Pertraction of methylene blue using a mixture of D2EHPA/M2EHPA and sesame oil as a liquid membrane

An experimental study on the pertraction of methylene blue (MB) through a supported liquid membrane (SLM) using a mixture of mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) and sesame oil as the liquid membrane (LM) was performed. Parameters affecting the pertraction of MB such as initial MB concentration, carrier concentration, feed phase pH, and stripping phase concentration were analyzed. Optimal experimental conditions for MB pertraction (permeability of 5.63 × 10^?6) were obtained after a 7 h separation with the MB concentration in the feed phase of 80 mg L^?1, D2EHPA/M2EHPA concentration in membrane phase of 40 vol. %, feed pH of 6, and acetic acid concentration in the stripping phase of 0.4 mol L^?1. Kinetics of transport and stability of the SLM system were also studied and the mass transfer coefficient for this system was evaluated. Scanning electron microscopy (SEM) was used to morphologically characterize the membrane surface.     

Dysprosium pertraction through facilitated supported liquid membrane using D2EHPA as carrier

The pertraction of dysprosium (Dy) through a supported liquid membrane (SLM) system consisting of PTFE (polytetrafluoroethylene) support, D2EHPA (di-2-ethylhexyl phosphoric acid) dissolved in kerosene as membrane solution, and HNO₃ solution as stripping solution, was studied. The experiments were designed by the Taguchi method in order to investigate the effects of initial Dy concentration, feed phase pH, different stripping solution concentration, and D2EHPA concentration in the membrane phase on Dy pertraction. Optimal experimental conditions for Dy pertraction were obtained using an analysis of variance (ANOVA) (feed concentration: 130 mg L^?1, D2EHPA concentration: 0.90 M, feed phase pH: 5, stripping phase concentration: 2 M). In addition, the stability of the carrier in terms of its leaching from the membrane support was studied over a period of 6 days and was found to be satisfactory over that time.     

Emulsion liquid membrane extraction of Ni(II) and Co(II) from acidic chloride solutions using bis-(2-ethylhexyl) phosphoric acid as extractant

An emulsion liquid membrane process using bis-(2-ethylhexyl) phosphoric acid (D2EHPA) to extract and separate Ni(II) and Co(II) from acidic chloride solutions is described. Liquid membrane consists of a diluent, a surfactant (Span 80), and an extractant (D2EHPA). Hydrochloric acid was used as the stripping solution. The important parameters governing the permeation of nickel and their effect on the separation process have been studied. These parameters are stirring speed, feed phase pH, surfactant concentration, extractant concentration, stripping phase concentration, phase ratio, initial concentration of metal, and treatment ratio. The optimum conditions have been determined. The separation factors of Ni(II) with respect to Co(II), based on initial feed concentration, have been experimentally determined. Furthermore, the extraction selectivity for Co(II) over Ni(II) has been improved by using D2EHPA during the initial minutes.     

Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb²⁺, Ni²⁺, Cd²⁺ and Cu²⁺ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L^?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L^?1, respectively. The relative SDs at 10 µg L^?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples.     

Simultaneous reactive extraction separation of amino acids from water with D2EHPA in hollow fiber contactors

Reactive extraction separation of binary amino acids from water using a microporous hollow fiber has been studied, in which the acidic extractant di(2-ethylhexyl)phosphoric acid (D2EHPA) was selected as an active carrier dissolved in kerosene. l-Phenylalanine (Phe) was extracted from an aqueous solution through the shell side of module to the organic phase through the lumen of fiber in the extraction module, in which l-Phe was then back-extracted to stripping phase in stripping module. Experiments were conducted as a function of the initial feed concentration of equimolar Phe and l-aspartic acid (l-Asp) (5 mol/m³), feed pH (3–5), the carrier concentration (0.1–0.5 mol/dm³), and stripping acidity (0.1–2 mol/dm³). The effect of process variables on the separation factor of Phe/Asp and the possible transport resistances including aqueous-layer diffusion, membrane diffusion, organic-layer, and interfacial chemical reaction were quantitatively studied and discussed. The high separation factor (β) of Phe/Asp was obtained to be 18.5 at feed pH 5 and 2 mol/dm³ of strip solution (HCl). The extraction and stripping processes appear to rely on pH dependence of the distribution coefficient of amino acids in reactive extraction system. The separation factor (β) was enhanced in hollow fiber membrane (HFM) process compared with conventional solvent process, which was a result of the counter transport of hydrogen ions.     

