Performance Evaluation of Cementless Composites with Alkali-Sulfate Activator for Field Application

This study analyzed the performance evaluation of alkali-activated composites (AAC) with an alkali-sulfate activator and determined the expected effects of applying AACs to actual sites. Results revealed that when the binder weight was increased by 100 kg/m³ at 7 days of age, the homogel strength of ordinary Portland cement (OPC) and AAC increased by 0.9 and 5.0 MPa, respectively. According to the analysis of the matrix microstructures at 7 days of age, calcium silicate hydrates (C–S–H, Ca_1.5SiO_3.5·H₂O) and ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O) were formed in AAC, which are similar hydration products as found in OPC. Furthermore, the acid resistance analysis showed that the mass change of AAC in HCl and H₂SO₄ solutions ranged from 36.1% to 88.0%, lower than that of OPC, indicating AAC’s superior acid resistance. Moreover, the OPC and AAC binder weight ranges satisfying the target geltime (20–50 s) were estimated as 180.1–471.1 kg/m³ and 261.2–469.9 kg/m³, respectively, and the global warming potential (GWP) according to binder weight range was 102.3–257.3 kg CO₂ eq/m³ and 72.9–126.0 kg CO₂ eq/m³. Therefore, by applying AAC to actual sites, GWP is expected to be 29.5 (28.8%)–131.3 (51.0%) kg CO₂ eq/m³ less than that of OPC.     

A framework for predicting global silicate weathering and CO2 drawdown rates over geologic time-scales

Global silicate weathering drives long-time-scale fluctuations in atmospheric CO₂. While tectonics, climate, and rock-type influence silicate weathering, it is unclear how these factors combine to drive global rates. Here, we explore whether local erosion rates, GCM-derived dust fluxes, temperature, and water balance can capture global variation in silicate weathering. Our spatially explicit approach predicts 1.9–4.6 × 10¹³ mols of Si weathered globally per year, within a factor of 4–10 of estimates of global silicate fluxes derived from riverine measurements. Similarly, our watershed-based estimates are within a factor of 4–18 (mean of 5.3) of the silica fluxes measured in the world's ten largest rivers. Eighty percent of total global silicate weathering product traveling as dissolved load occurs within a narrow range (0.01–0.5 mm/year) of erosion rates. Assuming each mol of Mg or Ca reacts with 1 mol of CO₂, 1.5–3.3 × 10⁸ tons/year of CO₂ is consumed by silicate weathering, consistent with previously published estimates. Approximately 50% of this drawdown occurs in the world's active mountain belts, emphasizing the importance of tectonic regulation of global climate over geologic timescales.     

Crystal-Chemical and Thermal Properties of Decorative Cement Composites

The advanced tendencies in building materials development are related to the design of cement composites with a reduced amount of Portland cement, contributing to reduced CO₂ emissions, sustainable development of used non-renewal raw materials, and decreased energy consumption. This work deals with water cured for 28 and 120 days cement composites: Sample A—reference (white Portland cement + sand + water); Sample B—white Portland cement + marble powder + water; and Sample C white Portland cement + marble powder + polycarboxylate-based water reducer + water. By powder X-ray diffraction and FTIR spectroscopy, the redistribution of CO₃²⁻, SO₄²⁻, SiO₄⁴⁻, AlO₄⁵⁻, and OH⁻ (as O-H bond in structural OH⁻ anions and O-H bond belonging to crystal bonded water molecules) from raw minerals to newly formed minerals have been studied, and the scheme of samples hydration has been defined. By thermal analysis, the ranges of the sample’s decomposition mechanisms were distinct: dehydration, dehydroxylation, decarbonation, and desulphuration. Using mass spectroscopic analysis of evolving gases during thermal analysis, the reaction mechanism of samples thermal decomposition has been determined. These results have both practical (architecture and construction) and fundamental (study of archaeological artifacts as ancient mortars) applications.     

