Nucleation of metastable aragonite CaCO 3 in seawater Sun, Wenhao; Jayaraman, Saivenkataraman; Chen, Wei ...
Proceedings of the National Academy of Sciences - PNAS,
03/2015, Letnik:
112, Številka:
11
Journal Article
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Significance
Crystallization from solution is a materials synthesis process common both in nature and in the laboratory. Unlike conventional high-temperature solid-state synthesis, solution-based ...syntheses often yield metastable phases, contrary to expectations from equilibrium thermodynamics. Using a recently developed ab initio scheme to calculate the surface energy of a critical nucleus in equilibrium with the aqueous environment, we present a framework to compare relative nucleation rates between competing polymorphs as a function of solution chemistry. We apply this approach to demonstrate how seawater chemistry can preferentially bias nucleation toward the metastable aragonite phase of calcium carbonate, rather than the stable phase calcite––which is of great relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification.
Predicting the conditions in which a compound adopts a metastable structure when it crystallizes out of solution is an unsolved and fundamental problem in materials synthesis, and one which, if understood and harnessed, could enable the rational design of synthesis pathways toward or away from metastable structures. Crystallization of metastable phases is particularly accessible via low-temperature solution-based routes, such as
chimie douce
and hydrothermal synthesis, but although the chemistry of the solution plays a crucial role in governing which polymorph forms, how it does so is poorly understood. Here, we demonstrate an ab initio technique to quantify thermodynamic parameters of surfaces and bulks in equilibrium with an aqueous environment, enabling the calculation of nucleation barriers of competing polymorphs as a function of solution chemistry, thereby predicting the solution conditions governing polymorph selection. We apply this approach to resolve the long-standing “calcite–aragonite problem”––the observation that calcium carbonate precipitates as the metastable aragonite polymorph in marine environments, rather than the stable phase calcite––which is of tremendous relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. We identify a direct relationship between the calcite surface energy and solution Mg–Ca ion concentrations, showing that the calcite nucleation barrier surpasses that of metastable aragonite in solutions with Mg:Ca ratios consistent with modern seawater, allowing aragonite to dominate the kinetics of nucleation. Our ability to quantify how solution parameters distinguish between polymorphs marks an important step toward the ab initio prediction of materials synthesis pathways in solution.
The AlCl3/ZnCl2 aqueous solution acts as a benign cellulose solvent, polymerization catalyst for acrylamide monomer, effective ion source for electron transport networks, and dynamic riveting point ...for hydrogel networks.
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The green synthesis strategy for cellulose-containing hydrogel electrolytes is significant for effectively managing resources, energy, and environmental concerns in the contemporary world. Herein, we propose an all-green strategy using AlCl3/ZnCl2/H2O solvent to create cellulose/polyacrylamide-based hydrogel (AZ-Cel/PAM) with expanded hierarchical topologies. The aqueous AlCl3/ZnCl2 facilitates the efficient dissolution of cellulose at room temperature, and the dispersed Al3+-Zn2+ ions autocatalytic system catalyzes in-situ polymerization of acrylamide (AM) monomer. This expands the AM network within the cellulose framework, forming multiple bonding interactions and stable ion channels. The resulting hybrid hydrogel exhibits improved mechanical properties (tensile strength of 56.54 kPa and compressive strength of 359.43 kPa) and enhanced ionic conductivity (1.99 S/m). Furthermore, it also demonstrates excellent adhesion, freeze resistance (−45 °C), and water retention capabilities. Quantum simulations further clarify the mechanical composition and ion transport mechanism of AZ-Cel/PAM hydrogels. The assembled supercapacitor with the hydrogel electrolyte, demonstrates an ideal area-specific capacitance of 203.80 mF/cm2. This all-green strategy presents a novel approach to developing sustainable energy storage devices.