Solid phase extraction of zinc(II) using a PVC-based polymer inclusion membrane with di(2-ethylhexyl)phosphoric acid (D2EHPA) as the carrier

A polymer inclusion membrane (PIM) is reported consisting of 45% (m/m) di(2-ethylhexyl)phosphoric acid (D2EHPA) immobilized in poly(vinyl chloride) (PVC) for use as a solid phase absorbent for selectively extracting Zn(II) from aqueous solutions in the presence of Cd(II), Co(II), Cu(II), Ni(II) and Fe(II). Interference from Fe(III) in the sample is eliminated by precipitation with orthophosphate prior to the extraction of Zn(II). Studies using a dual compartment transport cell have shown that the Zn(II) flux (2.58 × 10⁻⁶ mol m⁻² s⁻¹) is comparable to that observed for supported liquid membranes. The stoichiometry of the extracted complex is shown to be ZnR₂·HR, where R is the D2EHPA anion.     

Pertraction of cadmium and zinc ions using a supported liquid membrane impregnated with different carriers

An experimental study on the removal of Cd²⁺ and Zn²⁺ through a supported liquid membrane using a mixture of mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) as carriers is presented. Parameters affecting the Cd²⁺ and Zn²⁺ pertraction such as feed concentration, carrier concentration, pH of the stripping phase, and TBP (tributyl phosphate) concentration were analyzed using the Taguchi method. Optimal experimental conditions for Cd²⁺ and Zn²⁺ pertraction were obtained using the analysis of variance (ANOVA) after a 6 h separation with the initial feed concentration of 8.9 × 10^?4 mol L^?1, carrier concentration of 20 vol. %, TBP concentration of 4 vol. %, and pH of 0.5. Then, under optimum conditions, a comparison of M2EHPA, D2EHPA, and bis-(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302) was performed. Effective pertraction of Cd²⁺ and Zn²⁺ using these carriers was observed in the following order: mixture of M2EHPA and D2EHPA, D2EHPA, Cyanex 302. It was also found that the presence of one metal ion in the feed solution reduces the pertraction rate of the other one.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Flame atomic absorption spectrometric determination of Cd(II), Ni(II), Co(II) and Cu(II) in tea and water samples after simultaneous preconentration of dithizone loaded on naphthalene

A simultaneous preconcentration procedure for the determination of Cd(II), Ni(II), Co(II) and Cu(II) by atomic absorption spectrometry is described. The method is based on solid phase extraction of the metal ions on dithizone loaded on naphthalene in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The sorption conditions including NaOH concentration, sample volume and the amount of dithizone were optimized in order to attain the highest sensitivity. The calibration graph was linear in the range of 0.5–75.0 ng ml^?1 for Cd(II), 1.0–150.0 ng ml^?1 for Ni(II), 1.0–150.0 ng ml^?1 for Co(II) and 1.0–125.0 ng ml^?1 for Cu(II) in the initial solution. The limit of detection based on 3S_b was 0.13, 0.32, 0.33 and 0.43 ng ml^?1 for Cd(II), Ni(II), Co(II) and Cu(II), respectively. The relative standard deviations (R.S.D) for ten replicate measurements of 20 ng ml^?1of Cd(II), 100 ng ml^?1 of Ni(II), Co(II) and 75 ng ml^?1 of Cu(II) were 3.46, 2.43, 2.45 and 3.26%, respectively. The method was applied to the determination of Cd(II), Ni(II), Co(II) and Cu(II) in black tea, tap and river water samples.     

