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The aim of this study is to examine the role of different formulations of calcium carbonates on the inkjet printing quality, with the use of cationic carboxymethyl cellulose (CMC)‐starch as a binder in the formation of the coating structure of paper to use for inkjet printing. For this, GCC (ground calcium carbonate), PCC (precipitated calcium carbonate) and ECC (eggshell calcium carbonate), which have been tried as new coating materials in recent years, are mixed in different proportions to form a different coated formulation and plastered on the newly produced paper surface. Then, optical and physical tests of the obtained samples are carried out. Then, printing properties of the papers on which drop‐on‐demand system inkjet printing is made are examined. According to the obtained data, it is determined that the optical properties of coated paper with GCC + PCC blends outperformed papers coated with other blends. According to the physical test results, GCC + PCC blended coated papers showed the best performance in breaking length and tear indices. ECC + PCC blended coated papers however showed the best performance in burst indices. It is determined that as the particle size of the calcium carbonates in the coating materials decreased, the burst indices value also decreased. This situation is the opposite for breaking length and tear indices values. When the inkjet printing features are examined, it is seen that the best results are obtained from GCC + ECC coated papers in general. The most optimal metamerism indices results, measured under three different light sources, are obtained on GCC + PCC coated papers. [ABSTRACT FROM AUTHOR]

Due to the limitation of storage condition, paper cultural relics are constantly subject to human damage and natural aging, requiring rescue protection. In this study, a series of nanocellulose/calcium carbonate microcapsule/fluorine‐acrylamide styrene/acrylic copolymer composite protection materials were prepared and used as an efficient self‐healing composite coating for paper cultural relics protection. CaCO3 microcapsules were prepared by interfacial reaction method and doped into the polymer materials to obtain the self‐healing composite coating. The properties of composite protection materials were studied via the self‐healing experiment, dry heat accelerated aging test, and reversible experiment. The effects of composite protection materials on simulate paper cultural relics were analyzed. The results show that when the amount of hollow calcium carbonate microcapsules was 0.500 g, the composite protection materials had good comprehensive performances. The prepared materials work positive influence on the conservation of simulate paper cultural relics that could be one of the potential materials for application in protection of paper cultural relics. POLYM. ENG. SCI., 60: 288–296, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

FeSO4 was used to activate K2S2O8 mixed with paper sludge to condition activated sludge, and its effect on sludge dewaterability was investigated. Interaction effects of various parameters on sludge dewaterability were investigated and analysed by considering the moisture content of cake, specific resistance to filtration (SRF) and capillary suction time (CST) as indicators and the Box–Behnken design of response surface methodology (RSM). Results indicated that the moisture content of cake, SRF and CST decreased from 74.52 to 69.57%, 25.39 × 1012 to 11.80 × 1012 m/kg and 199.8 to 146.4 s, respectively, under optimal conditions. RSM results presented that only 0.13% of the response values cannot be interpreted with this model, and the three‐factor interaction was observed to be significant. Additionally, sludge dewaterability mechanism observed that K2S2O8 mixed with paper sludge used the strong oxidising properties of SO4−• to crack sludge flocs. Fine fibres and calcium carbonate in the paper sludge played important roles as the skeleton support in the sludge filtration process, and the internal moisture was rapidly eliminated. [ABSTRACT FROM AUTHOR]

Herzberg staining, a quick and convenient tool for distinguishing non-wood fibers from wood pulp, and Raman spectroscopy were employed to investigate three paper currencies issued under the reign of the Chinese Ming and Qing Emperors between 15th and 19th centuries - da ming bao chao (AMS C-14 Date: 1410-1435 AD, ±1σ) from the Early Ming Dynasty (1405-1433 AD) and da qing bao chao (1859 AD) and hu bu guan piao (1854-1858 AD) from the Late Qing Dynasty (1840-1911 AD). Fiber staining and microscopic examination revealed a predominance of bast fiber from probably mulberry trees and very few cotton fibers (supposed to be environment contamination) in da ming bao chao; fibers in da qing bao chao and hu bu guan piao turned out to be quite pure, which are also bast fibers but very likely came from ramie and paper mulberry trees, respectively. Raman analysis of red, blue, and black pigments on the investigated paper currencies showed that: (1) The reddish seal on da ming bao chao is not a vermilion (HgS) paste, as it is traditionally assumed, but instead a red lead (or minium, Pb3O4) one. The red pigments on both da qing bao chao and hu bu guan piao are vermilion (HgS). (2) Prussian blue (Fe7(CN)18⋅14-16H2O), a Western pigment, was identified as blue on both da qing bao chao and hu bu guan piao. (3) The black pigment on all these three paper currencies is amorphous carbon from soot. (4) Raman analysis of evenly distributed white pigment particles among the fibers in da qing bao chao confirmed the use of calcium carbonate (CaCO3) as coating pigment or fillers. Both microscopic examination of stained fibers and Raman analysis allowed, for the first time, the understanding of fiber and pigment use in producing ancient Chinese paper currencies. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Superhydrophobic and to some extent oleophobic paper surfaces are prepared using atmospheric pressure plasma etching. A novel dielectric barrier discharge operating in helium-oxygen mixture is used to rapidly etch organic material from paper surface and create hierarchical topography and subsequently a thin fluorocarbon film is deposited to modify the surface energy. The enhancement of surface topography is achieved via the selective removal of organic matter over inorganic calcium carbonate (calcite) fillers that co-exist in paper. The process led to the fabrication of roll-off superhydrophobic paper with water contact angles >150° and hysteresis <10° for all samples treated over 2 min with no deterioration of paper quality. Further treatment over 8 min resulted also in diiodomethane repellent surfaces. [ABSTRACT FROM AUTHOR]

Lime mud (LM) is a kind of industrial solid waste produced in alkali recovery in papermaking industry. LM is a global environmental challenge that both China and the United States are facing. With the support of the EcoPartnership Program under the 10‐year Sino‐US Energy and Environment Cooperation Framework, China Sun Paper Joint Stock Co., Ltd. has successfully formed a partnership with America Mineral Technologies Inc. (MTI). MTI has applied the production technology of calcium carbonate from LM produced by alkaline papermaking (PTCC) to the Sun Paper Company. Compared with the traditional treatment technology of LM in Sun Paper Company, the reduction efficiency of the PTCC technology can reach 97.99%. The waste residue is relatively more stable and poses less threat to the environment than traditional technology. The energy consumption is low, and 4.15 kgce can be saved by treating per ton of LM. It does not release carbon dioxide to the environment, but consumes 0.485 tons of carbon dioxide per ton of LM on the contrary. Because the calcium carbonate produced can be used as a product, RMB 531 yuan can be saved in the treatment of each ton of LM. The PTCC process is conducive to the coordinated development of economic, environmental, and social benefits, and realizes the sustainable development of the paper industry. [ABSTRACT FROM AUTHOR]

