Specific Cation Research Articles

Geochemical aspects on formation processes of vein-hosted pyrite in the Carboniferous-Permian rocks of the Karavanke/Karawanken tunnel, northwestern Slovenia

Abstract The Carboniferous-Permian organic-rich shale in the Karavanke/Karawanken tunnel exhibits extensive pyrite mineralization in the form of veins and impregnations. Significant thermal alteration, induced by the overlying Mesozoic rock sequences, led to the decomposition of organic matter into methane, which subsequently acted as a sulfate-reducing agent. The primary source of sulfate were the evaporitic layers hosted within the Paleozoic strata. Reduced sulfur species necessary for pyrite formation were produced through methane-mediated thermochemical sulfate reduction, catalyzed by specific cations (Ni2+, Fe2+) and clay minerals (montmorillonite). The mineralizing fluids originated from the expulsion of interstitial water and possibly from dehydration reactions related to the gypsum-to-anhydrite phase transition. The geochemical data indicate that the metals originated from the surrounding sedimentary rocks. These mineralizing fluids were characterized by low temperatures (< 300–350 °C), moderate reducing conditions, and low chlorinity. The low permeability of Carboniferous-Permian rocks, combined with the low trace element content of the investigated pyrite, mitigates the potential risk of environmental pollution.

A dual template ion imprinted polymer based on acrylamide monomer/modified graphene oxide for simultaneous adsorption of Ni (II)/Cd (II)

Utilizing ion imprinted polymers (IIPs) to target hazardous heavy metal ions presents an effective solution for addressing water pollution by recognizing and adsorbing specific metal cations. Although dual-template IIPs can...

New buffer systems for photopainting of single biomolecules.

We present newly developed buffer systems that significantly improve the efficiency of a photochemically induced surface modification at the single molecule level. Buffers with paramagnetic cations and radical oxygen promoting species facilitate laser-assisted protein adsorption by photobleaching (LAPAP) of single fluorescently labelled oligonucleotides or biotin onto multi-photon-lithography-structured 2D and 3D acrylate scaffolds. Single molecule fluorescence microscopy has been used to quantify photopainting efficiency. We identify specific cation interaction sites for members of the cyanine, coumarin and rhodamine classes of fluorophores using quantum mechanical calculations. We show that our buffer systems provide an up to three-fold LAPAP-efficiency increase for the cyanine fluorophore, while keeping excitation parameters constant.

Plasmonic synergism in tailored metal–carbon interfaces for real-time single molecular level sniffing of PFOS and PFOA

Generating plasmonic hot-spots through engineering of nanoscale interfaces offers exciting opportunities towards point-of-care analytical detection. The mutual trade-off between ultra-high sensitivity, specificity and reliability are major drawbacks for practical applicability with real-time samples. Fundamentally these originate from low photonic mode density, high ohmic losses, temporally fluctuating and chemically indistinguishable nature of electromagnetic hot-spots. This work describes synergism of metallic plasmons from tailored interfaces of Ag-Au nanoalloys with conical nanocavities of nanocarbon florets (NCF), leading to strong metal-dielectric interfacial coupling. Such, Ag-Au-NCF nanohybrid delivers an unprecedented 1517-fold enhancement in surface-plasmon coupled directed emission (SPCE) of Rhodamine B (RhB) leading to robust (relative standard deviation, RSD < 10 %) single-molecular-level detection of spectroscopically-silent perfluoroalkyl substances (PFAS). The limit-of-detection demonstrated (PFOS = 0.005 ppt) is one-thousand times better than WHO recommendation and surpasses all existing reports. The specific cation–anion interactions between RhB and PFAS are substantiated through density functional calculations that concur with experimental findings. Finally, the emission from this SPCE platform can be visually tracked through a smartphone camera over wide range of PFOS concentrations (0.005–5000000 ppt) in water samples (lake, river, tap, drinking and ocean) and blood-plasma, offering transformative opportunities in analytical sciences.

