M. Ashraf Chaudry

URANIUM(VI) TRANSPORT THROUGH TRI-n-BUTYLPHOSPHATE KEROSENE OIL LIQUID MEMBRANE SUPPORTED IN POLYPROPYLENE FILM

Transport of uranyl ions through liquid membranes consisting of tri-n-butylphosphate (TBP) in kerosene oil supported in Celgard 2400 polypropylene microporous film has been studied. Various parameters, such as the effect of nitric acid concentration in the feed solution, TBP concentration in the organic membrane phase, stripping agent concentration and temperature on the flux of uranium across the liquid membrane, have been investigated. The results obtained have been used to elucidate the mechanism of uranium transport and stoichiometry of the diffusing species.

Transport of Co(II) Ions through Di(2-ethylhexyl) Phosphoric Acid-CCl4 Supported Liquid Membranes

Abstract A liquid membrane transport study of Co(II) using di(2-ethylhexyl) phosphoric acid (D2EPHA) as carrier and CCl4, as diluent supported on polypropylene microporous film has been carried out. The carrier concentration in the membrane and HCl concentration in the stripping phase have been varied to see the effect on transport of Co(II) ions across the membrane. Maximum flux and permeability values of 1.23 × 10−5 mol · m−2 · s−1 and 7.66 × 10−11 m2/s, respectively, at a 0.87 mol/dm3 carrier concentration in the membrane have been found. At 1 mol/dm3 HCl concentration in the stripping phase the flux and permeability have maximum values of 1.4 mol · m−2 · s−1 and 5.27 × 10−11 m2/s, respectively. The distribution coefficient of Co(II) ions into organic phase has been found to increase with increasing carrier concentration. The diffusion coefficient determined varies from 13.73 × 10−11 to 0.83 × 10−11 m2/s, which is the reverse order of the values of the distribution coefficient and explains the permeabi...

Tri-n-octylamine-Xylene-Based Supported Liquid Membranes and Transport of Ce(IV) Ions

Abstract An extraction and stripping study of Ce(IV) ions by using supported liquid membranes has been performed. Tri-n-octylamine has been used as a carrier diluted in xylene. Sodium carbonate, ascorbic acid (AA), and mandelic acid (MA) have been used in the stripping phase. AA and MA reduce the Ce(IV) ions by their anion transport to the feed solution containing Ce(IV) ions and sulfuric acid. Transport of cerium ions has been observed with sodium carbonate as the strippant. The flux of these ions increases with an increase in the system operating temperature. Optimal conditions for the transport of cerium ions have been found to be 0.4 M H2SO4 in the feed and 0.2 M TOA in the membrane.

Transport of Mo(VI) ions through tri-n-octylamine-xylene based supported liquid membranes

Abstract The study of Mo(VI) ions transport through tri-n-octylamine (TOA)-xylene liquid membranes supported in polypropylene hydrophobic microporous film has been performed with varying concentrations of HC1, TOA, and NaOH in the feed membrane, strip solution, and temperature. Maximum flux of the order of 1.62 × 10−4 mol · m−2 · s−1 and permeability of 2.51 × 10−10 m2/s at 1.35 mol/dm3 TOA and 0.1 mol/dm3 NaOH at 35 ± 2°C have been observed. The flux of metal ions increases with an increase in temperature. Decomposition of [Mo7O24]6- ions into lower species appears to occur, and a pH decrease in the feed with the passage of time during transport of these metal ions is an indication of this effect. Mixed polymetal anions appear to be responsible for complexing with TOA molecules and the transport through the membrane. The transport mechanism of this metal ion through the membrane is based on the association of metal anions with protonated tri-n-octylamine (TOA) molecules on the feed-side interface, diffus...

Water and ions transport mechanism in hyperfiltration with symmetric cellulose acetate membranes

Abstract Hyperfiltration is carried out under reverse osmotic conditions by the application of mechanical energy to force the solvent from higher to lower concentration of solute across semipermeable membranes. In the present investigation, experimental work has been performed to measure the water and inorganic cation transport fluxes across cellulose acetate homogeneous hyperfiltration membranes. The osmosis, reverse osmosis, kinetic conductance and membrane potential measurements have helped to determine the hydrodynamic permeability coefficient (Lp), solute permeability coefficient (ω) and reflection coefficient (σ) for KCl, NaCl, CaCl2 and LaCl3 salts at varied temperatures. Kinetic conductance augmented with membrane potential measurement data has been used to determine molar distribution coefficient and ion exchange capacity, the ionic mobilities and diffusion coefficients of the ions using the theoretical equations relating various functions. The studies have proved useful in understanding the mechanism of water and ions transport through the given polymeric membranes. In the present paper solution diffusion theory has been considered and the amendments to be introduced in the related equations are explained.

