Role of hydrophobic bonding in the contraction of nylon 66 in phenolic solutions

Rate constants for intermolecular bond breaking (k₁) and bond re-formation (k₂) were calculated from contraction measurements. Variation of ΔH? and ΔS? for k₁ with phenol substituents and concentration suggests the existence of hydrophobic bonding between the solution and the polymer activated complex. This behavior has been substantiated by correlating ΔH? and ΔS? for k₁ with a parameter related to hydrophobicity.     

Comments on the reactivity of methoxy pentadecyl phenyl isocyanate isomers

The reactions of 2-methoxy-4-pentadecyl phenyl isocyanate and 4-methoxy-2-pentadecyl phenyl isocyanate with excess 2-ethyl hexanol originally reported by Ghatge and co-workers to follow zero order kinetics have been re-examined on the basis of their data and shown to follow more realistically the product catalyzed pseudo first order kinetics. The new rate constant, k_s (sec^?1) for the spontaneous reaction and k_p (li. mole^?1 sec^?1) for the product catalyzed reaction are found to be: k_s = 0.57 × 10^?6 and k_p = 34 × 10^?6 for 2-methoxy-4-pentadecyl phenyl isocyanate and k_s = 1.2 × 10^?6 and k_p = 82 × 10^?6 for 4-methoxy-2-pentadecyl phenyl isocyanate.     

In vitro Characterization of Enzymes Involved in the Synthesis of Nonproteinogenic Residue (2S,3S)‐β‐Methylphenylalanine in Glycopeptide Antibiotic Mannopeptimycin

Mannopeptimycin, a potent drug lead, has superior activity against difficult‐to‐treat multidrug‐resistant Gram‐positive pathogens such as methicillin‐resistant Staphylococcus aureus (MRSA). (2S,3S)‐β‐Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the synthesis of this residue is far from clear. We report here on the reaction order and the stereochemical course of reaction in the formation of (2S,3S)‐β‐methylphenylalanine. The reaction is executed by the enzymes MppJ and TyrB, an S‐adenosyl methionine (SAM)‐dependent methyltransferase and an (S)‐aromatic‐amino‐acid aminotransferase, respectively. Phenylpyruvic acid is methylated by MppJ at its benzylic position at the expense of one equivalent of SAM. The resulting β‐methyl phenylpyruvic acid is then converted to (2S,3S)‐β‐methylphenylalanine by TyrB. MppJ was further determined to be regioselective and stereoselective in its catalysis of the formation of (3S)‐β‐methylphenylpyruvic acid. The binding constant (K_D) of MppJ versus SAM is 26 μM . The kinetic constants with respect to k_{cat Ppy} and K_{M Ppy}, and k_{cat SAM} and K_{M SAM} are 0.8 s^?1 and 2.5 mM , and 8.15 s^?1 and 0.014 mM , respectively. These results suggest SAM has higher binding affinity for MppJ than Ppy, and the C? C bond formation in βmPpy might be the rate‐limiting step, as opposed to the C? S bond breakage in SAM.     

Extraction of Actinide(III,IV, V,VI) Ions and TcO4 − by N,N,N′,N′‐Tetraisobutyl‐3‐Oxa‐Glutaramide

