Dispersed Systems Research Articles

Investigation of serpentine entrainment reduction in pentlandite flotation using eco-friendly sodium alginate in suspension dispersion systems

Magnesium silicates pose severe environmental issues in hydrometallurgical processes. Copper-nickel sulfide ores are the primary source for nickel production, but their increasingly complex properties make separation difficult, causing slimy magnesium silicate minerals to be entrained into the concentrate with the foam, leading to magnesium contamination. Studies have found that sodium alginate (SA), as an environmentally friendly polymer reagent, can effectively inhibit serpentine. This work investigates the effect of SA on the flotation behavior of pentlandite and serpentine in a sodium hexametaphosphate (SHMP) system. Sedimentation tests show that only a low dosage of SA can effectively settle serpentine, while excessive SA disperses serpentine. Flotation tests indicate that SA can further increase the difference in recovery rates between pentlandite and serpentine based on SHMP. Results from artificial mixed ore tests demonstrate that the recovery rate of serpentine decreases from 51.22% to 37.37% with the addition of SA, with minimal impact on the recovery rate of pentlandite. To explain the impact of the SA adsorption process on the mineral states, the following tests and analyses were conducted: TOC and QCM-D results indicate that SA mainly adsorbs onto serpentine, forming rigid adsorption at low dosages and flexible adsorption at high dosages. Zeta potential tests reveal changes in the surface potential of the minerals, explaining the transition from electrostatic attraction to electrostatic repulsion between pentlandite and serpentine. FTIR and XPS results show that SA chemically reacts with the Mg and Si sites on the serpentine surface through its -COO- groups. In summary, in the SHMP system, the use of gel adsorption and the chemical interaction of SA to coagulate and depress serpentine reduces its entrainment into the concentrate, achieving efficient separation of pentlandite and serpentine. However, high dosages of SA do not yield satisfactory results.

Production sustained release dosage forms from deliquescent substances by solid dispersion systems

Introduction. The production of solid dosage forms from hygroscopic substances is a complex technological task. The addition of hygroscopic substances into a polymer matrix allows to reduce their moisture absorption capacity.Aim. Reducing the hygroscopicity of deliquescent substances and obtaining sustained release solid dosage forms by using solid dispersion systems.Materials and methods. Substance: DEAE; excipients: Kollidon® VA 64, Soluplus®, PEG 1500, PEG 6000, PEG 8000, Poloxamer Kolliphor® P 188 and Kolliphor® P 407; reagents: hydrochloric acid, sodium dihydrogen phosphate, potassium hydrogen phosphate. The melt of the components was obtained on a twin-screw laboratory extruder and cast into silicone molds. The resulting solid dosage forms were studied for disintegration in three environments corresponding to the sections of the human gastrointestinal tract.Results and discussion. The active pharmaceutical substance DEAE is characterized as deliquescent substance. The introduction of DEAE into PEG-polymer matrices made it possible to reduce the hygroscopicity of solid dosage forms in the form of bars. The introduction of solubilizers into the melt made it possible to obtain bars with the appropriate organoleptic properties. The release of DEAE from bear- or toroid-shaped bars occurs on average 29–47 % faster than from heart-shaped bars.Conclusion. Compositions based on Soluplus® and Kolliphor® P 407 have proven promising for further development of tiles containing DEAE. In order to create tiles with a slow release, it is recommended to use heart-shaped forms, as they have a smaller surface area.

Study on the inhibitory behavior of high-voltage electric field on the agglomeration and sedimentation of nanoparticles in suspension

Nanoparticles can improve the heat transfer effect of fluids, however, they are difficult to dissolve in the base fluid and are prone to fouling, agglomeration and sedimentation during flow, which affects their efficient heat transfer characteristics. In this paper, the inhibitory effect of high-voltage electric field on the agglomeration and deposition of TiO2 nanoparticles in suspension was comparatively studied by comprehensive gravity sedimentation, spectrophotometer, particle size analysis, and zeta potential method. Studies have shown that the absorbance of suspensions is basically the same in neutral and acidic environments. However, in a highly alkaline environment, the agglomeration rate of nanoparticles increases significantly, resulting in a decrease in the absorbance of the suspension. The high-voltage non-uniform electric field generated by the active Cu rod electrode can effectively inhibit the agglomeration of TiO2 nanoparticles. However, the suppression effect of an external electric field is not necessarily the higher the voltage, the better. Different nanomaterials have different critical voltages. The high-voltage electric field of 1 kV has the best inhibitory effect on the agglomeration and deposition of TiO2 nanoparticles. An in-depth analysis of the mechanisms of the movement and agglomeration of TiO2 particles in suspension under high-voltage electric field excitation was conducted. The result shows that the agglomeration and sedimentation of particles in suspension depend on the Zeta potential of the nano particles. The higher the absolute value, the more stable the dispersion system is.

