共查询到20条相似文献,搜索用时 46 毫秒
1.
Dr. Ryota Suwa Assoc. Prof. Masayuki Hatta Prof. Kazuhiko Ichikawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13656-13661
CaCO3‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca2++HCO3??CaCO3+H+; and reversible static physical precipitation/dissolution, Ca2++CO32??CaCO3. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/PCO2‐independent solubility product, [Ca2+][CO32?], may not be observed at pH below 8.5 because [Ca2+][CO32?]/([Ca2+][HCO3?]) ?1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and PCO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each PCO2/pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO3 saturation state Λ of 1.3 at PCO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at PCO2 ≈1000 ppm and pH ≈7.8. 相似文献
2.
Yaping Huang Qiang Shen Weiping Sui Meili Guo Ying Zhao Dujin Wang Duanfu Xu 《Colloid and polymer science》2007,285(6):641-647
An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic
additive in the precipitation process of calcium carbonate (CaCO3). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation
and crystallization of CaCO3. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown
CaCO3 crystals, depending upon the molar ratio of the initial Ca2+ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction,
and Fourier transform infrared spectroscopy on the precipitated CaCO3 crystals proved that concentrations of HBP-CMCS and Ca2+ exert great influence on the crystallization habit of CaCO3, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO3 particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO3 nanocrystals. 相似文献
3.
Qun Guan Le‐Le Zhou Fan‐Hong Lv Wen‐Yan Li Yan‐An Li Yu‐Bin Dong 《Angewandte Chemie (International ed. in English)》2020,59(41):18042-18047
Ca2+, a ubiquitous but nuanced modulator of cellular physiology, is meticulously controlled intracellularly. However, intracellular Ca2+ regulation, such as mitochondrial Ca2+ buffering capacity, can be disrupted by 1O2. Thus, the intracellular Ca2+ overload, which is recognized as one of the important cell pro‐death factors, can be logically achieved by the synergism of 1O2 with exogenous Ca2+ delivery. Reported herein is a nanoscale covalent organic framework (NCOF)‐based nanoagent, namely CaCO3@COF‐BODIPY‐2I@GAG ( 4 ), which is embedded with CaCO3 nanoparticle (NP) and surface‐decorated with BODIPY‐2I as photosensitizer (PS) and glycosaminoglycan (GAG) targeting agent for CD44 receptors on digestive tract tumor cells. Under illumination, the light‐triggered 1O2 not only kills the tumor cells directly, but also leads to their mitochondrial dysfunction and Ca2+ overload. An enhanced antitumor efficiency is achieved via photodynamic therapy (PDT) and Ca2+ overload synergistic therapy. 相似文献
4.
Here, agar hydrogel was selected as diffusion medium and template to control the biomimetic mineralization of calcium carbonate (CaCO3). Due to three dimensional network structures and abundant functional groups (such as, hydroxyl groups), Ca2+ ions were uniformly distributed in the network and electrostatically attracted. The diffusion speed and range of CO32? ions were mediated by the concentration of hydrogel medium. Under the synergistic effect of Mg2+ ions, the crystal CaCO3 was induced by gas phase diffusion method in the hydrogel system. The results showed that the concentrations of Mg2+ ions and agar hydrogel had no obvious effect on the calcite phase of CaCO3, but the morphologies and sizes changed with concentrations of medium and Mg2+ ions. Attribute to template effect, the crystallization behavior and growth rate of CaCO3 crystals were regulated. Since Mg2+ ions were easily adsorbed on the surfaces of unit cell, the unique structure of CaCO3 was precisely controlled. This study provides a useful reference and inspiration for the understandings of the contributions of ion supply rate in bio-mineralization and hydrogel medium in biomimetic mineralization. 相似文献
5.
In recent years, chitosan has been applied for wound management due to its properties of biocompatibility, biodegradability, antimicrobial activity, and low immunogenicity. But the poor water solubility in neutral pH limited its further application in clinical wound healing. To overcome this problem, acetate chitosan was developed and approved as commercial products for wound healing. However, the acidity of acetate chitosan was potentially allergenic, and the poor mechanical properties of its formed hydrogels also hindered the therapeutic efficacy in wound care. In this study, CaCO3 was simply doped into acetate chitosan to form the wound dressing. After absorbing water, the H+ of acetate chitosan reacted with CaCO3 to release Ca2+, resulting in acidity decreased. The production of Ca2+ and residue of CaCO3 cross‐linked with chitosan to form a tough hydrogel by electrostatic interaction. The physical characteristics, swelling, mechanical testing, and blood clotting were evaluated. The results in vitro demonstrated that after doping CaCO3 into acetate chitosan, the mechanical properties and blood clotting of the formed hydrogel were increased. Then, the evaluation of hydrogels in vivo revealed that it can also accelerate the wound healing by promoting re‐epithelization and collagen deposition. This simple way by doping CaCO3 into acetate chitosan can increase wound healing, and it can also broad the application of acetate chitosan in clinical use. 相似文献
6.
