Panu Danwanichakul | Thammasat University (original) (raw)

Papers by Panu Danwanichakul

Engineering Journal, Sep 30, 2021

Physica D: Nonlinear Phenomena, Apr 1, 2007

Random sequential adsorption of linear and square particles with excluded volume interaction is s... more Random sequential adsorption of linear and square particles with excluded volume interaction is studied numerically on planar lattices considering Gaussian distributions of lateral sizes of the incident particles, with several values of the average μ and of the width-to-average ratio w. When the coverage θ is plotted as function of the logarithm of time t, the maximum slope is attained at a time t M of the same order of the time τ of incidence of one monolayer, which is related to the molecular flux and/or sticking coefficients. For various μ and w, we obtain 1.5τ < t M < 5τ for linear particles and 0.3τ < t M < τ for square particles. At t M , the coverages with linear and square particles are near 0.3 and 0.2, respectively. Extrapolations show that coverages may vary with μ up to 20% and 2% for linear and square particles, respectively, for μ 64, fixed time, and constant w. All θ vs log t plots have approximately the same shape, but other quantities measured at times of order t M help to distinguish narrow and broad incident distributions. The adsorbed particle-size distributions are close to the incident ones up to long times for small w, but appreciably change in time for larger w, acquiring a monotonically decreasing shape for w = 1/2 at times of order 100τ . At t M , incident and adsorbed distributions are approximately the same for w 1/8 and show significant differences for w 1/2; this result may be used as a consistency test in applications of the model. The pair correlation function g(r,t) for w 1/8 has a well defined oscillatory structure at 10t M , with a minimum at r ≈ μ and maximum at r ≈ 1.5μ, but this structure is not observed for w 1/4.

This research is to investigate nanoporous electrospun structures obtained from electrospinning t... more This research is to investigate nanoporous electrospun structures obtained from electrospinning technique for using as filters. In the research, Nylon 6 and the blend of Nylon 6/chitosan nanostructures were fabricated from polymer solutions at various concentrations ranging from 30 to 35% w/v. The kinematic viscosity of the Nylon 6 and Nylon 6/Chitosan solutions was determined by using Cannon-Fenske (Reverse Flow) viscometer while the morphology of nanofibers was observed with Scanning Electron Microscope (SEM). The results showed that the solutions with a higher viscosity yielded fibers with larger diameters and pores. Although the solution of nylon 6/chitosan at a ratio of 50:1 (30% wt nylon) had the highest viscosity in the experiment, the formation of small sized ultrafine fiber group generated even much smaller pores. In the filtration test, the flow rate of the suspension of polystyrene particles in water was adjusted to 8 µm/s and the nanofibrous filters with the thickness in the range of 0.1±0.02 mm were used. The results showed complete removals of polystyrene particles when using nanofibrous filters for both pure Nylon 6 and Nylon 6/chitosan nanofibers, being compared with the filter paper and commercial nylon fabric with No. 80/55 and No. 150/35, which showed much lower performance, i.e. filtration efficiency of 2.71 to 14.50%.

Low-protein skim natural rubber latex suitable for manufacturing of special products for those wh... more Low-protein skim natural rubber latex suitable for manufacturing of special products for those who are allergic to proteins. Produced by centrifugation using water soluble polymer and surfactant. In this work, 6%wt/v polyethylene glycol solution was added into skim natural rubber latex and the mixture was centrifuged under various conditions, i.e. 1000, 2000, 3000 rpm and 5, 15, 20 min, to extract proteins from rubber particles in suspension before coagulation process. The skim natural rubber films were prepared from coagulated rubber and then was extracted with different extracting medium including water, 2%wt/v SDS, 2%wt/v TritonX-100 and 2%wt/v NaOH solution. The rubber film was centrifuged in the extracting medium at various conditions. The results of protein extractions from rubber particles and from the rubber film were found to be consistent. The extractable protein content at a low centrifugal speed increased with increasing centrifugal time. At a higher speed, increasing centrifugal time may not increase the extractable protein content. It was also found that 2%wt/v SDS solution could extract protein better than 2%wt/v NaOH, 2%wt/v TritonX-100 and distilled water, respectively.

Engineering Journal

The green exfoliation of graphite by using the serum from skim natural rubber latex together with... more The green exfoliation of graphite by using the serum from skim natural rubber latex together with ultrasonication was investigated. The rubber particles were coagulated with 0.7% w/v cationic polyacrylamides solution and the remaining serum containing ammonia was used as an exfoliating medium. The suspension with 25 mg graphite/ml serum was sonicated for 2 h at 29-53°C in an ultrasonic bath at 40 kHz and was left standing for 2 h at room temperature. The top part was centrifuged at 2000 rpm for 30 min and then the top section of this was centrifuged at 10500 rpm for 30 min to collect the solid. This process was repeated 2-3 times using the bottom part of the sedimentation. The yield of exfoliated graphite sample from each exfoliation process ranged from 0.20-0.35% and showed quality of multilayer graphene based on Raman spectroscopy results, which was comparable to the commercial graphene. The samples were also checked with scanning electron microscope and underwent some experiments, including sedimentation and methylene blue adsorption. It was found that the high-quality exfoliated sample showed better dispersion in water, resulting in 99% turbidity after 20-min sedimentation and yielded higher adsorption capacity than that of the commercial graphene.