Glyphosate/AMPA adsorption on magnetite under different conditions: The effect of pH and electrolytes

As a result of the frequent use, glyphosate (GLY) and its major metabolite, aminomethylphosphonic acid (AMPA), have emerged as ubiquitous environmental contaminants worldwide. Glyphosate, applied in agriculture, adsorbs on soil minerals, such as iron oxides, facilitating its fixation in soils and preventing leaching into groundwater sources. However, the adsorption capacity of various types of soils exhibits substantial variability. In this work the adsorption of GLY and AMPA on magnetite nanoparticles (MNPs) was studied under different conditions: at pH ∼ 6 and ∼ 8, and in the presence of 10 mmol/L NaCl, an indifferent electrolyte, and 10 mmol/L CaCl2, which contains a specific cation mainly present in soils. The pH-dependent zeta potential measurements revealed the difference between the effect of Na+ and Ca2+ ions on the charge state and aggregation of MNPs. The adsorption of GLY/AMPA shows significant pH dependence, with the bound amounts decreasing rapidly above pH ∼ 7 in both 10 mmol/L NaCl and CaCl2 solutions. The phosphonate adsorption capacity of MNPs, as determined from the fitting of the Langmuir isotherm equation, was approximately 0.35 mmol/g and 0,09 mmol/g at pH ∼ 6 and pH ∼ 8, respectively. The diverse bound amounts at different pHs are of environmental importance: under alkaline soil conditions, the mobilization of GLY may be more probable. GLY and AMPA bind to the surface of MNPs via complex formation at ≡Fe-OH sites, primarily involving phosphate groups, preferably at acidic pH, where the MNPs carry positive charges, and the near-surface concentration of phosphonate anions is higher due to electrostatic attraction. Furthermore, in the presence of Ca2+ ions, Ca-bridging occurs, as supported by the findings from the ATR-FTIR spectra. Additionally, it is worth noting that the complex formation between Ca2+ and phosphonates in the solution phase reduces the probability of Ca-bridge and surface complex formation, hindering the fixation of GLY/AMPA in soils.

Cation-induced changes in the inner- and outer-sphere mechanisms of electrocatalytic CO2 reduction

The underlying mechanism of cation effects on CO2RR remains debated. Herein, we study cation effects by simulating both outer-sphere electron transfer (OS-ET) and inner-sphere electron transfer (IS-ET) pathways during CO2RR via constrained density functional theory molecular dynamics (cDFT-MD) and slow-growth DFT-MD (SG-DFT-MD), respectively. Our results show without any cations, only OS-ET is feasible with a barrier of 1.21 eV. In the presence of K+ (Li+), OS-ET shows a very high barrier of 2.93 eV (4.15 eV) thus being prohibited. However, cations promote CO2 activation through IS-ET with the barrier of only 0.61 eV (K+) and 0.91 eV (Li+), generating the key intermediate (adsorbed CO{}_{2}^{delta -}). Without cations, CO2-to-CO{}_{2}^{delta -}(ads) conversion cannot proceed. Our findings reveal cation effects arise from short-range Coulomb interactions with reaction intermediates. These results disclose that cations modulate the inner- and outer-sphere pathways of CO2RR, offering substantial insights on the cation specificity in the initial CO2RR steps.

Building Surfaces with Controlled Site-Density of Anchored Human Serum Albumin.

Stable and uniform layers of protein molecules at the surface are important to build passive devices as well as active constructs for smart biointerfaces for a large number of biomedical applications. In this context, a strategy to build-up surfaces able to anchor protein molecules on specific and controlled surface sites has been developed. Human serum albumin (HSA) has been chosen as a model protein due to its important antithrombogenic properties and its features in cell response highly valuable for in vivo devices. Uniform self-assembled monolayers of 2,2':6'2″-terpyridines (SAM), whose sites were further employed to chelate copper and iron ions, forming SAM-Cu(II) and SAM-Fe(II) complexes, have been developed. The effect of two metal cations on the physicochemical features of SAM, including thickness, Young's modulus, and tip-monolayer adhesion factors, has been investigated. Protein adsorption at different concentrations showed that the copper ion-templated surfaces exhibit highly specific mass uptake, kinetic behavior, and recognition and anchoring of HSA molecules owing to the coordination sphere of the different cations. The results pave the way to the development of a more general strategy to obtain ordered and density-tuned arrays of specific metal cations, which in turn would drive the anchoring of precise proteins for different biological functions.

Raman Scattering Reveals Ion-Dependent G-Quadruplex Formation in the 15-mer Thrombin-Binding Aptamer upon Association with α-Thrombin.