Fillers are essential component of printing papers to increase the opacity, brightness, and to improve formation and printing properties. As a very little work has been reported so far on magnesium silicate (talc), the study was conducted with the filler of different particle size for papermaking. The sheets were made in the laboratory with refined mixed hardwood chemical pulp with five grades of talc, ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC) fillers with 15-24% ash level. Apparent density along with tensile, burst, tear index, Z-direction tensile strength (ZDTS) and bending stiffness index were evaluated for talc filled sheets, and compared with GCC and PCC. Physical strength properties of talc filled sheets were decreased at a faster rate on increasing filler loading in paper and decreasing the particle size of the filler. With same type of filler its particle size determines the physical properties of paper. The postulate was not found to be valid for all the three varieties of fillers viz., talc, PCC and GCC. Shape and geometry of the PCC and GCC fillers determine the individual property. © 2012 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This is a systematic study that examines several acid prewashes and water rinses on paper bearing latent prints before its treatment with a silver physical developer. Specimens or items processed with this method are usually pretreated with an acid wash to neutralize calcium carbonate from the paper before the treatment with a physical developer. Two different acids at varying concentrations were tested on fingerprints. Many different types of paper were examined in order to determine which acid prewash was the most beneficial. Various wash times as well as the addition of a water rinse step before the development were also examined. A pH study was included that monitored the acidity of the solution during the wash step. Scanning electron microscopy was used to verify surface calcium levels for the paper samples throughout the experiment. Malic acid at a concentration of 2.5% proved to be an ideal acid for most papers, providing good fingerprint development with minimal background development. Water rinses were deemed unnecessary before physical development. [ABSTRACT FROM AUTHOR]

An encrusting brown alga from subtidal habitats around the island of Oahu (Hawaiian Islands) represents only the second genus of the class Phaeophyceae to form calcium carbonate, which it deposits primarily as both extracellular and intracellular aragonite, admixed with small (3.3%) amounts of calcite. Plants form expanses 15–100+ cm in extent consisting of horizontally aligned imbricating tiers of distromatic blades 1–4 mm in diameter that are separated from one another by cementing layers of extracellular aragonite, the tiers forming stacks of dozens of laminae and anchored to coral substrata by a basement layer that adheres tightly without haptera or rhizoids. The hypodermal layer of each blade consists of lightly pigmented rectilinear cells bearing either one or two smaller deeply pigmented epidermal cells in cross-sectional profiles and three or four in long-sectional profiles, the cells of both layers becoming encased in rigid carbonate skeletons laid down in their outer wall matrices. The successive tiers become stacked by either overgrowing marginal proliferations or new blade primordia that arise from the hypodermal layer of surface laminae and initially spread centrifugally by means of continuous marginal meristems. Neither plurilocular nor unilocular reproductive structures are known. The alga is described as the new genus and species Newhousia imbricata Kraft, G.W. Saunders, Abbott et Haroun and is assigned on the basis of small subunit rDNA gene sequence analyses to the order Dictyotales, family Dictyotaceae, within a strongly supported monophyletic clade that includes Distromium, Lobophora, and Zonaria. [ABSTRACT FROM AUTHOR]

To enhance the ash in paper without reducing its strength property, ground calcium carbonate (GCC) filler was modified using polysaccharide prior to its addition at wet‐end of papermaking. Till now, modification of GCC filler using chitosan acetate (CH.A) is not explored. The novelty lies in showing the effect of CH.A as GCC filler modifier and its application in papermaking. The results showed that ash of paper get increased by around 18%, 53% and 63% after adding GCC modified using cationic starch (C.S) @ 20 kg/t of GCC, CH.A @ 5 kg/t of GCC and CH.A @ 10 kg/t of GCC respectively, in comparison to that attained by paper using unmodified GCC at the same dose at wet‐end of papermaking. The breaking length, burst factor and tear factor of paper having 11% ash (made using unmodified GCC) was found to be 2485 m, 21.73 and 47.63, respectively. The paper having 18% ash (made using GCC modified by CH.A 10 kg/t of GCC) showed breaking length, burst factor and tear factor as 2364 m, 22.24 and 46.72, respectively. This approach of using CH.A in papermaking will help the papermaker to improve profit and quality of paper. [ABSTRACT FROM AUTHOR]

This study was conducted to assess the effect of the pulping by‐products crude tall oil (CTO), distilled tall oil (DTO), and tall oil fatty acid (TOFA) on dynamic water vapor sorption behavior, interfiber strength, and thermal stability of cellulosic paper‐sheets. The results were compared against those obtained in cellulose papers treated with the conventional petroleum‐derived hydrophobic agent hydrowax and in untreated ones. The tall oil treatments caused strong reduction in equilibrium moisture content of the paper‐sheets during adsorption and desorption runs. The same trend was noticed for the hydrowax‐treated papers, however, it was less pronounced than the CTO‐treated and DTO‐treated samples in the relative humidity range of 75–95%. The sorption hysteresis was considerably decreased after the treatments. The ultimate dry‐tensile strengths of the paper‐sheets were significantly reduced by TOFA and hydrowax treatments, while CTO and DTO showed comparable strength as that of untreated control. The ultimate wet‐strengths of the paper‐sheets were improved after the treatments. The thermal stability of the specimens was improved by the tall oil treatments, and the hydrowax‐treated samples illustrated lower degradation temperature than the untreated control. The results are promising for the use of tall oils as alternative hydrophobic agents of cellulosic fiber‐based products, such as wood panels and paper packaging. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47303. [ABSTRACT FROM AUTHOR]

