Some effects of particle size in separation processes involving colloids

1997 ◽  
Vol 36 (4) ◽  
pp. 119-126 ◽  
Author(s):  
Charles R. O'Melia ◽  
Melinda W. Hahn ◽  
Cheng-Tyng Chen
Keyword(s):  
Particle Size ◽  
Mass Transport ◽  
Brownian Dynamics ◽  
Colloidal Particles ◽  
Colloidal Particle ◽  
Virus Transport ◽  
Separation Processes ◽  
Partial Explanation ◽  
Reversible Aggregation ◽  
Deposition Processes

The size of colloidal particles has long been considered to be a major factor in their mass transport in aquatic environments. In aggregation and deposition reactions, the mass transport rates of colloidal particles are expected to decrease with increasing particle size since thermal diffusion dominates this process. Particle size has also been considered to affect colloid chemical interactions, at least on theoretical grounds, with predicted rates of attachment in aggregation and deposition processes decreasing substantially as colloidal particle size is increased. Observations have failed to confirm this prediction. The situation becomes more complex and predictions more consistent with observations when reversible aggregation and deposition such as can occur in secondary minima are considered. This is done in this paper in simulations using a combination of Brownian dynamics and Monte Carlo (BDMC) techniques. Some experimental observations of virus transport in porous media are presented. The BDMC simulations provide a partial explanation for these results.

scholarly journals Impact of Particle Size Distribution of Colloidal Particles on Contaminant Transport in Porous Media

2019 ◽  
Vol 9 (5) ◽  
pp. 932 ◽  
Author(s):  
Jongmuk Won ◽  
Dongseop Lee ◽  
Khanh Pham ◽  
Hyobum Lee ◽  
Hangseok Choi
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Contaminant Transport ◽  
Colloidal Particles ◽  
Colloidal Particle ◽  
Transport Model ◽  
Breakthrough Curves ◽  
The Mean ◽  
The Impact

The presence of retained colloidal particles causes the retardation of contaminant transport when the contaminant is favorably adsorbed to colloidal particles. Although the particle size distribution affects the retention behavior of colloidal particles, the impact of particle size distribution on contaminant transport has not been reported to date. This study investigates the impact of the particle size distribution of the colloidal particles on contaminant transport through numerical simulation by representing the particle size distribution as a lognormal distribution function. In addition, the bed efficiency and contaminant saturation of simulated breakthrough curves were calculated, and a contaminant transport model with the Langmuir isotherm for the reaction between the contaminant–sand and contaminant–colloidal particle was introduced and validated with experimental data. The simulated breakthrough curves, bed efficiency, and contaminant saturation indicated that an increase in the mean and standard deviation of the particle size distribution causes the retardation of contaminant transport.

scholarly journals Modeling and theoretical description of magnetic hybrid materials—bridging from meso- to macro-scales

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Andreas M. Menzel ◽  
Hartmut Löwen
Keyword(s):  
Colloidal Particles ◽  
Colloidal Particle ◽  
Theoretical Description ◽  
Point Of View ◽  
Material Behavior ◽  
Theoretical Point ◽  
Mechanical Stiffness ◽  
Theoretical Approaches ◽  
Theoretical Predictions ◽  
Particle Level

Abstract Magnetic gels and elastomers consist of magnetic or magnetizable colloidal particles embedded in an elastic polymeric matrix. Outstanding properties of these materials comprise reversible changes in their mechanical stiffness or magnetostrictive distortions under the influence of external magnetic fields. To understand such types of overall material behavior from a theoretical point of view, it is essential to characterize the substances starting from the discrete colloidal particle level. It turns out that the macroscopic material response depends sensitively on the mesoscopic particle arrangement. We have utilized and developed several theoretical approaches to this end, allowing us both to reproduce experimental observations and to make theoretical predictions. Our hope is that both these paths help to further stimulate the interest in these fascinating materials.

scholarly journals Influence of size polydispersity on magnetic field tunable structures in magnetic nanofluids containing superparamagnetic nanoparticles.

2021 ◽  
Author(s):  
Dillip Kumar Mohapatra ◽  
Philip James Camp ◽  
John Philip
Keyword(s):  
Magnetic Field ◽  
Particle Size ◽  
Light Scattering ◽  
Optical Microscopy ◽  
Brownian Dynamics ◽  
Phase Contrast ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Nanofluids ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We probe the influence of particle size polydispersity on field-induced structures and structural transitions in magnetic fluids (ferrofluids) using phase contrast optical microscopy, light scattering and Brownian dynamics simulations. Three...