The discovery of DNA aptamers that bind biomolecular targets has enabled significant innovations in biosensing. Aptamers form secondary structures that exhibit selective high-affinity interactions with their binding partners. The binding of its target by an aptamer is often accompanied by conformational changes, and sensing by aptamers often relies on these changes to provide readout signals from extrinsic labels to detect target association. Many biosensing applications involve aptamers immobilized to surfaces, but methods to characterize conformations of immobilized aptamers and their in situ response have been lacking. To address this challenge, we have developed a structurally informative Raman spectroscopy method to determine conformations of the 15-mer thrombin-binding aptamer (TBA) immobilized on porous silica surfaces. The TBA is of interest because its binding of α-thrombin depends on the aptamer forming an antiparallel G-quadruplex, which is thought to drive signal changes that allow thrombin-binding to be detected. However, specific metal cations also stabilize the G-quadruplex conformation of the aptamer, even in the absence of its protein target. To develop a deeper understanding of the conformational response of the TBA, we utilize Raman spectroscopy to quantify the effects of the metal cations, K+ (stabilizing) and Li+ (nonstabilizing), on G-quadruplex versus unfolded populations of the TBA. In K+ or Li+ solutions, we then detect the association of α-thrombin with the immobilized aptamer, which can be observed in Raman scattering from the bound protein. The results show that the association of α-thrombin in K+ solutions produces no detectable change in aptamer conformation, which is found in the G-quadruplex form both before and after binding its target. In Li+ solutions, however, where the TBA is unfolded prior to α-thrombin association, protein binding occurs with the formation of a G-quadruplex by the aptamer.

Controlling molecular self-assembly of inverse-phosphocholine lipids at oxide interfaces with divalent cations

Sub-100 nm vesicles composed of inverse-phosphocholine (CP) lipids are versatile building blocks for interfacing with inorganic material surfaces and demonstrate unique chemical functionalities due to outward-facing phosphate groups. Compared to typical phospholipids, the surface presentation of CP lipids has enabled new covalent possibilities like click chemistry for drug delivery and imaging applications while utilizing this phosphate chemistry in noncovalent self-assembly contexts remains unexplored. Herein, we report that the presence of phosphate-binding divalent cations such as Ca2+ and Mg2+ can dramatically shift the self-assembly behavior of CP lipid vesicles on TiO2 and SiO2 surfaces, inhibiting spontaneous supported lipid bilayer (SLB) formation on TiO2 in cases where it typically occurs and promoting SLB formation on SiO2 in cases where lipid adsorption is otherwise negligible. Quartz crystal microbalance-dissipation (QCM-D) measurements were performed to track the corresponding adsorption kinetics and self-assembly outcomes. Importantly, an optimal combination of CP lipid fraction in vesicles and specific divalent cation type was also identified, which enabled SLB formation on both TiO2 and SiO2 surfaces under equivalent conditions. SLB fluidity on SiO2 surfaces was additionally confirmed by fluorescence recovery after photobleaching (FRAP) experiments. We rationalize these molecular-level phenomena in terms of vesicle stability and lipid-surface interactions, demonstrating a versatile approach to control CP lipid self-assembly with divalent cations.

In Situ Measurement of Effective Gate Bias Voltage in Ionic Liquid-Gated Organic Field-Effect Transistors: Exploring Intrinsic Performance and Trap Density of States.

Electric double layer (EDL)-mediated transistors with ionic liquid (IL) gating have garnered substantial interest due to their exceptional properties, such as high transconductance and low-voltage operation, positioning them as promising candidates for organic electronics. In this study, we present an in situ measurement of effective gate bias voltage (VGS,eff) in IL-gated organic field-effect transistors (IL-OFETs) using a modified current-voltage measurement configuration. The results reveal a significant deviation between VGS,eff and the applied gate bias (VGS,app), indicating that the EDL at the gate/IL interface screens the applied voltage. It is observed that the screening effect varies depending on the specific cation and anion present in the IL. The evaluation of VGS,eff plays a pivotal role in understanding the intrinsic behavior of IL-OFETs and addresses the challenges associated with accurate performance assessment. Inherently, IL-OFETs demonstrate high transconductance, achieving values of approximately 9 mS while operating at a low threshold voltage of around 0.55 V. Through the acquisition of VGS,eff, we have successfully addressed the limitations impeding the numerical estimation of the trap density of states (trap DOS) in IL-OFETs. Remarkably, our calculations reveal an exceptionally low density of deep traps, which serves as a crucial factor contributing to the near-ideal subthreshold swing (61-68 mV dec-1) observed in IL-OFETs. Further investigations unveil the neutral electrical nature of the IL bulk during OFET operation, confirming the hypothesis that the applied gate bias voltage in electrolyte-gated OFETs drops across the EDLs formed at the interfaces. The impedance spectroscopic (IS) analysis confirms the low contact resistance (≈1 Ω·m) of IL-OFETs calculated using the transition voltage method. The IS analysis also reveals the low-transmissive nature of the IL/organic semiconductor interface. The knowledge gained from this study holds significant implications for realizing high-performance electrolyte-gated OFETs in various applications including digital electronics, energy storage, and sensing. By unraveling the factors influencing the device performance, such as VGS,eff and trap DOS, this research contributes to the advancement of organic electronics and paves the way for future developments in the field.