Commercially available poly(propylene)(PP)(MOSTEN, MFR = 4 g/10 min) supplied by a Czech company Chemopetrol Litvínov and precipitated calcium carbonate (CaCO3) was used for this study. The CaCO3 particles were coated with surface agent improving their dispersion.The effect of the PP structure, the volume content and surface coating of particles on the decisive mechanical properties (dynamic modulus of elasticity and dynamic fracture toughness) was evaluated by means of dynamic mechanical thermal analysis (DMTA) and instrumented Charpy tester. The dispersion of the filler particles was qualitatively estimated by scanning electron microscopy (SEM). The change of solid phase PP ratio was evaluated utilizing differential scanning calorimetry (DSC) and nuclear magnetic resonance (pulsed 1H‐NMR).The composites in the study demonstrated the enhanced toughness with respect to the native PP. The correlation between the structure and fracture parameters was confirmed. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Calcium carbonate is one of the most common scaling minerals. In this paper we have used different electrical current modes (direct current [DC], pulsed DC, and alternating current [AC]) to control the amount, morphology, and distribution of calcium carbonate deposit on electroconductive epoxy/carbon nanofiber (CNF) coating. The effect of different current modes on surface scaling was visualized using scanning electron microscopy. It has been shown that both AC and DC anodic polarization limited scale deposition on epoxy/CNF coated surfaces, although the mechanisms of scale inhibition during AC and DC polarization were different. DC polarization of the coating at +2 V resulted in the smallest scale buildup without leading to coating degradation, while DC polarization at potentials as high as +5 V caused the coating to degrade. Interestingly, application of pulsed DC with high pulse frequency (50 Hz) inhibited the degradation. The type of current applied affected also the morphology of the precipitate at the cathode. The results presented in this work show, for the first time, how different modes of electrical current applied to electroconductive composite coatings can be used to control the morphology and distribution of calcium carbonate scale, and how the organic coating degradation at high polarization potentials can be avoided. [ABSTRACT FROM AUTHOR]

This paper firstly reports the size effect of typical micro‐ and nano‐ calcium carbonate additives on the friction properties of calcium sulfonate grease. The rheological and tribological performance of calcium sulfonate grease with typical micro‐ and nano‐ calcium carbonate additives were investigated at 30 or 80°C by Rheometer and Optimol SRV‐V tester. To its surprise, calcium sulfonate grease with 5% calcium carbonate microparticles behave remarkable lubrication performance than calcium sulfonate grease with 5% calcium carbonate nanoparticles under boundary lubrication condition according to the rheological analysis and tribological evaluation. The enhancement in excellence tribological performance can be attributed to the synergistic effect between calcium carbonate microparticles and calcium carbonate in thickener of calcium sulfonate grease. The thin film composed of CaCO3 and CaO on the worn surface generated by solid particles is conducive to reducing friction and wear. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP) has attracted much attention as a promising green technique for soil improvement. Despite the significance of precipitation pattern in mind, constitutive relations or numerical models considering the finite‐strain mechanical effects of the various precipitation patterns are rarely developed. In this paper, we propose a novel 3D DEM modeling scheme by using coarse particles to represent sand grains and fines as cementing agents, to reproduce the various precipitation patterns in MICP‐treated sand. Based on the topological relations with adjacent particles and the contribution to the mechanical improvement, the cementing fines are classified into effective, partially effective, surface coating, and pore filling ones. The microstructural characteristics and their evolution upon external loading are investigated quantitatively after a careful calibration and validation. The microstructural variation in experiments can be well reproduced, pinpointing this variation as a possible cause for the fluctuation in experimental data. Massive coating fines are produced accompanying the microstructural degradation, which is initiated by the breakage of effective bonds. The breakage of partially effective bonds may become dominating later in the medium to strong cemented specimens. One weakly cemented specimen shows diffuse failure with simultaneous bond‐breakage and friction. In contrast, the medium to strong cemented specimens show localized failure with the dominating mechanism transiting from bond‐breakage to friction producing notable pore filling fines. We propose a relation between unconfined compressive strength and the equivalent effective volume fraction of cementing agents normalized by the pretreatment porosity, which reveals the coupling effects of the initial configuration and the precipitation pattern on the mechanical improvement. [ABSTRACT FROM AUTHOR]

In various cementitious materials, the carbonation of tricalcium silicate (C3S) by the acidic oxygen‐containing groups located on the surface of graphene oxide (GO) can support cutting down the CO2 emissions, in addition to the formation of different crystalline CaCO3. The current work investigates the direct chemical reaction of dry‐C3S with 0.4 % GO solution and the mechanism of CH and CSH carbonation depending on the concept of Boehme's‐theorem. FTIR‐spectroscopy has been utilized to demonstrate and identify the effective transitions in the formulation of portlandite (Ca(OH)2), calcium‐silicate‐hydrate (CaO ⋅ SiO2 ⋅ H2O), and calcium carbonate (CaCO3) polymorphs during the reaction. This paper clarifies the relationship between XRD peak intensity and morphologies of CaCO3 crystals resulting from using various weights of dry‐C3S. Thus, the XRD peak intensity of CaCO3 varies according to their morphologies. XRD‐Rietveld Refinement has examined the quantity percentages of the crystalline phases. The differences in the dissociation temperature (TGA) illustrate the possible variation in the structure and properties of CaCO3 crystals formed during the carbonation of CH and CSH. SEM with different magnifications was selected to observe the prevalent morphology of vaterite, aragonite, and calcite crystalline phases during the transformation process. [ABSTRACT FROM AUTHOR]

The preparation of high‐filled composites by compounding with calcium carbonate (CaCO3) and polymer has received much attention. However, challenges such as enhancing the interaction between CaCO3 and the polymer and improving the performance of the resulting composites need to be addressed. In this paper, composites with a high filler content were made by adding fillers of various CaCO3 gradations into unsaturated polyester resin (UPR). The mechanical properties, curing degree, component distribution, and structural phases of resulting blends were analyzed by a universal testing machine, differential scanning calorimeter, Raman, and scanning electron microscope/energy‐dispersive x‐ray spectroscopy (EDX), respectively. Based on the research findings, optimizing the CaCO3 gradation significantly increased the strength of the resulting blends. The average flexural strength increased by 343.5%, while the average compressive strength increased by 888.9%. The composites with an optimized gradation of filler showed a significant reduction in uncured domains, leading to an improvement in the curing degree of the composites. The interfacial defects between the optimized graded CaCO3 filler and the UPR were reduced, resulting in a uniform distribution with no visible interface. The Raman and EDX analyses show that the gradation optimization technique has successfully prevented structural phase separation and enhanced the tendency to agglomerate between CaCO3 and UPR. This study proposes an effective method for developing high‐performance UPR/CaCO3 composites with a high filler content. Highlights: The optimized gradation of CaCO3 was used as filler to address the weak interaction of CaCO3 with the UPR in a high‐filled UPR/CaCO3 composite system while improving the performance of the composite.The gradation optimization of CaCO3 filler can improve the morphology and reduce the porosity of the high‐filled UPR composites.The gradation optimization of CaCO3 filler can effectively improve the curing effect of UPR.Optimizing the CaCO3 gradation resulted in a significant increase in the average flexural strength (by 343.5%) and average compressive strength (by 888.9%) of the resulting blends. [ABSTRACT FROM AUTHOR]