Abstract

The extraction behavior of U(VI), Np(V), Pu(IV), Am(III), and TcO₄ ^? with N,N,N′,N′‐tetraisobutyl‐3‐oxa‐glutaramide (TiBOGA) were investigated. An organic phase of 0.2 mol/L TiBOGA in 40/60% (V/V) 1‐octanol/kerosene showed good extractability for actinides (III, IV, V VI) and TcO₄ ^? from aqueous solutions of HNO₃ (0.1 to 4 mol/L). At 25°C, the distribution ratio of the actinide ions (D _An) generally increased as the concentration of HNO₃ in the aqueous phase was increased from 0.1 to 4 mol/L, while the D _Tc at first increased, then decreased, with a maximum of 3.0 at 2 mol/L HNO₃. Based on the slope analysis of the dependence of D _M (M=An or Tc) on the concentrations of reagents, the formula of extracted complexes were assumed to be UO₂L₂(NO₃)₂, NpO₂L₂(NO₃), PuL(NO₃)₄, AmL₃(NO₃)₃, and HL₂(TcO₄) where L=TiBOGA. The enthalpy and entropy of the corresponding extraction reactions, Δ_r H and Δ_r S, were calculated from the dependence of D on temperature in the range of 15–55°C. For U(VI), Np(V), Am(III) and TcO₄ ^?, the extraction reactions are enthalpy driven and disfavored by entropy (Δ_r H<0 and Δ_r S<0). In contrast, the extraction reaction of Pu(IV) is entropy driven and disfavored by enthalpy (Δ_r H>0 and Δ_r S>0). A test run with 0.2 mol/L TiBOGA in 40/60% 1‐octanol/kerosene was performed to separate actinides and TcO₄ ^? from a simulated acidic high‐level liquid waste (HLLW), using tracer amounts of ²³⁸U(VI), ²³⁷Np(V), ²³⁹Pu(IV), ²⁴¹Am(III) and ⁹⁹TcO₄ ^?. The distribution ratios of U(VI), Np(V), Pu(IV), Am(III) and TcO₄ ^? were 12.4, 3.9, 87, >1000 and 1.5, respectively, confirming that TiBOGA is a promising extractant for the separation of all actinides and TcO₄ ^? from acidic HLLW. It is noteworthy that the extractability of TiBOGA for Np(V) from acidic HLLW (D _Np(V)=3.9) is much higher than that of many other extractants that have been studied for the separation of actinides from HLLW.     

Synergistic extraction and separation study of rare earth elements from nitrate medium by mixtures of sec‐nonylphenoxy acetic acid and 2,2′‐bipyridyl

BACKGROUND: Synergistic extraction has been proven to enhance extractability and selectivity. Numerous types of synergistic extraction systems have been applied to rare earth elements, among which sec‐nonylphenoxyacetic acid (CA100) has proved to be an excellent synergistic extractant. In this study, the synergistic enhancement of the extraction of holmium(III) from nitrate medium by mixtures of CA100 (H₂A₂) with 2,2′‐bipyridyl (bipy, B) in n‐heptane has been investigated. The extraction of all other lanthanides (except polonium) and yttrium by the mixtures in n‐heptane has also been studied. RESULTS: Mixtures of CA100 and bipy have significant synergistic effects on all rare earth elements, for example holmium(III) is extracted as Ho(NO₃)₂HA₂B with the mixture instead of HoH₂A₅, which is extracted by CA100 alone. The thermodynamic functions, ΔH^o, ΔG^o, and ΔS^o have been calculated as 2.96 kJ mol^?1, ? 6.23 kJ mol^?1, and 31.34 J mol^?1 K^?1, respectively. CONCLUSION: Methods of slope analysis and constant molar ratio have been successfully applied to study the synergistic extraction stoichiometries of holmium(III) by mixtures of CA100 and bipy. Mixtures of these extractants have also shown various synergistic effects with other rare earth elements, making it possible to separate them. Thus CA100 + bipy may be used to separate yttrium from other lanthanides at appropriate ratios of the extractants. Copyright © 2011 Society of Chemical Industry     

Interaction Study of Anionic Surfactant with Aqueous Non‐Ionic Polymers from Conductivity,Density and Speed of Sound Measurements

In the present study, we have investigated in detail the interactions of the anionic surfactant sodium dodecyl sulfate (SDS) with aqueous polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and various PEG + PVP mixtures at 293.15, 303.15 and 313.15 K by applying conductivity, density and speed of sound techniques. From experimentally measured data, the critical micelle concentration (CMC) values, standard free energy of micellization (ΔG_m^o), standard enthalpy of micellization (ΔH_m^o), standard entropy of micellization (ΔS_m^o), isentropic compressibilities (κ_s), apparent molar volumes (?_v) and apparent molar isentropic compressions (?_k) of SDS in aqueous polymer mixtures have been calculated. The nature of the process of micellization has been evidenced from the magnitude of ΔG_m^o, ΔH_m^o and ΔS_m^o values. The trends of variations obtained in the various parameters have been explained in terms of the electrostatic as well as hydrophobic interactions pertaining in SDS?PEG/PVP?water systems.     

