Bulk Phase Research Articles

Double S-scheme Cu2−xSe/twinned-Cd0.5Zn0.5S homo-heterojunctions with surface plasmon effects for efficient photocatalytic H2 evolution

The enhancement of charge separation and utilization efficiency in both the bulk phase and interface of semiconductor photocatalysts, as well as the expansion of light absorption range, are crucial research topics in the field of photocatalysis. To address this issue, twinned Cd0.5Zn0.5S (T-CZS) homojunctions consisting of wurtzite Cd0.5Zn0.5S (WZ-CZS) and zinc blende Cd0.5Zn0.5S (ZB-CZS) were synthesized via a hydrothermal method to facilitate the bulk-phase charge separation. Meanwhile, Cu2−xSe with localized surface plasmon resonance effect (LSPR) generated by Cu vacancies was also obtained through a hydrothermal process. Due to their opposite electronegativity, a solvent evaporation strategy was employed to combine Cu2−xSe and T-CZS by intermolecular electrostatic. After optimization, the photocatalytic hydrogen (H2) evolution rate of 5 wt% Cu2−xSe/T-CZS reached an impressive value of 60 mmol∙h−1∙g−1, which was 4.6 and 66.6 times higher than that of pure Cu2−xSe and T-CZS, respectively. Furthermore, this composites demonstrated a remarkable rate of 0.46 mmol∙h−1∙g−1 under near-infrared (NIR) wavelength (>800 nm). The enhanced performance observed in Cu2−xSe/T-CZS can be attributed to its unique and efficient double S-scheme charge transfer mechanism which effectively suppresses rapid recombination of electron-hole pairs both within the bulk phase and at the surface interfaces; this conclusion is supported by Density Functional Theory (DFT) calculations as well as electron paramagnetic resonance spectroscopy analysis. Moreover, incorporation of Cu2−xSe enables effective utilization ultraviolet visible-near infrared (UV–Vis-NIR) light by the composites while facilitating injection “hot electrons” into T-CZS for promoting photocatalytic reactions. This study provides a potential strategy for achieving efficient solar energy conversion through synergistic integration of non-stoichiometric plasmonic materials with photocatalysts with twinned-twinned structures.

Porous media gravity current flow over an interbed layer: the impact of dispersion and distributed drainage

Motivated by buoyancy-driven flows within geological formations, we study the evolution of a (dense) gravity current in a porous medium bisected by a thin interbed layer. The gravity current experiences distributed drainage along this low-permeability boundary. Our theoretical description of this flow takes into account dispersive mass exchange with the surrounding ambient fluid by considering the evolution of the bulk and dispersed phases of the gravity current. In turn, we model basal draining by considering two bookend limits, i.e. no mixing versus perfect mixing in the lower layer. Our formulations are assessed by comparing model predictions against the output of complementary numerical simulations run using COMSOL. Numerical output is essential both for determining the value of the entrainment coefficient used within our theory and for assessing the reasonableness of key modelling assumptions. Our results suggest that the degree of dispersion depends on the dip angle and the depth and permeability of the interbed layer. We further find that the nose position predictions made by our theoretical models are reasonably accurate up to the point where the no mixing model predicts a retraction of the gravity current front. Thereafter, the no mixing model significantly under-predicts, and the perfect mixing model moderately over-predicts, numerical data. Reasons for the failure of the no mixing model are provided, highlighting the importance of convective instabilities in the lower layer. A regime diagram is presented that defines the parametric region where our theoretical models do versus do not yield predictions in good agreement with numerical simulations.

Cyclic formation characteristics of tetrabutylammonium bromide hydrates under concentration regulation enhanced by gas circulation

Hydrate cold storage technology offers a promising solution for effectively storing high energy density. Therefore, the aim of this study is to explore the cycling and gas circulation-enhanced formation characteristics of TBAB hydrate at different concentrations. Notably, it was observed that when the concentration of TBAB hydrate surpassed 25 wt%, the hydrate exhibited a consistent high formation efficiency without displaying any discernible decay characteristics. Upon reaching a TBAB concentration of 35 wt%, a notable concentration stratification phenomenon became evident following the complete dissociation of hydrates. Remarkably, the introduction of gas circulation to enhance hydrate formation yielded a bulk phase uniform nucleation mode for TBAB hydrate formation. This led to a remarkable 72 % reduction in the induction time. Even under conditions of 45 wt% concentration, the subcooling was as low as 4.35 °C. These research findings hold significant implications for the advancement of efficient hydrate cycling formation technology and its potential industrial applications.