Activities and intrinsic properties of the clayey fines four lateritic gravels

The aim of this study was to identify, classify and characterize the activities and correlations between the intrinsic properties of the four lateritic gravels used in construction. The grading curves of the four lateritic gravelly are spread out, but poorly calibrated. Lateritic gravel LG1 contains class B5 silty fines with low plasticity and low swelling. Lateritic gravels LG2, LG3 and LG4 contain clayey fines of low plasticity and medium swelling, class B6. The specific surface area and cation exchange capacity depend on the mineralogy, organic composition and texture of the lateritic gravel. The blue value of the soil characterizes the activity of the clay fines and reflects the surface activity of the lateritic gravels. The four lateritic gravels are inactive and contain minerals (kaolinite, quartz, goethite, hematite). The correlations obtained between the intrinsic properties are linear fits and between the liquidity limit and the specific surface area a non-linear fit of the ExpDec1 model with R2 (0.99). The relationship between activity and surface activity is simply the relative activity.

Tailoring Monovalent Ion Sieving in Graphene-Oxide Membranes with High Flux by Rationally Intercalating Crown Ethers.

Two-dimensional membranes have shown promising potential for ion-selective separation due to their well-defined interlayer channels. However, the typical "trade-off" effect of throughput and selectivity limits their developments. Herein, we report a precise tailoring of monovalent cation sieving technology with enhanced water throughput via the intercalation of graphene-oxide membranes with selective crown ethers. By tuning the lamellar spacing of graphene oxide, a critical interlayer distance (∼11.04 Å) is revealed to maximize water flux (53.4 mol m-2 h-2 bar-1) without sacrificing ion selectivity. As a result, the elaborately enlarged interlayer distance offers improved water permeance. Meanwhile, various specific cations with remarkably high selectivity can be separated in mixed solutions because of the strong chelation with crown ethers. This work opens up a new avenue for high-throughput and precise regulation of ion separations for various application scenarios.

Ca/Na concentration-constrained variations of dissolved organic matter leaching from groundwater-irrigation area soil in North China Plain.

This study investigates the quantity and quality variations of dissolved organic matter (DOM) leaching from the soil in groundwater irrigation area of the North China Plain, constrained by the concentration of Ca/Na. Soil samples with dominant humic-like (HLC) and protein-like (PLC) components were paired with parallel concentration gradients of Ca/Na extractants for equilibrium experiments. Fluorescence-PARAFAC, UV-visible spectroscopy, and multiple statistical analyses were combined for data analysis and interpretation. The results reveal that the primary DOM components remained dominant for specific soil sample, with a higher relative abundance of PLC (HLC) in Ca (Na) extract. HLC preferentially binds to soil phase in all extractions, while PLC is readily released into the solution. However, Ca inhibits HLC desorption and promotes PLC release more significantly than Na, as indicated by stronger ion/proton reaction (IPR) and electrostatic effect (ESE). The strongest IPR and ESE are seen in the HLC-dominated DOM extracted with Ca, suggesting a condition where Ca bridges to HLC and forms total dissolved organic carbon (DOC) that decreases. In contrast, Na extraction exhibits only a weaker ESE that is offset by soil-contained HLC and exchangeable Ca, resulting in subtle DOC decrease. The trends in leaching of HLC and PLC are self-dependent, and the level of variation in either component correlates with the increasing concentration of specific cations present. These findings underscore the crucial role of soil organic matter (SOM) composition and its interaction with leaching cations in soil management in large-scale groundwater irrigation areas, where SOM quality and groundwater chemistry vary.

