Particle Surface Wettability Research Articles

Effect of Surfactants on Eliminating Stable Ultrafine Chalcopyrite Froth.

Chalcopyrite is a primary source of copper in nature. However, with the increasing need to process low-grade and complex chalcopyrite ores, overly stable froth is becoming more and more common and poses operational and safety challenges. No reliable strategy has been developed to address the issue. As a new initiative, this study investigated three different structured surfactants, sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and pentadecafluorooctanoic acid (PFOA), which vary in hydrophobic group, aiming to modify the surfaces of ultrafine chalcopyrite particles and adjust the interfacial tension at the gas-liquid interface to eliminate stable ultrafine chalcopyrite froth. The fundamental hypothesis was that an ideal surfactant structure could adjust the particle surface wettability and interfacial tension to eliminate overly stable froth. Based on contact angle measurements and interfacial tension measurements using a Theta Flow tensiometer by the pendant drop method and the sessile drop method, it was demonstrated that the contact angle played a dominant role in defoaming, while the reduction of gas-liquid interfacial tension had an adverse effect. Additionally, defoaming tests indicated that SDBS had lower defoaming effectiveness than SDS at low surfactant concentrations due to the steric hindrance in its structure, whereas the addition of SDBS could achieve a froth reduction efficiency as high as 93.75% at higher surfactant concentrations due to its stronger hydrophobicity and adsorption capacity to chalcopyrite particles, which could reduce the contact angle from 70 to 37.62°. However, PFOA exhibited lower defoaming effectiveness than both SDS and SDBS due to its lipophobic fluorocarbon tail of PFOA and weaker adsorption capacity to chalcopyrite particles, making it unsuitable for eliminating stable ultrafine chalcopyrite froth.

A numerical study on the effect of particle surface wettability on homogeneous and heterogeneous condensation processes in supersonic flows

Supersonic separators are an emerging device for processing natural gas impurities. Natural gas contains solid particulate impurities in addition to gaseous impurities, which can trigger heterogeneous condensation within the supersonic separator. There is a lack of research on the effect of particle wettability on supersonic condensation flow, although there have been studies on the effect of particle surface wettability on heterogeneous condensation in this area. Therefore, in this paper, the supersonic condensation flow is modeled considering the contact angle, and the effects of particle contact angle on heterogeneous condensation and homogeneous condensation are investigated separately. The results show that homogeneous condensation is inhibited and heterogeneous condensation is promoted by decreasing the particle contact angle. The reason is the smaller contact angle leads to the reduction of the free energy barrier for heterogeneous nucleation, which makes the conditions for heterogeneous nucleation lower and condensation more likely to occur.

An experimental study on the impact of particle surface wettability on melt infiltration in particulate beds

Melt infiltration into porous media is an intriguing phenomenon that holds immense significance across various sciences and technologies. In this work, the problem of metallic melt infiltration in particulate beds is investigated for understanding and prediction of severe accident progression associated with a molten pool penetrating through an underlying debris bed which may form in the reactor core or in the lower head of a light water reactor.The present study aims to quantify the effect of particle surface’s wettability on melt infiltration kinetics. For this purpose, two categories of experiment are conceived and carried out to measure the wettability of different material surfaces by melt and to characterize melt infiltration kinetics in one-dimensional particulate beds, respectively. The melt material is tin–bismuth eutectic alloy with a melting point of 139 °C. Copper (Cu), stainless steel (SS), Tin (Sn) and tin-coated stainless steel (Sn-coated SS) are chosen as materials of substrates and particles in wettability measurement and melt infiltration study. The particulate beds, packed with 1.5 mm spheres, are preheated to 200 °C before the melt infiltration begins.The experimental data of wettability measurement shows that the contact angles of liquid Sn-Bi eutectic on the above-mentioned material surfaces range from 79° to 135°. The results of melt infiltration tests confirm the significant effect of wettability on melt penetration kinetics. The capillary force plays a significant role in the initial infiltration of particulate beds. Specifically, a wettable particulate bed enhances the initial melt infiltration, whereas non-wettable beds hinder it.