Tailored SrFeO3-δ for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a highly efficient process that converts two major greenhouse gases (CH4 and CO2) into syngas ready for the feedstock of liquid fuel production. One of the major obstacles facing this technology now is creating oxygen carriers that are stable and reactive. We fabricated high-performance Sr0.98Fe0.7Co0.3O3-δ perovskite-structured oxygen carrier by combining A-site defects and B-site doping of SrFeO3-δ. During isothermal CL-DRM tests at 850 °C, Sr0.98Fe0.7Co0.3O3-δ achieved 87% CH4 conversion and 94% CO selectivity in the CH4 partial oxidation reaction, followed by a syngas yield of 8.5 mmol/g, and CO yield of 4.2 mmol/g in CO2 decomposition. A-site defect engineering of the perovskite creates abundant oxygen vacancies and enhances oxygen storage capacity (OSC). Co-doping of the B-site of Sr0.98FeO3-δ increases oxygen mobility and CH4/CO2 activation, resulting in high activity in the CL-DRM process. This methodology resulted in high ionic mobility and facilitated the rapid diffusion of oxygen in the bulk phase, thereby increasing the redox properties of SrFeO3-δ. The oxygen carrier exhibits excellent structural stability and regeneration ability in successive redox cycles. This strategy offers a simple but very effective pathway to tailor OSC, oxygen mobility, and oxygen vacancies of perovskite-structured materials for chemical looping or redox-involved processes.

Multi-scale structural comparisons of W/O and O/W/O beeswax-based emulsions

O/W/O double emulsions are an advanced oil-structuring approach that has been attracting considerable interest in recent years. However, their structural characteristics remain unsolved compared to conventional W/O emulsions. To clarify the differences from a multi-scale perspective, we prepared W/O emulsions and O/W/O double emulsions with the same components. For the stabilization of the O/W interface, modified pea protein isolate (MPPI) was utilized. A combination of polyglycerol polyricinoleate (PGPR) and beeswax (BW) was used for the stabilization of the W/O emulsions. Then, texture and oil binding capacity (OBC), rheological properties, and microstructure of emulsions were recorded to compare the differences samples. Results showed that all the emulsions kept excellent storage stability and similar crystallization and melting profiles over two weeks of storage. Interestingly, texture exhibited significant variations, with oleogelled O/W/O double emulsions possessing an improved firmness and OBC compared to W/O emulsions. This was probably caused by a larger fraction of the dispersed phase and a higher wax concentration in the outer oil phase. Further, the stabilization mechanism of the emulsions was illustrated. BW, in synergy with PGPR, could stabilize the oil-water interface as Pickering particles, providing a physical barrier to improve the emulsion stability. Also, BW acted as the gelator of the bulk phase, forming a viscoelastic network to support the structural function of the emulsions. Additionally, the droplet-droplet interaction caused by the dispersed phase could promote the formation of the gelling network. Altogether, this research provides a multi-scale fundamental understanding on the structural comparison between W/O and O/W/O double emulsions, and indicates that O/W/O double emulsions with less wax or gelator content can achieve the same structural functionality as W/O emulsions, thus presenting superior industrial potential.

A new anode material for high rate and long life lithium/sodium storage

It is imperative to design suitable anode materials for both lithium-ion (LIBs) and sodium-ion batteries (SIBs) with a high-rate performance and ultralong cycling life. We fabricated a MoO2/MoS2 heterostructure that was then homogeneously distributed in N,S-doped carbon nanofibers (MoO2/MoS2@NSC) by electrospinning and sulfurization. The one-dimensional carbon fiber skeleton serves as a conductive frame to decrease the diffusion pathway of Li+/Na+, while the N/S doping creates abundant active sites and significantly improves the ion diffusion kinetics. Moreover, the deposition of MoS2 nanosheets on the MoO2 bulk phase produces an interface that enables fast Li+/Na+ transport, which is crucial for achieving high efficiency energy storage. Consequently, as the anode for LIBs, MoO2/MoS2@NSC gives an excellent cycling stability of 640 mAh g−1 for 2 000 cycles under 5.0 A g−1 with an ultralow average capacity drop of 0.002% per cycle and an exceptional rate capability of 614 mAh g−1 at 10.0 A g−1. In SIBs, it also produces a significantly better electrochemical performance (reversible capacity of 242 mAh g−1 under 2.0 A g−1 for 2 000 cycles and 261 mAh g−1 under 5.0 A g−1). This work shows how introducing a novel interface in the anode can produce rapid Li+/Na+ storage kinetics and a long cycling performance.

