De-agglomeration of hydrophobic and hydrophilic silica nano-powders in a high shear mixer

Enhancing the Techno-Functional Properties of Lentil Protein Isolate Dispersions Using In-Line High-Shear Rotor-Stator Mixing

In response to global challenges such as climate change and food insecurity, plant proteins have gained interest. Among these, lentils have emerged as a promising source of proteins due to their good nutritional profile and sustainability considerations. However, their widespread use in food products has been impeded by limited solubility. This study aimed to investigate the potential of high-shear mixing, a resource-efficient technique, to enhance lentil protein solubility and its functional properties. Red lentil protein isolate powders were rehydrated and subjected to a semi-continuous in-line high-shear treatment at 10,200 rpm for a timespan ranging from 0 to 15 min. The results highlighted a significant (p < 0.05) increase in solubility from 46.87 to 68.42% after 15 min of shearing and a reduction in particle size as a result of the intense shearing and disruption provided by the rotor and forced passage through the perforations of the stator. The volume-weighted mean diameter decreased from 5.13 to 1.72 µm after 15 min of shearing, also highlighted by the confocal micrographs which confirmed the breakdown of larger particles into smaller and more uniform particles. Rheological analysis indicated consistent Newtonian behaviour across all dispersions, with apparent viscosities ranging from 1.69 to 1.78 mPa.s. Surface hydrophobicity increased significantly (p < 0.05), from 830 to 1245, indicating exposure of otherwise buried hydrophobic groups. Furthermore, colloidal stability of the dispersion was improved, with separation rates decreasing from 71.23 to 24.16%·h-1. The significant enhancements in solubility, particle size reduction, and colloidal stability, highlight the potential of in-line high-shear mixing in improving the functional properties of lentil protein isolates for formulating sustainable food products with enhanced techno-functional properties.

Pickering phase change slurries

HYPOTHESIS

Phase change slurries (PCS) have emerged as a promising class of oil-in-water emulsions for energy applications, but stability remains an issue. Pickering phase change slurries (PPCS) stabilized solely by nanoparticles could offer enhanced stability. We hypothesize that stability in PPCS can be achieved by tuning environmental variables of salinity and temperature.

EXPERIMENTS

A paraffin-based PPCS stabilized using fumed silica nanoparticles was developed and assessed under varying NaCl concentrations (up to 150 mM) and temperatures (up to 70 °C). Extended-DLVO modeling, confocal, and cryogenic electron microscopy analyzed the silica-paraffin interactions. Rheological experiments examined the impact of effective volume fraction, thermal expansion, and salinity on the viscosity and shear stability of PPCS. The stability of the resulting formulation was assessed under high pressure and temperature conditions.

FINDINGS

Increased salinity did not change the packing density of the silica at the oil-water interface (82% ± 6%) but did increase the adsorbed layer thickness and network formation, enhancing the formulation's resistance to shear-induced instability. A critical volume fraction of 0.51 ± 0.01 was identified, beyond which viscosity increased significantly. The resulting formulations remained stable under high pressures and temperatures, regardless of salinity. These findings offer insights into the variables affecting PPCS properties, assisting in designing stable PPCS formulations for diverse applications.

Effect of Inlet Flow Strategies on the Dynamics of Pulsed Fluidized Bed of Nanopowder

The use of fluidization assistance can greatly enhance the fluidization hydrodynamics of powders that exhibit poor fluidization behavior. Compared to other assistance techniques, pulsed flow assistance is a promising technique for improving conventional fluidization because of its energy efficiency and ease of process implementation. However, the inlet flow configuration of pulsed flow can significantly affect the bed hydrodynamics. In this study, the conventional single drainage (SD) flow strategy was modified to purge the primary flow during the non-flow period of the pulse to eliminate pressure buildup in the inlet flow line while providing a second drainage path to the residual gas. The bed dynamics for both cases, namely, single drainage (SD) and modified double drainage (MDD), were carefully monitored by recording the overall and local pressure drop transients in different bed regions at two widely different pulsation frequencies of 0.05 and 0.25 Hz. The MDD strategy led to substantially faster bed dynamics and greater frictional pressure drop in lower bed regions with significantly mitigated segregation behavior. The spectral analysis of the local and global pressure transient data in the frequency domain revealed a pronounced difference between the two flow strategies. The application of the MDD inlet flow strategy eliminated the disturbances from the pulsed fluidized bed irrespective of the pulsation frequency.