Calcium Sulfoaluminate cements (CSA) are a more sustainable alternative to Portland Cement (PC). On top of that, they can outperform PC in mortars application. The addition of calcium carbonate to such a system is beneficial as it improves workability, accelerates the setting time, and stabilizes the ettringite in the hardened mortar. In this paper, we are investigating the influence of fine calcium carbonate flour on CSA‐C$‐based mortars. The hydration course was traced by the means of isothermal microcalorimetry. It was observed that with the addition of fine calcium carbonates the heat release due to the hydration of CSA started earlier and resulted in the higher hydration peak. Higher hydration degree was able to partially compensate for additional water used to maintain workability. The rheological properties were measured with the rotational viscometer. The results were compared to the mortars of the same composition where fine calcium carbonate was replaced with the ground quartz sand of similar particle size distribution. Surprisingly, no differences in rheology and mechanical parameters between these flours were found. [ABSTRACT FROM AUTHOR]

Copyright of Geomechanik und Tunnelbau is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plasticized starch (PS) materials hold a fundamental role in the design of novel biodegradable and compostable plastics aimed to reduce global single‐use plastic wastes. This work exemplifies the plasticization of postindustrial waste wheat starch (pWWS) and postindustrial corn starch (pWCS) with a comparison to food‐grade corn starch (pCS) by introducing technical waste glycerol (25%) along with urea (5%) and water. The PS (30%) is blended with 70% poly(butylene adipate‐co‐terephthalate) (PBAT) to design a matrix with optimized mechanical properties. As a result, the inclusion of pWCS and pCS shows similar impact strength and melt flow index (MFI) values. Further, the mineral fillers, i.e., talc and calcium carbonate (CaCO3) (25%), are introduced into the PBAT/PS (70%/30%) matrix to explore the effect on MFI, mechanical, thermal, and morphological properties. Scanning electron microscopy analysis reveals good dispersion of PS particles and mineral fillers into the PBAT. Adding talc into the PBAT/pWWS and PBAT/pCS blends shows significantly higher modulus (≈134% and ≈105%, respectively) and heat deflection temperature (HDT) (7.8% and 9.3%, respectively). The addition of 25% CaCO3 results in the impact strength of PBAT/pWWS being improved by ≈20%. Due to talc's lamellar platelet structure and better dispersion, the inclusion of talc into the PBAT/PS blends shows improved rheological properties compared to that of CaCO3. [ABSTRACT FROM AUTHOR]

Calcium chloride is widely used in various fields of society because of its good chemical stability and non‐toxic properties. As an inorganic salt with low ductility at low temperature, it is never used to prepare bulk materials but is usually used to prepare energy storage materials. The work in this paper presents the first synthesis of a moldable calcium chloride ceramic‐like material (flexural strength up to 32 MPa) using calcium chloride. The process results in occurring ion‐dipole interactions between calcium chloride and glycerol by means of direct heating and forms supramolecular structure. Due to the presence of dynamic and reversible non‐covalent bonds, the bonds break upon heating bringing good flowability; the re‐established bonds upon cooling allow the formation of rigid materials. The preparation is also a green and recyclable process, as the molded material can be reshaped by heating. Such a brilliant moldable property reveals the potential of this new approach for the design and production of calcium chloride materials with adjustable shapes. [ABSTRACT FROM AUTHOR]

This paper explores the application of Total Reflection X‐Ray Fluorescence (TXRF) spectrometry for chromate (CrO42−) and phosphate (PO43−) determinations in synthetic solutions after their adsorption onto dolomite. The competition between both contaminants is also evaluated. Adsorption processes are considered an inexpensive, non‐contaminating alternative for retaining, on a selected substrate, a variety of pollutants present in different effluents. For a specific adsorbent, an important factor to be taking into account is the competition among different possible species. Variables such as concentration, temperature, ionic strength and pH were evaluated. Dolomite, a natural mineral based on calcium and magnesium carbonates, was employed as adsorbent. TXRF is an efficient, fast trace element analytical technique and requires only minimum specimen preparation, for that reason is suitable for this study. The experiments were carried out in batch systems; pH and ionic strength of the solution were measured and controlled. The results obtained in individual systems (phosphate‐dolomite or chromate‐dolomite) indicate a 70.5% for phosphate and 22.7% for chromate removal. The adjustment of the ionic strength had no influence on the removal of the anions. According to this study, the adsorption of chromate was reduced to 14% when the pH increased; this fact did not affect phosphate removal. The removal of both ions increased at pH under than 6. The presence of both ions at different concentrations did not change the removal value for the phosphate, whereas the removal of chromate was almost null, indicating a strong interference of the phosphate in the removal of chromate. [ABSTRACT FROM AUTHOR]

In this paper, the retarding effect of a green additive, citric acid, towards calcium carbonate scale deposition is studied. Scale formation is one of the most common causes of malfunctions in process equipment. This is the reason it is crucial to retard scale precipitation, that is, in order to reduce economic damages. With this additive in the solution, experimental runs have been carried out in supersaturation conditions in terms of concentration of calcium carbonate at equilibrium, with a supersaturation ratio ranging from 16 to 280, at 25°C. Three different concentrations of citric acid have been investigated (0.520 × 10−3, 1.041 × 10−3 and 1.561 × 10−3 M) in a laboratory scale plant. Comparing results obtained in terms of induction time with previous experimental runs, performed without additives, citric acid has shown its significant capacity to retard calcium carbonate precipitation, by increasing induction time values. This behaviour is enhanced by raising the additive concentration in solution up to a specific threshold value, beyond which no benefit in terms of calcium scale inhibition is gained. Furthermore, interfacial tension has been computed without and with citric acid at 0.520 × 10−3 and 1.041 × 10−3 M, as a function of the different concentration amounts investigated. The values obtained are in good agreement with data reported in the literature. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach of using in-situ microbially induced Ca 2+ -alginate polymeric sealant for seepage control in porous materials. This process comprises two steps: (i) generation of insoluble calcium carbonate inside the pores of porous materials (such as sand) through a microbially induced carbonate precipitation (MICP) process in-situ and (ii) injection of sodium alginate for in-situ gelation via reaction between alginate and Ca 2+ ions. The experimental results showed that the hydraulic conductivity/permeability of sand decreased with the increase in alginate concentration. When 5% alginate was used with a CaCO 3 concentration of 0.18 g g -1 sand, the permeability of the alginate-treated sand reduced from 5.0 × 10 -4 to 2.2 × 10 -9  m s -1 . The scanning electron microscopy images revealed that a film-type coating was formed around sand particles with spherical round crystals embedded. Furthermore, the in-situ formed Ca-alginate polymeric sealant can also be used for the removal of Cu 2+ ion and suspended particles from contaminated water by more than 90%. Built on the current research, the envisioned practical application of the proposed method may include clogging fractured rock, reducing seepage and prevent piping through dams, excavation dewatering, and forming barriers for remediating specific contaminants., (© 2018 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)