Alkaline Leaching: A Facile Strategy to Improve the Surface Activity of Air Electrodes for Solid Oxide Electrochemical Cells

Solid oxide electrochemical cells (SOCs) have been focused on as next-generation energy conversion devices. However, since SOCs are operated at high temperatures (>800 °C), several issues are present, such as limited material selection and high system cost. Therefore, lowering the operating temperature and developing suitable electrode materials which have high oxygen evolution/reduction reaction (OER/ORR) activity at relatively low temperatures are crucial.In this manner, surface modification methods have been researched, such as nanocatalyst decoration, surface coating, and acid etching. However, nanocatalyst decoration and surface coating require a long annealing time and complicated vacuum devices, respectively, and acid etching is not favorable for rational control on the surface of the electrode. Therefore, a cost- and time-efficient surface modification method while maintaining reasonable controllability can have a meaningful advantage.We suggest a facile method of surface modification for electrodes of SOCs: alkaline leaching. During the water splitting in a conventional 3-electrode system with an alkaline medium, cations in perovskite oxide lattice are selectively dissolved into the alkaline solution, which is called as leaching phenomenon. As a result of leaching, the composition of the perovskite oxide surface differs from the pristine condition (e.g. the transition metal-rich surface). We adopted this phenomenon as a strategy to improve the activity of air electrodes for SOCs.In this study, we chose PrBa0.8Ca0.2Co2O5+δ (PBCC) as the air electrode material for the first case-study. Recently, PBCC has gained a lot of attention due to its outstanding OER/ORR activity even at relatively low temperatures (<650 °C). We compared the reactivity of PBCC electrodes in different alkaline leaching conditions by electrochemical impedance spectroscopy. After the surface treatment, area-specific resistance of 0.018 Ω·cm2 (at 650 °C) was recorded, corresponding to the 5-fold and 53-fold enhanced ORR reactivity compared to the pristine PBCC air electrode and commercialized La0.6Sr0.4Co0.2Fe0.8O3 air electrode, respectively.To elucidate the enhanced surface activity, various analyses were carried out. Scanning electron microscopy images showed the porous structure of the PBCC electrode and the removal of Ba-containing secondary phases on the PBCC surface, which are known to degrade surface activity. Transmission electron microscopy-energy dispersive spectroscopy results demonstrated that the surface of the PBCC electrode becomes amorphous and Co-rich, which are both known to be advantageous for ORR activity. Inductively coupled plasma-mass spectrometry results of the alkaline medium in the 3-electrode system revealed that specific cation species (i.e. Ba and Ca) were selectively dissolved into the alkaline medium and were more leached out by the applied anodic bias, resulting in the Co-rich surface. X-ray photoelectron spectroscopy results suggest that surface Ba species were decreased and defective O species were increased, leading to improved ORR activity.In this case, we showcased alkaline leaching as a strategy to enhance the PBCC electrodes for SOCs, but with the sufficient current collection, our method can be further applied to various perovskite oxides in various structures. Taking the various advantages of perovskite-oxide-based materials, the alkaline leaching method will be a novel strategy to achieve a high-performance (electro)chemical catalyst.

Chiral Cation Doping for Modulating Structural Symmetry of 2D Perovskites.

Cation mixing in two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) structures represents an important degree of freedom for modifying organic templating effects and tailoring inorganic structures. However, the limited number of known cation-mixed 2D HOIP systems generally employ a 1:1 cation ratio for stabilizing the 2D perovskite structure. Here, we demonstrate a chiral-chiral mixed-cation system wherein a controlled small amount (<10%) of chiral cation S-2-MeBA (S-2-MeBA = (S)-(-)-2-methylbutylammonium) can be doped into (S-BrMBA)2PbI4 (S-BrMBA = (S)-(-)-4-bromo-α-methylbenzylammonium), modulating the structural symmetry from a higher symmetry (C2) to the lowest symmetry state (P1). This structural change occurs when the concentration of S-2-MeBA, measured by solution nuclear magnetic resonance, exceeds a critical level─specifically, for 1.4 ± 0.6%, the structure remains as C2, whereas 3.9 ± 1.4% substitution induces the structure change to P1 (this structure is stable to ∼7% substitution). Atomic occupancy analysis suggests that one specific S-BrMBA cation site is preferentially substituted by S-2-MeBA in the unit cell. Density functional theory calculations indicate that the spin splitting along different k-paths can be modulated by cation doping. A true circular dichroism band at the exciton energy of the 3.9% doping phase shows polarity inversion and a ∼45 meV blue shift of the Cotton-effect-type line-shape relative to (S-BrMBA)2PbI4. A trend toward suppressed melting temperature with higher doping concentration is also noted. The chiral cation doping system and the associated doping-concentration-induced structural transition provide a material design strategy for modulating and enhancing those emergent properties that are sensitive to different types of symmetry breaking.