This work investigates the thermal decomposition of magnesian kutnahorite, which belongs to the dolomite group.The DTA curve measured in static air using a small amount of sample (5.0 mg) is quite different from those published previously. This difference might be due to the effect of a self-generated CO2 atmosphere.In a CO2 flow of 100 ml min?1, magnesian kutnahorite decomposes in four steps. Mg-kutnahorite → CaCO3 + Mg2MnO4 + Mn3O4 + MgO → CaCO3 + CaMnO3 + MgO → CaCO3 + CaMnO3 + Ca2MnO4 + MgO → CaMnO3 + Ca2MnO4 + MgO + CaO.However, in a mixed gas flow of CO2 at 95 ml min?1 and CO at 5 ml min?1, it decomposes, like dolomite, in two steps. Mg-kutnahorite → CaCO3 + (Mg,Mn) → (Ca, Mn)O + (Mg,Mn).It has been found that the equilibrium redistribution of Mn between (Ca, Mn) and (Mg, Mn) is achieved at the second decomposition step. This is supported by theoretical considerations.Consequently, when the O2 partial pressure in the atmosphere is low enough to keep Mn in a bivalent state, the Mn bearing dolomite group mineral decomposes in a similar manner to dolomite itself. 相似文献
7.
Transparent thin films of calcium‐ion‐incorporated polymer composites were synthesized with calcium carbonate (CaCO3) and polymers such as poly(acrylic acid) (PAA), poly(ethylene glycol) (PEG), and methylcellulose. The homogeneous distribution of Ca2+ in the composite films was observed because of the high concentration of COO? groups along the PAA backbone for the complexation of Ca2+ ions. The optical transparency of the composites depends on the weight percentages of the three polymers and the molar concentration of CaCO3 in the composites. Maximum transparency was obtained for a composite film with a PAA/CaCO3 ratio of 9:1. The results indicated that methylcellulose improved the film‐forming capabilities and that PEG improved the transparency of the composites. All polymer complexes were characterized with X‐ray diffraction, fourier transfer infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, dynamic mechanical analysis, and optical transparency measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4459–4465, 2004 相似文献
8.
A general method to find the rate constant and particle self-diffusion coefficient is suggested for a heterogeneous isotopic exchange reaction which is controlled by surface mass reaction or controlled by a combination of surface mass reaction and intraparticle diffusion. The values of the kinetic parameter, ξ1 (ratio of the forward surface mass reaction rate to the intraparticle diffusion rate), particle self-diffusion coefficient D and rate constant k are obtained by the proposed method for the isotopic exchange reaction systems CaCO3(s)/Ca2+(aq) and CaC2O4(s)/Ca2+(aq). 相似文献
9.
Fred von Lampe 《无机化学与普通化学杂志》1985,524(5):168-176
Investigations on Belites and Dicalcium Silicates. I. Investigations of the Oxidation Number and the Crystallographic Position of Mn-Ions in the Crystal Lattice of Mn-doped Ca2SiO4 Light-blue Mn-doped monocrystals of Ca2SiO4 were grown from a CaCl2 flux using raw mixes (2 CaCO3 + 1 SiO2) with different contents of MnCO3. The MnO content in these crystals ranges up to ~0.50% and decreases with increasing duration of crystal growth thus generating a Mn profile in the crystals obtained. The oxidation number of Mn is predominantly 2+, but a little amount of Mn with a higher oxidation degree is also present. Some experiments suggest the existence of Mn5+ ions in the crystals. Mn2+ ions substitute Ca2+ ions in their irregular coordination polyhedra (coordination number 7 and 8), whereas Mn ions of higher valency substitute Si4+ ions in tetrahedra. 相似文献
10.