A theoretical and experimental approach was applied to investigate phase relations in a system containing calcium carbonate and different ammonium phosphate solutions. Using laboratory experiments and thermodynamic modeling, this paper provides an insight into the formation of stable phase assemblages in the calcium carbonate and mono‐, di‐, triammonium phosphate aqueous system. Focus is placed on the morphological and mineralogical characterization and thermodynamic calculation of calcium phosphates precipitating due to the reaction between the calcium carbonate and ammonium phosphate solutions. Correlations between the formed stable calcium phosphate phases and the ammonium phosphate precursors are provided. Advantages and limitations of various analytical and modeling techniques used in this study such as geochemical equilibrium‐based modeling, X‐ray diffraction, scanning electron microscopy, and thermal analysis, are critically evaluated. Additionally, possible impacts of the ammonium phosphate solution type on the kinetics of phase transformations are discussed. [ABSTRACT FROM AUTHOR]

Calcium carbonate cements have emerged in the last few years as an attractive candidate for biomedical applications. They can be easily prepared by mixing water with two metastable calcium carbonate phases––amorphous calcium carbonate (ACC) and vaterite––which (re)crystallize into calcite during setting reaction. The transformation kinetics (and therefore the final surface cement composition) strongly depends on the initial mixture design and is controlled by the dissolution of ACC, whereas calcite nucleation typically controls their recrystallization in fluid batch experiments. Novel compositions are presented in this paper by incorporating organic molecules as a proxy to test their capability to carry on other biomolecules like proteins or antibiotics. The hardened samples are microporous and show excellent bioactivity rates, although their mechanical properties still remain poor. However, this would not be a handicap for in‐vivo applications such as bone filling, especially in low mechanical stress locations. [ABSTRACT FROM AUTHOR]

Etheria elliptica is a freshwater oyster that produces an adhesive that hardens underwater, allowing them to attach to other oysters, rocks, wood, and other natural substrates, producing complex oyster bed communities. Despite the importance of the adhesive in oyster bed formation, little is known about its chemical composition, structure, or mechanical properties. Through a combination of scanning electron microscopy (SEM), x‐ray photoemission electron microscopy (X‐PEEM), infrared (IR) spectroscopy, microhardness testing, and nanoindentation, it is found that the oyster adhesive consists entirely of aragonite nanoparticles that clump together into crystallites of varied shape, size, and orientation. The crystallite clumping density varies from the exterior of the adhesive to the interior, with the adhesive closest to the prismatic layer generally being denser. With this variation in density comes a variation in material properties with the exterior adhesive layer being softer and more flexible and the interior adhesive layer being harder and less elastic, or more similar to the prismatic and nacre shell structures produced by the E. elliptica. The resultant material exhibits varied materials properties, despite similar mineral composition. [ABSTRACT FROM AUTHOR]

BACKGROUND This paper presents a physicochemical comparison of the solid products obtained from two alternative processes that recycle waste sodium carbonate (Na2CO3) solution, which is produced following the absorption of CO2 in a biogas upgrading unit. Chemical regeneration processes offer an attractive alternative to the energetically demanding standard physical methods. In the first process, sodium hydroxide (NaOH) is regenerated as a precipitate from the chemical reaction of Na2CO3 with calcium hydroxide (Ca(OH)2). The second process shows a path to obtain a valuable sodium chloride (NaCl) and calcium carbonate (CaCO3) rich brine from calcium chloride (CaCl2) acting as a precipitant agent. In both processes, precipitated calcium carbonate (PCC) is obtained as the most valuable by‐product, but with varying properties owing to the different origin. RESULTS: The purpose of this work is to analyze physicochemically both variations of PCCs obtained and examine the differences between these solid samples in order to determine which method produces more desirable characteristics in the final product. To this end, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were employed as characterization methods. The results reflect that both PCCs have a calcite crystal structure, or morph, being as both PCC products originate from CaCl2 that is more similar to commercial calcium carbonate calcite. CONCLUSION: These results confirmed that a pure CaCO3 valuable by‐product can be obtained from a biogas upgrading unit with several industrial applications. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The microbial‐induced calcite precipitation (MICP) process for ground improvement uses microorganisms to hydrolyze urea, producing carbonate ions to induce in situ calcium carbonate (CaCO3) precipitation in soil to improve its strength. This paper proposes using the hydroxide‐based absorption of CO2 instead to provide the carbonate ion source. This study utilizes direct air capture (DAC) to absorb atmospheric CO2 using potassium hydroxide (KOH) in a semi‐batch bubble absorption column. Potassium carbonate (K2CO3) was then injected into sand with calcium hydroxide (Ca(OH)2 as a calcium source to precipitate CaCO3 and regenerate KOH. Batch and continuous flow precipitation methods produced a poor distribution of CaCO3, with more CaCO3 precipitated on top, resulting in unconfined compressive strength (UCS) of 6.9 to 19.6 kPa. Sand pre‐mixed with Ca(OH)2 gave well distributed CaCO3, precipitated throughout the sample with 7.56 wt% and 6.87 wt% CaCO3 content and UCS of 39.2 and 35.3 kPa before failing for batch and continuous flow precipitation respectively. This differs from MICP strength improvement of 1000 kPa with 5.3 wt% CaCO3 due to poor binding of sand with the precipitated CaCO3 crystals. However, this application provides a stable sequestration source for atmospheric CO2 in soil. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a novel approach of using in‐situ microbially induced Ca2+‐alginate polymeric sealant for seepage control in porous materials. This process comprises two steps: (i) generation of insoluble calcium carbonate inside the pores of porous materials (such as sand) through a microbially induced carbonate precipitation (MICP) process in‐situ and (ii) injection of sodium alginate for in‐situ gelation via reaction between alginate and Ca2+ ions. The experimental results showed that the hydraulic conductivity/permeability of sand decreased with the increase in alginate concentration. When 5% alginate was used with a CaCO3 concentration of 0.18 g g−1 sand, the permeability of the alginate‐treated sand reduced from 5.0 × 10−4 to 2.2 × 10−9 m s−1. The scanning electron microscopy images revealed that a film‐type coating was formed around sand particles with spherical round crystals embedded. Furthermore, the in‐situ formed Ca‐alginate polymeric sealant can also be used for the removal of Cu2+ ion and suspended particles from contaminated water by more than 90%. Built on the current research, the envisioned practical application of the proposed method may include clogging fractured rock, reducing seepage and prevent piping through dams, excavation dewatering, and forming barriers for remediating specific contaminants. A new system of in‐situ slow and controllable formation of Ca‐alginate polymeric sealant was developed, which resulted in a decrease in hydraulic conductivity from 5 × 10−4 to 2.2 × 10−9 m s−1. The Ca‐alginate sealant can also be used for removal of Cu2+ ion and suspended particle by more than 90%. [ABSTRACT FROM AUTHOR]