Multiscale observations of CO2, 13CO2, and pollutants at Four Corners for emission verification and attribution

There is a pressing need to verify air pollutant and greenhouse gas emissions from anthropogenic fossil energy sources to enforce current and future regulations. We demonstrate the feasibility of using simultaneous remote sensing observations of column abundances of CO₂, CO, and NO₂ to inform and verify emission inventories. We report, to our knowledge, the first ever simultaneous column enhancements in CO₂ (3–10 ppm) and NO₂ (1–3 Dobson Units), and evidence of δ¹³CO₂ depletion in an urban region with two large coal-fired power plants with distinct scrubbing technologies that have resulted in ∆NO_x/∆CO₂ emission ratios that differ by a factor of two. Ground-based total atmospheric column trace gas abundances change synchronously and correlate well with simultaneous in situ point measurements during plume interceptions. Emission ratios of ∆NO_x/∆CO₂ and ∆SO₂/∆CO₂ derived from in situ atmospheric observations agree with those reported by in-stack monitors. Forward simulations using in-stack emissions agree with remote column CO₂ and NO₂ plume observations after fine scale adjustments. Both observed and simulated column ∆NO₂/∆CO₂ ratios indicate that a large fraction (70–75%) of the region is polluted. We demonstrate that the column emission ratios of ∆NO₂/∆CO₂ can resolve changes from day-to-day variation in sources with distinct emission factors (clean and dirty power plants, urban, and fires). We apportion these sources by using NO₂, SO₂, and CO as signatures. Our high-frequency remote sensing observations of CO₂ and coemitted pollutants offer promise for the verification of power plant emission factors and abatement technologies from ground and space.Trace gas [nitrogen oxides (NO_x), sulfur dioxide (SO₂), and carbon monoxide (CO)] and carbon dioxide (CO₂) emissions from anthropogenic fossil energy production are major contributors to air pollution and global warming. Under the Clean Air Act, in the United States these emissions are considered a threat to public health and welfare and are regulated by the Environmental Protection Agency (EPA). Although reporting requirements for air pollutants are well established, they are still under development for CO₂. Reported inventories of CO₂ and pollutant gases are calculated for specific activities using emission factors that depend on fuel composition, combustion efficiency, and scrubbing methods. These bottom–up inventories are subject to significant uncertainties and manipulations (1). Alternatively, atmospheric observations offer an independent top–down method to verify emissions of pollutant trace gases that have low atmospheric background levels and exhibit large and distinct increases near various combustion sources. For example, satellite observations of NO₂ have been used to evaluate regional and local emissions (2), but they are only useful for trend analysis, because their large observational footprint can underestimate NO₂. In contrast, background levels of CO₂ are high with significant variability, making source attribution and verification by direct CO₂ measurements elusive (3), limiting our ability to develop an effective global climate treaty or carbon-trading scheme (4). We postulate that measurements of coemitted trace gases and isotopic composition can be used to isolate anthropogenic CO₂ emissions and identify contributions from specific sectors with distinct composition (trace gas-to-CO₂ emission ratios, ER_X = X/CO₂, or isotopic ratio ¹³CO₂/¹²CO₂). We hypothesize that remote column trace gas measurements over large scales, which are less sensitive to small-scale variability from meteorology than in situ point surface measurements, can provide a more precise method for identifying trends in emissions and emission factors (5). We evaluate this method by using extensive ground-based in situ and remote observations, and forward modeling using reported in-stack emissions at a site with large power plant emissions of CO₂ and pollutants.     

Phosphatidylinositol 4,5-bisphosphate (PIP2) stimulates the electrogenic Na/HCO3 cotransporter NBCe1-A expressed in Xenopus oocytes

