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Mechanisms of mercury ions separation by non-toxic organic liquid membrane via DFT, thermodynamics, kinetics and mass transfer model
(2023-01-25)
Traiwongsa, Natthapol
;
Suren, Sira
;
Pancharoen, Ura
;
Nootong, Kasidit
;
Maneeintr, Kreangkrai
This work focuses on the separation of mercury ions from synthetic produced wastewater via hollow fiber supported liquid membrane (HFSLM). Standard sunflower oil is used as a non-toxic extractant and solvent for mercury ions separation from wastewater. Under optimal conditions: 20 ppm NaCl in wastewater, 0.1 M thiourea in 0.5 M HCl as stripping solution, flow rates of feed and stripping solutions of 100 mL/min, and temperature 323 K, percentages of extraction and stripping reach 98% and 81%, respectively. The mechanisms of extraction and stripping reactions were investigated via the density functional theory (DFT). For the extraction, a linoleic acid extracted HgCl<inf>2</inf> and formed halogen bond. For the stripping, two protonated thiourea stripped HgCl<inf>2</inf> and formed covalent and halogen bonds. According to the thermodynamics study, extraction reaction is found to be endothermic (ΔH<inf>Ex</inf>0 = 1,001.00 J/mol), irreversible (ΔS<inf>Ex</inf>0 = 3.45 J/mol K), and spontaneous, (ΔG<inf>Ex@323K</inf>0 = −112.65 J/mol). Finally, the mathematical model including conservation, convection, diffusion, reaction, and accumulation was developed. The differences of mercury ions concentration in feed and stripping phases from the experiments and the predicted data from the mathematical model were 5% and 2%, respectively indicating that the model is acceptable.
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Separation of platinum(IV) across hollow fiber supported liquid membrane using non-toxic diluents: Mass transfer and thermodynamics
(2017-10-25)
Wongkaew, Krirkratthawit
;
Mohdee, Vanee
;
Pancharoen, Ura
;
Arpornwichanop, Amornchai
;
Lothongkum, Anchaleeporn W.
Non-toxic diluents were studied and compared with toxic diluents for separation of platinum(IV) across hollow fiber supported liquid membrane. 91.41% extraction and 81% stripping of platinum(IV) was observed for sunflower oils at 328.15 K. Overall mass transfer resistance (R) was 146.612 × 104 s/cm. The separation process was exothermic (ΔH<inf>ex</inf> 0 = −975.20 kJ/mol) and spontaneous (ΔG<inf>ex</inf> 0 = −326.447 J/mol). The E<inf>a</inf> of 1.673 kJ/mol indicated that the diffusion of complex species across the liquid membrane controlled the mass transfer step. Moreover, a modified Apelblat model gave an excellent match for predicting the extraction behavior of platinum(IV) at 1.2818% RMSD.
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Effect of diluent polarity on membrane stability in the separation of trace Pd(II) from wastewater by HFSLM using LIX84-I
(2015-01-25)
Wongkaew, Kraiwith
;
Pancharoen, Ura
;
Phatanasri, Suphot
;
Leepipatpiboon, Natchanun
;
Lothongkum, Anchaleeporn W.
In a liquid membrane, the type of diluents for the selected extractant plays an important role in membrane stability and separation efficiency. High Pd(II) extraction and stripping of 96% and 91%, respectively, were observed by HFSLM under a feed pH 2, 5% (v/v) LIX84-I dissolved in kerosene and a mixture of 0.8M NH<inf>2</inf>CSNH<inf>2</inf> with 1M HCl as a stripping solution. The highest stability was attained at 350min by using hexane as a diluent. Finally, the calculated activation energy (E<inf>a</inf>) of 30 kJ/mol implied that the separation of Pd(II) was controlled by the diffusion and chemical reaction.
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The effective recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane and its mass transfer related
(2011-01-12)
Wannachod, Pharannalak
;
Chaturabul, Srestha
;
Pancharoen, Ura
;
Lothongkum, Anchaleeporn W.
;
Patthaveekongka, Weerawat
The recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane (HFSLM) was examined. Bis(2,4,4-trimethylpentyl) phosphinic acid - known as Cyanex 272 - was used as an extractant carrier. The stripping solution was hydrochloric acid solution. The experiments examined in functions of the concentrations of the carrier in liquid membrane, the (initial) pH's of initial feed solution within the acidic-pH range, the concentrations of hydrochloric acid, the flow rates of feed and stripping solution, and the operation mode of runs through the hollow fiber module. In addition, the influence of circulation of the stripping solution at various numbers of runs through the HFSLM on the outlet concentration of praseodymium ions in the stripping solution was observed. Mass transfer mechanism in the system was investigated. Extraction equilibrium constant (K<inf>ex</inf>), distribution ratio (D), permeability (P) and mass transfer coefficients were determined. The aqueous-phase mass-transfer coefficient (k<inf>i</inf>) and organic-phase mass-transfer coefficient (k<inf>m</inf>) were reported to 0.0103 and 0.788 cm s-1, respectively, in which k<inf>m</inf> is much higher than the k<inf>i</inf>. Thus it suggests the rate-controlling step is the diffusion of praseodymium ions through the film layer between the feed solution and the liquid membrane. Model prediction of the dimensionless concentrations and separation factors were also put on trial in this paper. The results showed promising agreement with the experimental data. © 2010 Elsevier B.V. All rights reserved.

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