Removal of Ag(l), Cu(II) and Zn(ll) ions with a supported liquid membrane containing cryptands as carriers

The interface behaviour in the facilitated co-transport of Ag(I), Cu(II) and Zn(II) ions through supported liquid membranes (SLMs) made of a flat-sheet polypropylene membrane support containing cryptands (2.2.2 or 2.2.1) as carriers was studied. The liquid-liquid extraction tests showed a maximum distribution coefficient when the carrier concentration was greaterthan 10⁻⁴M. In transport experiments the transmembrane flux increased with increasing carrier concentration reaching a limiting value at greater than 10⁻³M concentration. The calculation ofthe diffusion coefficients in membranes showed ahigherdiffusivityof2.2.2-metal complexes with respect to 2.2.1-metal complexes for silver ions. A sequence of diffusivity D(Ag+)>D(Cu²⁺)>D(Zn²⁺) was obtained, but carrier 2.2.1 showed a higher selectivity through copper ions. A sequence of diffusivity D(Cu²⁺)>D(Zn²⁺)>D(Ag⁺) was obtained. The diffusivity was significantly higher when using Celgard 2500 support compared to Celgard 2400 or 2402. Variable metal ion concentrations in the feed phase fluxes almost zero, at less than 10⁻² M concentration, were obtained. In the transient state of the transport through the SLM, different molar flow rates at the feed-membrane and membrane-strip interfaces were observed. The selectivity of the interfaces containing 2.2.2 in the separation binary mixtures of ions showed the following separation factors: SF_AgZn = 2.50, SF_AgCu = 1.64, SF_cuZn = 1.42.     

π‐Complexation Studied by Fluorescence Technique: Application in Desulfurization of Petroleum Product using Magnetic π‐Complexation Sorbents

Abstract

Magnetic π‐complexation sorbents were studied for petroleum product desulfurization by fluorescent technique. The ability of metal cation to form π‐complexation decreases in the order following: Cu⁺>Ni²⁺>Co²⁺>Al³⁺. The order is consistent with that of desulfurization performance of their corresponding magnetic sorbents (γ‐Al₂O₃‐Cu(I)>γ‐Al₂O₃‐Ni(II)>γ‐Al₂O₃‐Co(II)>γ‐Al₂O₃). Both π‐complexation strength and desulfurization performance of the sorbents increase with temperature. The adsorptive performances of magnetic γ‐Al₂O₃‐Cu(I) sorbent to different compounds have the following orders: DBT>fluorene, and pyrene>naphthalene>benzene, respectively. In this study, dibenzothiophene (DBT) was used as a model sulphur‐containing compound for desulfurization. The maximal adsorption amount of magnetic γ‐Al₂O₃‐Cu(I), was 0.362 mmol DBT g^?1.     

Functionalized hectorite clay mineral for Ag(I) ions extraction from wastewater and preparation of silver nanoparticles supported clay

A novel clay mineral-based adsorbent for Ag(I) ions extraction was obtained by modifying hectorite with 2-(3-(2-aminoethylthio)propylthio)ethanamine (AEPE-hectorite). The modified hectorite was used to recover Ag(I) ions from wastewater for further preparation of silver nanoparticles supported hectorite. The parameters affecting silver ions extraction by AEPE-hectorite were investigated. The adsorbent could extract Ag(I) ions from solution in a wide pH range (1–8) and high extraction efficiencies were achieved in the solution pH ranged from 4 to 9. AEPE-hectorite showed a good selectivity toward Ag(I) ions over Co(II), Ni(II) and Cd(II) ions and the solution ionic strength had no significant effect on extraction efficiency. The adsorption of Ag(I) ions onto AEPE-hectorite followed the Freundlich isotherm model with maximum adsorption capacity observed in the experiment of 49.5 mg g^− 1. The adsorbent was successfully used to recover silver ions from a wastewater containing high concentration of silver and silver nanoparticles supported hectorite was obtained after reducing with NaBH₄. These results show an alternative in the preparation of silver nanoparticles supported clay.     

Photoelectro-Fenton combined with photocatalytic process for degradation of an azo dye using supported TiO2 nanoparticles and carbon nanotube cathode: Neural network modeling

In this work, treatment of an azo dye solution containing C.I. Basic Red 46 (BR46) by photoelectro-Fenton (PEF) combined with photocatalytic process was studied. Carbon nanotube-polytetrafluoroethylene (CNT-PTFE) electrode was used as cathode. The investigated photocatalyst was TiO₂ nanoparticles (Degussa P25) having 80% anatase and 20% rutile, specific surface area (BET) 50 m²/g, and particle size 21 nm immobilized on glass plates. A comparison of electro-Fenton (EF), UV/TiO₂, PEF and PEF/TiO₂ processes for decolorization of BR46 solution was performed. Results showed that color removal follows the decreasing order: PEF/TiO₂ > PEF > EF > UV/TiO₂. The influence of the basic operational parameters such as initial pH of the solution, initial dye concentration, the size of anode, applied current, kind of ultraviolet (UV) light and initial Fe³⁺ concentration on the degradation efficiency of BR46 was studied. The mineralization of the dye was investigated by total organic carbon (TOC) measurements that showed 98.8% mineralization of 20 mg/l dye at 6 h using PEF/TiO₂ process. An artificial neural network (ANN) model was developed to predict the decolorization of BR46 solution. The findings indicated that artificial neural network provided reasonable predictive performance (R² = 0.986).     

