Phase and morphology evolution of PCC precipitated during carbonation of calcium-rich solution with/without additives.
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•Rhombohedral calcite switched to spherical vaterite during the ...gas–liquid carbonation process.•Organic additives delay or change the phase transition pathway of PCC.•Pure spherical vaterite can be produced in the CO2 mineralization process.•Organic additives may influence the growth morphology by coordinating with a specific crystal plane of PCC.
The indirect CO2 mineralization by using Ca/Mg-containing industrial alkaline by-products or wastes is a promising way for mitigation of CO2 emissions and valorization of wastes, although plagued by the utilization of precipitated calcium carbonate (PCC) if low-value product is obtained. It is difficult to acquire specific PCC with targeted morphology for commercial use since many parameters change in the gas–liquid carbonation process. In this work, the phase transition and morphology evolution behavior of PCC precipitated during carbonation of 0.1 mol·L−1 NH4Cl Ca-rich solution were studied. Results show that the polymorph transformation from rhombohedral calcite to spherical vaterite was found during the gas–liquid carbonation process, which is different from the traditional carbonation process (aqueous carbonation of lime). A promising result is that pure spherical vaterite of industrial interest was obtained under the studied conditions. In addition, to achieve conversion of CO2(g) into desired morphology of PCC, the feasibility of introducing additives (ethylene glycol and citric acid) into the gas–liquid carbonation system was also evaluated in terms of CO2(g) adsorption and PCC polymorphs control. Finally, the mechanism of additives on the growth and morphology of crystalline CaCO3 was investigated by FTIR and interpreted at the atomic level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Hydroxyapatite (HAp) refers to a bioceramic broadly employed in bone tissue engineering since it has bioactive and osteoconductive properties. The synthesis of HAp will be more economically viable ...using waste materials because it is cheap, easy to find, and available in large quantities. Therefore, this study aimed to synthesize and characterize HAp from green mussel shells by hydrothermal method at various temperatures. Precipitated calcium carbonate (PCC), made from green mussel shell powder, is employed in this study. Utilizing a hydrothermal reactor for 14 hours at 120℃, 140℃, as well as 160℃, a combination of PCC and (NH4)2HPO4 with a Ca/P molar ratio of 1.67 was synthesized to form HAp. Note that the synthesis findings were categorized using scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), as well as X-ray diffraction (XRD) tests. Apart from that, the FTIR test showed the formation of HAp in all test variations because the results of –OH, and –PO4 were found. XRD results that have been analyzed using HighScore Plus software show the percentage of weight (%) and crystal size of HAp increases with increasing hydrothermal temperature. Other than that, HAp produced at hydrothermal temperature variations of 160℃ has a hexagonal crystal system with a percentage of weight (%) as well as a crystal size of 46.43 nm and 99.3%, whilst the amount of impurity (%) produced is 0.7%. The higher the hydrothermal temperature, the weight percentage (%), and the crystallite size in HAp are getting bigger while the number of impurities gets smaller.
•Vortex flows in a Taylor-Couette reactor produce metastable calcium carbonates such as vaterite.•Local mixing and increased mass transfer efficiencies produce uniform vaterite particle ...sizes.•Vaterite formation is also evident in leachates from realistic alkaline industrial residues.
The use of calcium bearing resources to facilitate solvent regeneration and CO2 reuse via carbon mineralization offers a low energy pathway for the production of calcium carbonate. However, a crucial challenge is the lack of specificity in the formation of various calcium carbonate polymorphs during carbon mineralization. One of the less explored but highly effective approaches to tune the morphology and crystal structure of specific carbonate phases involves tuning vortex flows. This approach is an alternative to utilizing chemical reagents that need to be regenerated for tuning the morphologies and crystalline structures to direct the formation of specific carbonate phases. In this study, the efficacy of using homogeneous vortex flows in limiting the agglomeration of carbonate particles and directing the formation of metastable vaterite phases is discussed and contrasted with the influence of inhomogeneous conventional feed flow patterns on precipitated calcium carbonate (PCC). Herein, a Taylor-Couette Carbonate Conversion (TC3) reactor is used to direct the formation of spherical vaterite particles with uniform particle size distribution preferentially over calcite and other phases. The formed vortex patterns inside TC3 reactor provide homogeneous reaction spaces conducive to PCC formation, ensuring uniform mixing throughout the process. By increasing the rotational speed and the residence time, higher purity carbonates with more uniform sizes are obtained. Furthermore, preferential vaterite formation is also observed in leachates obtained from alkaline industrial residues such as construction and demolition waste and steel slag. Thus, the proposed approach is effective in harnessing multiple waste streams such as CO2 emissions and alkaline industrial residues to produce calcium carbonate phases such as vaterite with structural and morphological specificity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Dolomitic marbles are used to synthesize pure CaCO3 nanoparticles.•Calcium-sucrate and sodium dodecyl sulfate are used as particle size controllers.•The CO2 and sodium carbonate are ...employed for the preparation of CaCO3.•Nanoparticles with rod-like and spheres are obtained by varying pH.
