temperatures of 5 and 40 °C. Mineralogical composition of hydrated samples was analyzed by X-Ray diffraction analysis (XRD) and by differential thermal analysis (DTA) in particular ages of hydration. Based on the results, it can be claimed that rate of decomposition of ternesite was related to conditions of storage. The rate of decomposition was significantly accelerated by the environment of carbonic acid and also by the elevated temperature. Presence of calcium carbonates in mineralogical forms of calcite, vaterite and aragonite, coupled with gypsum and thaumasite was identified.

Thermodynamics and kinetics of methane hydrate formation and dissociation in presence of calcium carbonate

Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca2+, CO32−, HCO3−, CO2, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10 wt%.

Chemical and microbiological evaluation of novel chemical treatment methods for acid sulfate soils

Naturally occurring sulfide rich deposits are common along the northern Baltic Sea coast that when exposed to air, release large amounts of acid and metals into receiving water bodies. This causes severe environmental implications for agriculture, forestry, and building of infrastructure. In this study, we investigated the efficiency of ultrafine-grained calcium carbonate and peat (both separately and in combination) to mitigate acid and metal release. The experiments were carried out aerobically that mimicked summer conditions when the groundwater level is low and acid sulfate soils are exposed to oxygen, and anaerobically that is similar to autumn to spring conditions. The ultrafine-grained calcium carbonate dissipated well in the soil and its effect alone and when mixed with peat raised the pH and reduced pyrite dissolution while peat alone was similar to the controls and did not halt metal and acid release. High throughput 16S rRNA gene sequencing identified populations most similar to characterized acidophiles in the control and peat treated incubations while the acidophilic like populations were altered in the calcium carbonate alone and calcium carbonate plus peat treated acid sulfate soils. Coupled with the geochemistry data, it was suggested that the acidophiles were inactivated by the high pH in the presence of calcium carbonate but catalyzed pyrite dissolution in the controls and peat incubations. In conclusion, the anaerobic conditions during winter would likely be sufficient to mitigate acid production and metal release from acid sulfate soils and in the summer, treatment with calcium carbonate was the best mitigation method.

The mineral sequestration of CO2 with the use of fly ash from the co-combustion of coal and biomass

Summary As a result of energy production processes, the power industry is the largest source of CO2 emissions in Poland. Emissions from the energy sector accounted for 52.37% (162 689.57 kt) of the total emissions in 2015, which was estimated at 310.64 million tons of CO2. In recent years, the tightening of regulations on the use of renewable energy sources has resulted in an increased amount of biomass used in the professional energy industry. This is due to the fact that the CO2 emissions from biomass combustion are not included in the total emissions from the combustion of fuels, resulting in the zero- emission factor for biomass. At the same time, according to the hierarchy of waste management methods, recycling is the preferred option for the management of by-products generated during energy production. The fly ashes resulting from the biomass combustion in pulverized boilers (which, due to their chemical composition, can be classified as silicate ash) were subjected to analysis. These ashes can be classified as waste 10 01 17 - fly ash from co-firing other than mentioned in 10 01 16 according to the Regulation of the Minister of the Environment of December 9, 2014 on waste catalogues. The maximum theoretical carbon dioxide binding capacity for the analyzed fly ashes resulting from the co-combustion of biomass is 8.03%. The phase composition analysis of the fly ashes subjected to carbonation process has shown, in addition to the components identified in pure fly ash samples (SiO2, mullite), the presence of calcium carbonate − calcite − the primary product of the carbonation process, as indicated by the results of both X-ray and thermogravimetric analysis.The degree of carbonation has been determined based on the analysis of the results of the phase composition of fly ash resulting from the co-firing of biomass and bituminous coal. The calculated degree of carbonation amounted to 1.51%. The carbonation process is also confirmed by the lowered pH of the water extracts, decreasing from 11.96 for pure ashes to 8.7 for CO2 treated fly ashes. In addition, the carbonation process has reduced the leaching of pollutants, most notably chlorides, sulphates, and potassium.

Impact of cation-exchange membrane scaling nature on the electrochemical characteristics of membrane system

Abstract The membrane fouling formation during electrodialysis of complex solutions is one of the main issues affecting the process performance and costs. This work was focused on the investigation of electrochemical behavior of membrane systems containing a cation-exchange membrane whose surface was affected by mineral fouling of different composition. Together with the scaled membranes, the pristine membrane was studied for comparison. For membrane without scaling on its surface, it was found that the limiting current value exceeded the one theoretically calculated by the convection-diffusion model. It is most likely related to equilibrium electroconvection developed at the membrane surface. The presence of magnesium and calcium hydroxides on the membrane surface leads to an intensification of water splitting at the depleted membrane surface, resulting in suppression of electroconvection and reduction of the overlimiting current. The presence of calcium carbonate on top of magnesium and calcium hydroxides prevents their contact with water molecules. The current-voltage characteristic of such membrane system was almost identical to the characteristics of the membrane system containing the pristine membrane. To our knowledge, it was the first time that the impact of scaling nature on the electrochemical behavior of membrane system was revealed and the relative mechanisms identified and explained.

Atmospheric NOx removal: Study of cement mortars with iron- and vanadium-doped TiO2 as visible light–sensitive photocatalysts

Mortars made with Portland cement, two different calcium aluminate cements and air lime were chosen to incorporate photocatalytic additives, because they have large exposed surfaces that boost the photochemical oxidation (PCO) of atmospheric pollutants such as nitrogen oxides. TiO2 as reference catalyst, and two doped titania, Fe-TiO2 and V-TiO2, which were expected to increase the sensitivity of the additives towards the visible light, were studied. Cementing matrices, particularly air lime and high alumina cement mortars, yielded significant amounts of NO removal under the three illumination conditions studied (UV, solar and visible light), with high selectivity response for NO abatement (up to 60–80%) and low NO2 release. The presence of calcium carbonate has been shown to have a synergistic effect, enhancing the PCO of these mortars under different light sources.