Determination of copper,nickel, manganese and cadmium ions in aqueous samples by flame atomic absorption spectrometry after simultaneous coprecipitation with Co(OH)2

A separation-preconcentration procedure was developed for the determination of trace amounts of copper, nickel, manganese and cadmium ions in water samples by flame atomic absorption spectrometry after coprecipitation by Co(OH)₂ as a carrier without a chelating agent. The influence of the various analytical parameters such as pH, amount of carrier reagent, standing time, centrifugation rate and time, sample volume and matrix effects on the recovery of the analyte ions was studied. Under the specified experimental conditions the calibration curves for Ni(II) and Cu(II) were linear from 0.5 to 200 ng mL^?1 and for Mn(II) and Cd(II) from 0.5 to 250 and 0.3 to 80 ng mL^?1, respectively. The relative standard deviations for seven replicate determinations of a mixture of 40.0 ng mL^?1 of Cu(II), Ni(II), Mn(II) and 20 ng mL^?1 of Cd(II) in the original solution were 1.9%, 1.7%, 1.8% and 2.1%, respectively. The detection limits based on 3S_b/m for Cu(II), Ni(II), Mn(II) and Cd(II) in the original solution were 0.2, 0.2, 0.3 and 0.07 ng mL^?1, respectively. The limits of quantification based on 10S_b/m for Cu(II), Ni(II), Mn(II) and Cd(II) in the original solution were 6.7, 6.7, 10.0 and 2.3 ng mL^?1, respectively. The proposed method has been applied to the determination of trace amounts of the analyte ions in two certified reference materials (the National Institute for Environment Studies (NIES) No. 1 Pepperbush and NIES No. 7 Tea Leaves) and water samples and satisfactory results were obtained.     

Transport of U(VI) from sulphuric acid medium across supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (D2EHPA)/n-dodecane as a carrier

This paper reports on the supported liquid membrane (SLM) based transport studies of U(VI) from sulphate medium using di-(2-ethylhexyl) phosphoric acid/n-dodecane as carrier. Polytetrafluoroethylene membrane was used as solid support and H₂SO₄ as receiver phase. The effects of various parameters such as receiver phase concentration, feed acidity, carrier concentration, U(VI) concentration, membrane thickness and membrane pore size on U(VI) transport had been investigated. With increase in H₂SO₄ concentrations and pH of feed solution there is an increase in U(VI) transport across the SLM. Similarly with increase in membrane thickness the U(VI) transport decrease whereas in case of pore size variation reverse results are obtained. The membrane thickness variation results showed that the U(VI) transport across the SLM is entirely diffusion controlled and the diffusion coefficient the D _(o) was calculated as 1.36 × 10^?7 cm² s^?1. Based on optimized condition, a scheme had been tested for selective recovery of U(VI) from ore leach solution containing a large number of other metal ions.     

Transfer rate and separation of Cd(II) and Zn(II) chloride species by a trilaurylammonium chloride—triethylbenzene supported liquid membrane

The transfer rate of Cd(II) and Zn(II) from aqueous feed chloride solutions to ammonium acetate strip solutions through a supported liquid membrane consisting of a trilaurylammonium chloride (TLAHCl) solution in triethylbenzene (t-e-b), adsorbed on a polypropylene microporous film, was studied. The influence of the stirring speed, feed chloride concentration, and TLAHCI carrier concentration was investigated. The data were explained by a previously derived equation in terms of membrane diffusion, aqueous film diffusion, and aqueous complex formation chemistry. The best experimental conditions to perform a Cd(II)Zn(II) separation were identified. The separation of Zn(II) and Cd(II) was experimentally studied.     

Facilitated Cd(II) transport across CTA polymer inclusion membrane using anion (Aliquat 336) and cation (D2EHPA) metal carriers

PIMs have been involved as affinity membranes for recovery of metals (Cd, Pb, Zn) by facilitated transport from aqueous solutions under different speciation forms, either anionic or cationic. The motivation of this work is to compare the efficiency of the recovery process in the case of Cd(II) using extractants such as D2EHPA and Aliquat 336 that can form complexes with the cation Cd²⁺ or the anions CdCl₃⁻ and CdCl₄²⁻, respectively. The maximal Cd(II) recovery factors obtained in 8 h are 97.5% and 91.8% with D2EHPA and Aliquat 336, respectively. Although the transport fluxes with both carriers are not strongly different (ca. 2 μmol m⁻² s⁻¹), the recovery process in case of mixture of metals is better achieved with Aliquat 336. PIMs have shown a very good stability and a constancy of the transmembrane transport flux over 12 replicate measurements, each one lasting for 8 h repeated every 24 h.     