Bicarbonate transporters are regulated by signaling molecules/ions such as protein kinases, ATP, and Ca²⁺. While phospholipids such as PIP₂ can stimulate Na-H exchanger activity, little is known about phospholipid regulation of bicarbonate transporters. We used the patch-clamp technique to study the function and regulation of heterologously expressed rat NBCe1-A in excised macropatches from Xenopus laevis oocytes. Exposing the cytosolic side of inside-out macropatches to a 5% CO₂/33 mM HCO₃⁻ solution elicited a mean inward current of 14 pA in 74% of macropatches attached to pipettes (−V_p = −60 mV) containing a low-Na⁺, nominally HCO₃⁻-free solution. The current was 80–90% smaller in the absence of Na⁺, approximately 75% smaller in the presence of 200 μM DIDS, and absent in macropatches from H₂O-injected oocytes. NBCe1-A currents exhibited time-dependent rundown that was inhibited by removing Mg²⁺ in the presence or absence of vanadate and F⁻ to reduce general phosphatase activity. Applying 5 or 10 μM PIP₂ (diC8) in the presence of HCO₃⁻ induced an inward current in 54% of macropatches from NBC-expressing, but not H₂O-injected oocytes. PIP₂-induced currents were HCO₃⁻-dependent and somewhat larger following more NBCe1-A rundown, 62% smaller in the absence of Na⁺, and 90% smaller in the presence of 200 μM DIDS. The polycation neomycin (250–500 μM) reduced the PIP₂-induced inward current by 69%; spermine (100 μM) reduced the current by 97%. Spermine, poly-D-lysine, and neomycin all reduced the baseline HCO₃⁻-induced inward currents by as much as 85%. In summary, PIP₂ stimulates NBCe1-A activity, and phosphoinositides are regulators of bicarbonate transporters.     

Integrating a Top-Gas Recycling and CO2 Electrolysis Process for H2-Rich Gas Injection and Reduce CO2 Emissions from an Ironmaking Blast Furnace

Introducing CO₂ electrochemical conversion technology to the iron-making blast furnace not only reduces CO₂ emissions, but also produces H₂ as a byproduct that can be used as an auxiliary reductant to further decrease carbon consumption and emissions. With adequate H₂ supply to the blast furnace, the injection of H₂ is limited because of the disadvantageous thermodynamic characteristics of the H₂ reduction reaction in the blast furnace. This paper presents thermodynamic analysis of H₂ behaviour at different stages with the thermal requirement consideration of an iron-making blast furnace. The effect of injecting CO₂ lean top gas and CO₂ conversion products H₂–CO gas through the raceway and/or shaft tuyeres are investigated under different operating conditions. H₂ utilisation efficiency and corresponding injection volume are studied by considering different reduction stages. The relationship between H₂ injection and coke rate is established. Injecting 7.9–10.9 m³/tHM of H₂ saved 1 kg/tHM coke rate, depending on injection position. Compared with the traditional blast furnace, injecting 80 m³/tHM of H₂ with a medium oxygen enrichment rate (9%) and integrating CO₂ capture and conversion reduces CO₂ emissions from 534 to 278 m³/tHM. However, increasing the hydrogen injection amount causes this iron-making process to consume more energy than a traditional blast furnace does.     

Crystal Evolution of Calcium Silicate Minerals Synthesized by Calcium Silicon Slag and Silica Fume with Increase of Hydrothermal Synthesis Temperature

In order to realize high-value utilization of calcium silicon slag (CSS) and silica fume (SF), the dynamic hydrothermal synthesis experiments of CSS and SF were carried out under different hydrothermal synthesis temperatures. In addition, phase category, microstructure, and micropore parameters of the synthesis product were analyzed through testing methods of XRD, SEM, EDS and micropore analysis. The results show that the main mechanism of synthesis reaction is that firstly β-Dicalcium silicate, the main mineral in CSS, hydrates to produce amorphous C–S–H and Ca(OH)₂, and the environment of system is induced to strong alkaline. Therefore, the highly polymerized Si-O bond of SF is broken under the polarization of OH⁻ to form (SiO₄) of Q⁰. Next, amorphous C–S–H, Ca(OH)₂ and (SiO₄) of Q⁰ react each other to gradually produce various of calcium silicate minerals. With an increase of synthesis temperature, the crystal evolution order for calcium silicate minerals is cocoon-like C–S–H, mesh-like C–S–H, large flake-like gyrolite, small flake-like gyrolite, petal-like gyrolite, square flake-like calcium silicate hydroxide hydrate, and strip-like tobermorite. In addition, petal-like calcium silicate with high average pore volume (APV), specific surface area (SSA) and low average pore diameter (APD) can be prepared under the 230 °C synthesis condition.     