Modification of red mud catalyst using oxalic acid-assisted UV treatment for toluene removal

An innovative simplified modification method for red mud had been proposed, which enabled its utilization as an active Fe2O3-rich component for catalytic oxidation of toluene. The Box-Behnken design, based on Response Surface Methodology (RSM), was employed to optimize the modification of bauxite residue using oxalic acid combined with UV irradiation. Based on the experimental conditions, the optimal conditions for three independent parameters were determined: acid leaching time (2 hours), UV irradiation time (1 hour), and acid dosage (150 ml),which was in order to enhance the maximum catalytic efficiency of toluene at 300 °C. Under the optimal preparation conditions provided by the Box-Behnken design, the catalytic efficiency of toluene at 300°C could reach 99.2%. In comparison to the acid-modified mud (MRM) and untreated bauxite residue (RM), the aluminum refinery residue modified with oxalic acid-assisted UV irradiation (MRM-UV) exhibited the formation of oxalate sub-iron precipitates, resulting in significantly lower catalytic temperatures (238°C). Furthermore, through XRF, XRD, XPS, O2-TPD, and H2-TPD analysis, it was discovered that a large amount of iron oxide and calcium oxide formed CaO+Fe2O3→Ca2Fe2O5, strengthening the interaction between iron and calcium, augmenting the migration rate of lattice oxygen from the bulk phase to the surface. Consequently, T50 were reduced by 20.9% and 31.8% when compared to MRM and RM. Moreover, the CO2 selectivity of MRM-UV increased from 8.6% to 70.5% compared to RM at 300°C. Using in situ DRIFTS, the reaction pathway of toluene on MRM-UV was identified as benzyl alcohol → benzaldehyde or benzoyl → benzoate→maleic anhydride→CO2 and H2O. The process refinement reduced VOCs emissions and promoted sustainable waste management by combining oxalic acid with catalytically active red mud.

Structural and dynamical equilibrium properties of hard board-like particles in parallel confinement.

We performed Monte Carlo and dynamic Monte Carlo simulations to model the diffusion of monodispersed suspensions composed of impenetrable cuboidal particles, specifically hard board-like particles (HBPs), in the presence of parallel hard walls. The impact of the walls was investigated by adjusting the size of the simulation box while maintaining constant packing fractions, fixed at η = 0.150, for systems consisting of HBPs with prolate, dual-shaped, and oblate geometries. We observed that increasing the distance between the walls led to the recovery of an isotropic bulk phase, while local particle organization near the walls remained stable. Due to their shape, oblate HBPs exhibit more efficient anchoring at wall surfaces compared to prolate shapes. The formation of nematic-like particle assemblies near the walls, confirmed by theoretical calculations based on density functional theory, significantly influenced local particle dynamics. This effect was particularly pronounced to the extent that a modest portion of cuboids near the walls tended to diffuse exclusively in planes parallel to the confinement, even more efficiently than observed in the bulk regions.

Synthesis, structural characterization of supramolecular cocrystals of bis(3-hydroxy-1-methylpyridin-1-ium iodide)-18-crown-6

Abstract A new supramolecular cocrystal of bis(3-hydroxy-1-methylpyridin-1-ium iodide)-18-crown-6 (I) has been synthesized successfully from 3-hydroxypyridine, methyl iodide and 18-crown-6 (18C6). The cocrystal was characterized by FT-IR, UV-DRS and PL spectroscopy, single crystal and powder X-ray diffraction (XRD) analysis, SEM and EDS analysis, and thermogravimetric analysis. The bulk phase purity of the compound is confirmed by powder XRD analysis, whereas single-crystal XRD confirms that it packs in a monoclinic system with centrosymmetric space group (P21/c). Single crystal XRD shows that the asymmetric unit is C6H12O3, [C6H8NO]+[I]¯. The presence of C–H⋯O, C–H⋯I and O–H⋯I intermolecular contacts helps to achieve crystal cohesion. The direct band gap energy has been estimated to be 3.21 eV using diffuse reflectance spectral measurements. Thermogravimetric analysis was employed to determine the compound’s thermal behaviour concerning temperature. EDS and SEM investigations were used to examine the elemental composition and surface morphology of the compound.