Solid phase extraction of Cd(II), Pb(II), Zn(II) and Ni(II) from food samples using multiwalled carbon nanotubes impregnated with 4-(2-thiazolylazo)resorcinol

Multiwalled carbon nanotubes were impregnated with 4-(2-thiazolylazo)resorcinol and used for the separation and preconcentration of Cd(II), Pb(II), Zn(II) and Ni(II) ions from food samples. The analytes were quantitatively recovered at pH 7.0 and eluted with 3?mol?L^?1 acetic acid. The effects of pH value, flow rate, eluent type and sample volume on the recoveries, and the effects of alkali, earth alkali and transition metals on the retention of the analytes were studied. The method was validated using the standard certified reference materials SRM 1570A (spinach leaves) and IAEA 336 (lichen), and the results were found to be compatible with the certified values of reference materials. The new enrichment procedure was applied to the determination of these ions in various food samples.

Separation and preconcentration of cadmium ions in natural water using a liquid membrane system with 2-acetylpyridine benzoylhydrazone as carrier by flame atomic absorption spectrometry

A method for the determination of Cd in natural water by flame atomic absorption spectrometry after separation and preconcentration with a bulk liquid membrane containing 2-acetylpyridine benzoylhydrazone as mobile carrier dissolved in toluene has been developed. Effects of carrier concentration, volume of organic phase and pH of feed and receiving solutions on the flux for Cd across the membrane have been studied, being optimized by the modified simplex method. Optimum values for these variables were: carrier concentration of 0.84 g l⁻¹, 74 ml of toluene, pH 7.8 in the feed solution and 0.06 mol l⁻¹ of HNO₃ in the receiving solution, allowing a preconcentration factor of 17.9. The preconcentration step required 7 h to be accomplished. The recovery of Cd at optimum conditions was 101.0±2.7%, even with saline matrix, with good relative standard deviation (2.5%) at 95% confidence level. The detection limit of blank sample was 6 ng l⁻¹ of Cd. The method was validated using a certified reference material (TMDA-62) and also applied successfully to the analysis of Cd in four samples of seawater collected from the coast of Huelva (Spain). The relative errors of determinations were −7.6% for certified reference material and ranging between +2.4 and +7.1%, for samples of seawater (obtained between the results of the proposed and differential pulse anodic stripping voltammetry methods).     

Synthesis and application of a novel magnetic nanosorbent for determination of trace Cd(II), Ni(II), Pb(II), and Zn(II) in environmental samples

In this work for the first time, Fe₃O₄@SiO₂ core–shell nanoparticles functionalized with isatin groups as a magnetic nanosorbent was applied for the simultaneous extraction of trace amounts of cadmium(II), nickel(II), lead(II), and zinc(II). The characterization of this nanosorbent was studied using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, vibrating sample magnetometer and thermogravimetric analysis. The effect of several factors such as pH, amount of sorbent, extraction time, type and volume of the eluent, sample volume, sorption capacity, and potentially interfering ions was investigated. In the selected conditions, it was observed that the limits of detection were 0.11 ng mL^?1 for Cd(II), 0.28 ng mL^?1 for Ni(II), 0.47 ng mL^?1 for Pb(II), and 0.21 ng mL^?1 for Zn(II), and the maximum sorption capacity of this suggested magnetic nanosorbent was 120, 112, 100, and 100 mg g^?1 for Cd(II), Ni(II), Pb(II), and Zn(II), respectively. Also, the precision of the method (RSD%) for ten replicate measurements was found 2.5, 2.5, 2.8, and 3.1%, for Cd(II), Ni(II), Pb(II), and Zn(II) ions, respectively. Finally, the suggested procedure was applied for determination of cadmium(II), nickel(II), lead(II), and zinc(II) at trace levels in different water and agricultural products with satisfactory results.     

