Liquid-phase microextraction in a single hollow fibre - determination of mass transfer coefficient

In this study, the mass transfer coefficient of two local anesthetics in liquid-phase microextraction (LPME), which is performed in a single hollow fibre, was investigated. Previously developed mathematical model has been applied for the determination of the overall mass transfer coefficient based on the acceptor phase, KA, in an unsteady-state LPMEPhysical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Application of ACD/LABS 12 program for determination of conditions for experimental membrane extraction of pesticides

This paper analyzes the conditions for membrane extraction of pesticides using ACD / LABS 12 program. The program contains a large database of more than 2000 compounds and their ionized species, for determining the pKa, further analysis includes 600 new compounds confirmed by Hammett’s equation, which gives more precise values for logD and solubility. The 16 pesticides of different classes (organophosphates, carbamates, carbamidas, neonicotinoids etc.) and polarities commonly used in Serbia were examined. The program is used to calculate logD, pKa and solubility at different pH values for the mixture of pesticides. Based on the calculated values, the conditions for the extraction of pesticides in water using two-phase liquid-liquid membrane extraction were optimized

Membrane-Assisted Liquid-Phase Extraction of Lu(III) in a U-Shaped Contactor with a Single Hollow Fiber Membrane

Extraction of Lu(III) from an aqueous LuCl3 solution at pH 3.5 into an organic phase containing 5% (v/v) di(2-ethylhexyl)phosphoric acid (DEHPA) in di-n-hexyl ether (DHE) immobilized within a polypropylene hollow fiber membrane and a simultaneous back extraction of Lu(III) into 2 mol dm(-3) HCl solution has been investigated using two miniaturized supported liquid membrane (SLM) systems: (i) a single hollow fiber membrane, with stagnant acceptor phase in the lumen, immersed into a donor phase reservoir; and (ii) a U-shaped module containing a single hollow fiber membrane with a closed loop recirculation of aqueous phases through the module. In the stagnant SLM system, the maximum extraction efficiency was 8.8% due to limited acceptor volume and absence of flow within the lumen. In recirculating SLM system, after 80 mm of operation at the donor phase flow rate of 5.3 cm(3) min(-1), the acceptor phase flow rate of 0.4 cm(3) min(-1) and the donor-to-acceptor phase volume ratio of 6.7, the equilibrium removal efficiency of Lu(III) reached 88% and less than 5% of Lu(III) extracted from the feed solution was kept in the organic phase. For shell side flow of the donor phase at Reynolds numbers of Re = 3-34, the overall mass-transfer coefficient was proportional to the donor flow rate raised to the power of 0.63 and increased from 2.3 x 10(-5) m s(-1) to 8.8 x 10(-5) m s(-1). The rate-limiting step was the mass transfer of Lu(III) within the boundary layer of the donor phase adjacent to the outer wall of the hollow fiber

Liquid-phase membrane extraction of targeted pesticides from manufacturing wastewaters in a hollow fibre contactor with feed-stream recycle

A two-phase membrane extraction in a hollow fibre contactor with feed-stream recycle was applied to remove selected pesticides (tebufenozide, linuron, imidacloprid, acetamiprid and dimethoate) from their mixed aqueous solutions. The contactor consisted of 50 polypropylene hollow fibres impregnated with 5% tri-n-octylphosphine oxide in di-n-hexyl ether. For low-polar pesticides with log P2 (tebufenozide and linuron), the maximum removal efficiency increased linearly from 85% to 96% with increasing the feed flow rate. The maximum removal efficiencies of more polar pesticides were significantly higher under feed recirculation (86%) than in a continuous single-pass operation (30%). It was found from the Wilsons plot that the mass transfer resistance of the liquid membrane can be neglected for low-polar pesticides. The pesticide removals from commercial formulations were similar to those from pure pesticide solutions, indicating that built-in adjuvants did not affect the extraction process

Removal of the Selected Pesticides from a Water Solution by Applying Hollow Fiber Liquid-Liquid Membrane Extraction

A supported liquid membrane extraction of different pesticides (acetamiprid, dimethoate, imidacloprid, linuron, and tebufenozide) from an aqueous solution containing 20 mg dm(-3) of each pesticide by 5% TOPO (tri-n-octylphosphine oxide) in DHE (di-n-hexyl ether) has been investigated in a hollow fiber contactor having an aqueous feed/organic interfacial area of 15.4 cm(2). In a single-pass operation, the maximum removal efficiency of 95% was achieved for the most nonpolar (log P = 4.38) pesticide tebufenozide at the feed flow rate of 0.5 cm(3) min(-1). The diffusion through the boundary layer of the feed stream was a rate-controlling step in the extraction of nonpolar pesticides (linuron and tebufenozide) with a mass-transfer coefficient in the feed stream being proportional to the feed flow rate raised to the power of 0.51-0.57. The maximum overall mass-transfer coefficient based on the feed phase of K-F = 0.18 cm min(-1) was obtained for tebufenozide at the feed flow rate of 1.8 cm(3) min(-1). The organic phase entrapped in the membrane pores offered a major resistance to the mass transfer of polar pesticides (log P LT 1) and accounted for 85% of the overall mass-transfer resistance for imidacloprid at 1.8 cm(3) min(-1). The pesticides removed from the feed solution were almost completely accumulated in the organic phase but were recovered from the membrane pores to a large extent (50-90%) by rinsing the membrane with methanol after extraction

