Zeta Potential Distribution Research Articles

Interaction of salicylhydroxamic acid with the surface of MgTi2O5: a study combined DFT and experiment

Salicylhydroxamic acid (SHA) is a typical chelate collector. This study elucidated the effect of steric hindrance on SHA adsorption on the MgTi2O5 surface using density functional theory. The geometry optimisation and electronic structures of SHA ion and the MgTi2O5 (110) surface were calculated. Subsequently, six adsorption configurations of SHA ion on the MgTi2O5 (110) surface were calculated and compared by analysing geometric configuration, bond length, adsorption energy, density of states (DOS), and Mulliken population. The results show that both the oxygen molecules of C╱╲=O and N╱╲O− in SHA ion can coordinate to the metal ion. Steric hindrance affects the formation of a five-membered ring structure. The four adsorption configurations of the newly established structure can effectively avoid steric hindrance, and stable chelate rings are formed. The adsorption energies of the four new configurations range from −300 kJ/mol to −400 kJ/mol, and the bond lengths are about 2 Å. DOS and Mulliken population results indicate that O atoms bond to Ti and Mg atoms. Traditional chelate collector adsorption theory ignores the presence of steric hindrance. At the same time, the species distribution of SHA solution, zeta potential and flotation have also been studied in this paper, and there is a consistency between the calculation and experiment results. This study provides insights into the adsorption mechanism of a chelate collector on a mineral surface.

Water Repellency Decreases Vapor Sorption of Clay Minerals

AbstractAs soils become dry, water primarily exists as vapor that adsorbs to and desorbs from particle surfaces. The drying process also often enhances soil water repellency, yet the effects of repellency on soil water vapor sorption and exchange are not well understood. The objective of this study was to quantify the water vapor sorption dynamics of two minerals (Ca2+ saturated kaolinite and montmorillonite), in which water repellency was induced using two organic agents: cetyl trimethylammonium bromide (~4% by mass) and stearic acid (0.5%, 5%, 10%, 20%, and 35% by mass). Samples were then analyzed for water vapor sorption isotherms, solid‐water contact angles, organic carbon content, mineral surface morphology, hydrophobic functional groups (using Fourier transform infrared spectroscopy), zeta potential, and particle size distributions. The results showed that the water repellent treatments altered particle surface potentials and decreased surface areas relative to the controls. As a result, those samples adsorbed significantly less water and had less hysteresis between adsorption and desorption isotherms than the nontreated controls (p < 0.05). Differences in water adsorption were most pronounced for water activities >0.6, where hydrophobic compounds may have inhibited water vapor condensation, even at low concentrations. In contrast, solid‐water contact angles were small in montmorillonite treatments with <10% stearic acid, suggesting that low levels of hydrophobic compounds may have greater effect on vapor sorption compared to liquid water imbibition. Altogether, these results imply that repellency may reduce water retention in dry soils and enhance water vapor losses.

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.

Effect of counterion on the properties of anionic waterborne polyurethane dispersions developed from cottonseed oil based polyol

A series of maleated cottonseed oil polyol (MAHCSO) based, DMPA (dimethylol propionic acid) free, catalyst free waterborne polyurethane dispersions (PUDs) were synthesized. Four different tertiary amines, were employed as neutralizing agents to investigate the role of countercation on the physico-chemical properties of PUDs and their corresponding cured films. The developed PUDs were characterized by particle size analysis, zeta potential distribution, viscosity and storage stability and the cured film samples were characterized by FT-IR (ATR), DMTA (Dynamic mechanical and thermal analysis), UTM (Universal testing machine) and contact angle analyses. It was found that the waterborne PUD with countercation having more number of hydroxy alkyl chains exhibit a larger particle size, a less negative zeta potential, higher viscosity and lower storage stability, where as the corresponding cured film possesses lower thermal stability, mechanical strength and poor surface properties.

