Sheet Supported Liquid Membrane Research Articles

Controlled Pertraction of Plutonium(III) Under Reducing Conditions From Acidic Feeds Using TODGA as the Carrier Extractant

Transport of Pu3+ across PTFE flat sheet supported liquid membranes (SLM) using N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) in n-dodecane as the carrier extractant was investigated. The feed solution was usually 3.0 M HNO3 while the receiver phase contained 0.1 M HNO3. In order to model the transport data, the two-phase liquid-liquid extraction experiments are also reported. A series of reducing agents viz. hydrazinium nitrate (HN), phenyl hydrazine (PH), hydroxyl ammonium nitrate (HAN), and ascorbic acid (AA) were evaluated to maintain plutonium in the +3 state in the feed, out of which phenyl hydrazine was found to be the most effective. Effectiveness of various strippants for quantitative and rapid transport of Pu was also evaluated. Additionally, the effects of feed acidity, carrier concentration, membrane thickness, effect of Pu carrier concentration, etc. were investigated. Membrane diffusion co-efficients were calculated and found to be 1.47 × 10−6 cm2/s for Pu(III). The stability of the SLM, investigated as a function of contact time, was found to be reasonably good even after 20 days of continuous operation.

Prediction of Ionic Cr (VI) Extraction Efficiency in Flat Sheet Supported Liquid Membrane Using Artificial Neural Networks (ANNs)

Artificial neural networks (ANNs) are computer techniques that attempt to simulate the functionality and decision-making processes of the human brain. In the past few decades, artificial neural networks (ANNs) have been extensively used in a wide range of engineering applications. There are only a few applications in liquid membrane process. The objective of this research was to develop artificial neural networks (ANNs) model to estimate Cr (VI) extraction efficiency in feed phase.Data set (413 experiment records) were obtained from a laboratory scale experimental study. Various combinations of experimental data, namely % (w/w) extractant Alamine 336 concentration in membrane phase, stirring speed in feed and stripping phase, flat sheet support type, stripping phase NaOH concentration, feed phase pH, diluents type, % (w/w) diluents concentration, polymer support type, extractant type, and time are used as inputs into the ANN so as to evaluate the degree of effect of each of these variables on Cr (VI) extraction efficiency in feed phase. The results of the ANN model is compared with multiple linear regression model (MLR). Mean square error (MSE), average absolute relative error (AARE) and coefficient of determination (R2) statistics are used as comparison criteria for the evaluation of the model performances. Based on the comparisons, it was found that the ANN model could be employed successfully in estimating the Cr (VI) extraction efficiency.

Transport of Thorium(IV) Across a Supported Liquid Membrane Containing N,N,N′,N′-Tetraoctyl-3-oxapentanediamide (TODGA) as the Extractant

The transport behavior of Th4+ was investigated from a feed containing 3.0 M HNO3 into a receiver phase containing 0.1 M oxalic acid across a PTFE flat sheet supported liquid membrane (SLM) which contained TODGA (N,N,N′,N′-Tetraoctyl-3-oxapentanediamide) in n-dodecane as the extractant. Effects of the nature of the strippant, extractant concentration, Th concentration in the feed, and feed acidity on the transport rates were investigated. The transport behavior apparently depended on the rate of extraction of the metal ion at the feed-membrane interface and was not diffusion controlled. Influence of Th concentration on flux was also investigated. Transport mechanism was elucidated and the diffusion coefficient was calculated to be 2.13 × 10−7 cm2/s. Solvent extraction studies at varying feed acidity and TODGA concentration were also carried out.

Separation of mercury from its aqueous solution through supported liquid membrane using environmentally benign diluent

Abstract This paper presents an experimental investigation on the facilitated transport of mercury through flat sheet supported liquid membrane (SLM) containing trioctylamine (TOA) as carrier and coconut oil, an environmentally benign solvent, as diluent. Co-transport mode of mercury transfer was studied using aqueous solution of NaOH as the strip phase. Various polymeric supports were tested in order to select the best SLM configuration. The SLM combination “PVDF–TOA–coconut oil” shows encouraging results and it was stable for a period of 98 h. The fundamental parameters, such as feed phase pH and concentration, strip phase concentration, carrier concentration, etc., affecting the transfer of mercury through the SLM were studied. It was observed that the extraction of mercury increases with increase in NaOH concentration in the strip phase, and becomes steady at a 0.3 M NaOH. The extraction process depends on feed phase pH and maximum extraction was achieved at a pH of 1. The carrier concentration had marginal effect on extraction as about 91% separation of mercury was achieved without any carrier in the SLM. Even at the most favourable operating condition ( viz. , 0.3 M NaOH, 4% TOA and pH 1), extraction of mercury was achieved up to 95%. Coconut oil showed better performance in the separation of mercury compared to other organic solvents such as dichloroethane and heptane.

