Zeta Potential Distribution Measurements Research Articles

Effect of Surfactants on 1,2-Dichloroethane-in-Water Droplet Impacts at Electrified Liquid-Liquid Interface

In this work, we used the electrified liquid-liquid interface (eLLI) to study the fusion of DCE-in-water organic droplets (soft particles) upon coming into contact with the soft interface. Our focus was to define the effect of the neutral (1-tetradodecanol) and ionic (cetyltrimethylammonium bromide and sodium dodecylsulfonate) surfactants that stabilize the colloidal solution on the electroanalytical output of the impact events. The electrochemically and interfacially active salt used in our work (tetramethylammonium tetrakis(4-chlorophenyl)borate) was always initially dissolved in the organic phase droplets. When the potential drop at the interface was set below the formal Galvani potential of the tetramethylammonium cation ion transfer, we observed ionic current events upon the fusion of the droplets at the eLLI, as studied by chronoamperometry. This phenomenon was found to be severely affected by the surfactants. Our system was investigated with several methods, including cyclic voltammetry, chronoamperometry, interfacial tension measurements, and finally zeta potential and droplet size distribution measurements based on dynamic light scattering.

Multi-faceted analysis of bacterial transformation of nitrofurantoin

Excessive presence of antibiotics and their residues can be dangerous to the natural environment. To reduce this negative effect, efficient strategies to remove them from the ecosystem are required. This study aimed to explore the potential of bacterial strains to degrade nitrofurantoin (NFT). Single strains isolated from contaminated areas, namely Stenotrophomonas acidaminiphila N0B, Pseudomonas indoloxydans WB, and Serratia marcescens ODW152 were employed in this study. Degradation efficiency and dynamic changes within the cells during NFT biodegradation were investigated. For this purpose, atomic force microscopy, flow cytometry, zeta potential, and particle size distribution measurements were applied. Serratia marcescens ODW152 showed the highest performance in removal of NFT (96 % in 28 days). The AFM images revealed modifications of cell shape and surface structure induced by NFT. Zeta potential showed significant variations during biodegradation. Cultures exposed to NFT had a broader size distribution than the control cultures due to increased cells agglomeration or aggregation. 1-Aminohydantoin and semicarbazide were detected as nitrofurantoin biotransformation products. They showed increased cytotoxicity toward bacteria as determined by spectroscopy and flow cytometry. Results of this study suggest that nitrofurantoin biodegradation leads to formation of stable transformation products that significantly affect the physiology and structure of bacterial cells.

Grafted Pullulan Derivatives for Reducing the Content of Some Pesticides from Simulated Wastewater.

The goal of the current article was to obtain data regarding the application of a series of grafted pullulan derivatives, as flocculating agents, for removal of some pesticide formulations from model wastewater. The pullulan derivatives are cationic polyelectrolytes, with various content and length of grafted poly[(3-acrylamidopropyl)-trimethylammonium chloride] chains onto the pullulan (P-g-pAPTAC)]. The commercial pesticides are either fungicide (Bordeaux Mixture) (BM) or insecticides (Decis (Dc)—active ingredient Deltamethrin, Confidor Oil (CO)—active ingredient Imidacloprid, Confidor Energy (CE)—active ingredients Deltamethrin and Imidacloprid and Novadim Progress (NP)—active ingredient Dimethoate). The removal efficiency has been assessed by UV-Vis spectroscopy measurements as a function of some parameters, namely polymer dose, grafted chains content and length, pesticides concentration. The P-g-pAPTAC samples showed good removal efficacy at doseop, more than 94% for BM, between 84 and 90% for DC, CO and CE and around 93% for NP. The maximum percentage removal decreased with the pesticides (DC, CO, CE, NP) concentration declining; no effect of BM concentration in suspension on its removal efficiency process has been noted. Differences indicated by zeta potential and particle size distribution measurements regarding the pesticides removal mechanisms by pullulan derivatives (charge neutralization, bridging, etc.) are discussed.

Enhancement of selective fine particle flotation by microbubbles generated through hydrodynamic cavitation

The flotation of fine particles less than 50 μm is challenging for the mining industry. By using hydrodynamic cavitation, a significant improvement on the recovery of fine particles has been found. This study aims to investigate the effect of hydrodynamic cavitation on the selective flotation of fine particles from detailed mechanism. Our single-bubble flotation results indicated that the bubble-particle collection efficiencies of fine silica particles (D50 = 6 μm and D50 = 16 μm) improved after hydrodynamic cavitation, especially for hydrophobized silica particles. The improved flotation performance of fine particles was investigated from three perspectives: (1) By zeta potential distribution measurements, bubble-frosting on hydrophobic particles was demonstrated after hydrodynamic cavitation. (2) The formation of large aggregates of hydrophobic fine particles after cavitation was revealed by slurry turbidity and particle size measurements, potentially contributing to the improved collision efficiency of the fine particles due to the bridging effect provided by microbubbles. (3) The attachment efficiency between a solid surface and flotation bubbles was enhanced if the surface was covered with hydrodynamic cavitation-generated microbubbles. Compared to the hydrophilic particles, the hydrophobic particles benefited from the hydrodynamic cavitation from the perspectives of bubble frosting, particle-bubble collision efficiency and attachment efficiency. Based on this study, it is expected that the separation efficiency for fine hydrophilic and hydrophobic particles can be improved by hydrodynamic cavitation.