Interaction Mechanism between Molybdenite and Kaolinite in Gypsum Solution Using Kerosene as the Flotation Collector

This paper aims to understand the fundamental interaction mechanism between molybdenite and kaolinite in gypsum solution using kerosene as collector. Micro-flotation tests were conducted to study the effect of gypsum solution on the flotation performance of mixed −74 μm molybdenite and −10 μm kaolinite mineral. The results showed that the recovery of molybdenite decreased from 86% to 74% while the gypsum solution concentration increased from 0 to 800 mg/L, indicating the detrimental effect of kaolinite on molybdenite flotation could be enhanced by gypsum solution. This is mainly caused by the slime coating of kaolinite on molybdenite through dissolved calcium ion of gypsum solution. In order to confirm the slime coating phenomenon, zeta potential distribution, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were used to investigate interaction characteristics and mechanisms. The zeta potential distribution results revealed that mixed samples had the value between signal molybdenite and kaolinite samples in gypsum solution, which proved the coating phenomenon of kaolinite on molybdenite. Moreover, the coating phenomenon was becoming more and more obvious with the gypsum solution concentration. The coating phenomenon of kaolinite on molybdenite surface was also directly observed from SEM results. The AFM results provided further evidence for the possibility of slime coating, as the adhesion force increased with the gypsum solution concentration, which means the aggregates of molybdenite and kaolinite were becoming more stable.

Stability testing of silver nanodisc suspensions for solar applications

In solar and optical applications, nanofluids can be exposed to intense light, high temperature, and variable pH levels. Over time these forces can destabilize particle suspensions by altering particle morphology, breaking functional groups, and inducing agglomeration. Since UV exposure has been a critical unknown for nanoparticle suspension stability in solar and optical applications, a modified ISO standard UV accelerated lifetime test method was developed and applied herein. Aqueous formulations of protective silica shells over silver nanodiscs (relative to unprotected silver) were investigated as indicative non-spherical nanoparticles that might be expected to survive these perturbations. As such, the dispersion stability of these suspensions was investigated before and after exposure to elevated temperature, UV light, and pH levels. Dispersion stability was determined using a few techniques – changes in spectral transmission, zeta potential, and particle size distribution via nanoparticle tracking analysis. A protective shell of silica deposited via a modified Stöber (using tetraethyl-orthosilicate – TEOS) method was found to provide stability against temperature, UV, and pH exposure, whereas uncoated silver nanoparticles or those with a shell grown using a sodium silicate silica source were considered relatively unstable. The TEOS silica shells also exhibited a beneficial UV curing effect, which can be explained by increased crosslinking throughout UV exposure.

Effect of Nanoplatelet Size on the Colloidal Stability of Coupled Nanocomposite of TiO2 and Zirconium Phosphate Nanoplatelets

The aggregation and sedimentation of nanoparticles affect the dispersion stability and application of nanosuspension. TiO2 nanoparticles were coupled on zirconium phosphate (ZrP) disks with different diameters to study the effect of ZrP size on the dispersion stability of nanocomposite suspensions. Four suspensions, namely, TiO2 nanosuspensions and three exfoliated TiO2 ‒ ZrP nanocomposite suspensions with diameters of 729.6, 1004.5 and 1168.5 nm were prepared. Dispersion stability was compared among the suspensions. The zeta potential, viscosity, particle morphology and particle size distribution of the suspensions were also tested to analyze the stability mechanism of the nanocomposite suspensions. Results of the stability tests within 100 days show that the TiO2 ‒ ZrP nanocomposite suspensions exhibited slower sedimentation, higher ultraviolet-visible absorbance, smaller light transmission and backscattering variation and lower Turbiscan Stability Index than those of the pure TiO2 suspension. Among the samples, the smallest TiO2 ‒ ZrP nanocomposites exhibited improved stability. The absolute zeta potential and viscosity of each nanocomposite suspension were comparable with one another, but higher than those of the TiO2 suspension. The transmission electron microscope images and particle size distribution suggest that TiO2 ‒ ZrP can better control the aggregation of small TiO2 nanoparticle clusters. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.18154

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.

Microwave assisted rapid green synthesis of gold nanoparticles using Annona squamosa L peel extract for the efficient catalytic reduction of organic pollutants

Here we demonstrate a rapid green synthetic approach for the production of gold nanoparticles (AuNPs) using microwave irradiation, in which Annona squamosa L (AS) fruit waste extract served as a sole agent for both reduction and stabilization. Synthetic conditions were optimized by monitoring the changes surface plasmon resonance (SPR) peak, zeta potential and DLS size distribution. TEM results revealed that under optimized synthetic conditions monodispersed and spherical nanoparticles with average diameter of 5 ± 2 nm could be achieved. The possible mechanism involved in the formation of AuNPs was interpreted by FTIR. The formed AuNPs dispersion remained stable to environmental conditions like temperature, ionic strength and pH of the medium and exhibited high shelf life. Further they exhibited admirable catalytic activity for the efficient reduction of Congo red & Methylene Blue and 4-Nitrophenol in the presence of NaBH4, which is stable even after five cycles of reaction.