Simultaneous separation of mercury and lignosulfonate from aqueous solution using supported liquid membrane

This paper presents an experimental investigation on facilitated and simultaneous transport of mercury and lignosulfonate (LS) through a flat sheet supported liquid membrane (SLM) having Nylon 6,6 as support, trioctylamine (TOA) as carrier and dichloroethane as solvent. The experiments were performed at various operating conditions such as strip phase concentration, feed pH, carrier concentration and feed concentration to find the best set of parameters that would yield the maximum separation of pure mercury as well as its mixture with LS. The experiments were performed in co-transport mode using NaOH as the strip phase. It was observed that extraction of mercury as well as its mixture increases with increase in concentration of NaOH up to a certain limit 0.1 M NaOH in case of pure solution and 0.2 M NaOH in case of mixture). Feed phase pH significantly affects the mercury separation process. However, initial feed concentration does not affect the extraction process appreciably. Separation of mixture of mercury and LS behaves in a similar way as their pure solution; however the extraction is low in comparison to pure solution. The extraction of mercury from its pure solution is about 81% in 1 h. The extraction of mercury and LS from their mixture is about 52.6% and 50.2%, respectively at optimum condition and in a period of 2 h.

Studies on uranium(VI) pertraction across a N,N,N′N′-tetraoctyldiglycolamide (TODGA) supported liquid membrane

Solvent extraction and pertraction behaviour of uranium(VI) is reported here using N,N,N′N′-tetraoctyl diglycolamide (TODGA) as the extractant. The nature of the extracted species from solvent extraction measurements conformed to UO 2(NO 3) 2·TODGA. The transport behaviour of UO 2 2+ was investigated from a feed containing 3.0 M HNO 3 into a receiver phase containing 0.1 M HNO 3 across a PTFE flat sheet supported liquid membrane (SLM) containing TODGA in n-dodecane as the carrier solvent. Effects of feed acidity, carrier extractant concentration, membrane pore size and U concentration in the feed on the transport rates were investigated. Membrane diffusion coefficients were measured using two different methods and were compared. The D o value was calculated to be 2.98 × 10 −6 cm 2/s using Danesi's model while the thickness of the aqueous diffusion layer in the feed compartment was measured to be (8.12 ± 0.72) × 10 −3 cm. Influence of metal ion concentration on flux was also investigated.

Selective separation and preconcentration studies of chromium(VI) with Alamine 336 supported liquid membrane

Chromium compounds have received considerable attention because these are used extensively in such industrial applications as electroplating, steelmaking, tanning of leather goods, and corrosion inhibition. The use of supported liquid membranes (SLMs) to remove metals from wastewaters has actively been pursued by the scientific and industrial community. In the present work, the selective separation and preconcentration of Cr(VI) ions has been studied by using a commercial amine as the membrane liquid on the porous polypropylene support. Permeation experiments were conducted on a laboratory scale batch reactor made up of perspex, with a memberane fixed amid the two chambers. The flux of Cr(VI) ions was found to be maximum (3.15 × 10−5 mol cm−2 s−1) around pH 1. Above and below this pH the flux decreases. Distribution studies show that an increase in the amine concentration leads to higher distribution coefficients at fixed pH values. At pH around unity, the distribution of Cr(VI) ions into the organic phase was found to be maximum, of the order of 56.3. The Cr(VI) transport through the membrane increases with rise in temperature. In order to check the long-term efficiency of the flat sheet SLM, an experiment was conducted with higher Cr(VI) concentration (5000 ppm) for 24 h, at optimised parameters. It was observed that in 24 h, about 1/5th of the feed Cr(VI) is left over while the rest is transported. However, minute organic droplets were also seen in the feed and strip compartments, after 1 day. This observation suggested the loss of membrane liquid. The feasibility of preconcentration of Cr(VI) by using the proposed SLM parameters, was also studied by using the hollow fibre (HF) system. Highest enrichment factor (E.F) value was obtained for 50 mg L−1 whereby all of the metal was transported to the stripping phase and the resulting Cr concentration was 688 mg L−1 (E.F = 13.8). It was observed that while treating more diluted solutions, the enrichment factor decreases. The values of E.F equal to 8.9 and 11.3 were found for initial Cr concentration of 10 and 30 mg L−1.

