Publications (11)30.51 Total impact
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ABSTRACT: Adsorption of charged colloidal particles to oppositely charged surfaces is usually an irreversible process. The interaction between a pair of particles can be modeled with an exponentially decaying potential originating from double layer interactions. This work explored the effect of the Debye length on monolayer structures using the integralequation theory which was successfully developed based on a binarymixture approximation to include the effect of particle size polydispersity. The theoretical results from the integral equations with a Percus–Yevick closure showed that upon increasing the Debye length, the radial distribution functions, g(r), as well as the structure factor, S(k), decreased, in good agreement with simulation results. When the effect of size distributions was investigated, the prominent peak of the radial distribution function increased nonlinearly with the product κσav, which followed the same trend as was reported for the case of the jamming coverage of the monolayer film.Physica A: Statistical Mechanics and its Applications 01/2010; · 1.68 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The adsorption of Hg(II) by natural rubber chips was investigated. First, the effect of chip size (5 mmx5 mm and 10 mmx10 mm) on the adsorption kinetics was studied. The pseudosecondorder modeling was found to explain the kinetics well. The smaller chips had higher adsorption rate so they were used for the rest of the research. Next the effects of sulfur, zinc oxide and carbon black on the adsorption capacity of Hg(II) at equilibrium conditions were investigated. The effect of sulfur was studied through different standard vulcanizing systems. The amount of zinc oxide was varied to be 3, 4 and 5 part per hundred parts of rubber (phr) while the carbon black (N330) loading was varied to be 0, 30 and 50 phr, respectively. It was found that adsorption capacity increased with the degree of crosslink density, generated by sulfur reacting with rubber molecules. In addition, the adsorption capacities of various amounts of zinc oxide corresponded with their crosslink densities while the addition of carbon black seemed to obstruct Hg(II) adsorption.Journal of Hazardous Materials 07/2008; 154(13):18. · 3.93 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In this work, the degree of reversibility in particle deposition was introduced by surface diffusion. The effect of mobile fraction of triangularwell particles on the surface among the immobile ones was explored by varying number of particles added at a time in modified sequential quenching model. It was found that at low temperatures, as the number of added mobile particles increased, the structures was composed of more compact clusters connecting to one another, thereby, decreasing the percolating density while at high temperatures, the structures are more disordered and the final structures were independent on the deposition flux, leading to the unchanged percolating density.Journal of Colloid and Interface Science 03/2008; 318(2):1529. · 3.17 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We studied the sequential quenching of prolate ellipsoids on a homogeneous surface by using our proposed pair potential whose repulsive part was that of hard ellipses and attractive part was the r6 pairwise attraction. Both the strength and range parameters for the attraction were functions of the orientations of the pair of ellipses and related by epsilon proportional, variantsigmalambda. The parameter lambda determines the relative strength of the sidebyside and endtoend attractions and thus plays an important role in determining the alignment of the particles. We adopted the value lambda=2.19 by using pointenergy additivity to compute the minimum energies for both of these configurations for a pair of ellipsoids of revolution with aspect ratio of 2:1. We investigated the effect of temperature and the parameter lambda on the alignments of ellipses. Both radial distribution function, g(r), and orientational correlation function, G(r), show the expected longer ranges of orientational correlation at lower temperatures and show higher degree of orientational order for lambda=3.5 than lambda=2.19 and 0.10. This can also be seen in the examples of configurations showing that for lambda=3.5, ellipses are more aligned than lambda=2.19 and 0.1.Journal of Colloid and Interface Science 06/2007; 309(2):38491. · 3.17 Impact Factor 
Article: Random sequential adsorption of polydisperse spherical particles: An integralequation theory
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ABSTRACT: Our previously developed integralequation theories were applied to incorporate the effect of polydispersity in the study of the random sequential addition of spherical particles. By using the simplest uniform size distribution, we found that results from theories were in consistence with the Monte Carlo simulation results. Some deviations were seen, which resulted from the exclusion effects of polydisperse particles. It was found in the simulations that with increasing densities, small particles adsorbed preferentially and the size distribution skewed towards the smaller particles. Therefore, to accurately predict the correct radial distribution functions, the more appropriate size distributions are needed. For all size ranges, which were 0.40d–1.60d, 0.75d–1.25d, and 0.90d–1.10d, the radial distribution functions from theory at number densities of 0.2, 0.4 and 0.65 were in good agreements with those from the simulations.Physica A: Statistical Mechanics and its Applications 01/2007; 377(1):102114. · 1.68 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We studied the various stages in the preparation of a submonolayer film by the sequential deposition of particles (sequential quenching model) from very low to very high temperatures, a limit at which the system becomes equivalent to random sequential adsorption. Due to the finite size of the simulation box, only one cluster can