Influence of Some Hofmeister Anions on the Krafft Temperature and Micelle Formation of Cetylpyridinium Bromide in Aqueous Solution

In this work, the effect of some Hofmeister anions on the Krafft temperature (T_K) and micelle formation of cetylpyridinium bromide (CPB) have been studied. The results show that more chaotropic anions increase, while the less chaotropic ones lower the T_K of the surfactant. More chaotropic I^? and SCN^? form contact ion pairs with the cetylpyridinium ion and reduce the electrostatic repulsion between the CPB molecules. As a result, these ions show salting‐out behavior, with a consequent increase in the T_K. In contrast, less chaotropic Cl^? and NO₃^? increase the activity of free water molecules and enhance hydration of CPB molecules, showing a decrease in the T_K. A rather unusual behavior was observed in the case of SO₄^2? and F^?. These strong kosmotropes shift from their usual position in the Hofmeister series and behave like moderate chaotropes, lowering the T_K of the surfactant. Because of the high charge density and the strong tendency for hydration these ions preferentially remain in the bulk. Rather than forming contact ion pairs, these ions stay away from the CPB molecules, decreasing the T_K of the surfactant. In term of decreasing the T_K, the ions follow the order NO₃^? > SO₄^2? > Cl^? > F^? > Br^? > SCN^? > I^?. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to the screening of the micelle surface charge by the excess counterions. The decreasing trend of the CMC in the presence of the salts follows the order SCN^? > I^? > SO₄^2? > NO₃^? > Br^? > Cl^? > F^?.     

Investigation on the Reaction of Powdered Tin as a Metallic Fuel with Some Pyrotechnic Oxidizers

Thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) have been used to examine the thermal behavior of Sn+KClO₃, Sn+KNO₃, and Sn+KClO₄ pyrotechnic systems and the results were compared with thermal characteristics of individual constituents. TG curves for tin powder, heated alone in air, showed a relatively slow oxidation above 570 °C. From thermal results the decomposition temperatures of KClO₃, KClO₄, and KNO₃, in nitrogen atmosphere, were measured at 472, 592 and 700 °C, respectively. For the Sn+KNO₃ pyrotechnic system, the tin oxidation was completed within the range of 480 to 500 °C. Replacing KNO₃ with KClO₄ led to an increase of thermal stability of the pyrotechnic mixture. Among above‐mentioned pyrotechnic mixtures, Sn+KClO₃ has the lowest ignition temperature at about 390 °C. The apparent activation energy (E), ΔG^#, ΔH^# and ΔS^# of the combustion processes were obtained from the DSC experiments. Based on these kinetic data and ignition temperatures, the relative reactivity of these mixtures was found to obey in the following order: Sn+KClO₃>Sn+KNO₃>Sn+KClO₄.     

Investigations on the Reactive Extraction of Glyoxylic Acid by Amberlite-LA2 Dissolved in Alcoholic Diluents

In this study, reactive extraction of glyoxylic acid (0.93 kmol·m^?3) using Amberlite-LA2 (0.24 to 1.67 kmol·m^?3) in five different alcoholic diluents is performed at 298 K. The extraction ability of Amberlite-LA2 is found to be in the order of isoamylalcohol (IAA) > nonan-1-ol > octan-1-ol > decan-1-ol > dodecanol. Maximum extraction efficiency, 98.92% is obtained at 1.67 kmol·m^?3 of Amberlite-LA2 in IAA. The values of stoichiometric coefficient (m), overall equilibrium constant (K_E) and individual constants (K₁₁, K₂₁, and K₁₂) are estimated. The effect of diluent on K_D is also quantified by applying LSER model using solvatochromic parameters of diluents.     