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Since their discovery over 100 years ago cyclodextrins (CDs) have been the subject of numerous scientific publications. In 2016 alone CDs were the subject of over 2200 research ...articles published in peer-reviewed journals and mentioned in over 2300 patents and patent applications, many of which were on pharmaceutical applications. Natural CDs and their derivatives are used as enabling pharmaceutical excipients that enhance aqueous solubility of poorly soluble drugs, increase drug permeability through biological membranes and improve drug bioavailability. Unlike conventional penetration enhancers, their hydrophilic structure and high molecular weight prevents them from penetrate into lipophilic membranes leaving biological membranes intact. The natural CDs and some of their derivatives have monographs in pharmacopeias and are also commonly used as food additives and in toiletry products. CDs form inclusion complexes with lipophilic moieties of hydrophobic drugs. Furthermore, CDs are able to form non-inclusion complexes and self-assembled aggregates; small and large complex aggregates with micellar-like structures that can enhance drug solubility. Excipients commonly used in pharmaceutical formulations may have additive or inhibiting effect on the CD solubilization. Here various methods used to investigate CD aggregate formation are reviewed as well as techniques that are used to increase the solubilizing effects of CDs; methods that enhance the apparent intrinsic solubility of drugs and/or the complexation efficacy and decrease the amount of CD needed to develop CD-containing pharmaceutical formulations. It will be explained how too much or too little CD can hamper drug bioavailability, and the role of CDs in solid dosage forms and parenteral formulations, and examples given on how CDs can enhance drug delivery after ocular, nasal and pulmonary administration.
Hollow V2O5 spheres constructed from plate-like particles exhibited a tremendous pseudocapacitance effect with a high capacitance of 479Fg−1.
•Hollow V2O5 spheres constructed from plate-like ...particles were synthesized and used as supercapacitor electrodes in a solution of 5M LiNO3.•These materials exhibited a tremendous pseudocapacitance effect with a high capacitance of 479Fg−1 at 5mVs−1.•The hollow V2O5 spheres was coated with PPy exhibited the capacitances of 559Fg−1 at 3Ag−1 by GCD and 566Fg−1 at 5mVs−1 by CV, respectively.
Hollow V2O5 spheres constructed from plate-like particles were synthesized. These materials exhibited a tremendous pseudocapacitance effect with a high capacitance of 479Fg−1 at 5mVs−1 when used as supercapacitor electrodes in a solution of 5M LiNO3. After the surface of hollow V2O5 spheres was coated with PPy, the composite electrode was formed and its electrochemical properties were also improved. This composite material exhibited the capacitances of 559Fg−1 at 3Ag−1 by GCD and 566Fg−1 at 5mVs−1 by CV, respectively. At the same time, the capacity retentions of 70% and 66% were respectively achieved even after 100 cycles.
Biodegradable plastics (BPs) have seen a continuous increase in annual production and application due to their environmentally sustainable characteristics. However, research on the formation of ...disinfection byproducts (DBPs) from biodegradable microplastics (BMPs) during chlorination is limited, and the effects of aqueous solution chemistry on this process have yet to be explored. Therefore, two biodegradable microplastics, polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT), were investigated in this study to examine the changes in their physicochemical properties before and after chlorination, and the formation of DBPs under different environmental conditions. The results showed that PLA was more chlorine-responsive, and generated more DBPs. The pH converted some of the intermediates into more stable DBPs by affecting the concentration of HClO and base-catalyzed reactions, whereas ionic strength slightly reduced DBP concentration by ion adsorption and promoting the aggregation of BMPs. Finally, since PLA has a slightly greater volume of mesopores and micropores compared to PBAT, it may more effectively adsorb DBP precursors beyond natural organic matter (NOM), such as some anthropogenic pollutants, thus potentially decreasing the formation of chlorinated DBPs in surface water. This research explored the potentiality for DBP formation by BMPs under different water quality conditions during the disinfection process, which is useful for assessing the environmental hazards of BMPs.
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•PLA yields more DBPs than PBAT with its porous structure and reactive ester bonds.•Rising pH converts DBP intermediates to stable DBPs.•NaCl may reduce DBP production by impacting BP reaction sites and agglomeration.•PLA might adsorb non-NOM DBP precursors in surface water to reduce DBP formation.
