Fine Particles In Water Research Articles

Characterization of aggregation and declustering tendency of hydrophobic fine particles in water

When hydrophobic particles are added to water, they form clusters by interparticle gas bridging. The hydrostatic, capillary and buoyancy forces acting on the submerged clusters can gradually mobilize the interparticle gas bubbles. As particles are released from the cluster gradually, the cluster is transformed into slurry state. We studied the clustering and declustering characteristics of hydrophobic granular particles (dyed quartz sand with 0.33 mm and 0.73 mm in diameter), which were applied to the water surface and submerged after forming clusters. Behavior of the particle clusters was evaluated to characterize (1) clustering tendency of particles, and (2) gradual particle declustering by mobilization, coalescence and release of air bubbles from the submerged cluster. Cluster formation and declustering rates of the particles were evaluated based on the experimental data and observations. Clustering tendency of the particles depends on the surface tension characteristics (or spreading tendency) of the particles on the water surface. On the other hand, stability of the submerged cluster is highly dependent on the surface roughness which we propose affects the ability of the microbubbles to coalesce within the submerged cluster. Particle cohesion coefficient for clustering tendency and particle declustering rate for transformation of the submerged aggregate to slurry state were estimated from experimental data.

Agglomeration of fine particles in water upon application of DC electric field

The influence of the properties of a slurry on the flocculation behaviour of fine particles in water upon the application of a DC electric field was investigated. In addition, the mechanism whereby particles in water can be flocculated through the application of the DC electric field was clarified. The particle flocculation efficiency was determined for aqueous and non-aqueous slurries to which a DC electric field was applied, by measuring the change in the turbidity of the sampled slurry.It is shown that, for aqueous slurries, the particle flocculation could be enhanced by applying a DC electric field provided the particles carried a charge and were surrounded by an electric double layer. It was also found that there was no enhancement of the flocculation for those slurries for which pH = pHIEP, as well as for non-aqueous slurries using rapeseed oil as their solvent, in which case the particles were not charged. In addition, merely stirring the slurry (thus increasing the number of particle collisions) did not cause the particles to flocculate, although the particle flocculation could be enhanced by applying a DC electric field while stirring the slurry, thus maintaining a constant particle concentration.These findings lead to the conclusion that the enhancement of the particle flocculation in an aqueous slurry through the application of a DC electric field is caused by the charged particles and their counter ions in an electric double layer forming an electric dipole due to the deformation of the electric double layer, thus creating an electrostatic attractive force between the particles.

Comparison of the behaviour of various geotextiles used in the filtration of clayey sludge: An experimental study

This paper presents the results of an experimental study of various geotextiles used to filter clayey sludge. The use of geotextiles to filter clayey sludge or suspensions of fine particles in water is more complex than that for filtering suspensions of granular soils. In practice, such applications generally use flocculants to postpone the formation of a low-permeability filter cake. The objective of the present study, which does not use flocculants, is to determine how geotextile characteristics affect the capacity of the geotextile to filter clayey sludge. Three key questions are addressed: (1) What are the main differences between vertical and horizontal filtration? (2) How do geotextile characteristics (nature, opening size, permeability, etc.) affect its capacity to filter clayey sludge (3) How do clayey sludge characteristics (i.e., grain size distribution and concentration)? and the type of flow (i.e., constant head or constant flow) affect the filtering capacity of geotextiles? To evaluate the capacity of a geotextile to filter clayey sludge, we propose three relevant criteria and analyse two filtration phases induced by different cake-formation processes (controlled by the geotextile and controlled by the filter cake). To determine the main differences between vertical and horizontal filtration, the settling of fines in the testing device and its influence on the results are analysed and discussed. This study shows that, for the various clayey sludge tested, the geotextiles (needle-punched nonwoven and thermally bonded nonwoven) with the smallest opening sizes (O90 ≤ 60 μm) give the most promising results for filtering fines without the use of flocculants. Of these geotextiles, the thermally bonded nonwoven structure seems to offer the best filtration performance for the largest range of fines concentration in the sludge.