This paper reports on the precipitation of CaCO3 polymorphs, having various crystal morphologies under different conditions. In particular, systems that were subject to ultrasonic irradiation were compared to the corresponding reference systems in the absence of such a treatment. The application of ultrasonic irradiation predominantly resulted in a change of particle size distribution and polymorphic composition of the precipitate, in comparison to the reference systems. Thus, it was found that the supersaturation and temperature influenced the size distribution, in both the reference and sonicated systems. A mixture of calcite, vaterite and aragonite was obtained in all reference systems, at 25 °C. At this temperature, the sonication caused the vaterite content to increase, while aragonite was not detected. In reference and sonicated systems at 80 °C, only aragonite precipitated. The results also indicate that the principle parameter responsible for the morphology of vaterite was the initial supersaturation: at higher supersaturation spherical vaterite particles precipitated, while at lower supersaturation hexagonal platelets were obtained. The morphological investigations also indicated different mechanisms of vaterite formation in the systems in which precipitation was initiated at higher supersaturation: spherulitic growth of vaterite was observed in sonicated systems, while the aggregation of primary particles was predominant in the reference systems. At lower supersaturation, the effect of c(Ca2+)/ c(CO32−) on the morphology of hexagonal platelets of vaterite was observed as well. By varying the c(Ca2+)/ c(CO32−), significant changes of the polymorphic composition were observed only in the sonicated systems, at 25 °C. [ABSTRACT FROM AUTHOR]

Abstract: Cytochrome P450 (CYP) is a superfamily of enzymes in charge of elimination of the majority of clinically used drugs and other xenobiotics. This study focuses on the development of a rapid microfluidic lateral flow assay to study human phase I metabolism reactions mediated by CYP2A6 isoenzyme, the major detoxification route for many known carcinogens and drugs, with coumarin 7‐hydroxylation, as the prototype model reaction. Assay fabrication utilizes custom‐designed porous functionalized calcium carbonate (FCC) coatings and inkjet‐printed fluid barriers. All materials used are novel and carefully chosen to preserve biocompatibility. The design comprises separate zones for reaction, separation and detection, and an absorbent pad to keep the assay wet for extended periods (up to 10 min) even when heated to physiological temperature. The concept enables CYP assays to be made at lower cost than conventional well‐plate assays, while providing increased selectivity at equally high speed, owing to the possibility for simultaneous chromatographic separation of the reaction products from the reactants on the FCC coating. The developed concept provides a viable rapid prediction of the interaction risks related to metabolic clearance of drugs and other xenobiotics, and exemplifies a novel coating technology illustrating the opportunity to broaden application functionality. [ABSTRACT FROM AUTHOR]

Abstract: Different polymorph and morphology of CaCO3 powder are prepared by spontaneous precipitation method in the presence of sodium citrate and NaOH at ambient temperature. The influence of spontaneous precipitation reaction parameters such as aging time, pH value, the concentration of complexing agent sodium citrate on the crystal phase, particle size and morphology of the precipitated calcium carbonate is studied in this paper. The prepared samples are characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The results show that the aging time, the pH of the solution and the concentration of sodium citrate turned out to be important for the morphologies and crystal phase of CaCO3. Increasing the aging time, the content of vaterite decreases slightly, whereas the opposite effect is observed for increasing pH. When pH value is 13, pure calcite irregular nanoparticles can be prepared. In the presence of sodium citrate, the content of vaterite increases as the increasing of sodium citrate. When the concentration of sodium citrate is increased to 0.1 m, uniform vaterite microsphere with 5 µm size can be obtained. [ABSTRACT FROM AUTHOR]

As one of the most widespread components in marine sediments, calcium carbonate (CaCO3) plays a crucial role in the global carbon cycle and climate changes. To efficiently semi‐quantify the CaCO3 concentration, a more effective, non‐destructive, economic, and accurate technique is required. Diffuse reflectance spectroscopy (DRS) has been widely used for the detection and quantification of minerals but has been less studied for CaCO3. This study synthesized a series of samples with well‐determined content of CaCO3 to analyze the visible and near‐infrared DRS characteristics. Results show that the intensity of the second derivative of Kubelka‐Munk (K‐M) remission functions of the DRS spectra at 2,340 nm (I2340) is linearly correlated with the CaCO3 content. Then, the new proxy I2340 was applied for marine sediments from the Pacific Ocean with known CaCO3 concentrations determined previously by chemical methods, and the robustness of the I2340 as the proxy for CaCO3 concentration was attested. Plain Language Summary: Calcium carbonate (CaCO3) is one of the most common components in marine sediments, and its content variations (precipitation and dissolution) play an important role in global environmental change and paleoclimate evolution. However, previous quantitative methods such as chemistry and X‐ray diffraction cannot simultaneously achieve efficiency, accuracy, and environmental protection. To solve the above problems, this study established a new proxy using visible and near‐infrared diffuse reflectance spectroscopy (DRS) technology that can detect calcium carbonate content in a fast, non‐destructive, economic, and eco‐friendly way. The verification results from synthetic standard samples and natural marine sediment samples indicate that the new DRS proxy can well reflect the variations in calcium carbonate content, which is more targeted for calcium carbonate with less interference compared with the traditional brightness proxy. Overall, this study provides a promising method for precisely quantifying calcium carbonate in marine sediments. Key Points: CaCO3 exhibits a significant absorption in the near‐infrared band between 2,300 and 2,400 nmA new spectral proxy I2340 is proposed to quantify marine sedimentary CaCO3 contentI2340 is more accurate in quantifying marine sedimentary CaCO3 than traditional brightness proxy [ABSTRACT FROM AUTHOR]