Synthesis of poly(methylphenylsiloxane) rich in syndiotacticity by Rh‐catalysed stereoselective cross‐dehydrocoupling polymerization of optically active 1,3‐dimethyl‐1,3‐diphenyldisiloxane derivatives

Cross‐dehydrocoupling reactions of (R)‐methyl(1‐naphthyl)phenylsilane (>99%ee) with (S)‐methyl(1‐naphthyl)phenylsilanol (>99% ee) proceeded with 82–99% retention of configuration of chiral silicon centres in the presence of various Rh‐catalysts. Cross‐dehydrocoupling polymerization of 1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane gave poly(methylphenylsiloxane) of moderate molecular weight in toluene at 60 °C in the presence of [RhCl(cod)]₂ (5.0 mol%) and triethylamine (1.0 equivalent). Assignment of the triad signals of the resulting polymer was made by ¹H NMR spectroscopy of the methyl proton (I = 0.04, H = 0.09 and S = 0.14 ppm) and ¹³C NMR spectroscopy of the ipso carbon of the phenyl group (S = 136.7, H = 136.9, and I = 137.1 ppm). Although the reaction of optically pure (S,S)‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane [(S,S):(S,R):(R,R)] = 84:16:0] gave a poly(methylphenylsiloxane) of rather low molecular weight, its triad tacticity was found to be rich in syndiotacticity (S:H:I = 60:32:8) by ¹³C NMR spectroscopy. © 2001 Society of Chemical Industry     

Syntheses and adsorption properties for Hg2+ of chelating resin of crosslinked polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole

A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g^?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (E_a), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol^?1, ‐5.99 kJ·mol^?1, 16.38 kJ·mol^?1, and 37.36, J·mol^?1·K^?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L^?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004     

Studies on the solvent extraction of rare earths from nitrate media with a combination of di‐(2‐ethylhexyl)phosphoric acid and sec‐octylphenoxyacetic acid

BACKGROUND: Di‐(2‐ethylhexyl)phosphoric acid (D2EHPA, H₂A₂) has been used extensively in hydrometallurgy for the extraction of rare earths, but it has some limitations. Synergistic extraction has attracted much attention because of its enhanced extractabilities and selectivities. In the present study, sec‐octylphenoxyacetic acid (CA12, H₂B₂) was added into D2EHPA systems for the extraction and separation of rare earths. The extraction mechanism of lanthanum with the mixtures and the separation of lanthanoids and yttrium were investigated. RESULTS: The synergistic enhancement coefficient for La³⁺ extracted with D2EHPA + CA12 was calculated as 3.63. La³⁺ was extracted as La(NO₃)₂H₂A₂B with the mixture. The logarithm of the equilibrium constant was determined as 0.80. The thermodynamic functions, ΔH, ΔG, and ΔS were calculated to be 4.03 kJ mol^?1, ? 1.96 kJ mol^?1, and 20.46 J mol^?1 K^?1, respectively. The mixtures have synergistic effects on Ce³⁺, Nd³⁺, and Y³⁺, with an especially strong synergistic effect on Y³⁺. Neither synergistic nor antagonistic effects on Dy³⁺ and weak antagonistic effects on Lu³⁺ were found. CONCLUSION: Mixtures of D2EHPA and CA12 exhibit evident synergistic effects when used to extract La³⁺ from nitric solution. The stoichiometries of the extracted complexes have been determined by graphical and numerical methods to be La(NO₃)₂H₂A₂B with the mixture. The extraction is an endothermic process. The mixture exhibits different extraction effects on rare earths, which provides possibilities for the separation of Y³⁺ from Ln³⁺ at a proper ratio of D2EHPA and CA12. Copyright © 2008 Society of Chemical Industry     

Aniline and some of its derivatives as corrosion inhibitors for nickel in 1 M HCl solution

The inhibiting action of aniline and some of its derivatives (o‐, m‐ and p‐anisidine) towards the corrosion behaviour of nickel in 1 M HCl solution has been studied using weight loss and polarization techniques. These compounds were found to retard the corrosion rate of nickel. At constant temperature, the corrosion rate decreases with increasing inhibitor concentration. On the other hand, at any inhibitor concentration, the increase in temperature leads to an increase in the corrosion rate. The activation energy, ΔE_a, the equilibrium constant, k, as well as the other thermodynamic parameters (ΔG, ΔH and ΔS) for inhibitor process were calculated and analysed. The inhibitor efficiencies calculated from both weight loss and polarization methods are in good agreement and were found to be in the order: p‐anisidine > o‐anisidine > m‐anisidine > aniline. The inhibitive action of these compounds was attributed to the adsorption of molecular species and their inhibitive efficiencies depend on the relative position of the  OCH₃ group in the aniline ring. © 1999 Society of Chemical Industry     