Prediction of Jetting Stability of Pigment Dispersions by Zeta Potential Distribution Measurement

Prediction of Jetting Stability of Pigment Dispersions by Zeta Potential Distribution Measurement

Effect of siderite dissolution on mineral particles interaction in aqueous suspension

Siderite dissolution and its effects on the interaction between siderite and quartz particle was investigated through focused beam reflectance measurement (FBRM) particle size analysis (a real-time particle characterization tool), zeta potential distribution measurement, and DLVO theoretical calculations, supplemented by dissolution tests, solution chemistry calculation, and X-ray photoelectron spectroscopy (XPS) analysis. The results of FBRM and zeta potential distribution measurement showed that the hetero-aggregation scarcely formed in the siderite-quartz mixture system, which was contrary with the calculated attraction energies (VTD) between siderite and quartz at pH 5.0. Dissolution test and solution chemistry calculation indicated that siderite could dissolve lattice ions, beside compression effects on the double electrode layer, the dissolved ferrous ions can also adsorb onto the negatively charged surface of quartz, which was confirmed by the results of zeta potential and XPS analysis. These would weaken the electrostatic attraction energies (VE) between siderite and quartz at pH 5.0, resulting in depressing the hetero-aggregation.

Room-temperature synthesis of water-dispersible sulfur-doped reduced graphene oxide without stabilizers.

Sulfur-Doped graphene has attracted significant attention because of its potential uses in sensors, catalysts, and energy storage applications. In conventional approaches, the sulfur-doped graphene is fabricated with graphene oxide and sulfur-containing compounds through thermal annealing or hydrothermal process, which generally involves special equipment and heat treatment, and requires additional stabilizers to make it solution-processable. In this work, we report a facile one-step approach to synthesize water-dispersible sulfur-doped reduced graphene oxide (S-rGO). Graphene oxide (GO) could be readily reduced and converted to S-rGO simultaneously by directly mixing GO dispersion with hydrosulfide hydrate (NaSH·xH2O) at room temperature. The sulfur doping is confirmed by high resolution S 2p XPS spectrum and element mapping. The colloidal dispersion state of S-rGO is confirmed by the investigation of Tyndall effect, the zeta potential and particle size distribution measurement. Compared with previously reported strategies, NaSH can initiate the reduction and sulfur doping at room temperature, demand no heat treatment, require no equipment and form stable aqueous S-rGO dispersion without using any stabilizer. These advantages will facilitate large-scale production of water-dispersible (sulfur doped) graphene and further boost their applications in sensors, catalysts and energy storage devices.

New insights into the slime coating caused by montmorillonite in the flotation of coal

Abstract Slime coating is a considerable problem in the flotation of coal. Although many works have been done, there are still some problems that have not been clarified. In this work, the subtle behaviors of montmorillonite coating on coal surface under finely divided slurry pHs (from 2.7 to 10.6) were studied systematically through micro-flotation test, zeta potential distribution measurement, atomic force microscopy and scanning electron microscopy. Several interesting findings are summarized below. The flotation of coal even the highly hydrophobic one will be markedly depressed by montmorillonite once when the pH of the slurry is less than 6.5. However, under neutral condition, the degree of inhibition on the flotation recovery is related to the inherent hydrophobicity of coal itself, since only parts of the coal surfaces are covered by montmorillonite due to the unstable hetero-coagulation by the weak adhesion force. A good dispersion between coal and montmorillonite will be achieved when the pH of the slurry is greater than 8.2, which means good flotation performance restores.

Heterocoagulation between coal and quartz particles studied by the mineral heterocoagulation quantifying system

Heterocoagulation between mineral particles, which is also called slime coating, is an intractable problem that deteriorates the separation efficiency in mineral flotation. To date, although diverse methods of characterizing mineral heterocoagulation are available, there is short of quantitative characterization. In the present work, a novel method named Mineral Heterocoagulation Quantifying System was developed to quantitatively characterize heterocoagulation. The heterocoagulation between coal and quartz particles was measured at different pH values and sodium hexametaphosphate (SHMP) concentrations. With the heterocoagulation degree given by the Mineral Heterocoagulation Quantifying System at different time, the heterocoagulation kinetics was analyzed for the first time. It was found that the heterocoagulation rate in the present work can be fitted to a classical first-order model. The zeta potential distribution measurements were also conducted to characterize heterocoagulation and the results were consistent with that given by the Mineral Heterocoagulation Quantifying System. The inter-particle force calculation based on the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory was conducted to validate the heterocoagulation results.