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•A novel Zeolite 4A/WO3/CuO composite catalyst was synthesized to degrade the anionic dyes simultaneously by the sonophotocatalytic process.•The composite catalyst system exhibited a ...specific surface area of 10.76 m2/g.•The findings indicate that the sonophotocatalytic process demonstrates high efficiency and performance.•The reusability of the Zeolite 4A/WO3/CuO catalyst showed that it maintained over 90% of its performance even after five cycles of reuse.•The findings suggest that the sonophotocatalytic process has a faster degradation rate and shorter half-life.•The Zeolite 4A/WO3/CuO composite can be confidently recommended as an efficient catalyst for dye removal from aqueous solutions using the sonophotocatalytic process.
In this study, a novel composite catalyst system, Zeolite 4A/WO3/CuO with a Z-scheme design, was synthesized for photocatalysis, sonocatalysis, and sono-photocatalysis methyl orange (MO) and indigo carmine (IC) dyes simultaneously. The properties of the Zeolite 4A/WO3/CuO composite were thoroughly investigated using various techniques, and the results confirmed the synthesis of the desired catalyst system. In the sono-photocatalytic process, using the Zeolite 4A/WO3/CuO composite, the maximum efficiency for MO (99.12 %) and IC (97.24 %) was achieved at pH of 2 and 3, with a catalyst dosage of 0.15 g/L, a dye concentration of 10 mg/L, a contact time of 25 min, and H2O2 dosage of 30 µL/100 mL. The dye elimination efficiency using the sono-photocatalytic process was reduced in the presence of Cl- and PO43- in the distilled water. The efficiency also declined in the medium of river and well water resources. Moreover, the Zeolite 4A/WO3/CuO catalyst maintained over 90 % of its performance even after five reuse cycles. Based on the kinetic study, the sono-photocatalytic process exhibited higher activation for the removal of MO (k: 0.1946 min−1 and t1/2: 3.561) and IC (k: 0.1433 min−1 and t1/2: 4.836) than other processes. The synergy values for the MO and IC degradation using the Zeolite 4A/WO3/CuO composite were determined to be 2.167 and 2.303, respectively. The impact of various scavengers demonstrated that in the degradation processes of the target dyes using the sono-photocatalytic process, different active species like OH•, e-, h+, and O2–• are involved. The purification of dye-laden water using the sono-photocatalytic process was not toxic for plant germination, microorganisms, and fish, highlighting the successful biocompatibility of the process for dye removal.
•Bubble nucleation, growth, collision, coalescence, and detachment in experiment and simulation.•Evolution of bubble damping oscillations during coalescence with various currents.•A hybrid ...DPM-VOF-DCTM model on predicting transient multiscale bubble motion.•A DCTM for bridging different scales of the hybrid models of VOF and DPM.
The present investigation demonstrates the transient multiscale bubble behaviors including the bubble homogeneous nucleation, continuous growth, disordered collision and coalescence, and disturbed detachment under the anode in the CuSO4 aqueous solution electrolysis process by experimental and numerical methods. The combined approach of the volume of fluid (VOF) method and discrete phase model (DPM) is applied to solve the macro bubbles’ surfaces and track the micro bubbles’ trajectories, respectively. The link between the macro continuous and micro dispersed bubbles is achieved by the discrete-continuum transition model (DCTM). The dumbbell and the gourd morphologies are revealed in both experiment and numerical simulation during the binary bubble collision and coalescence. The predicted maximum bubble thickness and maximum bubble coverage present reasonable matches to the experimental data. The results show that the large coalescing bubbles can extend the bubble collision period and increase the fluctuation amplitude of the bubble interface. Increasing the current will increase the bubble collision velocity and shorten the contact time before bubble coalescence, moreover, the recovery time of the oscillating bubble from coalescence to the stable state is also prolonged. Increasing inclined angles of the anode can increase the bubble velocity and decrease the bubble diameter.
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•Standard molar volumes of teotropine (tetramethylenediethylenetetramine – TMDETA) in water were determined densimetrically.•Density measurements were performed at temperatures from ...278.15 K to 318.15 K (with a step of 10 K) at ambient pressure.•Like the related aminal solute urotropine (hexamethylenetetramine – HMTA), TMDETA has a structure-making effect in water.•Structure packing of the hydration complex formed becomes denser and thermally more stable when going from HMTA to TMDETA.•Structure-forming effect (due to hydrophobic effects and H-bonding) is greater in aqueous TMDETA as a bulkier aminal solute.