E‐64c‐Hydrazide: A Lead Structure for the Development of Irreversible Cathepsin C Inhibitors

Cathepsin C is a papain‐like cysteine protease with dipeptidyl aminopeptidase activity that is thought to activate various granule‐associated serine proteases. Its exopeptidase activity is structurally explained by the so‐called exclusion domain, which blocks the active‐site cleft beyond the S2 site and, with its Asp 1 residue, provides an anchoring point for the N terminus of peptide and protein substrates. Here, the hydrazide of (2S,3S)‐trans‐epoxysuccinyl‐L ‐leucylamido‐3‐methylbutane (E‐64c) (k₂/K_i=140±5 M ^?1 s^?1) is demonstrated to be a lead structure for the development of irreversible cathepsin C inhibitors. The distal amino group of the hydrazide moiety addresses the acidic Asp 1 residue at the entrance of the S2 pocket by hydrogen bonding while also occupying the flat hydrophobic S1′–S2′ area with its leucine‐isoamylamide moiety. Furthermore, structure–activity relationship studies revealed that functionalization of this distal amino group with alkyl residues can be used to occupy the conserved hydrophobic S2 pocket. In particular, the n‐butyl derivative was identified as the most potent inhibitor of the series (k₂/K_i=56 000±1700 M ^?1 s^?1).     

Solvent extraction and separation of rare earths from chloride media using α-aminophosphonic acid extractant HEHAMP

Solvent extraction and separation of rare earths (REs: La ~ Lu, plus Y and Sc) by a novel synthesized extractant, (2-ethylhexylamino)methyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, abbreviated as H₂A₂), were investigated in chloride medium. The favorable separation factors (SFs) between adjacent heavy REs suggested that HEHAMP has a better separation performance than P507. The extracted complex of trivalent REs was determined to be REClH₂A₄ by the slope analysis method. Thermodynamic parameters (ΔH, ΔG, and ΔS) of Lu were calculated as 7.47 kJ mol^?1, ?6.05 kJ mol^?1, and 45.4 J mol^?1 K^?1 at 298.15 K, respectively, which indicate that the extraction reaction of Lu is an endothermic process. The loading capacity of 30% (v/v) HEHAMP toward Lu(III), Yb(III), and Y(III) was about 15.17 g Lu₂O₃/L, 14.46 g Yb₂O₃/L, and 12.64 g Y₂O₃/L, respectively. HCl is the most efficient stripping acid, and 92% of the loaded Yb(III) can be stripped by one-stage stripping with 2 mol/L HCl.     

A Non-Conventional Adsorbent for the Removal of Clofibric Acid from Aqueous Phase

The adsorption of Clofibric acid, one of the most frequently prescribed high environmental risk drugs, was studied using H₃PO₄ activated Schumannianthus dichotomus (ASD). The chemical characteristics of the adsorbent were established by Bohem’s titration, pH_PZC, FTIR, SEM, XRD, porosity, and surface area analysis. It was observed that the adsorbent was microporous-mesoporous in nature with BET surface area of 1199.98 m².g^?1. The influence of temperature (303-323 K), pH (2-10), textural properties, adsorbent load, and contact time was studied. The Langmuir equation was found to best represent the equilibrium data for clofibric acid-adsorbent system, yielding monolayer adsorption capacity of 258.39 mg.g^?1 at 303 K. The pseudo-second order model best explained (R² > 0.999) the adsorption kinetics with rate constant 0.037 g.mg^?1min^?1. The thermodynamics parameters, ΔG°, ΔH°, and ΔS°, evaluated as ?8.14 kJmol^?1, ?34.07 kJmol^?1, and ?85.5 JK^?1mol^?1, respectively, revealed that the adsorption process is feasible, spontaneous, and exothermic in nature. In the column mode, the adsorption capacity of ASD (267.93 mg.g^?1) was found to be higher than the batch mode of operation (258.39 mg.g^?1). The cost incurred per kg of the developed adsorbent was USD 14.36.     