Light source dependence on quantitative measurement for dispersibility of dark-colored colloidal dispersions

Abstract Colloidal particles are applied to manufacturing in various fields such as ink, food, and cosmetics etc. It is important to study about the dispersibility of colloidal particles because they are dispersed in some solvents. However, many of colloidal dispersions are dark colored and typical methods cannot evaluate the dispersibility. Therefore, dispersibility has been evaluated by naked eyes in almost all research papers. Therefore, we have fabricated quantitative dispersibility evaluation system (QDES) for the dark colloidal dispersion using light transparency by various light types and colors of bright lights. The obtained data were fitted with a stretched exponential function (SEF) to evaluate the dispersibility. As one of the examples of a dark colloidal particle, we chose graphene oxide (GO) which is applied to manufacturing with printing technology. From the measurement results, the red LED light is suitable for the QDES in terms of accuracy and applicability to the SEF.

Diffusion of N2/CH4/CO2 in Heptane-Containing Nanoblind Ends

The prevalence of micropores and nanopores in low-permeability reservoirs is a cause for concern, as it results in a sizeable quantity of oil reserves being trapped within them. The water-gas dispersion system has the capacity to expand the reservoirs’ wave volume and enhance oil recovery. While the microscopic oil repulsion mechanism has been the center of attention, the oil repulsion effect of three distinct types of gases (N2, CH4, and CO2) is of particular importance in understanding the displacement mechanism of N2/CH4/CO2 on heptane at the blind end of the nanometer. A molecular dynamics simulation using the LAMMPS software was employed to construct a model of a blind end of heptane on a SiO2 wall and an interface model with different types of gas molecules. This was done to investigate the microscopic mechanism of heptane replacement by gas molecules. The temperature (50 °C) and pressure (30 MPa) of the reservoir in the Changqing oil field are selected as the parameters for analysis. The findings indicate that all three types of gas molecules can enter the blind end and displace heptane. However, supercritical CO2 forms a mixed phase with heptane, which is more prone to extruding oil molecules situated near the inner wall surface of the blind end and desorbing the oil film. The results demonstrate that, in the context of the blind end, gaseous CO2 exhibits a lower solvation ability but superior extrusion diffusion ability for heptane compared to N2 and CH4. Furthermore, the interaction energy indicates that the interactions between two states of CO2 and heptane, as well as the thickness of the interface, increase with increasing pressure and temperature. The findings of this study elucidate the microscopic mechanism underlying the replacement of oil droplets or oil films at the blind end by different gases under reservoir conditions at the molecular level and offer further guidance for the selection of the gas phase and the replacement state in the water-gas dispersive drive system.

A Rootless Duckweed-Inspired Flexible Artificial Leaf from Plasmonic Photocatalysts.

The naturally existing leaves are ubiquitous two-dimensional flexible solar-to-chemical conversion systems that can run continuously in a sustainable manner. However, the current artificial photocatalytic systems are unable to achieve this due to the grand challenge in integrating existing photocatalysts in a flexible layout with high conversion efficiency and the ability to function independently. Here, we report on a rootless duckweed-inspired artificial leaf based on a lightweight, flexible, Janus plasmonic nanosheet-integrated sponge. The Janus plasmonic catalytically active nanosheet was made from self-assembled gold nanocube nanoassemblies grown on the porous sponges, which were further coated with an ultrathin palladium layer on one side via a ligand symmetry-breaking method. This sponge-based photocatalytic system is lightweight yet able to float on a water surface and conducts the gas-liquid reaction without auxiliary pumping and mixing devices. In a model reaction of 4-nitrophenol reduction, this floating leaf could achieve 2.5-fold and 65-fold higher efficiency than the corresponding dispersion and precipitation systems, respectively. The film theory is used to explain the sponge-based lightweight solar-to-chemical conversion system in a detailed kinetic and thermodynamic analysis, including the reaction rate constant, activation energy, enthalpy, entropy, Gibbs energy, and equilibrium constant.