Talie Zarei Shahriar Mirpour Hamed Nikmaram Mahmood Ghoranneviss Sahar Mirpour Davoud Dorranian 《Plasma Chemistry and Plasma Processing》2017,37(1):99-114
Effects of high frequency spark plasma discharge as a time efficiency method in order to softening the natural hard water has been investigated experimentally. A very hard water sample with 331 ± 19 mg/l of CaCO3 hardness was used. The current and voltage of each spike was about 9.6 A and 3.5 kV respectively at 16 kHz frequency with 35 μs pulse width. Hard water was treated for 2, 4, 6, and 8 min. The concentration of CaCO3, Ca2+ ions, Mg2+ ions and pH as well as water conductivity was controlled before and after treatment. The concentration of CaCO3 dropped by 70%, after 8 min treatment. During the treatment, the pH had a fluctuation about 1.5 and finally remained in neutral state. Also the elemental composition, crystalline structure and morphology of the precipitates were identified. Molecular dynamics simulation revealed that the ozone and hydroxyl play important roles in the softening of the hard water. 相似文献
11.
Guowang Tang Cangqin Jia Guihe Wang Peizhi Yu Haonan Zhang 《Molecules (Basel, Switzerland)》2021,26(20)
The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO3 crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO3 precipitate was obtained. Moreover, the reaction of Ca2+ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO3 precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO3 changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated. 相似文献
12.
Andrónico Neira-Carrillo Ranjith Krishna Pai M. Soledad Fernández Esteban Carre?o Patricio Vasquez Quitral Jose Luis Arias 《Colloid and polymer science》2009,287(4):385-393
The objective of this work was to synthesize a sulfonated polymethylsiloxane (S-PMS) by hydrosilylation and sulfonation reactions
and to investigate their effect on the growth of CaCO3 crystals using a gas diffusion method as a function of concentration, pH, and time. The result of IR and NMR shows good agreement
with all proposed structures. Scanning electron microscopy images of CaCO3 showed small well-defined calcite-forming short piles (ca 5 μm) and elongated calcite (ca 20 μm) crystals. The morphology
of the resultant CaCO3 crystals reflects the electrostatic interaction of sulfonate moieties and Ca2+ modulated by S-PMS adsorbed onto the CaCO3 surface. X-ray diffraction confirmed the crystalline calcite polymorph. Energy dispersive spectroscopy of CaCO3 crystals determined the presence of Si atoms from S-PMS. The use of PMS chemistry as an organic additive for the production
of CaCO3 particles is a viable approach for studying the biomineralization and could be useful for the design of novel materials with
desirable shape and properties. 相似文献
13.
T. Shahwan A. C. Atesin H. N. Erten A. Zararsiz 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(3):563-568
Ba2+ uptake by natural bentonite, CaCO3 in addition to a number of bentonite-CaCO3 mixtures with variable compositions as a function of pH and Ba2+ concentration was studied. Radiotracer method, EDXRF, and PXRD were used. The results of radiotracer experiments showed that the uptake of Ba2+ by CaCO3 was larger than its uptake by natural bentonite samples, particularly at low initial concentrations of Ba2+ and higher pH values. This finding was supported by the EDXRF results. According to the sorption data, the apparent DG° values of sorption were in the range -9±1 to -13±3 kJ/mol. The PXRD studies revealed the formation of BaCO3 upon sorption of Ba2+ on pure CaCO3 and on some of the bentonite-CaCO3 mixtures. 相似文献
14.
Fangjie Zhu Dr. Tatsuya Nishimura Dr. Takeshi Sakamoto Dr. Hidekazu Tomono Dr. Hiroki Nada Prof. Dr. Yasushi Okumura Prof. Dr. Hirotsugu Kikuchi Prof. Dr. Takashi Kato 《化学:亚洲杂志》2013,8(12):3002-3009
Thin‐film growth of aragonite CaCO3 on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg2+ into a supersaturated solution of CaCO3. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg2+ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg2+. Molecular dynamics simulation of the CaCO3 precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg2+. The role for ionic additives in the crystallization of CaCO3 on organic templates obtained in this study may provide useful information for the development of functional hybrid materials. 相似文献
15.
B. T. Stokke K. I. Drager Y. Yuguchi H. Urakawa K. Kajiwara 《Macromolecular Symposia》1997,120(1):91-101
The wide applicability of alginates is due to the ease of which gelation can be introduced and that the gelation conditions are compatible with requirements imposed by for instance living cells. The “egg-box” model describes the gel-inducing ions embodied in cavities formed by sequences of α-L-GulA of the alginate copolymers in a pairing reaction yielding junction zones. Small-angle X-ray scattering showed that the cross-sectional radius of gyration for an alginate with fraction of α-L-GulA, FG, = 0.39, increased from Rg,c = 3.5Å for alginate in solution to 7.6Å for homogeneous Ca-gels at [Ca2+] = 10 mM. The homogeneous Ca-alginate gels were obtained by in situ release of Ca2+ from Ca-EGTA or CaCO3 using a slowly hydrolyzing lactone. Either increasing the [Ca2+] for a given FG or increasing FG by selection of an alginate from a different seaweed specie and using constant [Ca2+], yielded larger initial slopes and curvature in the cross-sectional plots of the SAXS data. This indicate the coexistence of junction zones differing in multiplicity characterized by shifting the distribution towards larger multiplicity either for increasing FG or [Ca2+]. The present finding of junction zone formation by lateral condensation of α-L-GulA sequences depending on the composition of alginate and Ca-concentration are significant extensions of the “egg-box” model that correlate the sequential arrangement of α-L-GulA and β-D-ManA in alginate to the structure of the junction zones in the Ca-alginate gels. 相似文献
16.