Influence of anionic species on the molecular structure, nature of bonding, reactivity, and stability of ionic liquids-based on 1-butyl-3-methylimidazolium

The unique physicochemical properties of ionic liquids (ILs) have positioned them as a significant class of solvents, making them a subject of considerable interest. In this investigation, the experimental analysis involved solvothermal reflux techniques, while theoretical approaches utilized density functional theory (DFT) with the def2-SVP/ωB97XD computational approach to explore the electronic properties, reactivity, stability, and structural aspects of ILs based on the combinations of [BMIM]+ cation with [MeSO3]-, [BF4]-, [PF6]-, and [C2H3O2]- anions. The experimental and theoretical data exhibited good agreement, demonstrating that the choice of cation and anion greatly influences the stability of ILs. By employing Frontier molecular orbital analysis, the reactivity and stability of the studied ionic species were observed to follow the order of [BMIM]+[MeSO3]- > [BMIM]+[BF4]- > BMIM > [BMIM]+[PF6]- > [BMIM]+[C2H3O2]-, with corresponding energy gaps of 4.8474 > 3.1971 > 2.013 > 1.8830 and 1.3276 eV, respectively. The Natural Bond Orbital (NBO) analysis, encompassing second-order perturbation energy, revealed the strength of interactions within the investigated systems in the following order: [BMIM]+[PF6]- < [BMIM]+[MeSO3]- < [BMIM]+[BF4]- < [BMIM]+[C2H3O2]-. Topology analysis indicated a higher electron density (ρ(r)) value of 0.8966 a.u., indicating a denser distribution of electrons. Furthermore, the nature of bonding in the studied ion pairs displayed the following order: [BMIM]+[MeSO3]- > [BMIM]+[BF4]- > [BMIM]+[PF6]- > [BMIM]+[C2H3O2]-, signifying that [BMIM]+[MeSO3]- exhibited stronger interactions compared to the other combinations. The vibrational spectra and UV–vis results of the investigated ILs underscored the sensitivity of characteristic peaks in frequency and intensity to the specific cation–anion combination. These findings have the potential to guide experimental researchers in exploring the applications of the studied ionic species in diverse areas such as energy storage and catalysis.

Abrupt exciton quenching in blue fluorescent organic light-emitting diodes around turn-on voltage region

The quenching of electrically generated excitons in organic light-emitting diodes (OLEDs) serves as a limiting factor in fully exploiting the potential of organic emissive materials, ultimately resulting in a reduction of electroluminescence (EL) efficiency. As the quenching yield is contingent upon the density of species such as excitons and polarons, extensive efforts have been made to comprehend the mechanism under high excitation conditions. Herein, we present a sudden exciton quenching at the turn-on voltage region in a blue triplet–triplet upconversion (TTU)-based blue fluorescent OLED that limits overall EL efficiency. We confirmed that the photoluminescence intensity was quenched by ∼5% before injecting a current density of 0.1 mA cm−2. The quenching behavior strongly depended on the hole-transporting materials (HTMs), indicating that a specific radical cation of the HTMs triggers exciton-polaron annihilation events at the interface between the hole-transporting layer (HTL) and the emitting layer (EML). Furthermore, the voltage dependence of exciton quenching yield and EL spectra suggests a shift in the emission zone from the interface to the bulk of the EML with increasing voltage. These findings are critical for designing an optimized HTL/EML interface for highly efficient blue TTU-OLEDs.