From an oil with “antifoaming” properties to stabilization for foam: A novel approach for establishing a long-term stable foam system

Can a foam be synergistically stabilized by particles and oil? Sure it can. A new strategy for preparing “capillary foam” based on whey protein isolate particles (WPs) was designed by co-stabilization with coconut oil (CO) to improve foam stability. Unique aspect of the “capillary foam” presented here was the protein particle-facilitated diffusion of the minority oil around the bubble. The foamability and foam stability were evaluated based on size, ζ-potential, and surface wettability of particles, as well as different oil phase concentrations. Foam stability was significantly improved in the presence of a minor amount of CO (1%, v/v). The size and hydrophobicity of the particles become important factors in determining the stability of the “capillary foam”. The oil/water contact angle (θo/w) of the particles was close to 90° at pH 5.0, which makes it easier for particles to adsorb at the oil/water interface compared to the air/water interface, thus facilitating the formation of the special structure of the “capillary foam” with high stability. The distribution of the oil phase around the bubble surface raised with the increase of oil phase mass fraction, although the stability decreases slightly. This strategy provides useful tips and achieves a fundamental breakthrough, which means that the new idea of “capillary foam” is promised to furnish a new solution to the challenge of food foam stability.

Effect of dispersants on the stability of calcite in non-polar solutions

The surface modification of calcite has been widely used to improve the compatibility of calcite with non-polar solutions, but this method is complex, time-consuming and uneconomical. Thus, we propose to use dispersants for improving the compatibility of calcite with non-polar solutions and systematically study the dispersion effect and mechanism of various dispersants. Anionic bis (2-ethylhexyl) sulfosuccinate sodium (AOT), non-ionic sorbitol monooleate sodium (Span 80) and sorbitol trioleate (Span 85), cationic cetyltrimethylammonium bromide (CTAB), oleic acid (OA) and stearic acid (SA), are used to change the surface properties of calcite in nonpolar solutions. The results of sedimentation and rheology showed that the anionic dispersant AOT had the best dispersion performance and efficiency. All dispersants, except CTAB, can significantly improve the wettability of particle surface, and the calcite adsorbed AOT has the best hydrophobicity. XRD results showed that all dispersants were adsorbed on the surface of calcite. FT-IR and XPS confirmed that AOT adsorbed on the particle surface through the coordination between AOT and Ca2+. Zeta potential shows that the calcite system with anionic AOT has the highest surface charges, indicating that the strong electrostatic interaction is one reason of the stabilization of calcite particles. This work has guiding implications for the selection of dispersants to improve the compatibility of calcite with non-polar solvents.

Properties and potential application of ozone-oxidized starch for enhanced reverse flotation of fine hematite

In this study, ozone as an eco-friendly oxidant was employed to improve the depressive performance of starch in the reverse flotation of fine hematite. Micro-flotation results showed that ozone-oxidized starch (OS) better depressed hematite flotation as compared to the native starch (NS). Particle surface wettability and size distribution analysis suggested that OS rendered the hematite surface more hydrophilic in the presence of an amine collector while maintaining a comparable flocculation performance to that of NS. Solubility, rheology, carbonyl and carboxyl content measurements, together with atomic force microscopy (AFM) imaging were performed to examine the variations in the structure and properties of starch upon ozonation and their correlation with the depressive performance of starch. It was found that ozone treatment not only increased starch acidity and solubility, but also concurrently depolymerized starch with the yield of low molecular weight derivatives. These favorable changes appeared to be responsible for the superior performance of OS. Furthermore, the stronger interaction of OS with hematite was verified by X-ray photoelectron spectroscopy (XPS).