Recovery of phenol from aqueous solution by supported liquid membrane using vegetable oils as liquid membrane

The transport of phenol through a flat sheet supported liquid membrane (SLM) containing vegetable oil as liquid membrane (LM) has been investigated. The permeation of phenol was investigated by varying the experimental conditions like, selection of LM, support material, feed phase pH, stripping solution concentration, stirring speed and different initial concentration of phenol. It has been found that, each LM investigated in the present study shows the effective removal of phenol using polytetrafluoroethylene (PTFE) membrane and PP supported membrane as a solid support. Among the various oils tested, palm oil has chosen to be the best LM with permeability of 8.5 × 10 −6 m/s in acidic feed of pH 2.0 with 0.2 M sodium hydroxide as effective stripping agent. After 6 h all the phenol from the feed side gets transported to strip solution with an initial concentration of 100 mg/L. A concentration factor of five has been achieved in the present investigation easily with 0.2 M sodium hydroxide as stripping reagent. After 10 transport studies with one impregnation of LM, the LM showed no significant loss in the transport rate with average permeability of 7.9 × 10 −6 m/s with initial concentration 100 mg/L. Further study has also been attempted with cresols to explore the possibility of applying this to industrial wastewater under the optimized conditions for phenol. After 14 h of the transport studies in the phenol–formaldehyde industry wastewater, phenolic concentration in the feed solution was found to be below detectable level (1 × 10 −2 mg/L). For wood processing industry wastewater the transport takes place at the initial permeability of 7.1 × 10 −5 m/s. Thus it has been demonstrated the use of renewable, cheap, non toxic, naturally occurring vegetable oils as a novel, green liquid membrane for the recovery of phenol from aqueous solution in SLM, which has never been employed before in liquid membrane techniques.

Evaluation of a supported liquid membrane containing a macrocyclic ionophore for selective removal of strontium from nuclear waste solution

Transport behaviour of Sr(II) across a PTFE flat sheet supported liquid membrane (SLM) containing 4,4′(5′)di- t-butyl-cyclohexano-18-crown-6 (DtBuCH18C6) in 1-octanol as the carrier was investigated. The membrane based separation method was developed for the selective transport of Sr 2+ from aqueous nitrate medium. Linear dependence of the permeability coefficient ( P) on the crown ether concentration suggested that the ligand does not aggregate in the concentration range investigated. The P values increased with HNO 3 concentration as well as with nitrate ion concentration. However, in the presence of 2 M Al(NO 3) 3 in the feed phase, any increase in the HNO 3 concentration showed a decrease in the Sr(II) transport rate. Appreciable acid co-transport was observed in all the experiments which was attributed to the ligand assisted transport of the hydronium ion. A decrease in the transport rate was observed with increase in the membrane pore size. The transport rate was low as only ∼70% migration of Sr 2+ was observed in 24 h. The mechanism of transport has been discussed. A synthetic nuclear waste solution spiked with 85,89Sr tracer containing 1 M nitric acid has also been tested. The selectivity of the crown ether containing membrane is demonstrated as none of the other metal ions present in the synthetic nuclear waste solution could permeate through the PTFE membrane filter.

Mathematical modelling and simulation of cotransport phenomena through flat sheet-supported liquid membranes

A mathematical model of cotransport phenomena of metal ions across flat sheet-supported liquid membranes (FSSLM) is developed in the transient. The initial conditions of the FSSLM system, the physical characteristics of the membrane (porosity, tortuosity and thickness), the kinetics of the chemical reaction in the feed–membrane interface and the diffusion in the membrane phase are taken into account by the model. By using the electroneutrality principle, an expression of the concentration of cotransport species with the metal is deduced in terms of the temporal variation of the metal concentration in the feed phase. From the proposed model, the maximum percentage of metal transported is derived. Finally, a simulation is performed for the case of the transport of metal anions in alkaline solution and is checked against experimental data corresponding to the transport of Au(CN) 2 − in alkaline solution by LIX 79. The proposed model reproduces this transport phenomenon with great accuracy.