The interfacial stress and its distribution during impact of inorganic particulate-filled polymer composites were analyzed in the present paper by means of a three-dimensional (3D) finite element method, and the software used was the ANSYS/LS-DYNA (ANSYS Inc., Canonsburg, PA, USA). The simulation results showed that the normal stress, the shear stress, and the equivalent stress reached the maximum at the particle equator, and then they reduced quickly toward the direction of the particle pole along the interface between the particle and the matrix and achieved the minimum from about 0.5 to 2.0 µm from the equator. Finally, they tended to gently or somewhat increase. Furthermore, the ways and mechanisms of the major fail or fracture of the polyphenylene sulfide (PPS)/calcium carbonate (CaCO3) composites under impact load were discussed. The mechanism of impact fracture or failure of inorganic particle-filled PPS composites might be that the matrix around the neighboring inclusions will first yield owing to the stress concentration in the interface between the inclusion and the matrix to induce crazes and extend quickly. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper reports on the reinforcing effects of different types of fillers, namely, nanoclay (NC), micron size calcium carbonate (MCC), and micron size recycled powder coating waste (MPCW), on the ultimate properties of acrylonitrile butadiene rubber (NBR) compounds. The microcomposites and nanocomposites were characterized by X-ray diffraction and scanning electron microscopy, implying enlargement of d-spacing of NC or intercalation of NBR chains and formation of exfoliated structure, while some agglomerates of MCC were detected. Curing characteristics of the studied composites showed that incorporation of the fillers into the NBR, in particular the NC, causes an increase in the torque, indicating a higher degree of crosslinking. Furthermore, different from micron size MPCW and MCC, the NC accelerated the vulcanization reaction. It was also found that the use of NC and MPCW results in a remarkable increase in the mechanical and rheological properties compared with pure NBR. All in all, variations in the aforementioned criteria were attributable to the extent of matrix/filler interaction reflected by scanning electron micrographs. The correlation established between the microstructure and characteristics of the prepared NBR composites can shed some light on how to develop composites with enhanced properties by incorporating waste materials into the polymers. J. VINYL ADDIT. TECHNOL., 23:13-20, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this paper, the atomic structure of biogenic calcium carbonate is comprehensively reviewed with a focus on structural distinctions between biogenic and abiotic materials. We systematically describe most of the important experimental findings in this field from the first discovery of lattice distortions in biogenic aragonite, followed by observations that showed that anisotropic lattice distortions are widespread in biogenic calcite and aragonite produced by different organisms. We discuss the physical origin of this phenomenon and provide experimental evidences that lattice distortions originate from strong atomic interactions at organic/inorganic interfaces. We propose that lattice distortions are amplified at an early stage of biomineralization via an amorphous precursor and subsequent amorphous/crystalline phase transformation within a confined space outlined by organic macromolecules. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation has been proposed for soil stabilization, soil strengthening, and permeability reduction as an alternative to traditional cement and chemical grouts. In this paper, we evaluate the grouting of fine aperture rock fractures with calcium carbonate, precipitated through urea hydrolysis, by the bacteria Sporosarcina pasteurii. Calcium carbonate was precipitated within a small-scale and a near field-scale (3.1 m2) artificial fracture consisting of a rough rock lower surfaces and clear polycarbonate upper surfaces. The spatial distribution of the calcium carbonate precipitation was imaged using time-lapse photography and the influence on flow pathways revealed from tracer transport imaging. In the large-scale experiment, hydraulic aperture was reduced from 276 to 22 μm, corresponding to a transmissivity reduction of 1.71 × 10−5 to 8.75 × 10−9 m2/s, over a period of 12 days under constantly flowing conditions. With a modified injection strategy a similar three orders of magnitude reduction in transmissivity was achieved over a period of 3 days. Calcium carbonate precipitated over the entire artificial fracture with strong adhesion to both upper and lower surfaces and precipitation was controlled to prevent clogging of the injection well by manipulating the injection fluid velocity. These experiments demonstrate that microbially induced carbonate precipitation can successfully be used to grout a fracture under constantly flowing conditions and may be a viable alternative to cement based grouts when a high level of hydraulic sealing is required and chemical grouts when a more durable grout is required. [ABSTRACT FROM AUTHOR]

As an ecological and environment‐friendly building material, sticky rice mortar has attracted the attention of many researchers. Amylopectin is the most important organic matter of it, which can improve the mechanical properties and durability of sticky rice mortar by inducing mineralization of calcium carbonate (CaCO3). However, amylopectin induced formation of CaCO3 has not been reported. In this paper, mineralization of CaCO3 induced by gelatinized amylopectin is investigated. For comparison, the different morphologies of CaCO3 are studied in the presence of Mg2+, Fe3+. Moreover, these CaCO3 products with different morphologies are used to clean the waste water. The results indicate that gelatinized amylopectin is conducive to formation of pumpkin‐like vaterite. It forms uniform rod and dumbbell‐shaped calcite in the presence of Mg2+, form calcite with stepped depressions in the presence of Fe3+. The adsorption of Pb(II) can reach extremely high level (1445.86 mg g−1) with the rod‐like calcite. [ABSTRACT FROM AUTHOR]

A carbon dioxide capture, conversion, and utilization technology has been developed that can be powered by renewable energy with the potential to mitigate CO2 emissions. This relies on an electrochemical process whereby the dissolution of carbon dioxide into carbonate ions is accelerated by a locally induced pH change at the cathode. The carbonate ions can then complex with metal cations, such as Ca2+, Sr2+, or Mn2+, present in solution to form their respective metal carbonates, which precipitate out of solution. To ensure the cathode is not fouled by deposition of the insulating metal carbonate, the process is operated under hydrogen evolution conditions, thereby alleviating any significant attachment of the solid to the electrode. This process is demonstrated in CO2‐saturated solutions while the possibility of direct air capture is also shown, where the precipitation of CaCO3 from atmospherically dissolved CO2 during electrolysis is observed. The latter process can be significantly enhanced by using 5 vol.% of monoethanolamine (MEA) in the electrochemical cell. Finally, the process is investigated using seawater, which is also successful after the initial precipitation of metal sulfates from solution. In particular, the use of renewable energy to capture CO2 and create CaCO3 while also generating hydrogen may be of particular interest to the cement industry, which has a significant CO2 footprint. [ABSTRACT FROM AUTHOR]