Adsorption mechanism study of sour natural gas and sulfur in high-sulfur carbonate rock gas reservoirs

As the world pivots towards green and renewable energy sources, natural gas stands out as a clean and efficient alternative. In particular, there has been an upsurge in the exploration and development of gas fields rich in hydrogen sulfide (H2S). However, an escalating issue of sulfur deposition is notably pronounced in carbonate rock reservoirs predominantly comprised of dolomite, as exemplified in China's Yuan Ba gas field. This study examines sulfur adsorption in high-sulfur gas reservoirs and its effects on carbonate rock formations. Molecular simulation analysis reveals that the sour natural gas density in 20 Å dolomite nanopore structure experiences an average increase of 30% at the nanoscale. Notably, CO2 and H2S manifested strong adsorption tendencies in smaller pore sizes, with CO2's strong adsorption state layer thickness measuring approximately 2.93 Å, and H2S's at about 1.871 Å. Additionally, it was found that the adsorption energy of sour natural gas decreases with rising temperature and pore size, and falling pressure, yet the temperature's effect on excess adsorption density is minor above 40 MPa. As the pore size reaches 160 Å, the strong adsorption states of CO2 and H2S dissipate. Beyond 160 Å, the influence of nanoscale dimensions is negligible, with only a 2.23% increase in adsorbed phase density compared to the bulk phase. The introduction of S8 molecules amplified the adsorption proclivities of CO2 and H2S, urging them closer to the pore wall. The study reveals that CO2 or H2S reinjection into formations could effectively mitigate sulfur deposition in pores smaller than 160 Å, offering valuable insights for the development of high-sulfur gas fields.

Coherent Phase Change in Interstitial Solutions: A Hierarchy of Instabilities.

Metal hydrides or lithium ion battery electrodes can take the form of interstitial solid solutions with a miscibility gap. This work discusses theory approaches for locating, in temperature-composition space, coherent phase transformations during the charging/discharging of such systems and for identifying the associated transformation mechanisms. The focus is on the simplest scenario, where instabilities derive from the thermodynamics of the bulk phase alone, considering strain energy as the foremost consequence of coherency and admitting for stress relaxation at free surfaces. The extension of the approach to include capillarity is demonstrated by an example. The analysis rests on constrained equilibrium phase diagrams that are informed by geometry- and dimensionality-specific mechanical boundary conditions and on elastic instabilities-again geometry-specific-as implied by the theory of open-system elasticity. It is demonstrated that some scenarios afford the analysis of chemical stability to be based entirely on a linear stability analysis of the mechanical equilibrium, which provides closed-form solutions in a straightforward manner. Attention is on the impact of the system geometry (infinitely extended or of finite size) and on the chemical (closed or open system) and mechanical (incoherent or coherent) boundary conditions. Transformation mechanism maps are suggested for documenting the findings. The maps reveal a hierarchy of instabilities, which depend strongly on each of the above characteristics. Specifically, realistic, finite-sized systems differ qualitatively from idealized systems of infinite extension. Among the transformation mechanisms exposed by the analysis are a uniform switchover to the other phase when the open system reaches its chemical spinodal, practical coherent nucleation, as well as chemo-elastically coupled spontaneous buckling modes, which may take the form of either, single-phase or dual-phasestates.

A bimetal strategy for suppressing oxygen release of 4.6V high-voltage single-crystal high-nickel cathode