Simulation of Non-Linear Flow Density in Transition State from the Mathematical Model of the Diffusion of Metal Anions Through a Flat Sheet Supported Liquid Membrane

A mathematical model is developed for the carrier facilitated transport of metal ions through a flat sheet support liquid membrane (FSSLM) in transition state from Fick's second law. From this model, and from Fick's first law, the flow density is derived as a non-linear concentration gradient. Both expressions, concentration and flow density, depend on the thickness of the membrane and on time. Since the rate constant plays an important role in the model, it is considered as the parameter that controls the system and an equation for it is obtained. This equation explains the velocity of the co-transport process. The proposed model takes into account the species co-transported together with the metal ions. An equation for the number of moles of this species is obtained as a function of the metal species. The concentration gradient of this species explains the behaviour of pH in the feed phase during the process. The model is tested against experimental data corresponding to the transport of metal anions in acidic solution and it is shown that the co-transport process is reproduced with high accuracy.

Selective extraction of cesium ion with calix[4]arene crown ether through thin sheet supported liquid membranes

1,3-Dipropyloxycalix[4]arene crown ether ( CCE1) and 1,3-dipropyloxycalix[4]arene dibenzo crown ether ( CCE2) were successfully synthesized in a fixed 1,3-alternate conformation with good yields by the reaction of corresponding 1,3-dipropyloxycalix[4]arenes with pentaethylene glycol ditosylate and dibenzodimesylate, respectively in the presence of cesium carbonate as a base. Solvent extraction of cesium picrates and cesium nitrate from aqueous solutions into chloroform by CCE1 and CCE2 were investigated. D M value of calix[4]arene crown ether was 30–240 times of that of general crown ether and D M value of CCE2 was almost eight times of that of CCE1. Through permeation experiments using thin sheet supported liquid membranes (SLM), the effect of operating variables on permeation coefficients were obtained. Permeation coefficient of cesium ion in case of using CCE1 as extractant was higher than that of using CCE2.

EXTRACTION OF ALUMINUM FROM A PICKLING BATH WITH SUPPORTED LIQUID MEMBRANE EXTRACTION

ABSTRACT Large amounts of waste are produced yearly in the galvanic and chemical surface treatment industry. Bath liquids used in the various processes lose their function due to contamination. The spent bath liquids have to be replaced and treated prior to disposal, leading to high costs and a high environmental burden. In this paper, a proposed solution to the problem is investigated: the selective removal of the contaminant with supported liquid membrane extraction. The extraction of aluminum, a contaminant at high concentrations, from a pickling bath liquid with hydrofluoric acid and phosphoric acid as its main components has been carried out with the basic extractants Alamine 308 and Alamine 336 in a flat sheet-supported liquid membrane setup. Aluminum transport rates were obtained in the order of 10−6−10−5mol/(M2·s), which are normal values for this technique. The extraction was not completely selective as dissolved phosphorus was coextracted. In all experiments, precipitation took place on the surface of the liquid membrane and in the bulk of the strip phase. Increasing the stripping alkalinity from pH = 8 to pH = 13 reduced the amount of precipitation in the bulk of the strip phase but caused a substantial decrease in the aluminum flux. The precipitation prevents industrial application of the systems investigated.

EXTRACTION OF ALUMINUM FROM A PICKLING BATH WITH SUPPORTED LIQUID MEMBRANE EXTRACTION

ABSTRACT Large amounts of waste are produced yearly in the galvanic and chemical surface treatment industry. Bath liquids used in the various processes lose their function due to contamination. The spent bath liquids have to be replaced and treated prior to disposal, leading to high costs and a high environmental burden. In this paper, a proposed solution to the problem is investigated: the selective removal of the contaminant with supported liquid membrane extraction. The extraction of aluminum, a contaminant at high concentrations, from a pickling bath liquid with hydrofluoric acid and phosphoric acid as its main components has been carried out with the basic extractants Alamine 308 and Alamine 336 in a flat sheet-supported liquid membrane setup. Aluminum transport rates were obtained in the order of 10−6−10−5mol/(M2·s), which are normal values for this technique. The extraction was not completely selective as dissolved phosphorus was coextracted. In all experiments, precipitation took place on the surf...