An improved method for accurate and precise determination of metal to calcium ratio in mass limited calcium carbonate samples has been developed. We used an Agilent®5800 ICP‐OES for major element (Na/Mg/Sr to Ca) and an Agilent®8900 ICP‐QQQ‐MS for minor and trace element (Li/B/Na/Mg/Al/Mn/Fe/Zn/Sr/Cd/Ba/U to Ca) ratio determination. We report a long‐term precision of ≤1% (1σ) by repeat analysis, spread over ≥6 analytical sessions, of multiple external standards that spanned a large range of concentration. We quasi‐quantitatively eliminated potential matrix effect from high [Ca] by concentration matching samples and standards (∆[Ca] ≤ ±5%) during both ICP‐OES and ICP‐QQQ‐MS sessions. The ICP‐OES analyses were done on 200 μl of sample at 60 ppm [Ca], consuming ∼30 μg of CaCO3 per analysis. Whereas trace element analyses by ICP‐QQQ‐MS required ∼150 μl of sample at 20 ppm [Ca], consuming ∼7.5 µg of CaCO3 per analysis. Thus, the present method allows for high precision determination of TE/Ca in <40 μg of CaCO3. We present a comprehensive approach for optimization of ICP‐OES sensitivity and stability to select elemental (Ca/Na/Mg/Sr) wavelengths with minimal interferences, high sensitivity and linearity. For choice of Ca lines, we focused on the minimization of self‐matrix effect. For the ICP‐MS method, we improved reproducibility and precision by lowering [Ca] of analyte and preconditioning of cones. Furthermore, the present method allows for precise B/Ca determination sans the use of HF matrix. In summary, we present an easily adoptable method based on readily available instrumentation for determining element‐to‐calcium ratios that is suitable for analyzing mass‐limited carbonate samples. Key Points: We present a user‐friendly approach for determining trace element to calcium ratios using readily accessible and easy to use instrumentationThis method requires an extremely small sample size, <40 μg of CaCO3, for determining trace elemental ratios with an excellent limit of detectionOur method is characterized by better than 1% accuracy and precision during determination of TE/Ca using both ICP‐OES and ICP‐QQQ‐MS [ABSTRACT FROM AUTHOR]

Concrete, a widely used building material, often suffers from cracks that lead to corrosion and degradation. A promising solution to enhance its durability is the use of fungi as self‐healing agents, specifically by harnessing their ability to promote calcium carbonate (CaCO3) precipitation on their cell walls. However, the ideal conditions for CaCO3 precipitation by the filamentous fungal species Trichoderma reesei are still unclear. In this study, the biomineralization properties of T. reesei in liquid media are investigated. Two different calcium sources, calcium chloride (CaCl2) and calcium lactate are tested, at varying concentrations and in the presence of different nutritional sources that support growth of T. reesei. This study also explores the effects on fungal growth upon adding cement to the medium. Calcium lactate promotes greater fungal biomass production, although less crystals are formed as compared to samples with CaCl2. An increasing calcium concentration positively influences fungal growth and precipitation, but this effect is hindered upon the addition of cement. The highest amounts of biomass and calcium carbonate precipitation are achieved with potato dextrose broth as a nutritional source. By identifying the optimal conditions for CaCO3 precipitation by T. reesei, this study highlights its potential as a self‐healing agent in concrete. [ABSTRACT FROM AUTHOR]

An indirect CO2 mineral sequestration involving two separated steps with acetic acid as a recycling medium provides a promising method for CO2 sequestration as well as the minimum CO2 emission for calcium carbonate production. In such an indirect route, the calcium carbonate production in the second gas-liquid reactive crystallization step has been challenged by low carbonation efficiency. This paper describes significant enhancement of the second step by coupling reactive crystallization and solvent extraction with the introduction of the organic solvent, tributyl phosphate (TBP), to the process. Based on the reaction mechanism of this enhanced carbonation process, many influencing factors including stirring speed, phase ratio, reaction time, reaction temperature, CO2 partial pressure, and the composition of the initial aqueous solution, were studied. Given the operating conditions of 60 min reaction time, 500 rpm stirring speed, organic-to-aqueous phase volume ratio of 1, 80 °C reaction temperature, 4.0 MPa CO2 partial pressure, and initial pH of 7, the obtained crystallization conversion in the second step was found to increase from 20% to above 50%, with the incorporation of TBP and the addition of magnesium acetate. [ABSTRACT FROM AUTHOR]

It has been reported in the technical literature that whiskers of rodlike single crystals can be used in order to generate shish-kebab structures or other different lamellae morphologies during isothermal or dynamic crystallization of sheared or presheared polymer melts. The expected advantage of the changed crystalline structure is a reinforcing effect of the composite. A lot of papers reported about the application of inorganic and organic whiskers such as cellulose and chitin whiskers. This study reports on an attempt to use acicular PCC as appropriate whisker for improving mechanical properties of polypropylene. In this article special attention is given to demonstrate the effect of flow induced crystallization under varying shear conditions in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis, tensile testing, and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

A synthesis of a new dental material, based on nano-structured highly active calcium silicates and calcium carbonates, is described in this paper. Phase analysis of this material, before and after hydration, was performed by X-ray diffraction and showed that active silicate phases were transformed into tobermorite phase, while carbonates remained unchanged. The mechanism of hydration was fully described. The morphology of the sample was studied by SEM, and typical appearance of the present phases was particularly discussed. The mechanical properties and setting time of this material make it very promising for potential application in dental practice. [ABSTRACT FROM AUTHOR]

Amorphous calcium carbonate (ACC) is an important intermediate in the formation of crystalline CaCO3 biominerals, where its crystallization is controlled using soluble additives. However, although this transformation often occurs in the solid state, experiments mainly focus on the effect of additives on ACC crystallization in solution. This paper addresses this issue and compares the crystallization, in solution and in the solid state, of ACC precipitated in the presence of a range of additives. Surprisingly, these results show that some additives exhibit a Janus behavior, where they retard crystallization in solution, yet accelerate it in the solid state. This is observed for all of the larger molecules examined, while the small molecules retard crystallization in both solution and the solid state. [ABSTRACT FROM AUTHOR]

Carbonates are an important component of soil found in dry regions. The main aim of this paper is to investigate the origin of C in soil carbonate and to assess the effect of applied organic residues on carbonate dissolution and crystallization. We measured the δ13C of organic carbon (OC), active and total carbonates down to a depth of 260 cm of a calcareous soil developed in a tufa deposit. We found a parallel decrease of the active CaC03-δ13C and OC-δ13C from -10.5 to -13.6%o and from -24.6 to -26.4%0, respectively, in the soil profile. Furthermore, the active CaC03-δ13C and the concentrations of Ca and Mg in the soil solution during incubation of soil samples from the top 0- to 10-cm layer (soil δ13C = -11.5%o) with and without addition of pasteurized chicken manure (PCM, -23.2%o) were determined. The active CaC03-δ13C wasn't affected by time and treatment and with a δ13C 14.1%o higher than the soil organic matter (SOM). The sum of soil solution Ca and Mg concentrations in the PCM treatment decreased in the first days of the incubation and then increased linearly due to released protons by the nitrification processes. The tufa and the soil formed on it have two likely sources for the C in the active carbonate fraction; biogenic carbonates deposited during tufa formation and SOM mineralization and re-crystallization of soil carbonates. Application of an N-rich amendment to this calcareous soil enhanced the dissolution and re-crystallization of calcium carbonate. [ABSTRACT FROM AUTHOR]