Liquid-phase membrane extraction of targeted pesticides from manufacturing wastewaters in a hollow fibre contactor with feed-stream recycle

<p>A two-phase membrane extraction in a hollow fibre contactor with feed-stream recycle was applied to remove selected pesticides (tebufenozide, linuron, imidacloprid, acetamiprid and dimethoate) from their mixed aqueous solutions. The contactor consisted of 50 polypropylene hollow fibres impregnated with 5% tri-<i>n</i>-octylphosphine oxide in di-<i>n</i>-hexyl ether. For low-polar pesticides with log <i>P</i> ≥ 2 (tebufenozide and linuron), the maximum removal efficiency increased linearly from 85% to 96% with increasing the feed flow rate. The maximum removal efficiencies of more polar pesticides were significantly higher under feed recirculation (86%) than in a continuous single-pass operation (30%). It was found from the Wilson’s plot that the mass transfer resistance of the liquid membrane can be neglected for low-polar pesticides. The pesticide removals from commercial formulations were similar to those from pure pesticide solutions, indicating that built-in adjuvants did not affect the extraction process.</p

Extraction of lutetium(III) from aqueous solutions by employing a single fibre-supported liquid membrane

Transport behaviour of Lu(III) across a polypropylene hollow fibre-supported liquid membrane containing di(2-ethylhexyl)phosphoric acid (DEHPA) in dihexyl ether as a carrier has been studied. The donor phase was LuCl(3) in the buffer solution consisting of 0.2 M sodium acetate at pH 2.5-5.0. A miniaturised system with a single hollow fibre has been operated in a batch mode. The concentration of Lu(III) was determined by indirect voltammetric method using Zn-EDTA complex. The effect of pH and volume of the donor phase, DEHPA concentration in the organic (liquid membrane) phase, the time of extraction and the content of the acceptor phase on the Lu(III) extraction and stripping behaviour was investigated. The results were discussed in terms of the pertraction and removal efficiency, the memory effect and the mean flux of Lu(III). The optimal conditions for the removal of (177)Lu(III) from labelled (177)Lu-radiopharmaceuticals were discussed and identified. The removal efficiency of Lu(III) greater than 99% was achieved at pH of the donor phase between 3.5 and 5.0 using DEHPA concentration in the organic phase of 0.47 M and the ratio of the donor to the acceptor phase of 182

Novel Sr-90-Y-90 generator system based on a pertraction through supported liquid membrane in hollow fiber contactor

Separation of yttrium(III) from strontium(II) with 15% (v/v) di(2-ethylhexyl)phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The donor phase was a mixture of 5.7 mmol dm(-3) of Sr(II) and 0.23 mmol dm(-3) of Y(III) in 0.1 mol dm(-3) HCl, the acceptor solution was 3 mol dm(-3) HCl, and the donor to acceptor phase volume ratio was 6.2. At the donor flow rate of 4.7 cm(3) min(-1) and the acceptor flow rate of 0.8 cm(3) min(-1), the yield of Y(III) in the acceptor phase (in the form suitable for radiopharmaceutical preparation) reached 60% after 360 min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to 1:25 in the donor phase. The yield of Y(III) was 72% at the acceptor flow rate to 1.9 cm3 min(-1), but a breakthrough of Sr(II) through liquid membrane increased from 0.02 to 0.2%. (C) 2015 The Institution a Chemical Engineers. Published by Elsevier B.V. All rights reserved

Influence of module arrangements on solvent extraction of thallium(III) in hollow fiber contactors

The influence of module arrangements on solvent extraction of thallium(III) from NaCl/H2SO4 solution into butyl acetate has been studied using two laboratory-made modules consisting of hydrophobic polypropylene hollow fibers. The aqueous phase was recirculated between the module(s) and a mixed reservoir, and the organic phase was stagnant on the shell side. It was found that the extraction of Tl([Il) from aqueous phase strictly depends on aqueous flow rate and module arrangement. The results obtained are discussed in terms of the fraction of TI(III) removed from the aqueous phase reservoir, the flux of TI(III) through the interfacial area, and the best arrangement of modules for the production process of the radiopharmaceutical (TlCl)-Tl-201

Analysis of concentration boundary layer in thallium (III) extraction with butyl acetate using membrane modules of different length

The development of concentration boundary layer (CBL) inside the hollow fibers, based on the experimental data from membrane-based solvent extraction of thallium (III) from chloride-containing acidic solutions with butyl acetate, was investigated. The experiments have been performed using three laboratory made contactors, consisting of hydrophobic polypropylene or polyvinylidene fluoride fibers of different length. The feed solution flowed inside the fibers, while the organic phase was pumped counter-currently at the module shell side. The influence of aqueous flow rate on the mean mass transfer coefficient in the aqueous phase was investigated. The tube-side Sherwood number was proportional to the Graetz number raised to powers ranging between 0.4 and 0.81. A model for the determination of CBL thickness and entry length was developed and used for the numerical analysis of the process. The entry length, i.e. the axial distance from the fiber inlet at which CBL reaches the axis of the fibers, was directly proportional to the aqueous phase flow rate and inversely proportional to the number of fibers in a module.International Congress on Membranes and Membrane Processes (ICOM), Jul 07-12, 2002, Taulouse, Franc