Slime coating of kaolinite on chalcopyrite in saline water flotation

In saline water flotation, the salinity can cause a distinguishable slime coating of clay minerals on chalcopyrite particles through its effect on their electrical double layers in aqueous solutions. In this work, kaolinite was used as a representative clay mineral for studying slime coating during chalcopyrite flotation. The flotation of chalcopyrite in the presence and absence of kaolinite in tap water, seawater, and gypsum-saturated water and the stability of chalcopyrite and kaolinite particles in slurries are presented. Zeta-potential distributions and scanning electron microscopy images were used to characterize and explain the different slime coating degrees and the different flotation performances. Kaolinite particles induced slime coating on chalcopyrite surfaces and reduced chalcopyrite floatability to the greatest extent when the pH value was in the alkaline range. At 0.24wt% of kaolinite, the chalcopyrite floatability was depressed by more than 10% at alkaline pH levels in tap water. Salinity in seawater and gypsum-saturated water compressed the electrical double layers and resulted in extensive slime coating.

Synthesis and characterization of cationic carbon black pigment with quaternary ammonium groups and its dyeing properties for wool fabrics

In this paper, the cationic carbon black pigment with quaternary ammonium groups was fabricated via the quaternization reaction of N,N-dimethyldodecylamine and epichlorohydrin-modified CB@SiO2 core-shell structure composites. The CB@SiO2 composites were prepared by stöber method using tetraethyl orthosilicate as precursor and carbon black (CB) nanoparticles as core. Scanning and transmission electron microscopic techniques (SEM & TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction method (XRD), thermogravimetric analysis (TGA), zeta potential and particle size distribution were employed to characterize the structure and properties of the cationic CB pigment as well as the intermediates. When the molar ratio of TEOS to epichlorohydrin to N,N-dimethyldodecylamine was 1:2.5:2.5, the zeta potential of the cationic CB pigment in aqueous dispersion reached the maximum +48 mv. The average diameter of the cationic CB pigment was ca. 45 nm with ca. 9 nm thickness of shell. Wool fabrics were dyed with the optimum cationic CB pigment through exhaust dyeing process. The L*a*b* values and the color appearance of dyed wool fabrics showed that the cationic CB-dyed wool fabrics had darker black and better fastness properties than the pristine CB-dyed wool fabrics.

A label-free cellulose SERS biosensor chip with improvement of nanoparticle-enhanced LSPR effects for early diagnosis of subarachnoid hemorrhage-induced complications

It is very difficult to predict some complications after subarachnoid hemorrhage (SAH), despite rapid advances in medical science. Herein, we introduce a label-free cellulose surface-enhanced Raman spectroscopy (SERS) biosensor chip with pH-functionalized, gold nanoparticle (AuNP)-enhanced localized surface plasmon resonance (LSPR) effects for identification of SAH-induced cerebral vasospasm and hydrocephalus caused by cerebrospinal fluid (CSF). The SERS biosensor chip was implemented by the synthesis reaction of the AuNPs, which were charged positively through pH level adjustment, onto a negatively-charged cellulose substrate with ξ = –30.7 mV. The zeta potential, nanostructural properties, nanocrystallinity, and computational calculation-based electric field distributions of the cellulose-originated AuNPs were optimized to maximize LSPR phenomena and then characterized. Additionally, the performance of the SERS biosensor was compared under two representative excitation laser sources in the visible region (532 nm) and near-infrared region (785 nm). The Raman activities of our SERS biosensor chip were evaluated by trace small molecules (crystal violet, 2 µL), and the biosensor achieved an enhancement factor of 3.29 × 109 for the analytic concept with an excellent reproducibility of 8.5% relative standard deviation and a detection limit of 0.74 pM. Furthermore, the experimental results revealed that the five proposed SERS-based biomarkers could provide important information for identifying and predicting SAH-induced cerebral vasospasm and hydrocephalus complications (91.1% reliability and 19.3% reproducibility). Therefore, this facile and effective principle of our SERS biosensor chip may inspire the basis and strategies for the development of sensing platforms to predict critical complications in various neurosurgical diagnoses.