Stability of a Binary Colloidal Suspension and its effect on Colloidal Processing

1989 ◽  
Vol 155 ◽  
Author(s):  
Wan V. Shih ◽  
Wei-Heng Shih ◽  
Jun Liu ◽  
Ilhan A. Aksay
Keyword(s):  
Particle Size ◽  
Hard Sphere ◽  
Colloidal Particles ◽  
Colloidal Suspension ◽  
Fluid Phase ◽  
Ceramic Processing ◽  
Colloidal Processing ◽  
Interparticle Interactions ◽  
The Stability ◽  
Binary Suspension

The stability of a colloidal suspension plays an important role in colloidal processing of materials. The stability of the colloidal fluid phase is especially vital in achieving high green densities. By colloidal fluid phase, we refer to a phase in which colloidal particles are well separated and free to move about by Brownian motion, By controlling parameters such as pH, salt concentration, and surfactants, one can achieve high packing (green) densities in the repulsive regime where the suspension is well dispersed as a colloidal fluid, and low green densities in the attractive regime where the suspensions are flocculated [1,2]. While there is increasing interest in using bimodal suspensions to improve green densities, neither the stability of a binary suspension as a colloidal fluid nor the stability effects on the green densities have been studied in depth as yet. Traditionally, the effect of using bimodal-particle-size distribution has only been considered in terms of geometrical packing developed by Furnas and others [3,4]. This model is a simple packing concept and is used and useful for hard sphere-like repulsive interparticle interactions. With the advances in powder technology, smaller and smaller particles are available for ceramic processing. Thus, the traditional consideration of geometrial packing for the green densities of bimodal suspensions may not be enough. The interaction between particles must be taken into account.

scholarly journals Electric double layer and electrokinetic potential of pectic macromolecules in sugar beet

2008 ◽  
pp. 21-28
Author(s):  
Tatjana Kuljanin ◽  
Ljubinko Levic ◽  
Nevena Misljenovic ◽  
Gordana Koprivica
Keyword(s):  
Sugar Beet ◽  
Double Layer ◽  
Electric Double Layer ◽  
Colloidal Particles ◽  
Colloidal Particle ◽  
Electrokinetic Potential ◽  
Shear Plane ◽  
Colloidal System ◽  
Cu Ions ◽  
Measurable Property

Electrokinetic potential is an important property of colloidal particles and, regarding the fact that it is a well defined and easily measurable property, it is considered to be a permanent characteristic of a particular colloidal system. In fact, it is a measure of electrokinetic charge that surrounds the colloidal particle in a solution and is in direct proportion with the mobility of particles in an electric field. Gouy-Chapman-Stern-Graham's model of electric double layer was adopted and it was proven experimentally that the addition of Cu++ ions to sugar beet pectin caused a reduction in the negative electrokinetic potential proportional to the increase of Cu++ concentration. Higher Cu++ concentrations increased the proportion of cation specific adsorption (Cu++ and H+) with regard to electrostatic Coulombic forces. Consequently, there is a shift in the shear plane between the fixed and diffuse layers directed towards the diffuse layer, i.e. towards its compression and decrease in the electrokinetic potential or even charge inversion of pectin macromolecules.

scholarly journals Probing roto-translational diffusion of small anisotropic colloidal particles with a bright-field microscope

2021 ◽  
Vol 44 (4) ◽  
Author(s):  
Fabio Giavazzi ◽  
Antara Pal ◽  
Roberto Cerbino
Keyword(s):  
Particle Size ◽  
Rotational Motion ◽  
Colloidal Particles ◽  
Aqueous Suspension ◽  
Translational Motion ◽  
Translational Diffusion ◽  
Experimental Demonstration ◽  
Bright Field ◽  
Microscopic Scale ◽  
Bright Field Microscopy

Abstract Soft and biological materials are often composed of elementary constituents exhibiting an incessant roto-translational motion at the microscopic scale. Tracking this motion with a bright-field microscope becomes increasingly challenging when the particle size becomes smaller than the microscope resolution, a case which is frequently encountered. Here we demonstrate squared-gradient differential dynamic microscopy (SG-DDM) as a tool to successfully use bright-field microscopy to extract the roto-translational dynamics of small anisotropic colloidal particles, whose rotational motion cannot be tracked accurately in direct space. We provide analytical justification and experimental demonstration of the method by successful application to an aqueous suspension of peanut-shaped particles. Graphic abstract

scholarly journals Experimental and statistical study for leaching of niobium pentoxide from Pakistani ore