International Journal of Chemical Engineering and Applications, Jun 1, 2017

Sorption and desorption of toluene, m-xylene, p-cresol and water by natural rubber chips

We have developed an algorithm for predicting the structure of monolayer films generated through ... more We have developed an algorithm for predicting the structure of monolayer films generated through the random sequential adsorption (RSA) by modifying a set of Ornstein-Zernike equations (OZ). This type of integral-equation theory has long been used to estimate the structures of equilibrium three-dimensional and two-dimensional fluids. It was then modified to compute the structures built in a non-equilibrium situation, which are that of fluids adsorbing within disordered quenched matrix. This finally leads to the successful algorithm for RSA. In this model, fluid particles are added at random onto a surface one at a time. Once it reaches the surface, if it does not overlap with previously adsorbed particles, it will irreversibly adsorbed at that position. If it overlaps, a new insertion attempt is provoked. A new cycle of adsorption continues in this fashion. Our previous work on RSA assumed that particles were spheres of the same size. However, colloidal particles and bioparticles ar...

Engineering and Applied Science Research, 2016

The Delaunay triangulation is well-known in the field of computational geometry, holography, netw... more The Delaunay triangulation is well-known in the field of computational geometry, holography, networking and fingerprint matching. In our case, a matching image from the image database is proposed by using the Delaunay triangulation, which has the ability to perform multidimensional in matching. To prevent problems on the complexity of the dimensions, we proposed a method for the Delaunay triangulation matching with several medium dimensions from all feature vectors. Then, apply to match all the image’s databases. In this paper, we use the color histogram as a representation of multidimensional feature vectors to test the matching in several environments and illustrate the main issues. The results in matching accuracy are satisfactory.

Activated pyrolytic tire char was applied as adsorbents to remove dyes from contaminated water. T... more Activated pyrolytic tire char was applied as adsorbents to remove dyes from contaminated water. The method of surface treatment with ethanol solution, HCl solution and then activation with NaOH solution was proposed. After activation at 750 o C, the specific surface area (SSA) of activated char (AC) increased from 154.7 m 2 /g to 228.9 m 2 /g. The pore size increased slightly from 323.4 o A to 349.3 o A and iodine number increased from 95 mg/g to 137 mg/g. AC was then utilized in the adsorption of three dyes which were acid dye (AR131), basic dye (BR18) and disperse dye (DR167) in a shaker with a speed of 75 rpm at 26 o C. The initial concentration was varied to be 10-50 mg/L. The kinetic results were more consistent with pseudo-second-order model. Considering the adsorption rate constant, k2, it was found that kinetics for acid dye (AR131) was slower than basic dye (BR18) while kinetics for disperse dye (DR167) did not follow specific pattern since it cannot be dispersed well in water without any dispersing agent. Regarding adsorption equilibrium when the initial concentration was between 10-50 mg/L, the adsorption percentages for acid dye (AR131), basic dye (BR18) and disperse dye (DR167) were 88.2-100%, 100%, and 26.9-50.7%, respectively. In addition, the adsorption isotherms for acid dye (AR131) and basic dye (BR18) followed the Langmuir equation, whereas, that for disperse dye (DR167) was better fit with the Freundlich equation.

Songklanakarin Journal of Science and Technology (SJST), 2006

The transport mechanism of several pure liquid organic substances into natural rubber chips compo... more The transport mechanism of several pure liquid organic substances into natural rubber chips composed of different fillers was investigated. It was found that, for the same type of chips, the Fickian diffusion of toluene was the fastest, followed by m-xylene, water and p-cresol. The toluene uptake was highest which was as high as 3.42 times of the chip weight. This was closely followed by m- xylene uptake, which was much higher than p-cresol uptake and water uptake which was only 0.02 times of the chip weight, implying that natural rubber could be used to remove these organic substances contaminated in water. The desorption of substances into air followed the similar trend as sorption. Besides, for any substances, the results showed that unfilled chips had the largest sorption capacity, followed by ones with calcium carbonate and carbon black.