Developing a method of fabricating microchannels using plant root structure

Complicated three-dimensional (3D) microchannels are expected to be applied to a lab-on-a-chip, especially an organ-on-a-chip. There are fine microchannel networks such as blood vessels in a living organ. However, it is difficult to recreate the complicated 3D microchannels of real living structures. Plant roots have a similar structure to blood vessels. They spread radially and three-dimensionally, and become thinner as they branch. In this research, we propose a method of fabricating microchannels using a live plant root as a template to mimic a blood vessel structure. We grew a plant in ceramic slurry instead of soil. The slurry consists of ceramic powder, binder and water, so it plays a similar role to soil consisting of fine particles in water. After growing the plant, the roots inside the slurry were burned and a sintered ceramic body with channel structures was obtained by heating. We used two types of slurry with different composition ratios, and compared the internal channel structures before and after sintering.

Delamination of Na-montmorillonite particles in aqueous solutions and isopropanol under shear forces

ABSTRACTDelamination of montmorillonite (Na-MMT) is an outstanding property of the dispersed MMT particles. Na-MMT particles delaminated in water and isopropanol under shear forces have been studied in this work. The difference in the intercalation and delamination of Na-MMT by water and isopropanol was studied by molecule dynamic simulation and experiment. Molecule dynamic simulation was carried out on Material Studio (MS) 8.0. The experimental study was performed on a Na-MMT through the measurements of Stokes size, optical size, scanning electron microscope, atomic force microscope, and dynamic molecule simulation. The results demonstrated that under the effect of interlayer hydration, the Na+ that resides near the siloxane surface was moved to the middle plane of interlayer space, and the interlayer spacing was opened 1.38A. Compared with the interlayer hydration, the interlayer spacing was increased only a little (0.32A) treated by isopropanol; meanwhile, the interlayer sheets were joined together by isopropanol molecule. Because of that the effect of water and isopropanol in the interlayer of Na-MMT was totally different, the Na-MMT particles were indeed delaminated into plate-like super fine particles in water instead of in isopropanol, and delamination was closely correlated with shear force only if hydration was occurred in the interlayer.

Factors involving the solids-carrying flotation capacity of microbubbles

Dissolved air flotation (DAF) is a technique used extensively for separating fine particles in water and wastewater treatment, but, unfortunately, its use is still limited for froth flotation of minerals. This appear to be due to the very low lifting power of the microbubbles (40–70μm) and low airflow rate because of the low solubility of air in water. Thus, the efficiency of DAF in treating mineral particles has shown to be poor and as a solid/liquid separation technology is limited to slurries with no more than 3% solids. This work presents results showing (measuring) the limits of DAF as a function of particle size distribution, solids content and air superficial velocity. Interestingly, the microbubbles were found to be not selective with respect to particle size, floating both fine and coarse particles, which is most likely due to the existence of several mechanisms acting on the flotation of particles by these minute bubbles.

A contribution for predicting geotextile clogging during filtration of suspended solids

Predicting geotextile clogging by fine particles in suspension in water is possible by the use of an empirical model describing the increase of head loss in the geotextile due to clogging. The present paper describes this model and shows that it is possible to fit the model parameters and find their physical significance by means of geotextile clogging tests. This work makes it possible to estimate a maximum acceptable quantity of injected particles to the geotextile, before clogging. The model results are in good agreement with experimental results obtained for different geotextiles and soils, as well as for different concentrations of fine particles in water.

Unsaturated fatty acid content in seston and tropho-dynamic coupling in lakes.

