Publications (17)36.4 Total impact
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ABSTRACT: Protein extractions from skim natural rubber latex using 3 %w/v polyethylene glycol (PEG6000) via both low speed centrifugation and continuous flow were investigated. In centrifugal extraction, when the speed was 1000 rpm, the extractable protein (EP) content in serum increased with processing time from 5 to 30 min and when the time was fixed at 5 min, EP content increased with centrifugal speed. In addition, further washing deproteinized chips with 2 %w/v SDS solution could remove proteins with efficiencies corresponding to the efficiencies of protein removals in latex phase, implying the role of PEG in protein reduction in both steps. In continuous flow extraction, EP content increased with increasing Reynolds number or increasing mean residence time of the flow to a maximum and then dropped. The efficiencies of the centrifugal extraction and continuous flow extraction were 55.2 and 33.7%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39900.Journal of Applied Polymer Science 02/2014; 131(4). · 1.40 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The modified triangularwell potential model was applied to incorporate the effect of surface energy on the adsorption of particles or proteins on energetically heterogeneous surfaces. The method is convenient in simulating the adsorption on heterogeneous surface of which different region possesses different free energy. Spherical particles with attractive forces were added on the surface and underwent surface diffusion before they were quenched in place. It was seen that the ratio of surface energies of two regions had to be greater than 10 in order to simulate the adsorption in which the particles were selectively adsorbed on a favorable area. At a fixed ratio of surface energies, the obtained structures were similar. If the ratio was less than 10, the probability of adsorption on any site on the surface was not much different so the adsorption would be homogeneous adsorption. The method, thus, could be applied widely to simulate the adsorption of various conditions.BioMed Research International 01/2014; 2014:278098. · 2.71 Impact Factor  [Show abstract] [Hide abstract]
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. · 4.33 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. · 3.55 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. · 3.55 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. · 3.55 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. · 3.55 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. · 3.12 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. · 3.12 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. · 3.12 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: This work is focused on the influence of poly vinyl alcohol (PVA) on the formation of chitosan (CS) nanofiber. PVA with different molecular weights, 72,000 and 145,000, and CS with a molecular weight of 180,000 were used. Blend solution was prepared from chitosan and poly vinyl alcohol in water by varying %PVA for a given % of CS. The amount of PVA was varied from 1 to 11 % wt/vol and CS was varied 1 to 3 % wt/vol. It was found that the content of PVA had to be not less than 2% wt/vol to initiate the fiber formation for all chitosan contents. Spinnability was good when using chitosan contents of 1 and 1.5 % wt/vol. PVA with larger molecules seemed to help stabilize the spinnability when increasing the polymer concentration in the appropriate spinnable range and could prevent a sharp increase of nanofiber diameter for the whole range of polymer concentrations. In addition, chitosan/PVA nanofibers seemed to have fewer defects than PVA nanofibers.  [Show abstract] [Hide abstract]
ABSTRACT: A study of riboflavin (vitamin B 2) release from the nanofiber mats obtained from electrospinning process was investigated. The spinning solution was prepared from 3% chitooligosaccaride or water soluble chitosan, 13% PVA, and 0.004% riboflavin. Prior to applying the nanofiber mats, the structures underwent crosslinking either with GA vapor or TPP solution. The structures after soaking in TPP solution showed some degree of swelling, whereas, the structures after GA were still the same, the form of nanofibers with many beads. The release media chosen in this study were deionized water, NaCl solution, HCl solution at pH 1.5 and the solution of NaCl and HCl at pH 1.5. The average values of the release rate obtained in deionized water, NaCl solution, HCl solution, and NaCl and HCl solution for GA crosslinked mats were 0.1276, 0.1655, 0.1619, and 0.14811/h respectively. For TPP crosslinked mats, they were 0.0986, 0.1484, 0.1070, and 0.1206 1/h, respectively. This implies that GA crosslinked mats release riboflavin more rapidly than TPP crosslinked mats. For both types of crosslinking, the release in NaCl solution was the fastest while the release in deionized water was the slowest. The mats seemed to withstand the dissolution in acidic solution better than in the salt solution.  [Show abstract] [Hide abstract]
ABSTRACT: This research aims to simulate the deposition of nanofibers on a surface of a collector. The production of the nanofibers is from electrospinning technique which is easy to operate and it is wellstudied by various research groups. Since the nanofibrous structures contain many tiny pores with size ranging from nanoscale to microscale, it is of interest to utilize such structures for processes involving surface activity. These include catalysis, drug release, sensing, and filtration. Among which, the filtration has long been applied commercially. In the simulation methods, the 2dimensional connected structures of nanofibers will be constructed by assuming a nanofiber as an ellipse with an aspect ratio of 100 via Monte Carlo algorithm. Importantly, the size of nanofiber is assumed polydisperse during the deposition process unlike other theoretical works. This was studied as a factor influencing the average size and size distribution of pores. The configurations generated via the simulations resembled the real structures of nanofibers with polydisperse diameters. The statistics showed that the variation of size polydisperse around the same average value does not make any different to the coverage of fibers deposited on the surface but show differences in porous areas for the systems at low fiber density. In addition, the pore size distribution was found different for all samples of size variations. Interestingly, the one with smaller particles could produce the nanostructures with smaller pore size which is basically important in nanoscale properties.  [Show abstract] [Hide abstract]
ABSTRACT: The hybridization of a pair of bioparticles was investigated qualitatively by Monte Carlo simulations using sequential quenching model, which is suitable for irreversible attachment of particles on a solid surface. The given condition for pairing up is that both particles are in 2.5d range of each other where d is a particle diameter. It is found that the decrease in adsorption area facilitated the hybridization process due to the increase in system density. By using the squarewell potential at T*=0.001 and λ =2.5 with the numbers of move equal to 100000, it is found that on a surface of the area 200d 2 there is no chance to complete 100% hybridization, whereas on surfaces of the area 100d 2 and 50d 2 the 100% hybridization could occur and it is required less density of probe particles to complete 100% hybridization when the area is larger. Finally, the effects of both probe and target concentrations on hybridization are investigated. The increases of both target and probe particle concentrations could increase hybridization percentage. The phenomena show synergistic effects when the concentration of target particles was high enough, yielding the exponential increase in degree of hybridization. As a result, the kinetics of hybridization could then be improved.
Publication Stats
15  Citations  
36.40  Total Impact Points  
Top Journals
Institutions

2004–2014

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


2010

Chulalongkorn University
 Department of Chemical Engineering
Bangkok, Bangkok, Thailand


2000–2001

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