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

The diffusion of sulfate (SO₄²⁻) and chloride (Cl⁻) ions from rivers, salt lakes and saline soil into reinforced concrete is one of the main factors that contributes to the corrosion of steel reinforcing bars, thus reducing their mechanical properties. This work experimentally investigated the corrosion process involving various concentrations of NaCl-Na₂SO₄ leading to the coupled erosion of concrete. The appearance, weight, and mechanical properties of the concrete were measured throughout the erosion process, and the Cl⁻ and SO₄²⁻ contents in concrete were determined using Cl⁻ rapid testing and spectrophotometry, respectively. Scanning electron microscopy, energy spectrometry, X-ray diffractometry, and mercury porosimetry were also employed to analyze microstructural changes and complex mineral combinations in these samples. The results showed that with higher Na₂SO₄ concentration and longer exposure time, the mass, compressive strength, and relative dynamic elastic modulus gradually increased and large pores gradually transitioned to medium and small pores. When the Na₂SO₄ mass fraction in the salt solution was ≥10 wt%, there was a downward trend in the mechanical properties after exposure for a certain period of time. The Cl⁻ diffusion rate was thus related to Na₂SO₄ concentration. When the Na₂SO₄ mass fraction in solution was ≤5 wt% and exposure time short, SO₄²⁻ and cement hydration/corrosion products hindered Cl⁻ migration. In a concentrated Na₂SO₄ environment (≥10 wt%), the Cl⁻ diffusion rate was accelerated in the later stages of exposure. These experiments further revealed that the Cl⁻ migration rate was higher than that of SO₄²⁻.     

Electron-transfer sensitization of H2 oxidation and CO2 reduction catalysts using a single chromophore

Energy-storing artificial-photosynthetic systems for CO₂ reduction must derive the reducing equivalents from a renewable source rather than from sacrificial donors. To this end, a homogeneous, integrated chromophore/two-catalyst system is described that is thermodynamically capable of photochemically driving the energy-storing reverse water–gas shift reaction (CO₂ + H₂ → CO + H₂O), where the reducing equivalents are provided by renewable H₂. The system consists of the chromophore zinc tetraphenylporphyrin (ZnTPP), H₂ oxidation catalysts of the form [Cp^RCr(CO)₃]^–, and CO₂ reduction catalysts of the type Re(bpy-4,4′-R₂)(CO)₃Cl. Using time-resolved spectroscopic methods, a comprehensive mechanistic and kinetic picture of the photoinitiated reactions of mixtures of these compounds has been developed. It has been found that absorption of a single photon by broadly absorbing ZnTPP sensitizes intercatalyst electron transfer to produce the substrate-active forms of each. The initial photochemical step is the heretofore unobserved reductive quenching of the low-energy T₁ state of ZnTPP. Under the experimental conditions, the catalytically competent state decays with a second-order half-life of ∼15 μs, which is of the right magnitude for substrate trapping of sensitized catalyst intermediates.The inexorable growth of global energy consumption and concern over its attendant environmental consequences has spurred considerable research into developing means to store solar energy in the form of renewable chemical fuels (1, 2). Among the potential feedstocks for these solar fuels, CO₂ is a desirable target because it is the end product of the combustion of fossil fuels. Thus, developing solar-driven mechanisms for chemically reducing CO₂ to energy-rich products holds the potential to recycle conventional fuels and mitigate their carbon impact (3–7).Numerous studies over the past 30 y have investigated homogeneous artificial-photosynthetic systems for CO₂ reduction, in which a photoexcited chromophore accomplishes the transfer of electrons from a source of reducing equivalents to a CO₂ reduction catalyst (8–14). With very rare exceptions (15), the reducing equivalents consumed in these photochemical CO₂ reduction reactions have been supplied by sacrificial electron donors. These reagents are used because their prompt decomposition following photoinitiated oxidation suppresses unproductive back-electron-transfer pathways, which are generally fast compared with substrate transformation, and because their decomposition products can provide additional reducing equivalents needed for some CO₂ reduction reactions, thus circumventing the one-photon/one-electron limit of molecular photosensitizers. Offsetting these practical advantages, however, is the fact that the stoichiometric consumption of conventional sacrificial donors in these reactions negates their energy-storing potential. In order for homogeneous systems to drive CO₂ reduction reactions that store energy, these sacrificial reagents must be replaced by a second catalytic cycle that extracts the reducing equivalents from a renewable source (16).Neumann and coworkers recently reported a photochemical system for the reduction of CO₂ to CO in which the reducing equivalents are derived from the oxidation of H₂ by colloidal platinum (15). This system, which contains a [Re^I(phen)(CO)₃L]⁺ (phen is 1,10-phenanthroline) CO₂ reduction catalyst linked with a polyoxometalate cluster, drives the reverse water–gas-shift reaction (RWGS) (CO₂ + H₂ → CO + H₂O), using light as the energy source, via the reactions shown in Eqs. 1–3. Unlike photochemical reactions that consume sacrificial donors, this energy-storing system [ΔH_f = 41.2 kJ⋅mol^–1 (17)] catalytically extracts renewable reducing equivalents that can be sourced to water.H₂→2e^? + 2H⁺[1]CO₂ + 2e^? + 2H⁺→CO + H₂O[2]CO₂ + H₂→CO + H₂O[3]The mechanistic, thermodynamic, and kinetic integration of two catalytic cycles with a chromophore is a general challenge that cuts across homogeneous molecular approaches to forming solar fuels from CO₂ and H₂O. A photochemical system for the RWGS reaction that used a homogeneous H₂ oxidation catalyst would both provide insights into the fundamental factors that govern this integration and opportunities to exert greater control over them than is possible with heterogeneous catalysts. Motivated by these possibilities, we report here the photochemistry of a homogeneous system composed of a photosensitizer, CO₂-reduction catalyst, and H₂-oxidation catalyst that, upon excitation with long-wavelength light (λ > 590 nm), yields a product state thermodynamically capable of accomplishing the RWGS reaction. The system operates via reductive quenching of the low-energy T₁ excited state of the common chromophore zinc tetraphenylporphyrin (ZnTPP) by a compound of the form Cp^RCr(CO)₃^– (1^–; Cp^R = η⁵-cyclopentadienyl), followed by thermal electron transfer from the product ZnTPP^– radical to a complex of the type Re(bpy-4,4′-R₂)(CO)₃Cl (2; bpy is 2,2′-bipyridyl). The electron-transfer-sensitized radical products of these reactions—Cp^RCr(CO)₃ (1•) and [Re(bpy-4,4′-R₂)(CO)₃Cl]^– (2^–)—can initiate the oxidation of H₂ and reduction of CO₂, respectively. The ligand substituents within each of these classes of compounds allow control over the driving forces and, thus, the rates of the productive (and unproductive) electron-transfer reactions available to the components. A comprehensive picture of the mechanism and kinetics of this system has been elucidated using time-resolved spectroscopic methods.     