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.     

Uranium membrane separation from binary aqueous solutions of UO22+-K+ and UO22+-Ca2+ by the nanofiltration process

The performance of the nanofiltration process was investigated for uranium separation from binary aqueous solutions of UO₂²⁺-K⁺ and UO₂²⁺-Ca²⁺ containing uranium in high concentration ranges. Rejection coefficient, permeate flux, and membrane selectivity of PES-2, NF-1, and NF-2 membranes under various operational conditions of pH, pressure, and concentration of interfering cation were evaluated. In most cases, the order of metal rejections with these membranes was UO₂²⁺ > Ca²⁺ > K⁺. According to the obtained results, the nanofiltration process could be effectively used for selective uranium separation from aqueous solutions containing uranium and other monovalent and divalent cations.     

Dynamic Behavior of a PEM Fuel Cell During Electrochemical CO Oxidation on a PtRu Anode

The dynamic behaviour of a single PEM fuel cell (PEMFC) with a PtRu/C anode catalyst using CO containing H₂ as anode feed was investigated at ambient temperature. The autonomous oscillations of the cell potential were observed during the galvanostatic operation with hydrogen anode feed containing CO up to 1000 ppm. The oscillations were ascribed to the coupling of the adsorption of CO (the poisoning step) and the subsequent electrochemical oxidation of CO (the regeneration step) on the anode catalyst. The oscillations were dependent on the CO concentration of the feed gas and the applied current density. Furthermore, it was found that with CO containing feed gas, the time average power output was remarkably higher under potential oscillatory conditions in the galvanostatic mode than during potentiostatic operation. Accompanying these self-sustained potential oscillations, oscillation patterns of the anode outlet CO concentration were also detected at low current density (<100 mA/cm²). The online measurements of the anode outlet CO concentrations revealed that CO in the anode CO/H₂ feed was partially electrochemically removed during galvanostatic operation. More than 90% CO conversion was obtained at the current densities above 125 mA/cm² with low feed flow rates (100–200 mL/min).     

Extraction and recovery of gold from KAu(CN)2 using cetyltrimethylammonium bromide microemulsions

Extraction and stripping of KAu(CN)₂ from alkaline solution by a w/o microemulsion formed with cetyltrimethylammonium bromide (CTAB) using ¹⁹⁸Au(I) tracer has been investigated. Various parameters, such as the Au(I) concentration in aqueous phase, concentrations of halide ions, NH₄SCN and thiodiethylene glycol in stripping solution as well as the relationship between water and Au(I) concentration in the organic phase in the extraction and stripping of Au(I) were studied. The results show that almost all of the Au(I) in the aqueous phase was extracted into the organic phase. The water content decreased significantly with an increase in Au(I) concentration in the organic phase, contrary to the results of a system with tributyl phosphate (TBP) as cosolvent. Almost all of the extracted Au(I) (～98%) can be recovered with pure thiodiethylene glycol as the stripping agent, and ～93% of the Au(I) is stripped with high concentrations of NH₄SCN(>3.0 mol dm^?3) or KI (>2.0 mol dm^?3). © 2001 Society of Chemical Industry     

Optimization of Preparation Conditions for PDMS-Silica Composite Pervaporation Membranes Using Response Surface Methodology

In this article, response surface methodology was used to optimize the preparation conditions of fumed silica filled polydimethylsiloxane/cellulose acetate composite membranes. The silica loading, polydimethylsiloxane concentration, and NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio were considered as factors. Two regression equations, which described the effects of the three factors on the permeation flux and selectivity of the membranes, were derived from the results of 20 experiments by using a statistical software Design-Expert 7.1.4. The results revealed that the three factors had important effects on the permeation flux and the selectivity. The obtained regression equations were confirmed with another four groups of experiments. According to the regression equations, for the separation of an ethanol aqueous solution with the concentration of 10 wt%, the maximum selectivity of the membrane, 11.5 could be obtained at the feed temperature of 40°C, and the corresponding permeation flux was 197.3 g · m^?2 · h^?1. The preparation conditions for making the composite membrane with the above separation performances were: the silica loading was 5.21 wt%, the polydimethylsiloxane concentration was 13.36 wt%, and the NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio was 0.59.     