2018 ◽  
Vol 24 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Muhammad Irfan ◽  
Muhammad Ahmad ◽  
Sadia Akhtar ◽  
Muhammad Khan ◽  
Muhammad Khan
Keyword(s):  
Particle Size ◽  
Reaction Temperature ◽  
Batch Reactor ◽  
Niobium Pentoxide ◽  
Mass Ratio ◽  
Separation And Purification ◽  
Separation Processes ◽  
Separation Science ◽  
Low Concentration ◽  
Environmentally Friendly Process

The growing demand for niobium pentoxide, based on its use in separation processes, established its prominent significance as a leading candidate in the field of separation science and technology. This study reports the extraction of niobium pentoxide from pyrochlore ore occurring in Sillai Patai, KPK, Pakistan. It is difficult to recover niobium pentoxide from Pakistani ore due to its low concentration. Niobium pentoxide is an important material used in manufacturing industries for different purposes. Most of the commercially employed extraction processes are associated with serious environmental impacts and are not efficient in extracting niobium pentoxide from low concentration pyrochlore. Alkali potash has been used for separation and purification of niobium pentoxide because it is efficient and an environmentally friendly process. The leaching of niobium pentoxide is carried out in a batch reactor using alkali potash as a leachant. Various process parameters, including ore particle size, reaction temperature, reaction time and alkali to ore mass ratio, were examined statistically during the leaching process. It was observed that reaction temperature and ore particle size were more significant compared to other parameters. The maximum percent recovery of niobium pentoxide (95%) was obtained at 280?C in 90 min, while keeping the ore particle size 44 ?m and alkali to ore mass ratio of 7:1.

High Uniformity of ZnO Nanoparticles Synthesized by Surfactant-Assisted Solvothermal Technique

2015 ◽  
Vol 1131 ◽  
pp. 43-48 ◽  
Author(s):  
Atthaphon Maneedaeng
Keyword(s):  
Particle Size ◽  
Zno Nanoparticles ◽  
Colloidal Particles ◽  
Hydrothermal Reaction ◽  
Solvothermal Reaction ◽  
Exciton Peak ◽  
Solvothermal Technique ◽  
Tauc Plot ◽  
High Uniformity ◽  
Surfactant Assisted

The aim of this study is to develop the synthetic procedure of Zinc Oxide (ZnO) nanoparticles by using surfactant-assisted solvothermal technique in order to produce highly uniform nanosize of ZnO particles. The solvothermal reaction evidently produces smaller ZnO particle sizes compared with those obtained from hydrothermal reaction. The zwitterionic surfactant is employed in this work and it typically works well under extremely conditions i.e. high pH levels, strong electrolytes, and high temperature. The key success of surfactant utilization in the solvothermal reaction is to create reversed micelles which act as nanoreactors or templates. Because micelle consist of polar cores that may occupy a finite amount of water forming a water pool for ZnO nanomaterial synthesis. Synthesized ZnO nanoparticles were obtained from solvothermal reaction at 180°C and 18 hours in a hydrothermal reactor. The ZnO colloidal particles were separated by paper filter and cellulose nitrate membrane, respectively. The XRD pattern shows that the structure of the synthesized ZnO nanoparticles is hexagonal wurtzite and the use of surfactant does not interfere the crystal growth and structure. The particle size distribution reveals a high uniform ZnO nanoparticles obtained via this method. The UV absorption spectrum of ZnO nanoparticles synthesized by this method presents exciton peak at approximate value of 365 nanometers. The energy band gap determined by Tauc plot is 3.31 eV. Moreover, TEM images confirm the particle size consistency showing the morphology of the prepared ZnO nanoparticles.

Self and Directed Colloidal Assembly on Patterned Electrodes

2005 ◽  
Author(s):  
P. Bahukudumbi ◽  
Michael A. Bevan ◽  
Ali Beskok
Keyword(s):  
Electric Fields ◽  
Colloidal Particles ◽  
Colloidal Particle ◽  
Three Dimensional ◽  
Directed Assembly ◽  
Ordered Structures ◽  
Colloidal Assembly ◽  
Electrode Surfaces ◽  
External Electric Fields ◽  
Potential Energy Landscapes

Clustering of colloidal particles near an electrode surface during and after electrophoretic deposition has been reported in the literature [1, 2, 3, 4]. The aggregation of colloidal particles has made the precise assembly of two and three dimensional colloidal crystals possible. In this paper, we demonstrate the use of external electric fields to sensitively tune the interactions between colloidal particles to form ordered structures. The directed assembly of colloidal particles on patterned electrode surfaces is also investigated as a means of building three-dimensional nanostructures. Finally, a new method to map potential energy landscapes of templated substrates using a diffusing colloidal particle as a sensitive local energy probe is described.

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