Comparison of On-Sky Wavelength Calibration Methods for Integral Field Spectrograph

With advancements in technology, scientists are delving deeper in their explorations of the universe. Integral field spectrograph (IFS) play a significant role in investigating the physical properties of supermassive black holes at the centers of galaxies, the nuclei of galaxies, and the star formation processes within galaxies, including under extreme conditions such as those present in galaxy mergers, ultra-low-metallicity galaxies, and star-forming galaxies with strong feedback. IFS transform the spatial field into a linear field using an image slicer and obtain the spectra of targets in each spatial resolution element through a grating. Through scientific processing, two-dimensional images for each target band can be obtained. IFS use concave gratings as dispersion systems to decompose the polychromatic light emitted by celestial bodies into monochromatic light, arranged linearly according to wavelength. In this experiment, the working environment of a star was simulated in the laboratory to facilitate the wavelength calibration of the space integral field spectrometer. Tools necessary for the calibration process were also explored. A mercury–argon lamp was employed as the light source to extract characteristic information from each pixel in the detector, facilitating the wavelength calibration of the spatial IFS. The optimal peak-finding method was selected by contrasting the center of weight, polynomial fitting, and Gaussian fitting methods. Ultimately, employing the 4FFT-LMG algorithm to fit Gaussian curves enabled the determination of the spectral peak positions, yielding wavelength calibration coefficients for a spatial IFS within the range of 360 nm to 600 nm. The correlation of the fitting results between the detector pixel positions and corresponding wavelengths was >99.99%. The calibration accuracy during wavelength calibration was 0.0067 nm, reaching a very high level.

Synergistic Tribological Effects of Ti3C2Tx MXene and ZDDP under Simple Grafting Strategies for Efficient Lubrication.

MXenes, a novel class of two-dimensional materials, possess exceptional physical and chemical properties, positioning them as promising candidates for lubricant additives. However, their potential is constrained by challenges in dispersion and stability, coupled with a paucity of research on interactions with additives in full-formula oils. In this study, hexadecylphosphonic acid (HDPA) is grafted onto Ti3C2Tx to formulate a polyalkylene glycol dispersion system. The findings reveal that the HDPA-modified Ti3C2Tx (HDPA-Ti3C2) is successfully synthesized, demonstrating superior dispersion stability and notable friction-reduction and antiwear properties. Notably, when combined with zinc dialkyl dithiophosphate (ZDDP), the HDPA-Ti3C2/ZDDP composite additive outperforms single additives in tribological performance, suggesting synergistic effects between them. This enhanced performance may be attributed to the formation of an amorphous polyphosphate tribofilm offering wear resistance, followed by the generation of a TiO2 tribofilm that further safeguards and repairs the worn surface, thereby enhancing the load-bearing capacity. Concurrently, the interlayer sliding mechanism of nanosheets, which substitutes the relative motion of the friction pair, reduces friction under boundary lubrication, ensuring prolonged effective lubrication. This work broadens the application prospects of Ti3C2Tx MXene for the design and development of commercial lubricating additives.

In vitro and in vivo performance of amorphous solid dispersions of ursolic acid as a function of polymer type and excipient addition.

The objective of this research was to enhance the bioavailability of ursolic acid (UA) by preparing multielement amorphous solid dispersion (ASD) systems comprising excipients. The ASDs were prepared via the solvent evaporation method, characterized by a range of techniques, and investigated with respect to permeability of human colorectal adenocarcinoma cell line (Caco-2) cells monolayers and pharmacokinetics, with comparisons made to the physical mixture and the pure drug. The (UA-choline)-Polyethylcaprolactam-polyvinyl acetate-polyethylene glycol grafted copolymer (Soluplus)-Vitamin E polyethylene glycol succinate (TPGS) ASD demonstrated superior dissolution properties compared to the corresponding binary solid dispersions and ternary solid dispersions (P<.05). The permeability studies of Caco-2 cell monolayers revealed that the ASD exhibited moderate permeability, with an efflux rate that was significantly lower than that of the UA raw material (P<.05). Pharmacokinetic studies in rats demonstrated that the oral bioavailability of the ASD was 19.0 times higher than that of UA (P<.01). The research indicated that the multielement ASD could be employed as an efficacious drug delivery system for UA. Furthermore, the Soluplus/TPGS/choline combination represents a promising candidate for the fabrication of ASDs that can load weakly acidic and poorly soluble drugs.