Characterization of NI/Zeolite Catalyst Including Specific Surface Area, Acidity, Si/Al Ratio, Cation Content in Zeolite

Specific Surface Area, acidity, Si/Al ratio, and cation concentration in zeolite catalysts have all been studied in relation to Ni/zeolite catalysts. The zeolite was submerged in water for 24 hours, dried, and then calcined for 3 hours at 400 oC before being incubated for 2 hours to create the Ni/zeolite catalyst. then 24 hours of stirring soaking in 6 M HCl, followed by 3 hours of refluxing with 1 M NH4Cl and 2 hours of oxygen gas oxidation. The zeolite will subsequently be impregnated with Ni, oxidized for three hours, and reduced with hydrogen gas for two hours. Additionally, a Ni/zeolite catalyst was acquired. The catalyst's metal concentration was then determined by characterizing the Ni/zeolite mixture, Si/Al ratio, specific surface area, and acidity of the catalyst. The outcomes of the characterisation are as follows: Ca and Fe are the main metals present in the Ni/zeolite catalyst, with only trace amounts of Na, Mg, and other metals (5 mg/gram of catalyst) present. In the meantime, the catalyst's acidity was 0.24 mmol/gram catalyst acidity, its surface area was 2.18 m2/gram catalyst surface area, and its Si/Al catalyst ratio was 10.21

PH: A core node of interaction networks among soil organo-mineral fractions

Mineral-associated organic matter (MAOM) is the largest soil organic carbon (OC) pool with the longest turnover. MAOM is expected to have relatively little sensitivity to climate change due to mineral protection, but its persistence involves several organo-mineral fractions. The uncertainty in the response of specific organo-mineral fractions to climate change hampers the reliability of predictions of MAOM preservation in the future. Here, we applied a sequential chemical fractionation method integrated with network analysis to investigate MAOM stabilization mechanisms across five alpine ecosystems: alpine desert, alpine steppe, alpine meadow, alpine wetland, and alpine forest. Hierarchical cluster analysis revealed grouping of seven extractable OM fractions in MAOM into three OM clusters: a cluster with weak bondings consisting of water-soluble OM (WSOM) and weakly adsorbed fractions (2.1–21.3% of total OC); a cluster with metal-bound complexes comprising Ca-OM complexes and Fe/Al-OM complexes (3.8–12.2% of total OC); and a cluster with strong bonding composed of Al oxyhydroxides, carbonates and Fe oxyhydroxides (12.2–33.5% of total OC). The relative percentages of OM from soils of the five ecosystems in the three clusters exhibited distinct pH dependence patterns. With the increase in pH, the cluster with weak bondings decreased, and that with strong bondings increased, while the one with metal-bound complexes showed a maximum at weakly acidic pH. Organo-mineral fractions and metal cations in MAOM constructed a complex network with pH as the central node. Results suggest that precipitation does not only alter vegetation type and microbial biomass but also regulate soil pH, which is balanced by specific metal cations, thus resulting in particular pH preference of specific OM clusters. These findings demonstrate that soil pH plays a central role in unveiling MAOM dynamics and can serve as a good predictor of soil organo-mineral fractions across alpine ecosystems.

Physicochemical and mineral characteristics of soil materials developed naturally on two ∼ 50 years old coal combustion residue disposal sites in Croatia

Coal combustion has been one of the most dominant sources of energy for the last two centuries, generating tonnes of coal combustion residue (CCR). Rapid soil formation has been observed at old CCR disposal sites, altering the physiochemical and mineral properties of CCR, affecting contaminant release mechanisms and nutrient availability. Although ubiquitous, pedological properties of weathered CCR have been studied at only a small number of disposal sites. This study characterized two CCR landfills of similar age (∼50 years) using a range of parameters, including pH, total nitrogen and organic carbon content, major oxides (Al2O3, CaO, and SiO2), and macronutrients (Ca, K, Mg, P, and S), as well as textural and mineralogical data. In addition, specific surface area and cation exchange capacity were determined to assess particle properties, and 13C and 29Si NMR spectra were examined to characterize the organic matter and degree of polymerization of the coal ash glassy phase. Such comprehensive approach aimed to determine indicators of soil formation and to characterize the capacity of such landfills to retain water, nutrients, and contaminants. Both landfills displayed evidence of pedogenesis reflected in the pH decrease, formation of secondary minerals (such as ettringite, hydrotalcite, gypsum, and calcite), and changes in the C:N ratio. The Plaški landfill seems to have a better capacity to hold water, nutrients, and contaminants evident by higher clay content, CEC, and SSA values, possibly explaining why it developed more rapidly than Štrmac despite their similar age. The presence of montmorillonite in Plaški could be one of the main factors accelerating pedogenesis. 13C NMR spectra point to the unburned coal particles as the main origin of organic matter and 29Si NMR spectra showed higher depolymerization of a non-crystalline fraction in bare ash samples than in vegetated ash samples.