Flow characteristics and thickness distribution of liquid film in trickle bed reactor

In trickle bed reactor (TBR), the gas-liquid mass transfer is closely related to the thickness of liquid film and the wetting of catalyst particles. Therefore, knowledge on the flow and distribution of liquid film on particle surface is critical for evaluating the performance of TBR. In this work, high-speed camera was used to study the flow behavior of liquid film by using continuous droplets impacting on the top of particles with several layers. It was found that liquid tends to accumulating toward the contact point between adjacent particles due to capillary force. When the liquid inlet flow rate doubles, the wetting ratio of the particle surface increases by about 30%, while the liquid film thickness doubles. With the particle surface wettability increasing, the wetting ratio of particle surface can be improved while the liquid film thickness remains almost unchanged. • Liquid film flow behavior of continuous droplets impacting particles was studied. • Spatial and temporal distributions of liquid film on particle surface were analyzed. • The liquid film thickness and its distribution on particle surface were obtained. • Effects of liquid inlet velocity and wettability of particle surface were discussed.

Research of reagent interaction on induction time during bubble–particle interaction

ABSTRACT This paper focuses on the influence of reagent interaction on induction time in the process of bubble–particle interaction. Induction time instrument was used to investigate the influence of single reagent and reagent interaction on induction time. Meanwhile, the influence mechanism of reagent interaction on coal particle surface wettability, surface tension, and surface functional groups was studied combined with contact angle and FTIR. The results showed that when the collector interacted with the frother, the addition of the frother reduced the induction time and increased the hydrophobicity of the coal particle surface. Compared with raw coal, the surface contact angle of collector-frother-reacted coal particles increased, and its change law was inconsistent with that of collector-reacted coal particles. The larger the contact angle, the lower the surface tension, the higher the interfacial surface tension between coal particles and water, the lower the wettability and the more hydrophobic the particle surface. FTIR spectra indicated that the influence of collector–frother interaction on the surface functional groups of coal particles was mainly reflected in the absorption peaks at 3436 cm−1 and 1400 ~ 1000 cm−1. The effect of interaction varied with the structure of the reagent. 2-Octanol can produce multi-point adsorption on the surface of coal particles and promote the hydrophobic modification of coal particle surface. When ether alcohols interacted with arene, reverse adsorption occurred. Throughout this study, the mechanism affecting the adhesion characteristics of coal particles and bubbles caused by reagent interaction was clarified.

Insights into the fluid wetting law and fractal characteristics of coal particles during water injection based on nuclear magnetic resonance

In order to reveal the migration mechanism of dynamic water between coal particles in the process of coal seam water injection, in this study, nuclear magnetic resonance experiments (NMR) were carried out on wetted coal samples, the transverse relaxation time (T2) spectra of samples presenting different degrees of metamorphism and particle size ranges were measured over different time periods of the wetting process, and the fractal dimension (DNMR) of the wetting phase distribution in the migration channel was calculated. (1) The average values of T2g decrease percentage Δ of the three coal samples are 84%, 71.25%, and 57.75%, indicating that the order of the wettability strength is Daliuta coal sample (DLT) > Xinglongzhuang coal sample (XLZ) > Qincheng (QC), this shows that the coal samples are more easily wetted as the degree of metamorphism decreases. (2) Sodium dodecyl sulfate (SDS) will make the wetting process between coal and water smoother, and in the range of 60–80 mesh and 100–120 mesh particle size, compared to the solution properties change, the particle size has relatively little influence on the wetting process when its change is not large. (3) The surface tension reduction caused by the addition of surfactants in the water, the narrowing of the pore space caused by the reduction of the overall size of the particles, and the decrease of the particle surface wettability caused by the increase in the metamorphic degree of coal sample will lead to the decrease of DNMR measured in the experiment. Based on the above research, it can provide a theoretical basis for improving the effect of coal seam wetting and dust reduction.

Simulating the collision of a moving droplet against a moving particle: Impact of Bond number, wettability, size ratio, and eccentricity