High-voltage cathode materials, such as single-crystal high-nickel layered oxide materials, are a necessary condition for achieving high energy density lithium-ion batteries, but they have to be accompanied by the structural instability and irreversible release of lattice oxygen during operation, posing serious safety hazards. Here, to solve the lattice oxygen release issue of single-crystal high-nickel cathode, we propose an improved strategy for overall cathode by synchronously addressing interface and lattice instability, ensuring stable operation at a high voltage up to 4.6 V. By Al-doping, in the bulk phase, we intensify the charge transfer between transition metals and oxygen, and the columnar effect caused by doped atoms effectively alleviates internal strain, thereby significantly limiting lattice shrinkage and then suppressing oxygen release. On the other hand, the protective layer of LiNbO3 as the fast ion conductor formed at the cathode interface suppresses parasitic reactions and hinders lattice oxygen loss caused by dissolution of transition metals. Therefore, after 200 cycles at a cut-off voltage of 4.6 V, our cathode material still maintains a capacity retention rate of 89.1%. Density functional theory (DFT) calculations predict the effective suppression of oxygen release for the modified cathode materials, which has been further confirmed by differential electrochemical mass spectrometry (DEMS) tests. This work provides a new perspective for solving the problem of oxygen release under high cut-off voltage conditions for single crystal high nickel cathode.

Diffusivity of CO2 in H2O: A Review of Experimental Studies and Molecular Simulations in the Bulk and in Confinement.

An in-depth review of the available experimental and molecular simulation studies of CO2 diffusion in H2O, which is a central property in important industrial and environmental processes, such as carbon capture and storage, enhanced oil recovery, and in the food industry is presented. The cases of both bulk and confined systems are covered. The experimental and molecular simulation data gathered are analyzed, and simple and computationally efficient correlations are devised. These correlations are applicable to conditions from 273 K and 0.1 MPa up to 473 K and 45 MPa. The available experimental data for diffusion coefficients of CO2 in brines are also collected, and their dependency on temperature, pressure, and salinity is examined in detail. Other engineering models and correlations reported in literature are also presented. The review of the simulation studies focuses on the force field combinations, the data for diffusivities at low and high pressures, finite-size effects, and the correlations developed based on the Molecular Dynamics data. Regarding the confined systems, we review the main methods to measure and compute the diffusivity of confined CO2 and discuss the main natural and artificial confining media (i.e., smectites, calcites, silica, MOFs, and carbon materials). Detailed discussion is provided regarding the driving force for diffusion of CO2 and H2O under confinement, and on the role of effects such as H2O adsorption on hydrophilic confining media on the diffusivity of CO2. Finally, an outlook of future research paths for advancing the field of CO2 diffusivity in H2O at the bulk phase and in confinement is laid out.

Deep eutectic solvent assisted electrodialysis towards selective resource recovery from model spent batteries effluents

Critical minerals will remain major active ingredients to most battery technologies for decades and innovation to improve extractive operations during spent battery effluent recycling must be carried out. Although the recovery of metal-ions in aqueous solutions has been demonstrated with membrane systems, including electrodialysis, process intensification to increase the diffusion rate at the membrane/liquid interface must be achieved to improve recovery efficiency. This manuscript presents a unique approach to increase the rate of recovery and transfer of Li+ and Co2+ ions from a membrane bulk phase to an organic liquid phase by applying deep eutectic solvent (DES) instead of an aqueous solution as the permeate stream during electrodialysis. The DES, based on choline chloride and urea at a molar ratio of 1:2, is considered green and relatively non-toxic valuable for solvent extraction purpose. Here, electrodialysis tests were conducted with this solvent on the permeate side using commercial Neosepta and laboratory-made cobalt selective membranes. The DES significantly affected cobalt transport across the membranes and separation factor which increased from 247 to 516, leading to cobalt recovery as high as 66 %. Furthermore, the use of DES on the permeate side greatly improved the energy efficiency increasing the amount of recovered cobalt per Joule of energy by over 20 %.

Hydrogen adsorption and diffusion behavior in kaolinite slit for underground hydrogen storage: A hybrid GCMC-MD simulation study

Underground hydrogen storage (UHS) in reservoirs offers the opportunity for large-scale and long-term storage of hydrogen. In order to understand the fundamental mechanisms of hydrogen storage and transportation, it is crucial to study the adsorption and diffusion behavior of hydrogen in reservoirs. By utilizing a hybrid GCMC and MD simulation procedure, we investigated the adsorption and diffusion behavior of hydrogen in kaolinite slit with pore sizes ranging from 1 to 20 nm at pressures up to 30 MPa and temperatures ranging from 303 to 423 K. Hydrogen distribution, excess adsorption, diffusion coefficient, and gas–solid interaction energy were analyzed in relation to pore size, temperature, pressure, and mineralogy. When pores are larger than 5 nm, most of the hydrogen is located in the bulk phase, resulting in insignificant hydrogen loss due to adsorption. Therefore, reservoirs with pores larger than 5 nm are suitable for UHS. Reservoirs with low temperatures and high hydrogen pressures are conducive to UHS, but the hydrogen mobility is reduced. The mineralogy of the formation results in pore surfaces with different charge properties, which significantly affects hydrogen storage. Although van der Waals interaction dominates the gas–solid interaction, Coulomb interaction remains important. The negatively charged pore surface mitigates the gas–solid Coulomb interaction, thereby preventing hydrogen loss through adsorption. This study enhances our understanding of hydrogen storage mechanisms in subsurface porous media and elucidates the influence of various factors. Consequently, it provides a theoretical framework for selecting UHS sites.