Synthesis of nanomaterials from readily available minerals for industrial applications is a growing research area. Understanding the causes of their properties becomes handy in utilization. In this study, an effective sucrose solution based method was employed for the extraction of calcium from dolomite to synthesize precipitated calcium carbonate nanostructures with different morphologies and sizes. It was found that 30% (w/v) sucrose solution extracted approximately 91% of calcium from dolomite forming a calcium-sucrate complex. Carbonation was achieved by CO2 bubbling and aqueous sodium carbonate addition. Precipitation was performed under different pH values of 7.5, 10.5 and 12.5 in the absence of an anionic surfactant and in the template of sodium dodecyl sulfate (SDS)/calcium-sucrate at pH 12.5. It was found that CO2 bubbling slightly promotes smaller particles. The anionic surfactant enables particle size and agglomeration reduction while introducing some hydrophobicity. The smallest particles were achieved at a range of 40–55 nm in the presence of SDS/sucrose template and were of spherical morphology. By changing the pH, a tendency to form different polymorphs and shapes of calcium carbonate was observed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ca-source of green mussel shells (Perna-Viridis) recovered into precipitated calcium carbonate (PCC) powders via a calcination-dissolution-precipitation pathway is a prospective feedstock for the ...rapid synthesis of monocalcium phosphate monohydrate (MCPM). In the study, a potential aqueous crystallization process was implemented for MCPM synthesis by blending PCC powders with vaterite (55.20 wt. %) and calcite (44.80 wt.%) in strongly phosphoric acid with a molarity of 85 % (w/w) and varying amounts of water (2-6 ml), followed by rapid evaporation and drying. The resulting product contained at least 90 wt. % MCPM and minor monetite according to XRD and FTIR analyses. The morphology of the MCPM product is a prismatic-like shape with grain sizes ranging from 3 to 9 μm, as observed using SEM techniques. DTA/DTG/TG analysis confirms the stability of MCPM products at temperatures up to 100 °C providing benefits for food industries and communities as a stable food additive commodity.
•A green mussel shell calcination-dissolution-precipitation pathway for precipitated calcium carbonate (PCC) product.•Synthesis of monocalcium phosphate in a strong acidic phosphoric solution using PCC powders as feedstock.•Monocalcium phosphate and monetite were synthesized quickly and easily at room temperature.•High purity monocalcium phosphate with plate-like morphology was generated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Calcium carbide residue (CCR) is a waste obtained from the production of acetylene gas by the hydration reaction of calcium carbide. This residue is generated in large quantities annually and ...requires appropriate disposal. The main composition of the residue is calcium hydroxide (Ca(OH)2). Ca(OH)2 can react with CO2 gas and form CaCO3 particles. This process is well known but not very attractive since Ca(OH)2 is obtained from limestone using an energy-intensive thermal conversion process. This paper examined the synthesis of CaCO3 from CCR solutions by capturing CO2 with the aid of triethanolamine (TEA) solutions at doses of 0, 5, 10 and 20% w/w. The precipitated CaCO3 was characterized, and the application of CaCO3 as a filler in epoxy resin was tested. The results showed that the precipitated CaCO3 was mainly calcite, with a 76.6% yield. Cubic calcite was primarily obtained in TEA solutions, whereas small and agglomerated spherical vaterite and cubic calcite particles were formed in non-TEA solutions. The CaCO3-filled epoxy composites showed higher compressive strength than the neat resin. However, the transparency of specimen plates was reduced. These results can serve as guidelines for the application of CCR slurry filtrate obtained from the sedimentation ponds of acetylene plants and help to reduce the amount of wastewater that needs to be treated. CO2 gas from industrial flue gas combined with TEA solution could be applied to precipitate CaCO3 for carbon-neutral manufacturing.
•CaCO3 was synthesized from CCR solutions by capturing CO2/triethanolamine.•Precipitated CaCO3 was mainly cubic calcite with 76.6% yield.•Compressive strength of CaCO3-filled epoxy composites was improved.•Transparency of CaCO3-filled specimen plates was reduced to translucent object.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Investigated cyclical CO2 mineralisation process with hydrotalcite to reduce cost.•Chloride removal efficiency reached 98% under optimal experimental parameters.•Gaseous CO2 and ...Na2CO3 solution as recharging agents were tested to displace Cl−.•Chloride removal efficiency of regenerative hydrotalcite stayed over 70% for cycles.•Carbonate conversion efficiency of over 90% Ca2+ from brine was achieved.