Enhanced Homogeneity in Perovskite Photovoltaic Films via Antisolvent Extraction of a Methylamine-Based Gel Precursor.

Solution-processed perovskite solar cells (PSCs) are at the forefront of next-generation photovoltaics, exhibiting outstanding photoelectric performance and cost-effective manufacturing. However, the prevalent use of polar aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide in the preparation of perovskite precursor solution hinders complete solvent removal during film formation. Their high boiling points and strong coordinating abilities lead to solvated intermediates and heterogeneous perovskite crystal nucleation, particularly in the absence of the antisolvent-assisted crystallization. To address this, we developed a methylamine (MA)-based gel dispersion system that significantly improves the uniformity of perovskite films. By employing ethyl acetate (EA) antisolvent extraction, the gel precursor is extracted from a solution of MAI and PbI2 in MA ethanol, which is then diluted in pure acetonitrile (ACN) solvent to form a clear perovskite precursor solution. Benefiting from the highly volatile nature of the ACN-based gel perovskite precursor solution and its rich concentration of high-valent PbIn2-n coordination compounds, this approach enables the fabrication of high-quality MAPbI3 perovskite films, yielding PCEs of 21.34% for PSC and 19.77% for a 5 × 5 cm2 mini-module. This MA-based gel perovskite precursor strategy offers a promising avenue for potential applications in the scalable manufacture of PSCs.

Effects of Particle Size and Shape on the Texture Property of a Solid-Liquid Dispersion System With Gel Particles.

Food texture is one of the most important factors for assessing the quality and acceptability of food. However, the study of food texture has been delayed compared with other factors, such as flavor and taste, due to the difficulty of quantitative analysis related to real physiological senses. Furthermore, the numerical and systematic evaluation of the texture property of dispersion systems, in which solid particles are dispersed in a liquid medium, is very difficult, despite most foods being in a solid-liquid dispersion state during mastication in the human mouth. In this study, the texture property of a solid-liquid dispersion system with spherical and cubic gel particles of agar and konjac was examined to evaluate the physical behavior of food during mastication using the back extrusion method. The yield stress of the system strongly depended on the size and shape of the particles, the mixing ratio of particles of different sizes and shapes, and the concentration of components in the particles. The proposed index, reflecting the size, shape, and number of particles and the yield stress of a single particle, expressed well the measured yield stress of the entire dispersion system. However, the adhesiveness and recoverability showed relatively little dependence on particle size. The findings obtained in this study will contribute to elucidating the texture property of various foods and to the development of new and novel food products and cuisines, thereby benefiting food science and industry.

Peakons and compactons of the (2+1)-dimensional modified dispersive water-wave system

For a higher-dimensional nonlinear dynamical system, there exist abundant coherent excitations. The variable-separated method is a powerful approach to deriving these structures, as its solutions allow for arbitrary functions. Previous works have produced numerous results, including solitons, chaos and fractals. As the molecule structure appears, constructing the multi-soliton molecule through this technology is a meaningful work, especially considering the local peakons and compactons that were seldom discussed before. In this paper, after taking the Bäcklund transformation, the variable-separated solution for the (2+1)-dimensional modified dispersive water-wave system is first derived, which is an important physical model in describing the nonlinear and dispersive long gravity waves. As a result, the multi-peakons and multi-compactons are constructed through the derived universal formula with the aid of the variable functions p and q. These solitons include two general clusters of M × N peakons and compactons, from which the multi-soliton molecules and their interactions are presented.

Features of High-Precision Photothermal Analysis of Liquid Systems by Dual-Beam Thermal Lens Spectrometry.