Effect of electrolytes on electrokinetics and flocculation behavior of bentonite-polyacrylamide dispersions

Abstract In this study, the influence of electrolytes on bentonite dispersions flocculated with different polyacrylamides varying in charge type, density and molecular weights has been investigated. The presence of electrolytes was found to induce profound impact on the flocculation behavior of bentonite-polyacrylamide dispersions, which was analyzed by means of residual turbidity, zeta potential and floc size distribution tests. Electrolytes enhanced the adsorption of anionic polyacrylamide chains on negative bentonite surface, while hindering adsorption of cationic polyacrylamides. Electric double layer compression and mediated flocculation by metal cations were the principle mechanisms involved in the improvement of flocculation behavior. High molecular weight and charge density variants greatly reduced the turbidity and negative zeta potential of dispersions for anionic polyacrylamides. Furthermore, charge density of metal ions was found to be a determining factor. Divalent salts were more efficient for flocculating dispersions using anionic polyacrylamides, while monovalent salts were preferable for cationic polyacrylamides owing to electrostatic repulsions. Amphoteric polyacrylamides displayed similar results based on their anionic/cationic nature. Similar observations were recorded for floc size measurements. High charge density variants of anionic polyacrylamides in the presence of divalent salts like CaCl2 produced large flocs. On the other hand, no significant changes in floc sizes were observed for cationic polyacrylamides in the presence of salts. Overall, this study successfully determines the effect of electrolytes on the flocculation behavior of bentonite dispersions.

Prediction of hydrocarbon yield from wet Botryococcus braunii: The influences of colony surface charge and diameter on the amount of extractable hydrocarbon

A colonial microalga, Botryococcus braunii synthesizes extracellular polysaccharides (EPS) forming a sheath around its colonies, which limits the extraction of hydrocarbons from this microalga. As thermal or mechanical pretreatment of B. braunii improves the hydrocarbon yield, the EPS removal and degree of algal colony disruption before and after pretreatment were evaluated using zeta potential and particle size distribution (PSD) to predict hydrocarbon yield from the alga. Since zeta potential can evaluate the ionizable state of particles, the zeta potential of B. braunii would be able to evaluate the removal degree of EPS and this feature had the potential to determine hydrocarbon yield quickly. The zeta potential of algal samples without pretreatment was −30.5 mV at pH 9, whereas that with pretreatment ranged from −29.7 to −18.8 mV. The elevation of zeta potential and EPS removal had a linear relationship (R-squared value = 0.96). The hydrocarbon yields exponentially increased in proportion to the degree of colony disruption after mechanical treatments (R-squared value = 0.81). These findings suggest that the zeta potential and PSD of B. braunii may be used as indicators for EPS removal and hydrocarbon yield.

Electromagnetohydrodynamic flow in a rectangular microchannel

Recently, electromagnetohydrodynamic (EMHD) flow has often been exploited for fluid transport in narrow confinements through combined electrokinetic and electromagnetic actuation mechanisms. This study aims to theoretically investigate the EMHD flow through a rectangular microchannel. Analytical solutions expressed in the form of eigenfunction expansions are derived, which are determined by the Debye parameter, the Hartmann number, the aspect ratio of the channel, the deviation angle between the channel and the imposed electric field, and the distribution of zeta potentials on channel walls. The influences of these factors on primary and secondary flows are critically examined. Compared with the flow through two-infinite-plate channel, the lateral walls of the rectangular channel have significant effects on both primary and secondary flows. It is also revealed that, by horizontally placing the channel along a direction that deviates from the imposed electric field by an angle, a remarkable increment of the primary flow rate can be achieved without improving the strength of the electric field. The findings in the present study may help one to look for a suitable configuration for the optimum performance of EMHD-based micropumps.

Electrophoretic deposition of plasma activated sub-micron alumina powder

The positive effect of plasma mediated treatment of powder fraction in water-based dispersion is a rather well documented fact. Despite its importance for ceramic processing, the applicability of plasma treatment of ceramic particles in a non-aqueous dispersions remains unexplored. In the presented article, a specific planar type of dielectric barrier discharge - Diffuse Coplanar Surface Barrier Discharge (DCSBD), operated in atmospheric pressure air was used for the surface activation of sub-micron alumina particles. These were consequently dispersed in organic solvent of 2-propanol and evaluated for the performance during the process of electrophoretic deposition (EPD). The surface of ceramic particles and the dispersion behaviour were investigated using thermogravimetric analysis, XPS, measurement of zeta potential and particle size distribution. Plasma treatment of ceramic particles had a substantial effect on the deposition rate, which caused a significant reduction of surface roughness and slight improvement of the density and mean grain size of the fabricated coatings. Moreover, the plasma treatment resulted in a simultaneous anodic and cathodic EPD.