Selective Removal of Carbon Dioxide from Wet CO2/H2 Mixtures via Facilitated Transport Membranes containing Amine Blends as Carriers

The selective separation of carbon dioxide (CO₂) from a wet gaseous mixture of CO₂/H₂ through facilitated transport membranes containing immobilized aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), ethylenediamine (EDA) and monoprotonated ethylenediamine (EDAH⁺) and their blends was experimentally investigated. The effect of CO₂ partial pressure, amine concentration, feed side pressure and amine species on the CO₂ and H₂ permeances were studied. The CO₂ permeability through amine solution membranes decreased with increasing CO₂ feed partial pressure but the H₂ permeance was almost independent of the H₂ partial pressure. A comparison of experimental results showed that single or blended amines with low viscosity and a moderate equilibrium constant, i.e., large forward and reverse reaction rate of CO₂‐amine, are suitable for effective separation of CO₂. The permeability of CO₂ generally increased with an increase in amine concentration, although this increase may be compromised by the salting out effect and decrease in diffusivities of species. The results obtained indicated that CO₂ permeance across a variety of amines are in the order of DEA (2 M) > MD (2 M) > MD (1 M) > MEA (2 M) > MEA (4 M) > MD (4 M) > DEA (1 M) > DEA (4 M) > MEA (1 M) for various concentrations of MEA + DEA blend and are in the order of EDAH⁺ (2 M) > DEA (2 M) > MH (2 M) > DH (2 M) > ED (2 M) > EDA (2 M) > MEA (2 M) for various blends of amine.     

The Synthesis and Characterization of New Schiff Bases and Investigating them in Solvent Extraction of Chromium and Copper

New Schiff bases containing nitrogen, sulfur and oxygen donor atoms, were designed and synthesized in a multi—step reaction sequence. The Schiff base(I) was used in solvent extraction of metal chlorides such as Cu(II) from aqueous phase to the organic phase. The influences of the parameter functions, such as pH, solvent, ionic strength of aqueous phase, aqueous to organic phase, and concentration of the extractant were investigated to shed light on their chemical extracting properties upon the extractability of metal ions. The effect of chloroform, dichloromethane, and nitrobenzene as organic solvents over the metal chlorides extraction was investigated at 25 ± 0.1°C by using flame atomic absorption and the result is that the ability of extraction in solvents as follows C₆H₅NO₂ > CHCl₃ > CH₂Cl₂.     

Application of Ti/RuO2-Ta2O5 electrodes in the electrooxidation of ethanol and derivants: Reactivity versus electrocatalytic efficiency

The influence of the preparation method on the performance of RuO₂-Ta₂O₅ electrodes was evaluated toward the ethanol oxidation reaction (EOR). Freshly prepared RuO₂-Ta₂O₅ thin films containing between 30 and 80 at.% Ru were prepared by two different methods: the modified Pechini-Adams method (DPP) and standard thermal decomposition (STD). Electrochemical investigation of the electrode containing RuO₂-Ta₂O₅ thin films was conducted as a function of electrode composition in a 0.5-mol dm⁻³ H₂SO₄ solution, in the presence and absence of ethanol and its derivants (acetaldehyde and acetic acid).At a low ethanol concentration (5 mmol dm⁻³), ethanol oxidation leads to high yields of acetic acid and CO₂. On the other hand, an increase in ethanol concentration (15-1000 mmol dm⁻³) favors acetaldehyde formation, so acetic acid and CO₂ production is hindered, in this case.Electrodes prepared by DPP provide higher current efficiency than STD electrodes for all the investigated ethanol concentrations. This may be explained by the increase in electrode area obtained with the DPP preparation method compared with STD.     

Liquid Membrane Transport of Hg(II) by an Azocalix[4]arene Derivative

Abstract

A kinetic study of Hg(II) transport from an aqueous donor solution into an aqueous acceptor solution through a liquid membrane containing 25,26,27–tribenzoyloxy‐28‐hydroxy‐5,11,17,23‐tetra‐(4‐n‐butylphenylazo)calix[4]arene 1 as a carrier was studied. The kinetic parameters (k ₁, k ₂, R _m ^max, t _max, J _d ^max, J _a ^max) for the transport were investigated in terms of the effect of temperature, the stirring rate, the carrier concentration, and the type of solvent. The kinetics of transport was analyzed in the formalism of two consecutive irreversible first‐order reactions. The membrane entrance rate, and exit rate constants were increased with increasing of temperature stirring rate, and carrier concentration. The membrane entrance rate and exit rate constants depended on the type of solvent and was found to be in order of CH₂Cl₂> CHCl₃> CCl₄. The activation energy values are calculated as 30.67±2.64 and 57.33±4.90 kj mol^?1 for extraction and reextraction, respectively. The values of calculated activation energy indicate that the process is diffusionally controlled by species.     