be found in a system at very low temperatures (T* = 0.01 and 0.1) and its size grows linearly with increasing density. At higher temperatures (T* = 0.3 or higher), on the other hand, the same systems show a crossover from a nucleation regime to a growth regime. It is best revealed in a plot showing the distribution of monomers on the surface versus density, where the crossover region appears as a peak on a curve. At densities above the crossover, any new addition tends to contribute to the growth of an existing cluster rather than to nucleating new one.Journal of Colloid and Interface Science 03/2006; 294(1):3846. · 3.17 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In previous work we pointed out that clusters of particles built through sequential quenching show increasing degrees of order as the temperature is lowered. In the lowtemperature limit, a twodimensional model system with a nondegenerate ground state would result in a perfect crystal. The opposite, hightemperature, limit corresponds to the case of random sequential addition (RSA). In the present work we study the continuous evolution from disorder to order at intermediate states using a triangular well potential to represent particle interactions. We investigate radial and bondorientation correlation functions and the bond order parameter as measures of the degree of crystallinity of the structures up to a reduced number density of 0.65, which is close to the jamming limit of RSA.Chemical Engineering Communications 11/2005; 192(11):14051423. · 1.05 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The strength of attractive interaction among particles on a surface, which was studied in our previous work, leads to different degrees of clustering and ordering. A growing structure percolates when all clusters connect and become one and finally the structure is jammed when there is no space large enough to accommodate one more particle. The lowest jamming limit reported is for structures from the random sequential adsorption. We studied here, by means of Monte Carlo simulation, structures built through sequential deposition of particles, into which surface diffusion and various degrees of attractive forces are incorporated and reported jamming limits along with the percolation thresholds. The higher the strength of attractive interactions, the larger the percolation densities and jamming limits are. These results were shown in a diagram as a function of temperature (or equivalently the strength of attractive interaction), ranging from very low temperature to very high temperature (RSA limit).Journal of Colloid and Interface Science 04/2005; 283(1):418. · 3.17 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We applied the integralequation theory to the connectedness problem. The method originally applied to the study of continuum percolation in various equilibrium systems was modified for our sequential quenching model, a particular limit of an irreversible adsorption. The development of the theory based on the (quenchedannealed) binarymixture approximation includes the OrnsteinZernike equation, the PercusYevick closure, and an additional term involving the threebody connectedness function. This function is simplified by introducing a Kirkwoodlike superposition approximation. We studied the threedimensional (3D) system of randomly placed spheres and 2D systems of squarewell particles, both with a narrow and with a wide well. The results from our integralequation theory are in good accordance with simulation results within a certain range of densities.The Journal of Chemical Physics 11/2004; 121(19):968492. · 3.16 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In previous work we discussed the integralequation formalism for the computation of the structure of systems built through sequential addition, equilibration and irreversible quenching in place of individual particles. This sequential quenching model, appropriate for slow irreversible deposition, can be investigated by the techniques of equilibrium liquid theory. In the case of hard particles the problem is identical to that of random sequential addition. Our earlier calculations showed that the integral equation results for hard disks are in good agreement with simulation. In this paper we explore the structures arising from sequential quenching of squarewell disks, which are found to be very different from those for the corresponding equilibrium case. The most interesting result is the much higher degree of clustering observed when particles are quenched one by one, as opposed to what is observed from the instantaneous quenching of an entire equilibrium system. © 2001 American Institute of Physics.The Journal of Chemical Physics 01/2001; 114(4):17851790. · 3.16 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present an integralequation solution of the structure of systems built through the sequential quenching of particles. The theory is based on the Replica Ornstein–Zernike equations that describe the structure of equilibrium fluids within random porous matrices. The quenched particles are treated as a polydisperse system, each of them labeled by the total density at the time of its arrival. The diagrammatic expansions of the correlation functions lead to the development of the liquidtheory closures appropriate for the present case. Numerical solutions for the deposition of hard disks show excellent agreement with simulation. We also discuss a binarymixture treatment, which is shown to provide a very good approximation to the polydisperse approach. © 2000 American Institute of Physics.The Journal of Chemical Physics 04/2000; 112(15):67336738. · 3.16 Impact Factor
Publication Stats
13  Citations  
30.51  Total Impact Points  
Top Journals
Institutions

2010

Chulalongkorn University
 Department of Chemical Engineering
Bangkok, Bangkok, Thailand


2004–2010

Thammasat University
 Department of Chemical Engineering
Krung Thep, Bangkok, Thailand


2000–2001

University of Pennsylvania
 Department of Chemical and Biomolecular Engineering
Philadelphia, PA, United States