In this research the optimum conditions to prepare films from corn and tapioca starch were determ... more In this research the optimum conditions to prepare films from corn and tapioca starch were determined. It was found that the suitable condition for obtaining gelatinized starch solutions was at temperature around 80-85°C and they were then dried at 100°C for 24 hours. Films from both corn and tapioca starch appeared homogeneous and suitable for utilization. To study the effect of glycerol used as a plasticizer on the properties of the film, starch was mixed with different amount of glycerol to obtain different mass ratio of starch to glycerol of 6:4, 7:3 and 8:2, respectively. As a result, for both types of starch, when increasing the amount of glycerol, both tensile strength and water absorbability of the film were decreased while film flexibility and water vapor permeability were increased. When comparing at the same glycerol content, it was found that the film allowing higher flux of water vapor and higher elongation percentage was from corn starch, whereas the film showing highe...

The viscosity of field latex was determined with the horizontal capillary viscometer connected to... more The viscosity of field latex was determined with the horizontal capillary viscometer connected to the vertical reservoir tube. The height of the liquid in the vertical tube could adjust the pressure of the liquid at the inlet of the horizontal capillary. The flow behavior shows that viscosity of field rubber latex and those of diluted latexes increased exponentially with dry rubber content (DRC). The linear relation was obtained between viscosity and DRC when the DRC is less than 8%. However, dilution seems to give more discrepancies because of experimental errors. Therefore, the maximum DRC that is still on the linear relation should be applied in this technique in order to minimize the experimental errors while making the effect of dissolved solids negligible. The viscosity of diluted latex was also checked with the rotational viscometer, which gave the confirmation that dilution could shield the effect of dissolved solids. The correlation between DRC and latex viscosity yields a ...

Thammasat International Journal of Science and Technology, 2010

A study of riboflavin (vitamin B2) release from the nanofiber mats obtained from electrospinning ... more A study of riboflavin (vitamin B2) 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 crosslink...

The protein extraction from skim rubber particles in continuous flow using polyethylene glycol so... more The protein extraction from skim rubber particles in continuous flow using polyethylene glycol solution at a concentration of 6%w/v PEG with an average molecular weight of 6000 (PEG6000) was studied. The flow rate of skim natural rubber was varied to be 7.5, 11 and 14 ml/min at a constant PEG flow rate of 7.6 ml/min and vice versa. The extractable protein content was determined by Bradford assay. The result revealed that when using a tube with a diameter of 4 mm, the extractable protein content in serum was increased with increasing the skim latex flow rate. When increasing the PEG solution, the flow rate with the concentration of, the extractable protein content was decreased. In addition, increasing tube diameter from 4 mm to 5 mm and increasing the tube length from 45 cm to 90 cm could increase the extractable protein content in the flow extraction. The key factors influencing the efficiency of the extraction process were degree of turbulence and the residence time (contact time ...

Integral-equation theories of the Random Sequential Addition (RSA) model have been proposed in ou... more Integral-equation theories of the Random Sequential Addition (RSA) model have been proposed in our previous work. It has been extensively studied as a two-dimensional problem representing an irreversible adsorption of large particles on a surface. This RSA model is, however, flexible enough to be applied to situations in other dimensions. It was used to model the growth of a polymer chain or a car-parking problem in one dimension and model a random sequential packing in three dimensions. We used the Fourier transform to solve the Ornstein-Zernrke integral equation and its Percus-Yevick closure, both derived by utilizing the assumption of a binary mixture of quenched and annealed particles. In this work, we therefore applied the corresponding Fourier transform to one, two and three dimensions to compute the radial distribution functions, g(r), and found that they are in good agreement with the results from Monte Carlo simulations. This confirms the validity of the theory.

Chitosan-grafted poly(vinyl alcohol)/poly(vinyl alcohol) (CS-g-PVA/PVA) membrane has been synthes... more Chitosan-grafted poly(vinyl alcohol)/poly(vinyl alcohol) (CS-g-PVA/PVA) membrane has been synthesized and studied for use as a polyelectrolyte membrane for direct methanol fuel cells because of its high water absorbability and low methanol permeability. Besides, it has high mechanical strength in the wet state. In this work, the increase of ionic conductivity is our focus. The enhancement was by filling the membrane with self-dispersible carbon black (SDCB) nanoparticles having hydrophilic carboxylic group (COO-) on their surfaces. Moreover, crosslinking with sulfuric acid was also used to increase ion conductivity of the membrane. The conductivity of CS-g-PVA/PVA membrane obtained had a low ionic conductivity of 0.258 mS/cm, slightly greater than that of chitosan membrane, which was 0.223 mS/cm. Upon crosslinking with increasing concentration of sulfuric acid solution up to 6%, the ionic conductivity was found to increase. At its maximum, the conductivity was 7.713 mS/cm, 30 times ...

Third International Conference on Advances In Civil, Structural and Environmental Engineering- ACSEE 2015, Oct 11, 2015