This paper presents a direct numerical simulation for the collision of a moving droplet against a moving particle under gravity, based on the pseudopotential lattice Boltzmann model. The effects of Bond number (Bo), particle surface wettability, particle–droplet size ratio (α), and eccentricity ratio (B) on the collision processes are investigated comprehensively. Six findings are reported and analyzed for the first time: (1) an agglomeration process is observed for the collision with a very small Bond number. During the agglomeration process, the vertical velocity of the particle will experience a deceleration, and the deceleration will become weak against the increase in the Bond number. (2) The wettability will influence the variation of the vertical velocity of the moving particle remarkably. The vertical velocity of the neutral particle is nearly linearly accelerated, but the lyophilic particle experiences an obvious deceleration. In addition, the velocity history of the lyophobic particle shows a nonlinear acceleration. (3) The increase in the particle–droplet size ratio will postpone the emergence of the deceleration process. Therefore, the appearance of the peak vertical velocity is delayed against the increase in the particle–droplet size ratio. (4) For different eccentricity ratios, the differences of the velocities (e.g., the horizontal, vertical, and angular velocity) are very small in the beginning of collision, while a big difference appears with time elapses. Besides, the variation of velocities becomes very obvious. (5) There is a critical value for B, where the horizontal velocity, vertical velocity, and angular velocity of the particle investigated in the work all will reach their maximum values. (6) A rebound regime is observed when a moving droplet collides vertically against a moving particle. In the available literature, a rebound regime was observed only when a droplet colliding against a fixed particle, but never for a vertically moving particle. The present research reveals when a rebound process will appear. The finding here may shed some light on the mechanism of the collision of a moving droplet against a moving particle.

The effect of surfactant concentration on nanoparticles surface wettability during wettability alteration of oil-wet carbonate rock

Previous studies reported that the presence of surfactant increases nanoparticles surface wettability by in-situ surface activation. On the other hand, the excess of surfactant concentration has an inverse effect on particle hydrophobicity by altering it to be hydrophilic back. Hence, this study presents an experimental investigation of wettability alteration by using a surfactant-nanoparticles system by using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactant, and hydrophilic silicon dioxide (SiO2) and partially hydrophobic silicon dioxide (PH SiO2) nanoparticles. The nanoparticles surface wettability and the wettability alteration of oil-wet carbonate rock were measured by using the contact angle method. The result shows that the contact angle of the oil-wet carbonate rock was most reduced by using CTAB-hydrophilic SiO2, from 112.00o to 28.35o. The excess of surfactant concentration (beyond CMC) shows an inverse effect on particle surface wettability, however, induces the water-wetness of the carbonate rock. Besides, the hydrophilic SiO2 shows a more effective effect as a wettability modifier than the PH SiO2, in the absence and presence of CTAB or SDS surfactant.

Influence of surfactant on the penetration time of hydrophilic microparticles impacting into the gas–liquid interface at low impact velocities

The micro-mechanics of particle-interface collision is fundamental for revealing the separation mechanism of gas-borne particles in the bubble column. This study further investigates the particle penetration time under different concentrations of anionic and nonionic surfactant solutions at low impact velocities (up0 ≤ 0.5 m/s) utilizing high-speed imaging technique. The results show that the penetration time exhibits a power function to the particle size, which remains constant with increasing the concentration of surfactants. The variation of interfacial deformation width wi and three-phase contact line dTPCL controls the cavity shape and capillary force exerted on the particle, further influencing the penetration time. The increased concentration of surfactant slightly improves the particle surface wettability, while the interfacial deformation width wi exhibits quite different features before and after reaching the critical micelle concentration (CMC). When csurfactant < CMC, the impact cavity will cause the uneven distribution of interfacial concentration and induce the Marangoni effect. When csurfactant> CMC, the disintegration of micelles can supply the monomers and eliminate the Marangoni effect. The model of penetration time has been extended to include the variation of surfactant at pre- and post- CMC.

Drag coefficient and settling velocity of fine particles with varying surface wettability

The surface wettability of micron particles affects many engineering applications, such as forth flotation and dust removing. The settling velocities of glass beads with diameters in the range 15–100 μm and varying surface wettability were obtained using a high-speed dynamic system. The results showed that the surface wettability of the particle surface has a significant effect on the terminal settling velocity (VT) when the particle dimensionless diameter (d∗ = (∆g/v2)1/3d) is less than two. As the contact angles increase, the VT increases and the drag coefficient (CD) decreases. The classical Stokes model does not reflect this change; consequently, a modified Stokes model that considers surface wettability is proposed. Experimental results indicate that the average relative error of the proposed model is 3.10% for the modified settling velocity formula, and 3.06% for modified drag coefficient formula. Both modified formulas were validated using the experimental data of spherical aluminum oxide (Al2O3) particles.