Reactive collisions of sulfur dioxide with molten carbonates

Molecular beam scattering experiments are used to investigate reactions of SO₂ at the surface of a molten alkali carbonate eutectic at 683 K. We find that two-thirds of the SO₂ molecules that thermalize at the surface of the melt are converted to gaseous CO₂ via the reaction . The CO₂ product is formed from SO₂ in less than 10^-6 s, implying that the reaction takes place in a shallow liquid region less than 100 Å deep. The reaction probability does not vary between 683 and 883 K, further implying a compensation between decreasing SO₂ residence time in the near-interfacial region and increasing reactivity at higher temperatures. These results demonstrate the remarkable efficiency of SO₂ → CO₂ conversion by molten carbonates, which appear to be much more reactive than dry calcium carbonate or wet slurries commonly used for flue gas desulfurization in coal-burning power plants.     

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

This research focused on the modification effects on recycled concrete (RC) prepared with nano-SiO₂ and CO₂ cured recycled coarse aggregates (RCA) subjected to an aggressive ions environment. For this purpose, RCA was first simply crushed and modified by nano-SiO₂ and CO_2, respectively, and the compressive strength, ions permeability as well as the macro properties and features of the interface transition zone (ITZ) of RC were investigated after soaking in 3.5% NaCl solution and 5% Na₂SO₄ solution for 30 days, respectively. The results show that nano-SiO₂ modified RC displays higher compressive strength and ions penetration resistance than that treated by carbonation. Besides, we find that ions attack has a significant influence on the microcracks width and micro-hardness of the ITZ between old aggregate and old mortar. The surface topography, elemental distribution and micro-hardness demonstrate that nano-SiO₂ curing can significantly decrease the microcracks width as well as Cl⁻ and SO₄²⁻ penetration in ITZ, thus increasing the micro-hardness, compared with CO₂ treatment.     