Improvement of magnetite adsorption performance for Pb (II) by introducing defects

Surface defect engineering is an efficient strategy to enhance the adsorption properties of materials. After calcination in argon, the adsorption capacity of natural magnetite to Pb (II) is significantly improved. The Rietveld refinement, Mössbauer spectrum, and XPS were used to prove the existence of oxygen and cation vacancies in the crystal structure of magnetite after calcination, and it is found that the vacancy content is linearly related to the adsorption amount of Pb (II). This indicates that the increase in the adsorption performance of magnetite after calcination is determined by the vacancy. The adsorption capacity increases from 8 to 26 mg/g when the calcination temperature reaches 700°C. The equilibrium adsorption process of Pb (II) on magnetite can be well fitted to the Langmuir model, and the kinetic adsorption followed a pseudo-second-order mechanism. The improvement of the adsorption performance of magnetite is mainly due to the change in its structure, which depends on the oxidation degree and surface effect of magnetite in the calcination process. This work also provides a theoretical basis for the broad application of magnetite as environmental material.

Effects of Mechanical Activation on Physical and Chemical Characteristics of Coal-Gasification Slag

Coal-gasification slag (CGS) was subjected to mechanical grinding by three different methods. We studied the effects of mechanical activation on various physical and chemical characteristics of the CGS, including particle-size distribution, specific surface area, mineral composition, degree of crystallinity, particle morphology, chemical bonding, surface activity and binding energy, anionic-polymerization degree and hydration properties. The results show that there are different effects on CGS characteristics depending on the type of activation applied. Mechanical activation also can increase the specific surface area and the dissolution rates of activated SiO2 and Al2O3, and the major elements (O, Si, Al, Ca) in CGS, whereas the degree of crystallinity and of polymerization of [SiO4] and [AlO6] are reduced by mechanical activation. We also found that the effects of different mechanical-activation methods on the compressive strength and activity were similar and could accelerate the hydration process.

The role of bulk micro-nanobubbles in reagent desorption and potential implication in flotation separation of highly hydrophobized minerals

Micro-nanobubbles (MNBs) generated during hydrodynamic cavitation (HC) have been extensively studied in mineral processing field in the past two decades. Many researchers have claimed that MNBs can effectively promote the collection of fine particles in flotation, while studies on MNBs assisted mineral separation are rare. In this study, the role of bulk MNBs in desorbing flotation reagent was investigated, with the aim of illustrating the potential effects of MNBs on minerals separation. The results showed that bulk MNBs could efficiently remove the sodium oleate (NaOl) from diaspore surfaces, reducing the residual concentration of NaOl on solids, which was more significant when the amount of NaOl pre-adsorbed was relatively small. Furthermore, lower residual concentration of NaOl on solids caused by MNBs cleaning made the particles less hydrophobic and flocs more friable. Given that gangue entrapment in flocs was one of the main limits for high-selective flotation, the roles of MNBs in enhancing reagent desorption and associated flocs breakup and reorganization probably contribute to higher separation efficiency of different minerals, which was confirmed by the flotation results of diaspore/kaolinite mixture.

Nanopowder Fluidization Using the Combined Assisted Fluidization Techniques of Particle Mixing and Flow Pulsation

In the present study, we report the fluidization behavior of ultrafine nanopowder using the assisted fluidization technique of particle mixing, which was further superimposed with the pulsation of the inlet gas flow to the fluidized bed. The powder selected in the present study was hydrophilic nanosilica, which shows strong agglomeration behavior leading to poor fluidization hydrodynamics. For particle mixing, small proportions of inert particles of Geldart group A classification were used. The inlet gas flow to the fluidized bed was pulsed with a square wave of frequency 0.1 Hz with the help of a solenoid valve controlled using the data acquisition system (DAQ). In addition to the gas flow rate to the fluidized bed, pressure transients were carefully monitored using sensitive pressure transducers connected to the DAQ. Our results indicate a substantial reduction in the effective agglomerate size as a result of the simultaneous implementation of the assisted fluidization techniques of particle mixing and flow pulsation.

Enhancement of CO2 Removal Efficacy of Fluidized Bed Using Particle Mixing

The present study proposes a cost-effective assisted fluidization technique of particle mixing to improve the carbon capture effectiveness of a fluidized bed containing fine adsorbent powder. Using activated carbon as the adsorbent, we mixed external particle of Geldart group B classification in different fractions to examine the effectiveness of the proposed strategy of particle mixing. Four different particle-mixing cases were considered by varying the amount of added particle—0, 5, 10, and 30 wt %—on external particle-free basis. The inlet flow of the nitrogen was fixed, while two different flows of carbon dioxide were used. The adsorption experiment consisted of a three step procedure comprising purging using pure nitrogen, followed by adsorption with fixed inlet CO2 concentration, and finally the desorption step. Inlet flows of both nitrogen and CO2 were separately controlled using electronic mass flow controllers with the help of data acquisition system (DAQ). The CO2 breakthrough was carefully monitored using the CO2/O2 analyzer, whose analog output was recorded using the DAQ. Best results were obtained with 10% external particles. This is in conformity with the results of our previous study of bed hydrodynamics, which pointed to clear improvement in the fluidization behavior with particle mixing.