Heterogeneous condensation of magnetized water vapor on fine SiO2 particles

The emission of fine particles from coal-fired power plants is one of the major healthy and environmental concerns. The enlargement of particles seems to be a promising pretreatment technology due to the low removal efficiency of traditional dusting devices. The study of particle amplification by heterogeneous condensation of magnetized water vapor was carried out based on the growth tube. And, the major component of particles from coal combustion SiO2 was tested. The experimental results indicate that the particle growth is more favored by the magnetized water compared with non-magnetized water. And the particle growth is closely related to the magnetic field strength. Additionally, the surface tension of magnetized water is reduced and the wettability of particle surface is improved to some extent. Meanwhile, the particle concentration has stronger effect on the particle growth with magnetized water at lower level of supersaturation. Numerical calculation results demonstrate that the critical supersaturation is lower and nucleation rate is elevated when the water magnetized. This work reveals the facilitating process of particle growth by magnetized water that is the physical method of ameliorating particle surface performance.

Effect of surface wettability of TiO2 particles on evaporation enhancement of silicone oil in the bulk of electrorheological suspensions

Hydrophilic, oleophilic and raw TiO2 particles are dispered respectively in silicone oil to form electrorheological suspensions and the effect of surface wettability of TiO2 particles on evaporation enhancement of silicone oil is studied. The results show that the evaporation rate of silicone oil increases with the decrease of surface wettability of the particle and the increase of the depth of suspension which indicates that the evaporation mainly occurs in the bulk. The observed phenomena have been explained mainly on the basis of heterogeneous nucleation theory of bubbles. In the bulk of suspensions, the less wettable surface of nanoparticles, the less critical activation energy needed for bubble nucleation, the easier it is to form bubbles which is the origin of the evaporation.

Gelatin-Based Nanocomplex-Stabilized Pickering Emulsions: Regulating Droplet Size and Wettability through Assembly with Glucomannan.

Particle size and surface wettability play leading roles in the distribution of particles on the oil-water interface and the stability of emulsions. This work utilized nanocomplexes assembled from gelatin and tannic acid to stabilize Pickering emulsions. The sizes and surface wettability of particles were further regulated by using a polysaccharide. The sizes of nanocomplexes ranged from 205.8 to 422.2 nm and increased with the addition of polysaccharide. Their contact angles decreased from 84.1° to 59.3°, revealing their hydrophilic nature. Results of fluorescence microscopy and cryo-scanning electron microscopy indicated that nanocomplexes were located at the oil-water interface. Interfacial shear and dilatational rheological data revealed a fast and irreversible adsorption behavior, which differed from rearrangement of gelatin molecules at the oil-water interface. The minimal concentration of nanocomplexes required to stabilize emulsions was 0.1 wt %. Our results demonstrated that protein-polyphenol-polysaccharide nanocomplexes had the potential to be applied to form stable surfactant-free food emulsions for the delivery of nutraceuticals.

On wetting characteristics of droplet on a spherical particle in film boiling regime

This study reports droplet-particle interaction of size ratio less than unity in the film boiling regime on a highly thermally conductive spherical particle surface. Specifically, the effects of impact Weber number (We) of subcooled state droplets comprising water (We=3.9–103.6) and isopropyl alcohol (IPA) (We=8.6–194.6) were studied using high speed imaging technique in the particle temperature range of 250–350°C. In general, non-wetting interaction behaviour was observed with two distinct outcomes – rebound and complete disintegration demarcated by a critical Weber number range instead of a single threshold value. Extent of surface wetting was characterised by the maximum droplet spread diameter parameter which was found to scale with impact Weber number in a power law form which agrees with the theoretical scaling argument. Additionally, an energy balance model was developed to compute this parameter which provided good agreement with the experimental measurements in the lower Weber number regime, however, higher deviations were noted near the transition regime. Also quantified from experiments was the droplet-particle contact time which exhibited a power law dependency on Weber number in the rebound regime, however, was noted to be almost independent of Weber number in the disintegration regime. Particle surface wettability was characterised by the experimentally measured dynamic contact angles which were found to vary in the range of 120–160o in low Weber number regime manifesting the hydrophobic nature of particle surface in film boiling regime. Also, all the parameters such as contact line velocity, particle temperature and droplet size apparently had relatively insignificant influence on the variation of dynamic contact angle. Temporal variation of non-dimensional spreading parameter exhibited a self-similar behaviour wherein all data collapsed on a single power law profile. It was further shown that the behaviour could also be described by a recovery type exponential profile through suitable non-dimensionalization and both profiles can be utilized to produce a spreading kinetics.