The Assessment of Heavy Metals Content in Total and Bioavailable forms in the Soils Surrounding Cementownia Chelm S.A. in Chelm, Poland

The study consisted in assessing the impact of the cement industry on the selected physicochemical properties and total and bioavailable content of heavy metals in soils located in the vicinity of the factory. The sampling points were located in the four transects to the east, west, north and south of the plant, at an increasing distance of 0 - 250 - 500 - 1500 and 2000 m. The soil samples were collected from the depth of 0-20 cm. The analysed soils were characterised by the significant presence of calcium carbonate, distributed evenly in all directions. Concentrations of heavy metals were characterised by high variation, depending on the direction and distance from the cement factory. The percentages of bioavailable forms of heavy metals in the general pool did not exceed 10%.

Microbially assisted cementation – A biotechnological approach to improve mechanical properties of cement

Microbially induced calcium carbonate precipitation (MICCP) is a promising technology used in various engineering applications. Urease produced by soil microorganisms hydrolyses urea, producing carbon dioxide which forms calcium carbonate in presence of calcium ions, which gets precipitated and enhances the mechanical properties of cementitious materials. An attempt was made to enhance the properties of ordinary Portland cement (OPC) using soil microbial solution with lentil seed (Lens culinaris) powder as protein source and sugar as carbon source. Bio-OPC specimens using microbial solution instead of water were prepared. Significant increase in compressive strength was observed in bio-OPC specimens as compared to the specimens prepared using water.

Transformations of calcium sulphates in solidified carbonated volatile fluidized ashes

Abstract Carbonation of volatile fluidized ashes with the use of carbon dioxide can be a means to their transformation into a product with a possible application as an additive to cement and concrete. Currently, due to its physical-chemical characteristics and particularly because of the high concentration of free calcium oxide, the possible applications of this product are highly limited, perhaps even none existent. A significant reduction or even the complete elimination of CaO can be achieved by its transformation into calcium carbonate. In carbonated volatile fluidized ashes, two components relevant to the binding time of mortar, as well as its durability, can be found: calcium carbonates and calcium sulphates. During the investigation it was assumed that calcium carbonate, being poorly water-soluble, would not react with the remaining components of the porous water of the volatile fluidized ash. Crystalline phases of calcium sulphates, anhydrite, gypsum and bassanite occurring in bound volatile fluidized ashes after carbonation demonstrate the possibility of crystallization in the presence of calcium carbonate. In particular, a change in the concentration of bassanite indicates that this phase, as a precursor to the crystallization of gypsum, may play a significant role in the process of binding carbonated volatile ashes.

Calcite passivation by gypsum: the role of the cooperative effect

The overgrowth of gypsum (CaSO4·2H2O) on calcite (CaCO3), used as a substrate, has been obtained in order to verify the hypothesis of a crystallographic fit between the two phases. Lattice coincidences show that many orientations of gypsum with respect to calcite can occur. Experimentally, only two among these are fulfilled during the early stages of growth, the selection criterion reasonably being the adhesion energy. Moreover, it has been shown that the presence of calcium carbonate as a specific surface impurity in solution modifies the growth habit of gypsum acting on the growth rate and surface morphology of some gypsum forms. At high concentration, the calcium carbonate in solution promotes the twinning of gypsum according to the Montmartre law.

Effect of addition of calcium ions and hydrothermal treatment on the morphology of calcium phosphates

Chemical precipitation followed by hydrothermal processing is conducted to obtained different phases of calcium phosphate. The hydrothermal treatment time affects the calcium phosphate phases obtained. The aging time does not influence the calcium phosphate phases obtained but it has an effect on crystallinity. On the other hand, the presence of calcium carbonate, together with hydrothermal treatment, promotes the formation of hydroxyapatite with rod-shape.

Formation of cerussite and hydrocerussite during adsorption of lead from aqueous solution on oxidized carbons by cold oxygen plasma

A new procedure of elimination of Pb2+ from aqueous solution using carbon adsorbents, in which high amounts of cerussite and hydrocerussite are deposited on the carbon surfaces, is reported. The procedure includes the preparation of carbons from selected lignocellulosic wastes (pecan nut shells and peach stones) by single carbonization and further oxidation with cold oxygen plasma. The materials prior and after the oxidation treatment were characterized using elemental analysis, FT-IR spectroscopy, SEM/EDX analysis, adsorption of N2 at −196°C and X-ray photoelectron spectroscopy. The adsorption of Pb2+ was carried out in batch systems under constant agitation. The formation of cerussite and hydrocerussite on the spent carbon surfaces was confirmed by XRD, SEM/EDX and FT-IR. A Pb2+ removal mechanism is proposed in which a co-precipitation of lead nitrate and calcium carbonate would render the formation of the lead carbonates. In such mechanism, the occurrence of CaCO3 on the surface of the adsorbents plays a crucial role. The presence of calcium carbonate on the precursors is understood on the basis of the thermal evolution of calcium oxalate originally present in the biomass. The oxygen plasma treatment helps to expose the calcium carbonate nanocrystals thus improving dramatically the removal capacity of Pb2+. Accordingly, retention capacities as high as 63mg of Pb2+ per gram of adsorbent have been attained.