Production and Characterization of Superhydrophobic and Antibacterial Coated Fabrics Utilizing ZnO Nanocatalyst

Dirt and microorganisms are the major problems in textiles which can generate unpleasant odor during their growth. Here, zinc oxide (ZnO) nanoparticles prepared by sol-gel method were loaded on the cotton fabrics using spin coating technique to enhance their antimicrobial properties and water repellency. The effects of ZnO precursor concentration, precursor solution pH, number of coating runs, and Mg doping percent on the structures, morphologies, and water contact angles (WCA) of the ZnO-coated fabrics were addressed. At 0.5 M concentration and pH7, more homogeneous and smaller ZnO nanoparticles were grown along the preferred (0 0 2) direction and uniformly distributed on the fabric with a crystallite size 17.98 nm and dislocation density 3.09 × 10−3 dislocation/nm2. The substitution of Zn2+ with Mg2+ ions slightly shifted the (002) peak position to a higher angle. Also, the zeta potential and particle size distribution were measured for ZnO nanoparticle suspension. A superhydrophobic WCA = 154° was measured for the fabric that coated at 0.5 M precursor solution, pH 7, 20 runs and 0% Mg doping. Moreover, the antibacterial activities of the ZnO-coated fabric were investigated against some gram-positive and gram-negative bacteria such as Salmonella typhimurium, Klebsiella pneumonia, Escherichia coli, and Bacillus subtilis.

Effects of Zn/B nanofertilizer on biophysical characteristics and growth of coffee seedlings in a greenhouse

The effects of Zn/B nanofertilizer on the biophysical characteristics and growth of coffee seedlings in a greenhouse were investigated. Zn/B nanofertilizer was prepared by loading ZnSO4 and H3BO3 on a chitosan nanoparticles emulsion that was prepared by ionic gelation with tripolyphosphate. The nanofertilizer was characterized by TEM, SEM, zeta potential value and size distribution. The nanofertilizer was sprayed on the leaves of coffee seedlings in five different doses of 0, 10, 20, 30 and 40 ppm. Application of the nanofertilizer enhanced the uptake of zinc, nitrogen and phosphorus. The results were found to increase the chlorophyll content and photosynthesis of the coffee. Finally, the nanofertilizer promoted growth of the coffee plants in the leaf area, height of plant and stem diameter. The nanofertilizer seems to be a great potential foliar feed for the growth of coffee and other plants.

Matrix effect in case of purification of oily waters by membrane separation combined with pre-ozonation.

In the present study, oil in water emulsions (coil = 100ppm; doil droplets < 2μm) was purified with ozonation followed by microfiltration using polyethersulfone (PES) membrane (dpore = 0.2μm). The effects of pre-ozonation on membrane microfiltration were investigated in detail both in case of ultrapure and model groundwater matrices, applying different durations (0, 5, 10, and 20min) of pre-ozonation. Simultaneously, the effects of added inorganic water components on the combined method were investigated. Size distribution of oil droplets, zeta potentials, fluxes, and purification efficiencies were measured and fouling mechanisms were described in all cases. It was found that the matrix significantly affected the size distribution and adherence ability of oil droplets onto the membrane surface, therefore fouling mechanisms also were strongly dependent on the matrix. In case of low salt concentration, the total resistance was caused mainly by reversible resistance, which could be significantly reduced (eliminated) by pre-ozonation. In case of model groundwater matrix, nearly twice higher total resistance was measured, and irreversible resistance was dominant, because of the higher adhesion ability of the oil droplets onto the membrane surface. In this case, pre-ozonation resulted in much lower irreversible, but higher reversible resistance. Increased duration of pre-ozonation raised the total resistance and reduced the elimination efficiency (due to fragmented oil droplets and water soluble oxidation by-products) in both cases, therefore short pre-ozonation can be recommended both from economic and performance aspects.

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.