Collapse of Particle-Laden Interfaces under Compression: Buckling vs Particle Expulsion.

Colloidal particles can bind to fluid interfaces with a capillary energy that is thousands of times the thermal energy. This phenomenon offers an effective route to emulsion and foam stabilization where the stability is influenced by the phase behavior of the particle-laden interface under deformation. Despite the vast interest in particle-laden interfaces, the key factors that determine the collapse of such an interface under compression have remained relatively unexplored. In this study, we illustrate the significance of the particle surface wettability and presence of electrolyte in the subphase on interparticle interactions at the interface and the resulting collapse mode. Various collapse mechanisms including buckling, particle expulsion, and multilayer formation are reported and interpreted in terms of particle-particle and particle-interface interactions.

Temperature responsive polymers as multiple function reagents in mineral processing

A processing scheme which uses a single chemical that has multiple functions to achieve both efficient mineral flotation and solids dewatering is presented. Temperature sensitive polymers which display hydrophilic/hydrophobic transitions in response to changes in temperature such as poly ( N-isopropyl acrylamide) (PNIPAM) have been found to be useful as such multiple function reagents. This polymer can cause the mineral particles’ surfaces to be hydrophilic at temperature below the critical solution temperature (CST = 32 °C) and hydrophobic at temperature above the CST. Therefore, both particle surface wettability and inter-particle interaction forces are reversibly controllable. When the surface is hydrophilic, particle dispersion is achieved by repulsive inter-particle forces whereas when the surface is hydrophobic, particle aggregation is induced by inter-particle hydrophobic attractive forces. In addition, the hydrophobic surface condition allows for the attachment of particles to bubbles. Flotation and solid settling tests have been conducted with silica and kaolinite suspensions treated with (PNIPAM). Both effective suspension dispersion or hydrophobic aggregation and flotation without any additional collector have been demonstrated. In solid/liquid separation, rapid settling was obtained with hydrophobic aggregation at temperature above the CST and further sediment consolidation (and water release) occurred at temperature below the CST. The approach has the potential to reduce the amount and types of reagents required for mineral processing.

Barrier properties of polymer/alumina nanocomposite membranes fabricated by atomic layer deposition

Novel polymer/ceramic nanocomposite membranes were fabricated, characterized and tested for their barrier performance. Atomic layer deposition (ALD) was used to deposit alumina films on primary, micron-sized (16 and 60 μm) high-density polyethylene (HDPE) particles at a rate of ∼0.5 nm/cycle at 77 °C. Well-dispersed polymer/ceramic nanocomposites were obtained by extruding alumina coated HDPE particles. The dispersion of alumina flakes can be controlled by varying the number of ALD coating cycles and substrate polymer particle size. The diffusion coefficient of fabricated nanocomposite membranes can be reduced to half with the inclusion of 7.29 vol.% alumina flakes. However, a corresponding increase in permeability was also observed due to the voids formed at or near the interface of the polymer and alumina flakes during the extrusion process, as evidenced by electron microscopy. The low surface wettability of the alumina outerlayers was believed to be one of the main reasons of void formation. Particle surface wettability was improved using 3-aminopropyltriethoxysilane (APS) to coat the particle ALD surface modified polymer particles prior to extrusion. The diffusion coefficient and permeability of the membrane using surfactant-modified particles decreased by 20%, relative to the non-modified case.