The isomorphous substitution of Si(4Al) with P in FAU zeolite and its stabilization effect

It's a dream to make zeolites more stable so as to keep the activity and stability of the catalyst. Phosphorus modification is an effective method, however, the known post-modification predominantly presents as non-framework P, and the P-loss is a big trouble in application. We have discovered that in the reaction of PCl3 or SiCl4 + PCl3 with NaY zeolite, a portion of P enters the framework of the zeolite, forming a PO4-AlO4 structure. Further investigations revealed that P cannot be incorporated into the framework through P for Al isomorphous substitution, but rather through isomorphous substitution with Si(4Al). PCl3 exhibits two effects in reaction: at lower quantities, it mainly undergoes isomorphous substitution with Si(4Al); at higher quantities, it leads to zeolite dealumination generating aluminum vacancies, which disrupt the zeolite framework or promotes Si for Al isomorphous substitution. After hydrothermal aging at 800 °C for 4 h, the stable presence of framework PO4-AlO4 implies that the weakest site Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. Compared with the JPY (prepared by impregnating (NH4)2HPO4 solution to high silica Y zeolite) sample, after 10 cycles of hydrothermal and water washing treatment, the P2O5 loss rate of DPY (prepared by SiCl4 + PCl3 with NaY) zeolite ranged from 0.4 % to 3.5 %, significantly lower compared to the range of 18.7 % to 25.9 % observed in the JPY sample. This indicates that in DPY zeolite, the interaction between P and the zeolite is stronger and less prone to loss. Moreover, P is more uniformly distributed on the surface and bulk phase of DPY than JPY sample.

Synthesis, crystal structure, spectroscopic properties, thermal behavior and DFT studies of a new organic-inorganic hybrid [4FBzTPP]2[CoBr4]

A new organic-inorganic hybrid [4FBzTPP]2[CoBr4](1) (4FBzTPP = 4-fluorobenzyltriphenylphosphonium) was synthesized and characterized by X-ray diffraction, DTA-TG measurement, FT-IR and Raman spectroscopies, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and UV–vis diffuse reflectance spectrum. [4FBzTPP]2[CoBr4] crystallized in monoclinic system with P21/c space group, consisting of two [4FBzTPP]+ cations and one distorted tetrahedral [CoBr4]2− anion. Powder X-ray diffraction analysis confirmed the bulk phase purity and homogeneity of the material. The UV–vis-DRS result indicated that the energy gap value of the electron transition was 1.60 eV, which was quite distant from the calculated value of 1.64 eV. The material showed fluorescent emission at 389 nm, 414 nm, 448 nm, and 495 nm under the excitation of UV light at 380 nm. Theoretical calculations were performed using the density functional theory method to derive the dipole moment and first hyperpolarizability of the as-synthesized molecule. The first hyperpolarizability value (βtot) was more than 11,600 times higher than those of standard KDP crystals, indicating that [4FBzTPP]2[CoBr4] was an excellent material for applications.

Scaling behavior in membrane distillation: Effect of Biopolymers and Antiscalants