Sulfidization flotation performance of malachite in the presence of calcite

The effect of calcite on malachite sulfidization flotation was investigated by micro-flotation tests, adsorption, sedimentation and zeta potential test. The micro-flotation results showed that the finer the calcite particles size is, the lower the malachite recovery will be in the sulfidization flotation of malachite at around pH 9.5. The addition of calcite slimes prevented the S species adsorption at malachite surface. Zeta potential distribution measurements confirmed that slimes coating of calcite on malachite surface is detrimental to sulfidization flotation of malachite.

Effects of lizardite on pentlandite flotation at different pH: Implications for the role of particle-particle interaction

Despite that the negative effects of lizardite on pentlandite flotation have been realized, the lizardite effects under different slurry pH have not been sufficiently investigated. Micro-flotation test results showed that pentlandite recovery gradually decreased with the increase in slurry pH when lizardite slime existed. Both electro-kinetic tests and turbidity measurements indicated that hetero-coagulation between the pentlandite and lizardite particles occurred in the entire pH range, which failed to explain the lower recovery at high slurry pH. Zeta potential distribution measurements and sedimentation tests suggested that self-coagulation among lizardite particles occurred at higher pH, which increased the amount of lizardite slime coated on the pentlandite surfaces and thus reducing collector adsorption and flotation recovery. The particle interaction in the pentlandite/lizardite flotation system was investigated using DLVO theory and microscope observation. The findings of the study will contribute to the improvement in pentlandite flotation by regulating the particle interactions.

Recent Advances in Studying Colloidal Interactions in Mineral Processing

Colloidal interactions play a critical role in mineral processing, including grinding, physical separation (particularly flotation), dewatering, and tailings management. Despite great energy input in comminution to liberate valuables from gangues, hetero-coagulation between valuables and gangues would prevent the separation of valuables from gangues. On the other hand, selective coagulation/flocculation to increase the size of desired fine particles could enhance physical separation and dewatering, while dispersion is needed for fine grinding. To control the state of colloidal dispersions by creating favorable conditions, it is of paramount importance to study colloidal interactions in a relevant system and understand underlying mechanisms. This review summarizes recent advances in developing the-state-of-the-art techniques and novel methods of measuring colloidal forces, including atomic force microscope, surface force apparatus, zeta potential distribution measurement, quartz crystal microbalance with dissipation, and our recently developed integrated dynamic force apparatus. The basic principle of each technique was introduced first, followed by a summary of critical information derived for the relevant mineral processing systems. Finally, the pros and cons of each technique were discussed to emphasize the use of complementary techniques that assist in solving fundamental problems in mineral processing.

Interaction of gangue minerals with malachite and implications for the sulfidization flotation of malachite

The role of gangue minerals including quartz and calcite slimes in the sulfidization flotation of malachite was investigated by micro-flotation tests, sedimentation analysis, zeta potential distribution measurements and DLVO calculations. The micro-flotation results showed that calcite slime depressed malachite flotation at pH 9.5 while quartz slime does not appear to influence malachite flotation. Sedimentation tests showed that hetero-coagulation occurred in both of malachite-calcite and malachite-quartz systems. The zeta potential distribution of individual minerals and mixed minerals measurements were used to describe the observed depression of sulfidization flotation of malachite by calcite but not quartz slime addition. DLVO calculation can be explained the hetero-coagulation in malachite-calcite system but not in malachite-quartz system, this may be attributed to the dissolved species of malachite adsorbed on quartz surface in malachite-quartz system.

Inhibiting heterocoagulation between microcrystalline graphite and quartz by pH modification and sodium hexametaphosphate

This paper investigates the heterocoagulation between microcrystalline graphite and quartz particles using the in-situ particle size distribution and zeta potential distribution measurements. It was found that the heterocoagulation was significant at acidic pH but negligible at alkaline pH. Additionally, the heterocoagulation was eliminated by the addition of sodium hexametaphosphate (SHMP). The heterocoagulation mechanism was accounted for by the interparticle force analysis based on the Deyaguin-Landau-Verwey-Overbeek theory. The separation efficiency of the mixture of graphite and quartz was improved when pH was modified to alkaline or sodium hexametaphosphate was added due to the inhibition of heterocoagulation.