Improving Fluidization Hydrodynamics of Group C Particles by Mixing with Group B Particles

We have developed a new particle-mixing strategy for improving the fluidization hydrodynamics of Geldart group C powders by mixing with small proportions of group B particles. Two different group C particles with widely different physical properties, i.e., 1 μm calcium hydroxide powder and 27 μm porous activated carbon, were selected for investigation in the present work. A carefully sieved sample of inert sand was used as external group B particles for mixing. Fluidization experiments were carried out, and the quality of the fluidization was assessed using the fluidization index. For the monocomponent fluidization of fine calcium hydroxide powder, pressure drop was sometimes as much as 250% higher than the effective weight of the bed. The proposed strategy of particle mixing substantially improved its fluidization hydrodynamics. On the other hand, the development of channels and cracks during the monocomponent fluidization of the activated carbon led to gas bypassing, resulting in low pressure drop and poor contact of phases. Particle mixing was found to improve fluidization behavior, and the chi-squared test showed that the best results were obtained with 13 wt% particle mixing.

Effects of dissolved metal chlorides on the behavior of silica nanoparticles in aqueous media

Effects of chlorides of univalent (LiCl, NaCl, KCl), bivalent (MgCl2, BaCl2) and trivalent (AlCl3) metals at different concentration (0.001–0.1 M) on the behavior of nanosilica A-200 (0.5–5 wt.%) in aqueous media are analyzed using photon correlation spectroscopy (particle size distribution, PSD), electrophoresis (zeta potential ζ), potentiometric titration (surface charge density), and estimation of screening length of primary particles and their aggregates. The zeta potential and the PSD are affected by silica content, pH, and concentration and type of dissolved salts. Smaller but more strongly hydrated Li+ cations caused stronger nonlinear dependences of the zeta potential on pH and salt content than Na+ or K+. This nonlinearity is much stronger at a lower content of silica (0.5–1 wt.%) than at C A-200 = 2.5 or 5 wt.%. At a high concentration of nanosilica (5 wt.%) the effect of K+ ions causes stronger diminution of the negative value of the zeta potential due to better adsorption of larger cations. Therefore, the influence of K+ on increasing screening length is stronger than that of Na+ for both primary nanoparticles and their aggregates. A similar difference in the ζ values is observed for different in size cations Ba2+ and Mg2+.

A green, rapid and size-controlled production of high-quality graphene sheets by hydrodynamic forces

The synergistic enhancement of shear forces and collision effects can result in effective exfoliation of ultrathin graphene nanosheets.

Multi-walled carbon nanotubes (Baytubes): approach for derivation of occupational exposure limit

Carbon nanotubes come in a variety of types, but one of the most common forms is multi-walled carbon nanotubes (MWCNT). This paper focuses on the dose-response and time course of pulmonary toxicity of Baytubes, a more flexible MWCNT type with the tendency to form assemblages of nanotubes. This MWCNT has been examined in previous single and repeated exposure 13-week rat inhalation studies. Kinetic endpoints and the potential to translocate to extrapulmonary organs have been examined during postexposure periods of 3 and 6 months, respectively. The focus of both studies was to compare dosimetric endpoints and the time course of pulmonary inflammation characterized by repeated bronchoalveolar lavage and histopathology during the respective follow-up periods. To better understand the etiopathology of pulmonary inflammation and time-related lung remodeling, two metrics of retained lung dose were compared. The first used the mass metric based on the exposure concentration obtained by filter analyses and aerodynamic particle size of airborne MWCNT. The second was based on calculated volumetric lung burdens of retained MWCNT. Kinetic analyses of lung burdens support the conclusion that Baytubes, in principal, act like poorly soluble agglomerated carbonaceous particulates. However, the difference in pulmonary toxic potency (mass-based) appears to be associated with the low-density (approximately 0.1-0.3g/m(3)) of the MWCNT assemblages. Of note is that assemblages of MWCNT were found predominantly both in the exposure atmosphere and in digested alveolar macrophages. Isolated fibers were not observed in exposure atmospheres or biological specimens. All findings support the conclusion that the low specific density of microstructures was conducive to attaining the volumetric lung overload-related inflammatory response conditions earlier than conventional particles. Evidence of extrapulmonary translocation or toxicity was not found in any study. Thus, pulmonary overload is believed to trigger the cascade of events leading to a stasis of clearance and consequently increased MWCNT doses high enough to trigger sustained pulmonary inflammation. This mechanism served as conceptual basis for the calculation of the human equivalent concentration. Accordingly, multiple interspecies adjustments were necessary which included species-specific differences in alveolar deposition, differences in ventilation, and the time-dependent particle accumulation accounting for the known species-specific differences in particle clearance half-times in rats and humans. Based on this rationale and the NOAEL (no-observed adverse effect level) from the 13-week subchronic inhalation study on rats, an occupational exposure limit (OEL) of 0.05 mg Baytubes/m(3) (time weighted average) is considered to be reasonably protective to prevent lung injury to occur in the workplace environment.