Fouling and scaling are inherent characteristics of membrane-based separation. They lead to a reduced membrane throughput. In the case of membrane distillation (MD), they can possibly result in pore wetting and irreversible failure to sustain the mass transfer interface. Most prior research on understanding fouling and scaling uses indirect measurements (flux) or ex-situ analyses methods (such as SEM and EDX), which limit the outcomes to indirect qualitative conclusions. Particularly, studying scaling tends to be more challenging due to the complexity of the experiments and the method of investigation; it is imperative to distinguish the contributions from the bulk phase and heterogeneous nucleation. In this work, we established a non-invasive, in-situ, real-time imaging experimental apparatus to study the scaling mechanism. Our experimental setup assisted us in distinguishing distinct phases of scaling during the filtration tests. We studied the scaling mechanism of various single-component systems (sodium chloride, strontium sulfate, calcium sulfate, and calcium carbonate) in vacuum MD filtration. The effect of natural organic matter and antiscalants on gypsum scaling were systematically investigated. Overall, organic fouling on the membrane surface expedited heterogeneous crystallization while decelerating crystal growth in the bulk phase. For instance, deposited humic acid (HA) on the membrane surface promoted gypsum heterogeneous nucleation on the membrane surface due to the interactions between HA carboxylic functional groups and calcium ions. The adsorption of HA on the salt crystal also decelerated crystal growth in the bulk phase. Antiscalants delayed and decelerated both crystal nucleation and crystal growth. PAA, a polycarboxylate antiscalant at 5 ppm, was found to effectively delay the onset of nucleation and crystal growth in the bulk phase, while phosphorous antiscalants at 5 ppm only delayed the onset of nucleation in the bulk phase with a negligible influence on crystal growth. Real-time, in-situ, and non-invasive monitoring shed light on the scaling mechanism and can further be used to identify mitigation strategies.

Structure of liquid-vapor interfaces: Perspectives from liquid state theory, large-scale simulations, and potential grazing-incidence x-ray diffraction.

Grazing-incidence x-ray diffraction (GIXRD) is a scattering technique that allows one to characterize the structure of fluid interfaces down to the molecular scale, including the measurement of surface tension and interface roughness. However, the corresponding standard data analysis at nonzero wave numbers has been criticized as to be inconclusive because the scattering intensity is polluted by the unavoidable scattering from the bulk. Here, we overcome this ambiguity by proposing a physically consistent model of the bulk contribution based on a minimal set of assumptions of experimental relevance. To this end, we derive an explicit integral expression for the background scattering, which can be determined numerically from the static structure factors of the coexisting bulk phases as independent input. Concerning the interpretation of GIXRD data inferred from computer simulations, we extend the model to account also for the finite sizes of the bulk phases, which are unavoidable in simulations. The corresponding leading-order correction beyond the dominant contribution to the scattered intensity is revealed by asymptotic analysis, which is characterized by the competition between the linear system size and the x-ray penetration depth in the case of simulations. Specifically, we have calculated the expected GIXRD intensity for scattering at the planar liquid-vapor interface of Lennard-Jones fluids with truncated pair interactions via extensive, high-precision computer simulations. The reported data cover interfacial and bulk properties of fluid states along the whole liquid-vapor coexistence line. A sensitivity analysis shows that our findings are robust with respect to the detailed definition of the mean interface position. We conclude that previous claims of an enhanced surface tension at mesoscopic scales are amenable to unambiguous tests via scattering experiments.

Enhancement of N2O decomposition performance by co-doping of Ni and Y to Co3O4 catalyst

Co3O4, Y2O3-Co3O4 and NiO-Y2O3-Co3O4 samples were prepared by the simple co-precipitation method, and their N2O catalytic decomposition performance was evaluated. Experimental results disclose that the order of catalytic activity among the three catalysts is NiO-Y2O3-Co3O4 > Y2O3-Co3O4 >> Co3O4. N2O conversion over NiO-Y2O3-Co3O4 catalyst reached 100 % at 360 °C, which was 20 °C and 60 °C lower than those over Y2O3-Co3O4 and Co3O4, respectively. In addition, NiO-Y2O3-Co3O4 catalyst shows better water resistance compared with Co3O4 and Y2O3-Co3O4. Systems-based characterization techniques, it is confirm that Y and Ni were successfully doped into Co3O4, where Y was on the surface and Ni was mainly in the bulk phase. Due to the co-doping of Y and Ni, NiO-Y2O3-Co3O4 catalyst has smaller average particle size and reinforced surface alkalinity. Furthermore, the surface modification of Y enhances the electron-donating capacity of Co2+ and oxygen desorption ability, while bulk phase doping of Ni facilitates the reduction of Co3+ to Co2+ and weakens Co-O bond in Co3O4, which endow NiO-Y2O3-Co3O4 sample with lower Ea for N2O decomposition. Therefore, NiO-Y2O3-Co3O4 catalyst exhibits the best N2O catalytic decomposition performance.