Micellar-Promoted Stereospecific Hydrolysis of Amino Acid Esters Catalyzed by Peptide-Like Nucleophiles

The efficiency of peptide-type nucleophiles (Z-L-Leu-L-His ( 2a ), Z-D-Leu-L-His ( 2b , Z-L-His-L-Leu ( 2c ), Z-L-Ala-L-His-OMe ( 2d ), Z-L-Leu-L-His-OMe ( 2e ), Z-L-Phe-L-His-OMe ( 2f ), Z-L-Leu-L-His-L-Leu ( 3a ), Z-D-Leu-L-His-L-Leu ( 3b ), and Z-L-Leu-L-Leu-L-His ( 3c )) in the stereospecific hydrolysis of p-nitrophenyl N-acyl-phenylalanates ( 4a -b) was examined at 10–30°C (pH 7.68) in an solution of hexadecyltrimethylammonium bromide ( 5 ). The hydrophobic and chiral amino acid group which is adjacent to the nucleophilic L-histidine part in 2a -f (or 3a-c ) was found to play an important role in determining the closeness of approach between the reactive nucelophile and substrate. The nucleophiles 2a and 3a gave high reactivity and stereospecificity in the hydrolysis of 4b possessing a long N-acyl chain, and the maximum enantiomer rate ratio (L/D), 16.1 (25°C) or 26.2 (10°C), was obtained with mixed micelles of 3a and 5. The structural effect of the nucleophiles on the stereospecific esterolysis of 4a-b is also discussed in detail on the basis of kinetic parameters (K_b/N, k_m, ΔH^‡, and ΔS^‡).     

Effect of pressure on the extractive biocatalysis of ethanol

The effect of pressure on the esterification reaction of ethanol with water-immiscible organic acids, catalysed by a lipase from Mucor miehei (pH 4.5; 30°C), was studied through analysis of the kinetics and equilibrium parameters. An increase of the ethanol distribution between the aqueous and organic phases was observed by the addition of lipase and the increase of the pressure in the system. Furthermore, the enzyme showed high specificity for the acid substrate, esterifying preferentially long chain fatty acids (C₈-C₁₈). In the studies described oleic acid was used as substrate for the esterification reaction. A kinetic study with the free enzyme, showed that pressure affected the extraction system, increasing the maximum reaction rate (> V_max), the affinity (< K_m) and the specificity (> V_max/K_m = k_sp) of the enzyme to the substrate, probably due to the effect of pressure on the electrostatic interactions in biological systems. The enzyme operational stability, at 30°C, improved significantly with the increase of pressure, having lower values for the deactivation constant (k) (8.3 × 10^?3 h^?1) and higher values for the half-life times (t_1/2) (77 h) in comparison with those obtained under atmospheric pressure conditions (k = 2.3 × 10^?2h^?1; t_1/2 = 30 h).     

Kinetic Study of an Effective Pb(II) Transport through a Bulk Liquid Membrane Containing Calix[6]arene Hexaester Derivative as a Carrier

The article describes transport of Pb(II) through bulk liquid membrane (BLM) containing calix[6]arene hexaester derivative (1) as a carrier. The effect of various parameters such as temperature, carrier concentration, stirring speed and type of solvent on the Pb(II) transport efficiency of the carrier through BLM was evaluated. The activation energy values for the extraction and re-extraction were found as 56.33 kJ mol^?1 and 14.79 kJ mol^?1, respectively. These values demonstrate that the process is diffusionally controlled by Pb(II). Observations indicate that the membrane entrance and exit rate constants (k₁, k₂) increase with increasing stirring speed as well as carrier concentration and decrease with increasing temperature. The effect of solvent on k₁ and k₂ was found to be in the order of CH₂Cl₂ > CHCl₃ > CCl₄.