Template-Mediated Synthesis of Hierarchically Porous Metal–Organic Frameworks for Efficient CO2/N2 Separation

Carbon dioxide (CO₂) is generally unavoidable during the production of fuel gases such as hydrogen (H₂) from steam reformation and syngas composed of carbon monoxide (CO) and hydrogen (H₂). Efficient separation of CO₂ from these gases is highly important to improve the energetic utilization efficiency and prevent poisoning during specific applications. Metal–organic frameworks (MOFs), featuring ordered porous frameworks, high surface areas and tunable pore structures, are emerging porous materials utilized as solid adsorbents for efficient CO₂ capture and separation. Furthermore, the construction of hierarchical MOFs with micropores and mesopores could further promote the dynamic separation processes, accelerating the diffusion of gas flow and exposing more adsorptive pore surface. Herein, we report a simple, efficient, one-pot template-mediated strategy to fabricate a hierarchically porous CuBTC (CuBTC-Water, BTC = 1,3,5-benzenetricarboxylate) for CO₂ separation, which demonstrates abundant mesopores and the superb dynamic separation ability of CO₂/N₂. Therefore, CuBTC-Water demonstrated a CO₂ uptake of 180.529 cm³ g⁻¹ at 273 K and 1 bar, and 94.147 cm³ g⁻¹ at 298 K and 1 bar, with selectivity for CO₂/N₂ mixtures as high as 56.547 at 273 K, much higher than microporous CuBTC. This work opens up a novel avenue to facilely fabricate hierarchically porous MOFs through one-pot synthesis for efficient dynamic CO₂ separation.     

Proton and Oxygen-Ion Conductivities of Hexagonal Perovskite Ba5In2Al2ZrO13

The hexagonal perovskite Ba₅In₂Al₂ZrO₁₃ and In³⁺-doped phase Ba₅In_2.1Al₂Zr_0.9O_12.95 were prepared by the solid-state synthesis method. The introduction of indium in the Zr-sublattice was accompanied by an increase in the unit cell parameters: a = 5.967 Å, c = 24.006 Å vs. a = 5.970 Å, c = 24.011 Å for doped phase (space group of P6₃/mmc). Both phases were capable of incorporating water from the gas phase. The ability of water incorporation was due to the presence of oxygen deficient blocks in the structure, and due to the introduction of oxygen vacancies during doping. According to thermogravimetric (TG) measurements the compositions of the hydrated samples corresponded to Ba₅In₂Al₂ZrO_12.7(OH)_0.6 and Ba₅In_2.1Al₂Zr_0.9O_12.54(OH)_0.82. The presence of different types of OH⁻-groups in the structure, which participate in different hydrogen bonds, was confirmed by infrared (IR) investigations. The measurements of bulk conductivity by the impedance spectroscopy method showed that In³⁺-doping led to an increase in conductivity by 0.5 order of magnitude in wet air (pH₂O = 1.92·10⁻² atm); in this case, the activation energies decreased from 0.27 to 0.19 eV. The conductivity−pO₂ measurements showed that both the phases were dominant proton conductors at T < 500 °C in wet conditions. The composition Ba₅In_2.1Al₂Zr_0.9O_12.95 exhibited a proton conductivity ~10⁻⁴ S·cm⁻¹ at 500 °C. The analysis of partial (O²⁻, H⁺, h^•) conductivities of the investigated phases has been carried out. Both phases in dry air (pH₂O = 3.5·10⁻⁵ atm) showed a mixed (oxygen-ion and hole) type of conductivity. The obtained results indicated that the investigated phases of Ba₅In₂Al₂ZrO₁₃ and Ba₅In_2.1Al₂Zr_0.9O_12.95 might be promising proton-conducting oxides in the future applications in electrochemical devices, such as solid oxide fuel cells. Further modification of the composition and search for the optimal dopant concentrations can improve the H⁺-conductivity.     