A study on separation and extraction of four main alkaloids in Macleaya cordata (Willd) R. Br. with strip dispersion hybrid liquid membrane

A technique based on strip dispersion hybrid liquid membrane was developed for the separation and extraction of four main alkaloids from fruits of Macleaya cordata (Willd) R. Br. A microporous polypropylene membrane impregnated with an organic membrane solution comprised the heart of the strip dispersion hybrid liquid membrane system. The membrane solution was made by dissolving a cationic carrier, di‐(2‐ethylhexyl) phosphoric acid in an inexpensive, less toxic membrane solvent, kerosene. The transport of alkaloids from an aqueous feed solution through the membrane to a strip dispersion phase was driven by the concentration gradient of H⁺ and facilitated by di‐(2‐ethylhexyl) phosphoric acid. The effects of the extraction time and reuse times of the membrane, the strip solution composition, the carrier concentration, the volume ratio of the aqueous strip solution to the organic membrane solution, and the flow rates of the feed solution and the strip dispersion phase on the transport of alkaloids were investigated. Under the optimal conditions, the permeability coefficients obtained for the four main alkaloids allocryptopine, protopine, sanguinarine, and chelerythrine were 1.66, 1.99, 2.98, and 3.06×10^?4 cm/s, and the transport efficiencies were as high as 68, 77, 83, and 85%, respectively.     

Differential Pulse Polarographic Determination of Cd(II) and Pb(II) in Milk Samples after Solid‐Phase Extraction Using Amberlite XAD‐2 Resin Modified with 2,2′‐DPED3P

In the present paper novel column solid phase extraction procedure was developed for the determination of Cd(II) and Pb(II) in cows', goats', ewes', buffalos' and humans' milk samples using newly synthesized reagent 2,2′‐DPED₃P (2,2′‐{[1,2‐diphenylethane‐1,2‐diylidene]dinitrilo}diphenol) for preconcentration and separation prior to differential pulse polarography using amberlite XAD‐2 in the ranges of pH 4.0–5.0. The sorbed elements were subsequently eluted with 10 mL of 2 M HCl elutes were analysed by differential pulse polarography (DPP). The interference of foreign ions has also been studied. Effects of various instrumental parameters are investigated and received conditions are optimized. The total metal concentration of the milk samples in the study area were in the following ranges 0.030–0.090 μg L^?1 of Cd(II), 0.009–0.026 μg L^?1 of Pb(II) respectively. The limits of detections were found to be 0.020 and 0.024 μg L^?1 for Cd(II) and Pb(II) respectively by applying a preconcentration factor ～40. The proposed enrichment method was applied successfully for the determination of metal ions in cows', goats', ewes', buffalos' and humans' milk samples.     

A novel method for the simultaneous determination of Pb (II), Cd (II) and Zn (II) in environmental water samples

A novel UV-VIS spectrophotometric method was developed in this study by using solid phase extraction procedure for the simultaneous preconcentration, separation and determination of trace levels of Pb (II), Cd (II) and Zn (II) ions in various water samples by using Amberlite N,N-bis(salicylidene)cyclohexanediamine (SCHD) resin. This study presents the results of experimental procedures carried out like the adsorption of analytes to the resin, influences of some analytical parameters that effect the recovery such as pH, sample volume, sample flow rate, eluent type and concentration, eluent volume, eluent flow rate and the effects of alkaline metals, earth alkaline metals and some other transition metals. The analytes in the samples with the adjusted pH range of 4–7 were adsorbed on XAD-4-SCHD resin and eluted by using 1.0 mol L^?1 nitric acid. The amounts of ions were determined by using UV-VIS spectrometer. The limits of detection were 0.03, 0.07 and 0.05 µg mL^?1 for Pb (II), Cd (II) and Zn (II), respectively. The accuracy of the method was assured by the analysis of the certified standard water sample NW-TMDA-70.2 and the observed recoveries were above 93%. Different environmental water samples that contain trace amounts of Pb (II), Cd (II) and Zn (II) were analysed by using the method developed in this study. Same samples were also analysed by ICP-MS for comparison and almost the similar results were observed. The method developed in this study was successfully applied to the various environmental water samples to determine the trace levels of Pb (II), Cd (II) and Zn (II) ions.