The densities of aqueous solutions of tetramethylenediethylenetetramine (the teotropine pharmaceutical) with the solute molality from (0.01 to 0.12) mol·(kg water)−1 were measured at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and p = 0.1 MPa. The uncertainty in density measured using the Anton Paar DMA 5000 M densimeter (equipped with an oscillating U-tube) was estimated to be 0.03 kg m−3 or lower. The standard (apparent at infinite dilution) molar volumes and expansibilities of teotropine were computed. Based on the analysis of contributions to the standard molar volume in terms of the Scaled Particle Theory was confirmed that a bulkier molecule of teotropine interacts with water stronger than it does a molecule of urotropine or hexamethylenetetramine – the related aminal (cage-like) compound.
Aqueous electrolytes come with an intrinsic narrow electrochemical stability window (1.23 V). Expanding this window represents significant benefits in both fundamental science and practical battery ...applications. Recent breakthroughs made via super-concentration have resulted in >3.0 V windows, but fundamental understanding of the related mechanism is still absent. In the present work, we examined the widened window (2.55 V) of a super-concentrated (unsaturated) aqueous solution of LiNO3 through both theoretical and spectral analyses and discovered that a local structure of intimate Li+-water interaction arises at super-concentration, generating (Li+(H2O)2)n polymer-like chains to replace the ubiquitous hydrogen bonding between water molecules. Such structure is mainly responsible for the expanded electrochemical stability window. Further theoretical and experimental analyses quantitatively differentiate the contributions to this window, identifying the kinetic factor (desolvation) as the main contributor. Such molecular-level and quantitative understanding will further assist in tailor designing more effective approaches to stabilizing water electrochemically.
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•The widened window of a super-concentrated aqueous LiNO3 solution was demonstrated•A local structure of (Li+(H2O)2)n polymer-like chains was discovered•The local structure is mainly responsible for the expanded electrochemical window
Because of their non-flammable nature, low toxicity, and low production cost, aqueous Li-ion batteries (LIBs) promise very tempting alternatives to the state-of-the-art LIBs that rely on highly flammable and toxic non-aqueous electrolytes. However, the intrinsic narrow electrochemical stability window (1.23 V) of water sets an upper limit on the practical voltage and energy output. Here, we report a super-concentrated (unsaturated) LiNO3-based aqueous electrolyte that effectively expands the aqueous stability window to 2.55 V. We further revealed that a unique local structure with (Li+(H2O)2)n polymer-like aggregation arises at the super-concentration, which assists in stabilizing the aqueous solution at extreme potentials via both thermodynamic and kinetic contributions. This fundamental revelation of liquid structure and its effect on the electrochemical stability window provides a new pathway for designing high-voltage aqueous electrolytes.
The unique local structure with (Li+(H2O)2)n polymer-like aggregation in super-concentrated LiNO3 aqueous solution assists in stabilizing the aqueous solution at extreme potentials. Such molecular-level and quantitative understanding will further assist in tailor designing more effective approaches to stabilizing water electrochemically.
The CuSO4 aqueous solution electrolysis experiment is conducted to investigate the electrical bubble dynamics using the slotted anode to reveal the gas removal mechanism. A three-dimensional ...transient mathematical model coupled discrete phase model (DPM) − discrete-continuum transition model (DCTM) − volume of fluid (VOF) method is developed to track the dispersed bubble trajectory, bridge the dispersed bubble to continuous gas, and resolve the deformed bubble surface, respectively. The slotted anode decreases the bubble diameter compared with the traditional anode because the slot shortens the bubble motion distance to decrease the bubble residence time. The slot width smaller than the detached bubble diameter can limit the bubble deformation. Increasing current plays a dual role in bubble motion in the experiment: it accelerates the bubble coalescence process but decreases the bubble collision probability. The longitudinal slot is more conducive to reducing the maximum bubble coverage and increasing the bubble release frequency than the transverse slot.
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•Comparison of specific bubble group behavior between traditional and slotted anodes in experiment and simulation.•A coupled DPM-DCTM-VOF model on predicting transient multiscale bubble motion.•A novel DCTM for bridging discrete and continuous phases of the hybrid VOF-DPM model.
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