Calculation of site-specific carbon-isotope fractionation in pedogenic oxide minerals

Ab initio molecular dynamics and quantum chemistry techniques are used to calculate the structure, vibrational frequencies, and carbon-isotope fractionation factors of the carbon dioxide component [CO₂(m)] of soil (oxy)hydroxide minerals goethite, diaspore, and gibbsite. We have identified two possible pathways of incorporation of CO₂(m) into (oxy)hydroxide crystal structures: one in which the C⁴⁺ substitutes for four H⁺ [CO₂(m)_A] and another in which C⁴⁺ substitutes for (Al³⁺,Fe³⁺) + H⁺ [CO₂(m)_B]. Calculations of isotope fractionation factors give large differences between the two structures, with the CO₂(m)_A being isotopically lighter than CO₂(m)_B by ≈10 per mil in the case of gibbsite and nearly 20 per mil in the case of goethite. The reduced partition function ratio of CO₂(m)_B structure in goethite differs from CO₂(g) by <1 per mil. The predicted fractionation for gibbsite is >10 per mil higher, close to those measured for calcite and aragonite. The surprisingly large difference in the carbon-isotope fractionation factor between the CO₂(m)_A and CO₂(m)_B structures within a given mineral suggests that the isotopic signatures of soil (oxy)hydroxide could be heterogeneous.     

Studies of Selective Recovery of Zinc and Manganese from Alkaline Batteries Scrap by Leaching and Precipitation

Recovery of zinc and manganese from scrapped alkaline batteries were carried out in the following way: leaching in H₂SO₄ and selective precipitation of zinc and manganese by alkalization/neutralization. As a result of non-selective leaching, 95.6–99.7% Zn was leached and 83.7–99.3% Mn was leached. A critical technological parameter is the liquid/solid treatment (l/s) ratio, which should be at least 20 mL∙g⁻¹. Selective leaching, which allows the leaching of zinc only, takes place with a leaching yield of 84.8–98.5% Zn, with minimal manganese co-leaching, 0.7–12.3%. The optimal H₂SO₄ concentration is 0.25 mol∙L⁻¹. Precipitation of zinc and manganese from the solution after non-selective leaching, with the use of NaOH at pH = 13, and then with H₂SO₄ to pH = 9, turned out to be ineffective: the manganese concentrate contained 19.9 wt.% Zn and zinc concentrate, and 21.46 wt.% Mn. Better selectivity results were obtained if zinc was precipitated from the solution after selective leaching: at pH = 6.5, 90% of Zn precipitated, and only 2% manganese. Moreover, the obtained concentrate contained over 90% of ZnO. The precipitation of zinc with sodium phosphate and sodium carbonate is non-selective, despite its relatively high efficiency: up to 93.70% of Zn and 4.48–93.18% of Mn and up to 95.22% of Zn and 19.55–99.71% Mn, respectively for Na₃PO₄ and Na₂CO₃. Recovered zinc and manganese compounds could have commercial values with suitable refining processes.     

Structure and charging of hydrophobic material/water interfaces studied by phase-sensitive sum-frequency vibrational spectroscopy

We have studied the hydrophobic water/octadecyltrichlorosilane (OTS) interface by using the phase-sensitive sum-frequency vibrational spectroscopy (PS-SFVS), and we obtained detailed structural information of the interface at the molecular level. Excess ions emerging at the interface were detected by changes of the surface vibrational spectrum induced by the surface field created by the excess ions. Both hydronium (H₃O⁺) and hydroxide (OH⁻) ions were found to adsorb at the interface, and so did other negative ions such as Cl⁻. By varying the ion concentrations in the bulk water, their adsorption isotherms were measured. It was seen that among the three, OH⁻ has the highest adsorption energy, and H₃O⁺ has the lowest; OH⁻ also has the highest saturation coverage, and Cl⁻ has the lowest. The result shows that even the neat water/OTS interface is not neutral, but charged with OH⁻ ions. The result also explains the surprising observation that the isoelectric point appeared at ∼3.0 when HCl was used to decrease the pH starting from neat water.     

