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Kinetics and Equilibrium Modeling of Sterol Adsorption on Styrene-Divinylbenzene Cation-Exchange Resins
(2019-04-01)
Yuangsawad, Ratanaporn
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Sinpichai, Sarawut
;
Bhamarasuta, Thanutchaporn
;
Ladadok, Chinakrit
;
Panchanon, Surakan
The potential of recovering phytosterols from fatty acid methyl esters by an adsorption-desorption process is demonstrated using a strong-acid ion-exchange styrene-divinylbenzene resin (SA-R) as an adsorbent and ethanol as a desorbent. Since the operating cost of the overall process significantly depends on the efficiency of SA-R in the adsorption step, the behavior of SA-R in sterol adsorption is investigated in detail using a model solution of stigmasterol in n-heptane. The results indicate that stigmasterol was associatively and exothermically adsorbed on SA-R. Based on the experimental results, a simple pseudo-second-order model and a modified Langmuir isotherm with their parameters, which well predicted kinetics and adsorption capacity of SA-R, are proposed.
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Kinetics, isotherm and thermodynamics of sterol adsorption on styrene-divinylbenzene anion-exchange resins
(2018-10-01)
Ladadok, Chinakrit
;
Yamaki, Takehiro
;
Matsuda, Keigo
;
Matsumoto, Hideyuki
;
Na-Ranong, Duangkamol
Phytosterols can be recovered from natural resources using molecular distillation, cold crystallization, which require large energy consumption. Adsorption was considered as a feasible alternative method. In this study, kinetics, isotherm and thermodynamics of stigmasterol adsorption on styrene-divinylbenzene with two different functional groups, strong base (SB-R) and weak base (WB-R), were investigated using a model solution of stigmasterol in n-heptane. Isothermal adsorption experiments were performed in temperature range of 298-313 K and concentration range of 0.3-6.0 mg/g<inf>sol</inf>. For both SB-R and WB-R cases, kinetics of adsorption was analysed based on pseudofirst- order and pseudo-second-order models and the results revealed that pseudo-second-order model agreed with the experimental data much better than pseudo-first-order model. Analysis of isotherm data based on Langmuir, Freundlich and linear models showed that Freundlich was the best model that could predict behaviour of sterol adsorption for both SB-R and WB-R cases. In addition, thermodynamics parameters (δG, δH andδS) indicated that the sterol adsorptions on these adsorbents were spontaneous, exothermic and favourable at low temperature.
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Kinetics, isotherm, and thermodynamics of adsorption of sterol on strong acid ion exchange resin
(2018-01-01)
Ladadok, Chinakrit
;
Yamaki, Takehiro
;
Matsuda, Keigo
;
Matsumoto, Hideyuki
;
Na-Ranong, Duangkamol
Kinetics, isotherm and thermodynamics of sterol adsorption on styrene-divinylbenzene based ion-exchange resin with strong acid was investigated at temperature in the range of 298 to 313 K using a model solution of stigmasterol in n-heptane with initial concentration in the range of 0.3×10-3 to 1.8×10-3 kg/kg-solution. Adsorbent (5 wt%) was added to the model solution and isothermal adsorption was performed at 3.33 rps for 7.2×103 s. Kinetics of sterol adsorption was analysed based on pseudo-first-order and pseudo-second-order models. The results revealed that pseudo-second-order model agreed with the experimental data, much better than pseudofirst- order model. At the equilibrium of adsorption, adsorption capacity (qe) decreased when the temperature was increased. This result indicated that sterol adsorption was exothermic. Analysis of adsorption isotherm data based on Langmuir, Freundlich and linear models showed that Freundlich was the best model that could predict the adsorption isotherm data. Adsorption equilibrium constants calculated based on Freundlich model at various temperatures were used to calculate Gibb's free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS). The increase of ΔG with respect to temperature indicated that the adsorption was more favourable at lower temperatures. The negative value of ΔH indicated that the adsorption was exothermic and agreed well with the effect of temperature on adsorption capacity. The negative value of ΔS indicated associative adsorption and decrease of the randomness between the solid/liquid interfaces due to the adsorption.
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Synthesis of moleculary imprinted polymer originated from TFMAA and TRIM for sterol separation
(2018-01-01)
Ladadok, Chinakrit
;
Sinpichai, Sarawut
;
Nonthanasin, Nattawat
;
Binabdullah, Krittin
;
Na-Ranong, Duangkamol
Molecular imprinted polymer (MIP) was synthesized bulk polymerization using 2-(trifluoromethyl)acrylic acid (TFMAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a cross-linker, benzoyl peroxide as an initiator, acetone as porogen solvent, and stigmasterol as template molecule to obtain adsorbent having high affinity and selectivity to stigmasterol for separation of stigmasterol or other sterols in liquid phase. Functional groups and the morphology of the obtained MIP were investigated by Fourier transform infrared (FTIR) and scanning electron microscope (SEM), respectively. The performance in sterol adsorption of MIPs synthesized under various conditions was investigated using a model solution of sterol mixture in n-heptane with initial concentration of 1.40×10-4 kg/kg-solution comparing with non-imprinted polymer (NIP). Adsorbent (1 wt%) was added to model solution and shaken in an orbital shaker at 3.67 rps, 303 K for 2.16×104 s. The analysis of variance (ANOVA) suggested that the cross-linker was more influential factor on the adsorption performance of MIP as compared to the template molecule and solvent. The optimization showed that MIP synthesized at 0.5×10-3 mol of cross-linker, 1.0×10-4 mol of template molecule, and 1.0×10-5 m3 of solvent had highest percentage adsorption of 57.73 % which was 1.37 times of NIP.

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