The application of nanofluids for recovery of asphaltenic oil

ABSTRACTIn the recent years, requirement of suitable enhanced oil recovery (EOR) technique as a more proficient technology becomes significant because of increasing demand for energy. Nanofluids have great potential in order to improve oil recovery. In our study, the effect of SiO2, Al2O3, and MgO nanoparticles on oil recovery was investigated by using core flooding apparatus. Zeta potential and particle size distribution measurements were carried out to investigate the stability of nano particles and results showed SiO2 has more stability than other ones. Interfacial tension and contact angle measurements between nanofluids and crude oil used to demonstrate that how nanoparticles enhance oil recovery. Experimental data reveals that SiO2 nanoparticles introduce as the greatest agent among these nanoparticles for enhanced oil recovery. Lowest damage for SiO2 nanofluids was observed and also it was observed that the concentration and injection rate have straight effects on permeability reductions.

Magnetic polystyrene–palygorskite nanocomposite obtained by heterogeneous phase polymerization to apply in the treatment of oily waters

ABSTRACTWater contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe3O4‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46162.

Effect of agitation on the interaction of coal and kaolinite in flotation

In this work, the interaction behavior and underlying mechanism of coal and kaolinite particles in the presence of agitation was investigated by flotation tests, homo and hetero settling tests, turbidity meter, zeta potential distribution, focused beam reflectance measurement (FBRM) and scanning electron microscope (SEM). The results show that, in the presence of kaolinite, the flotation combustible matter recovery of coal decreases from 0rpm to 1200rpm and then increases from 1200rpm to 2000rpm, indicating that the mild agitation enhances kaolinite-coating and the high intensity agitation mitigates the kaolinite-coating, which is demonstrated by the zeta potential distribution and turbidity measurements. However, the degree of the heterocoagulation between coal and kaolinite is not serious. It is found that the kaolinite particles partially cover on the coal surface by two morphologies includes individuals and aggregates through the size-based scanning electron microscope analysis. In addition, the affinity between fine kaolinite and fine coal particles is more pronounced. The kaolinite-coating enhancement caused by the mild agitation is explained by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory.

Heterocoagulation of alumina and quartz studied by zeta potential distribution and particle size distribution measurements

This paper presents a new approach to characterizing heterocoagulation (i.e. coagulation of mixtures of dissimilar particles) by measuring the zeta potential distribution and the particle size distribution of individual and combined alumina and quartz at pHs 5, 7, and 10. The results show that the heterocoagulation of alumina and quartz would occur at pHs 5 and 7 but not at pH10. For the alumina and quartz particles under study, the aggregate size was mainly between 1.3 and 8.7μm and the quartz would act as the core particle and the alumina as the surrounding particles in the heterocoagulation process. The heterocoagulation and dispersion at different pHs and the aggregate structure at pHs 5 and 7 were verified by the scanning electron microscope analysis. The heterocoagulation and dispersion of alumina and quartz at different pHs can be accounted for by the interparticle force revealed by force analysis in the framework of the Deyaguin-Landau-Verwey-Overbeek theory.

Mechanochemical synthesis and in vitro studies of chitosan-coated InAs/ZnS mixed nanocrystals

In this paper, InAs/ZnS mixed nanocrystals were synthesized by dry high-energy milling approach in the first step. The obtained nanocrystals were characterized from structural point of view by X-ray diffraction analysis and Raman spectroscopy, and from the morphological point of view by scanning electron microscopy. In the next step, the nanocrystals were subjected to wet ultra-fine milling in order to obtain a nanosuspension of chitosan-coated InAs/ZnS nanocrystals with bio-imaging properties. The stability of the nanosuspension was examined by zeta potential and particle size distribution measurements. The prepared nanosuspension was stable with high values of zeta potential. Its optical properties were also studied using UV–Vis and PL spectroscopies. The determined fluorescent properties confirming the potential in bio-imaging applications were verified on cancer cell lines Caco-2, HCT116, HeLa, and MCF7.

Dispersion and microwave processing of nano-sized ITO powder for the fabrication of transparent conductive oxides

Aqueous dispersions of tin-doped indium oxide (ITO) nanopowder were prepared and the effect of the addition of PEG 400, Tween 80 and β-alanine as dispersants was investigated using zeta potential and particle size distribution measurements. Both PEG 400 and β-alanine were found to produce stable dispersions that were used to deposit ITO thin films on glass substrates by dip and spin coating methods. The ITO thin films were heat-treated using both conventional and microwave heat treatment in order to improve the inter-particle connections and hence the resistivity and transparency of the films. All the films exhibited an average transmittance of >80% over the visible spectrum after being subjected to the heat treatment process. ITO films prepared with no dispersant showed very high resistivity values for both heating methods, however addition of 2wt% PEG 400 to the dispersion yielded a reduction in the resistivity values to 1.4×10−1Ωcm and 3.8×10−2Ωcm for conventionally and microwave treated films, respectively. The surface morphological studies confirmed that addition of dispersants improved the film uniformity and inter-particle connections of the ITO films considerably.