Electrochemical Production of Bismuth in the KCl–PbCl2 Melt

An anode dissolution of binary metallic lead–bismuth alloys with different concentrations of components has been studied in the KCl–PbCl₂ molten eutectic. The dissolution of lead is found to be a basic process for the alloys of Pb–Bi (59.3–40.7), Pb–Bi (32.5–67.5), Pb–Bi (7.0–93.0) compositions in the whole interval of studied anode current densities. A limiting diffusion current of lead dissolution was observed at 2 A/cm² and 0.1 A/cm² for the alloys of Pb–Bi (5.0–95.0) and Pb–Bi (3.0–97.0) compositions, respectively. The dissolution of bismuth takes place at the anode current densities exceeding the mentioned values. The number of electrons participating in the electrode reactions is detected for each mechanism. Based on the theoretical analysis, the experimental electrolysis of bismuth was performed in the laboratory-scale electrolytic cell with a porous ceramic diaphragm. The final product contained pure bismuth with a lead concentration of 3.5 wt.%.     

CO2 Capture and Separation Properties in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Nonafluorobutylsulfonate

Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO₂ in ILs. In the present work, solubility measurements of CO₂ in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate [C₄mim][CF₃CF₂CF₂CF₂SO₃] were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H₂, N₂, and O₂ in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry’s law constants, enthalpies, and entropies of absorption for CO₂ in the IL were also determined and presented. The CO₂ solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO₂ in these ILs follows the sequence: [C₄mim][CF₃CF₂CF₂CF₂SO₃] ≈ [C₄mim][Tf₂N] > [C₄mim][CF₃CF₂CF₂COO] > [C₄mim][BF₄], and the solubility selectivity of CO₂ relative to O₂, N₂, and H₂ in [C₄mim][CF₃CF₂CF₂CF₂SO₃] was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO₂.     

Studies on Cement Pastes Exposed to Water and Solutions of Biological Waste

The paper presents studies on the early stages of biological corrosion of ordinary Portland cements (OPC) subjected to the reactive media from the agricultural industry. For ten months, cement pastes of CEM I type with various chemical compositions were exposed to pig slurry, and water was used as a reference. The phase composition and structure of hydrating cement pastes were characterized by X-ray diffraction (XRD), thermal analysis (DTA/TG/DTG/EGA), and infrared spectroscopy (FT-IR). The mechanical strength of the cement pastes was examined. A 10 to 16% decrease in the mechanical strength of the samples subjected to pig slurry was observed. The results indicated the presence of thaumasite (C₃S·CO₂·SO₃·15H₂O) as a biological corrosion product, likely formed by the reaction of cement components with living matter resulting from the presence of bacteria in pig slurry. Apart from thaumasite, portlandite (Ca(OH)₂)—the product of hydration—as well as ettringite (C₃A·3CaSO₄·32H₂O) were also observed. The study showed the increase in the calcium carbonate (CaCO₃) phase. The occurrence of unreacted phases of cement clinker, i.e., dicalcium silicate (C₂S) and tricalcium aluminate (C₃A), in the samples was confirmed. The presence of thaumasite phase and the exposure condition-dependent disappearance of CSH phase (calcium silicate hydrate), resulting from the hydration of the cements, were demonstrated.     

In vivo assessment of pyruvate dehydrogenase flux in the heart using hyperpolarized carbon-13 magnetic resonance

The advent of hyperpolarized ¹³C magnetic resonance (MR) has provided new potential for the real-time visualization of in vivo metabolic processes. The aim of this work was to use hyperpolarized [1-¹³C]pyruvate as a metabolic tracer to assess noninvasively the flux through the mitochondrial enzyme complex pyruvate dehydrogenase (PDH) in the rat heart, by measuring the production of bicarbonate (H¹³CO₃⁻), a byproduct of the PDH-catalyzed conversion of [1-¹³C]pyruvate to acetyl-CoA. By noninvasively observing a 74% decrease in H¹³CO₃⁻ production in fasted rats compared with fed controls, we have demonstrated that hyperpolarized ¹³C MR is sensitive to physiological perturbations in PDH flux. Further, we evaluated the ability of the hyperpolarized ¹³C MR technique to monitor disease progression by examining PDH flux before and 5 days after streptozotocin induction of type 1 diabetes. We detected decreased H¹³CO₃⁻ production with the onset of diabetes that correlated with disease severity. These observations were supported by in vitro investigations of PDH activity as reported in the literature and provided evidence that flux through the PDH enzyme complex can be monitored noninvasively, in vivo, by using hyperpolarized ¹³C MR.