Transport Study of Hafnium(IV) and Zirconium(IV) Ions Mutual Separation by Using Tri-n-butyl Phosphate-Xylene-Based Supported Liquid Membranes

Abstract A Hf transport study through supported liquid membranes has been carried out to determine flux and permeability data for this metal ion. Tri-n-butyl phosphate (TBP)-xylene-based liquid membranes supported in polypropylene hydrophobic microporous film have been used. These data for hafnium and the previous data for zirconium have furnished the Zr to Hf flux ratio (S) as a function of nitric acid and TBP concentrations of the order of 12 in a single stage at room temperature. Optimum conditions for the separation of these two metal ions appear to be 5–6 TBP mol/dm3, HNO3, concentrations  2.93 mol/dm3, and 10°C. The value of S from an aqueous solution containing 2.4% Hf with respect to Zr has been found to be >125 at 10°C and 1.78 mol/dm3 TBP concentration in the membrane. The technique appears to be feasible for purification of Zr with respect to Hf or vice versa.

Coupled Transport of Zr(IV) through Tri-n-butylphosphate-Xylene-Based Supported Liquid Membranes

Abstract The transport of Zr(IV) through tri-n-butylphosphate-xylene-based liquid membranes, supported in a polypropylene hydrophobic microporous film, has been studied. The concentration of HNO3 in the feed solution and tri-n-butylphosphate (TBP) carrier in the membrane were varied, and the flux and permeability coefficients were determined. The optimum conditions found for maximum flux were determined to be 10 mol/dm3 HNO3 and 2.93 mol/dm3 TBP with a flux value of 12.9 × 10−6 mol · m−2 · s−1. The solvent extraction study revealed that 1.25 to 3.5 protons are involved in zirconium transport, and that two molecules of TBP are involved in the complex formation. The value of protons involved varies with acid concentration. The zirconium ion transport is coupled with nitrate ions transport.

Extraction of Pd(II) ions using tri-n-octylamine xylene base supported liquid membranes

Membranes, based on tri-n-octylamine (TOA) xylene liquid, supported in hydrophobic microporous films have been used to study the transport of Pd(II) ions, after extraction into the membrane. Various parameters, such as the effect of hydrochloric acid concentration in the feed solution, TOA concentration in the membrane phase, effect of stripping agent like nitric acid concentration, and temperature on the flux of Pd(II) ions across the liquid membranes have been investigated. The optimum conditions of transport for these metal ions determined are, TOA concentration, 1.25 mol·dm−3, HCl concentration in the feed solution, 5 mol·dm−3, and concentration of nitric acid used as a stripping, agent 5 mol·dm−3. The maximum values of the flux and permeability determined under the optimum condition are 23·10−6 mol·m−2·s−1 and 2.40·103 m2·s−1 at 25°C. The results obtained have been used to elucidate the mechanism of palladium transport.

Transport of U(VI) ions in high concentrations across coupled transport TBP-kerosene oil supported liquid membranes

Work so far has been done with low uranium concentrations in the feed solution in supported liquid coupled transport systems of metal ion separations. In the present work the uranium concentration range is 0.1–28.5%. The flux values have been found to increase with increasing uranium concentration. This indicates reduced overall supporting device area. Thicker membranes serve the purpose better than the thinner ones due to their longer membrane life.

Extraction and stripping study of strontium ions across D2EHPA-TBP-kerosene oil based supported liquid membranes

A Sr ion transport study across D2EHPA-TBP kerosene oil based liquid membranes supported on microporous polypropylene film has been performed. The parameters studied were the effect of di(2-ethylhexyl)phosphoric acid (D2EHPA) and TBP concentration variation in the membrane liquid, HNO3 concentration variation in the stripping phase and citric acid concentration variation in the feed solution. The optimum conditions of transport are 0.3 mol/dm3 D2EHPA, 0.1 mol/dm3 TBP, 0.01 mol/dm3 citric acid in feed and 2 mol/dm3 HNO3 in the stripping phase. The mechanism of transport observed is counter-ion coupled transport. The coupling ions are protons. The maximum flux for Sr ion transport observed is 5.33·10−5 mol·m−2·s−1 and maximum permeability under optimum conditions observed is 8.08·10−11 m−2·s−1.