Thermal lens spectrometry is a high-sensitivity method for measuring the optical and thermal parameters of samples of different nature. To obtain both thermal diffusivity and absorbance-based signal measurements with high accuracy and precision, it is necessary to pay attention to the factors that influence the trueness of photothermal measurements. In this study, the features of liquid objects are studied, and the influence of optical and thermal effects accompanying photothermal phenomena are investigated. Thermal lens analysis of dispersed solutions and systems with photoinduced activity is associated with a large number of side effects, the impact of which on trueness is not always possible to determine. It is necessary to take into account the physicochemical properties and optical and morphological features of the nanophase and components exhibiting photoinduced activity. The results obtained make it possible to reduce systematic and random errors in determining the thermal-diffusivity-based and absorbance-based photothermal signals for liquid objects, and also contribute to a deeper understanding of the physicochemical processes in the sample.

Study on the crystallinity of PEG on the crystalline size of flavonoids in a crystalline dispersion system

Poor water solubility and low bioavailability of flavonoids present significant barriers to their development and application. To address these challenges, this study explores the use of crystalline solid dispersions (CSDs) to reduce drug crystalline size and enhance in vivo bioavailability. The CSDs were prepared using a spray-drying technique with chrysin (CHY) and quercetin (QUR) as model drugs and various molecular weights of polyethylene glycol (PEG) as carriers. The authors systematically investigated the factors influencing the interaction between flavonoids and PEG in CSDs. These factors included the relationships between intermolecular interactions and PEG molecular weight, crystallinity, microstructures such as crystalline domain size and crystal morphology of the flavonoids and PEG in CSDs, crystalline size of the drug in CSDs, and in vitro dissolution rate and in vivo pharmacokinetics. Our results indicated that the interaction between flavonoids and PEG in CSDs was influenced more by PEG crystallinity than by its molecular weight. Lower crystallinity of PEG, achieved through recrystallization, led to stronger intermolecular interactions with the drugs. Specifically, PEG8000 exhibited the lowest crystallinity, indicating a higher content of PEG in the amorphous state, which interacted more effectively with the amorphous drug in CSDs. This interaction significantly inhibited drug crystallization growth, resulting in a marked decrease in drug crystalline domain size and crystalline size. Consequently, PEG8000 was identified as the optimal carrier for preparing CSDs, achieving the best cumulative dissolution percentage. The QUR/PEG8000-CSD formulation increased the cumulative dissolution percentage and oral bioavailability of QUR by 18.76 and 20.66 times, respectively, compared to QUR alone. This study demonstrates that PEG crystallinity, following recrystallization, directly affects its intermolecular interactions with the drug, thereby impacting drug crystalline size and dissolution rate.

Application of surfactants for the resolution of emulsions and suspensions in slop oil storage tanks, cleaning, and final disposal

AbstractIn order to provide environmental solutions for the treatment of oily residues (slop oil) from refineries, formulations with surfactants were proposed according to the type of dispersed system of the slop (crude oil emulsified with water and/or solid particles). Samples were collected in 12 tanks located at the Oxialquilados Venezolanos C.A., Barcelona Plant (Anzoátegui, Venezuela), performing physicochemical tests for the identification of the dispersed system (solubility, wettability, stability, water content) and microscopic observations (morphology and particle size). The results indicated heterogeneous slop samples with a water content of 2%–60% vol/vol consisting of single or multiple emulsions, with droplet sizes between approximately 10 and 30 micron; others formed by sludge or suspension (solids/oil/water). For the destabilization of these systems, aqueous and organic cleaning solutions were designed, determining the percentage of oil separated in the bottle tests at optimal and simulated field conditions. Field tests with volume scaling of the slop tank reported efficiencies of 63%, 85%, and 100% when treating the slop TK‐17, TK‐36, EE, respectively; for the mixture (Pulmon‐2) an efficiency of 47%. By combining heat treatment and two demulsifiers was possible to treat the slop TK‐17 (multiple emulsion). A considerable volume of water can be drained from the tanks for use in the plant. In conclusion, the surfactant formulas were effective in the recovery of a significant amount of crude oil, making it feasible to return it to the generating entity.