CO2 mineralisation is a process that can store the CO2 as a solid mineral permanently. Brines rich in alkaline earth metals present an opportunity to trap CO2 in the form of insoluble carbonates. Moreover, this can be accomplished in this work, using flue gas concentrations of CO2 and at near-ambient temperatures, eliminating the energy-intensive CO2 capture step. Alkali or pH-buffering substances to neutralise the acidification of brines caused by CO2 dissolution is one of the primary costs that limits the technology deployment. Hence, we herein developed a process to remove chloride anions from brines by ion-exchange, namely hydrotalcites (HT), while avoiding the addition of alkali. These layered double hydroxides release hydroxyl groups in exchange for chloride, sufficiently raising the pH of brines by dechlorination to enable the precipitation of carbonates during CO2 mineralisation. Moreover, the HT is recyclable for multiple usage by taking advantage of the ‘memory effect’ property. Gaseous CO2 and Na2CO3 solution were tested as the recharging agents, to replace the chloride anions from the spent HT interlayers and intercalate with HCO3− or CO32−, followed by a calcination process to produce the reusable calcined-HT; the approach of gaseous CO2 regeneration is newly proposed. It was found that the chloride removal efficiency remains over 70% after multiple cycles, and calcium utilisation efficiency of the brine carbonation process can surpass 90%. This unique cyclical closed-loop HT process presents a potentially more cost- and energy-effective approach to brine carbonation than our previous studies. In addition, the precipitated calcium carbonates are of sufficient quality for a variety of applications that can reduce the process cost and accelerate the progress of CO2 capture, utilisation and sequestration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
► Ca extraction efficiency. ► Grain size and solid to liquid ratio. ► Production of PCC.
Producing precipitated calcium carbonate (PCC) from steelmaking slag is a technology that contributes to the ...reduction of carbon dioxide emissions from iron and steel industries. While the carbon dioxide emissions from the sector are large, it could benefit from this option by utilizing its own by-products, i.e. steelmaking slags for fixation of CO2. Since the calcium content of the steelmaking slag is high, a calcium carbonate precipitate can be produced with the method which we have recently developed, and, if fulfilling the requirements (e.g. purity and crystal shape), it can be utilized as PCC. Therefore, the objective of this study is to further evaluate the feasibility of this method. Calcium was extracted selectively from the slag with aqueous solution of ammonium salt (NH4NO3, CH3COONH4 or NH4Cl) in an extraction reactor. After removal of the residual slag, the calcium-rich solution reacted with CO2 in a carbonation reactor producing PCC. Based on the experimental results, the slag’s grain size has a clear effect on the calcium extraction efficiency; the smaller the steel converter slag’s grain size, the larger the surface area, and the better the mass transfer rate which in turn results in a higher extraction efficiency. Grinding to smaller sizes is therefore one strategy towards improved efficiencies and chemical conversion rates. Solid to liquid ratio is another important parameter for improving extraction efficiency. The smallest solid to liquid ratio 5g/l resulted in the maximum calcium extraction efficiency (73%) while the highest solid to liquid ratio 100g/l resulted in the lowest extraction efficiency (6%). Consequently this option will be operationally expensive because of larger reactor volumes. The PCC produced from the calcium rich solution is comparable to the PCC produced with conventional methods.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study aimed to investigate the effect of ultrasonic application on the production of precipitated calcium carbonate (PCC) particles from desulfurization gypsum via direct mineral carbonation ...method using conventional and venturi tube reactors in the presence of different alkali sources (NaOH, KOH and NH4OH). The venturi tube was designed to determine the effect of ultrasonication on PCC production. Ultrasonic application was performed three times (before, during, and after PCC production) to evaluate its exact effect on the properties of the PCC particles. Scanning electron microscope (SEM), X-ray diffraction (XRD), Atomic force microscope (AFM), specific surface area (SSA), Fourier transform infrared spectrometry (FTIR), and particle size analyses were performed. Results revealed the strong influence of the reactor types on the nucleation rate of PCC particles. The presence of Na+ or K+ ions in the production resulted in producing PCC particles containing only calcite crystals, while a mixture of vaterite and calcite crystals was observed if NH4+ ions were present. The use of ultrasonic power during PCC production resulted in producing cubic calcite rather than vaterite crystals in the presence of all ions. It was determined that ultrasonic power should be conducted in the venturi tube before PCC production to obtain PCC particles with superior properties (uniform particle size, nanosized crystals, and high SSA value). The resulting PCC particles in this study can be suitably used in paint, paper, and plastic industries according to the ASTM standards.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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