Determining the factors that control food web interactions is a key issue in ecology. The empirical relationship between nutrient loading (total phosphorus) and phytoplankton standing stock (chlorophyll a) in lakes was described about 30 years ago and is central for managing surface water quality. The efficiency with which biomass and energy are transferred through the food web and sustain the production of higher trophic levels (such as fish) declines with nutrient loading and system productivity, but the underlying mechanisms are poorly understood. Here we show that in seston (fine particles in water) during summer, specific omega3-polyunsaturated fatty acids (omega3-PUFAs), which are important for zooplankton, are significantly correlated to the trophic status of the lake. The omega3-PUFAs octadecatetraenoic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid, but not alpha-linolenic acid, decrease on a double-logarithmic scale with increasing total phosphorus. By combining the empirical relationship between EPA-to-carbon content and total phosphorus with functional models relating EPA-to-carbon content to the growth and egg production of daphnids, we predict secondary production for this key consumer. Thus, the decreasing efficiency in energy transfer with increasing lake productivity can be explained by differences in omega3-PUFA-associated food quality at the plant-animal interface.

Characteristics of dispersion behavior of fine particles in different liquid media

The dispersion behavior of fine particles in water, ethanol and kerosene media has been studied by sedimentation analysis. It was found that the dispersion behavior of fine particles complies with the principle of polarity compatibility. The dispersion effect can be improved when the surface polarity of particles approaches that of liquid media. Adsorption models of oleic acid on the surface of particles in water and ethanol are proposed.

Dispersion characteristics of fine particles in water, ethanol and kerosene

Dispersion behavior of hydrophilic calcium carbonate particles and hydrophobic talcum particles in water, ethanol and kerosene media has been studied by sedimentation analysis. It is found that the dispersion of fine particles complies with the principle of polarity compatibility. That is to say, the dispersion effect will be improved when surface polarity of particles is similar to that of liquid media. The adsorption modets of oleic acid on the surface of particles in water and ethanol are proposed.

Carry-over of water and suspension of fines by coarser particulate solids — Its influence on the design of DMS regeneration circuits

In dense medium separation (DMS) systems, a particulate (ore or coal) is treated in a suspension of fine particles in water having a density intermediate between the densities of the mineral phases to be separated. During the process the water and the fine particles constituting the medium adhere to the coarse particles and are carried over from the draining to the washing screen, so that they are extracted from the medium circuit. This extraction is selective, i.e., it is different for water and solids particles; it depends on the size of the particulate and on the viscosity and density of the medium stream considered. For a correct design of the medium regeneration circuit it is important to know all the above mentioned data. Therefore laboratory research was performed in order to determine the carry-over of fine particles and water due to a particulate. The paper reports the results of this research and gives information useful for the analysis and the design of medium circuits of dense medium separation plants.

分散剤の最適濃度の一決定法

The optimum dispersive condition for fine particles in water was determined from the measurements of the zeta potential, the mass and specific volume of sediments and the particle size distribution at concentrations of sodium-hexametaphosphate, Na-HMP showing strong dispersive power. As a result, it was recognized that the optimum dispersion was established at the concentration of Na-HMP giving the lowest specific volume of sediment which has already been known and also at the concentration of Na-HMP giving the lowest mass of sediment. Therefore, it seems that this method of finding a Na-HMP concentration to give the lowest mass of sediment could be adopted to conveniently determine the optimum concentration of a dispersant.

カ焼造粒モンモリロナイトによる放射性イオンの吸着

Although montmorillonite has a high cation exchange capacity, it has undesirable characteristics such as swelling and disintegrating into very fine particles in water, which causes the difficulty to separate them from aqueous phase. To improve these faults, a new stable exchanger has been prepared by the calcination of granular montmorillonite.The decrease of ion exchange capacity due to the calcination was improved by the treatment with hydrochloric acid or sodium hydroxide.It was foud that the Na-form exchanger treated with sodium hydroxide was excellent in the exchange capacity and the decontamination factor for radioactive ions. The linear relationship was foud between the concentration of co-existing Na ion and the adsorbed equilibrium of 137Cs on the montmorillonite, and also between breakthrough ratio of radioactive ion and the effluent volume in the range of rather low breakthrough ratio. It is possible to adopt this new product for the decontamination of radioactive ion in water by the column operation process.