Optimization of synthesis of cationic starches for wastewater sludge and microalgae separation

The implementation of stricter water protection legislation requires the development of novel environmentally friendly water treatment materials. A new method for the preparation of water soluble cationic starch flocculants using potato starch, 3-chloro-2-hydroxypropyltrimethylammonium chloride and CaO additive was developed and surface response methodology was successfully utilized for the optimization of degree of substitution in the cationization of potato starch with and without CaO additive. Based on the results of destabilization studies of model kaolin, wastewater sludge, and microalgae dispersion systems, optimized conditions ware proposed for obtaining an efficient, soluble, and biodegradable cationic starch flocculant with optimal structure. The duration of starch etherification reaction was reduced to <12 h to obtain soluble cationic starch derivatives with a degree of substitution of quaternary ammonium groups of 0.25, which retained the granular structure during synthesis. An efficient flocculation technology using anionic polymer and high content of biodegradable cationic flocculant was proposed. The highly efficient flocculation of microalgae suspensions using developed cationic starch derivative with the degree of substitution of cationic groups of 0.25 has been also achieved. The developed environmentally friendly cationic starches with tailored flocculation properties proofed to have a great potential in various water cleaning and separation technologies with prospects in wastewater treatment, agriculture or energy sectors.

Effect of Guest Particles on the Functional Dielectric Properties of Materials for Display Application

AbstractIn this study the dielectric properties are experimentally studied and also analyzed the influence of guest particles on the functional properties of various liquid crystals. The polar and elastic energy of the nanoparticles is found to affect the functional energy of pure suspension. In addition to this, the functional dielectric anisotropy of the dispersed system takes modified form. In this study experiments are performed on various materials to find dielectric anisotropy and also found in good agreement with theoretical explanation.

Foreign experience in determining the group hydrocarbon composition of petroleum feedstock and petroleum products

Determination of the group hydrocarbon composition (saturated and aromatic hydrocarbons, resins, asphaltenes) of petroleum dispersed systems is predominantly carried out using chromatographic analysis methods: liquid adsorption chromatography, high-performance liquid chromatography, thin-layer chromatography with flame ionization detection. The specificity of standard methods developed for the analysis of petroleum feedstock and petroleum products using a particular method often results in the incompatibility of results both in terms of the nomenclature of the identified hydrocarbon groups and the determined concentration values. This review provides a comparative assessment of chromatographic methods for analyzing the group hydrocarbon composition of petroleum feedstock and petroleum products, their features, advantages, and disadvantages. The main options for modifying standard methods aimed at achieving correlation between the results obtained by different analysis methods are described.

Properties of palladium-phosphorus catalysts supported on HZSM-5 zeolite in the direct synthesis of hydrogen peroxide

The properties of Pd/HZSM-5 and Pd–nP/HZSM-5 catalysts in direct synthesis and side processes of decomposition and hydrogenation of H2O2 under mild conditions in ethanol and aqueous-ethanol medium in the presence of an acid inhibitor were studied. Using HR-TEM, XRD and ICP MS methods, it was shown that as a result of modification with phosphorus, X-ray amorphous highly dispersed systems are formed, which represent structurally disordered solid solutions of phosphorus in palladium. The main reasons for the promoting effect of phosphorus on the yield of H2O2 are considered. It has been established that, along with phosphorus and acid modifiers, the use of a zeolite support in the H-form favors the inhibition of the side process of H2O2 decomposition.

Drug Delivery System That Self-Emulsify: Transportation of Drug From Gut to Target Organs

Microemulsions are highly popular for their specific uses, including vivid applications and this is due to their special properties, which include very high interfacial interactions with demonstrated stability from a thermodynamics point of view, and on the other hand, also very low interfacial tension, which is required to solubilize highly immiscible dispersions. This review’s goal is to briefly outline potential uses of micro-emulsion systems, their uses, limitations and possible in-vitro and in-vivo techniques. To characterise such dispersion systems, it is commonly known that adding the right surfactant or surfactant mixture can combine large amounts of two non-dissolving-target liquids, such as water and oil, into a single phase that is macroscopically homogeneous but microscopically heterogeneous. Owing to the advantages of lymph drug delivery, the drug-lipid conjugates, when they enter the lymph route, become an ideal approach for enhancing the absorption of such drugs to combat metastatic cancers of the lymph nodes and their drainage to specific organ systems where the cancer is already spread. As the route of lymph delivery is important where a tumor has already been cancerous, this formulation approach has distinct opportunities to transport needy molecules to cancerous sites in various organs, which also includes the lymph nodes. This review, particularly, lays more stress on an overview of microemulsions in general, the in-vivo and in-vitro characterization methods and potential applications related to target drug delivery via the lymphatic circulatory system.