Rotating disc reactor
(RDR) was constructed to conduct gas–liquid–solid reactions with
controlled reagent transfer from gaseous to liquid phase. The concept is based
on continuous formation of thin liquid films at a surface of rotating discs
where the mass transfer proceed in diffusion–convective way.
The reactor was employed
to run precipitation reaction of CaCO3 via carbon dioxide
absorption in lime slurry. During each reaction pH changes and Ca2+
concentration in time were measured. Disc rotations and gas flows were changed
during the experiment and their influence on the obtained CaCO3
powders has been examined and fully discussed. 相似文献
17.
This paper discusses the influence of graft chain length and dosage of comb‐type superplasticizers on adsorption and dispersion mechanisms, and their subsequent effect on the fluidity of concentrated limestone suspensions. Contrary to the results obtained from interparticle potential calculations, the fluidity of concentrated suspension is improved by the use of comb‐type polymers having shorter grafted chain length. The dispersion mechanism of comb‐type polymers in a concentrated suspension is evaluated from the perspective of molecular structure, the amount of adsorbed polymer, and the amount of entrapped water in the clusters of CaCO3 particles. Furthermore, the addition of certain soluble salts, which can effect the concentration of Ca2+ in liquid phase of CaCO3 suspensions, has been observed to decrease the adsorption of comb‐type polymers on CaCO3. Thus, the polymer adsorption process on solid surfaces can be selectively influenced by certain types of ions. 相似文献
18.
Single-phase AB-type carbonate apatites were prepared by sintering appropriate mixtures of CaHPO4 and CaCO3 at 870°C in a CO2 atmosphere with a partial water vapor pressure of 5 mm Hg. Chemical and physical analyses indicate that at a constant CO32?/OH? ratio in the hydroxyl sublattice, carbonate substitutes for phosphate on a 1:1 mole basis. For every three PO43? ions substituted, two vacancies in the Ca2+ sublattice and one in the OH? sublattice are created. The same substitution mechanism seems to apply in pure B-type carbonate apatite. 相似文献
19.
碳酸钙晶须合成过程中可溶性磷酸盐的作用机理研究 总被引:2,自引:0,他引:2
以可溶性磷酸盐为控制剂,一步碳化法制备了文石相碳酸钙晶须。借助于XRD和FTIR,分析了可溶性磷酸盐在碳酸钙晶须合成过程中的作用机理。研究结果表明:通入CO2进行碳化反应前,可溶性磷酸盐与Ca(OH)2反应生成了热力学上最稳定的磷酸钙化合物——羟基磷灰石;在通入CO2初期,[CO32-(OH)]进入到羟基磷灰石的晶格,部分替代[PO43-],生成碳酸羟基磷灰石,然后以此为结晶中心诱导文石相的异相成核,Ca2+、CO32-不断叠加,进而生长为碳酸钙晶须。 相似文献
20.
A novel signal-generation tag based on polyaspartic acid (PASA)-doped CaCO3 nanospheres was utilized for development of the electrochemical immunosensing protocol with a calcium ion-selective electrode (Ca-ISE). The organic-inorganic hybrid nanospheres were synthesized via the reverse micellar method, and functionalized with the detection antibody through the carbodiimide coupling. Upon target analyte introduction, a sandwiched immunoreaction was carried out on the microplate between capture antibody and the labeled detection antibody on the CaCO3 nanospheres. The carried CaCO3 was dissolved under acidic conditions, and the released Ca2 + ions were detected on a Ca-ISE. The detectable electronic signal increased with the increasing target concentration. By monitoring the shift in the potential, the concentration of the analyte could be quantitatively evaluated by using a portable ion-selective electrode. Importantly, our strategy can be readily applied in other electrochemical detection systems (e.g., DNA sensors, immunosensors and aptasensors) by controlling the corresponding labels on the CaCO3 nanospheres. 相似文献