Kinetic Studies on the Exchange of Bivalent Metal Ions on Amberlite IRC‐718—An Iminodiacetate Resin

Abstract

The rate of uptake of alkaline earth metals, copper, and lead have been investigated by a chelating ion exchange resin containing iminodiacetic acid as ligand attached to the copolymer of styrene and divinyl benzene of macroporous matrix structure. It binds alkaline earth metals, Cu, and Pb by the formation of chelate complexes with the carboxylate group of this resin. The experiments discussed in this work have allowed to establish the paramount importance of the presence of this chelating group in obtaining practically useful rates of metal ion uptake. The kinetic parameters like diffusion coefficient (D _o), activation energies (ΔE _a) and entropy of activation have been evaluated under the conditions favoring a particle diffusion control mechanism and the study followed the three models i.e., Nernst Planck, B _t technique and Ash model. K _d values in demineralised water (DMW) were found in the order Cu²⁺ > Pb²⁺ > Mg²⁺ > Sr²⁺ > Ba²⁺ > Ca²⁺.     

Synthesis and characterization of gallic acid derivatives and their utilized as organic photo-stabilizers for poly (vinyl chloride)

The photo-stabilization of poly (vinyl chloride) containing 1,3,4-thiadiazole derivatives derived from Gallic acid as additives were studied. The four different substituents of 1,3,4-thiadiazole-gallic derivatives, 2-(4-substituted-phenyl)-5-(3,4,5-trimethoxyphenyl)-1,3,4-thiadiazole, (R1-R4) were prepared starting from Gallic acid and characterized by FTIR, ¹HNMR and elemental analysis. The 5% concentration by weight of these derivatives (R1-R4) in PVC polymer was used to study the photo-stabilization of PVC. The photo-stabilization of PVC films were studied at room temperature under irradiation of U.V light with λ = 385 nm and an intensity of 7.75 × 10^?7 Einstein dm^?3 s^?1. The photo-stabilization activity of these compounds was determined by monitoring the carbonyl (I_CO), polyene (I_po) and hydroxyl (I_OH) indices and weight loss method with irradiation time. It was found that the (I_CO), (I_po) and (I_OH) index values increased with the irradiation time increase, this increase found to depend on the type of additives, also it was found that the PVC films in the presence of additives (R1-R4) were arranged as the following trend: PVC + R1 > PVC + R2 > PVC + R3 > PVC + R4.     

Synthesis and Properties of a Novel Branched Polyether Surfactant

A novel branched polyether surfactant (TPE) was prepared by anion polymerization with different proportions of propylene oxide (PO) and ethylene oxide (EO) using 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane as a core. The structures and average molecular weight (M _n ) of the TPE were characterized by ¹H NMR and GPC. The cloud point was determined by turbidimetry in the presence of inorganic salts. Inorganic salts decreased the cloud point of TPE polyether in the following order: Na₂CO₃ > Na₂SO₄ > NaCl > CaCl₂ > MgCl₂. The effects of inorganic salts (NaCl, MgCl₂, CaCl₂, and NaSCN) and temperature on the surface activity of TPE in aqueous solution were investigated by surface tension measurements. The surface activity parameters and the thermodynamic parameters were calculated from surface tension data. Similar to the effect of increasing temperature, the salting-out inorganic salts such as NaCl, MgCl₂, and CaCl₂ favor the micellization and increase the maximum surface excess concentration, while the salting-in NaSCN has the opposite effect. The influence of NaCl on the morphology of micelles was investigated by TEM. The micellization is entropy-driven at low temperature and enthalpy-driven at higher temperature. The TPE polyether has large surface activity and can be used as a demulsifier to break up crude oil emulsions.     

Sonochemical Synthesis,Characterization and Sonocatalytic Performance of Terbium-Doped CdS Nanoparticles

Terbium-doped cadmium sulfide nanoparticles with different terbium contents were successfully synthesized via sonochemical route. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, photoelectron X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy techniques. The as-prepared nanocatalyst were used for sonocatalytic degradation of Methylene Blue. Among the different amounts of dopant, 8 % Tb-doped CdS showed the highest sonocatalytic activity. The order of inhibitory effect of radical scavengers was 1, 4 Benzoquinone > SO₃ ^2? > CO₂ ^3?> I^?. The effects of various parameters such as initial dye concentration, catalyst loading, ultrasonic power, and the presence of radical scavengers were investigated.     

Nitrate percolation and discharge in cropped Andosols and Gray lowland soils of Japan

Contamination of groundwater with nitrate (NO₃) derived from agricultural activity is serious problem in many countries worldwide. We investigated the annual (growing and non-growing seasons) behavior of NO₃–N in the soil pore water of cropped Andosols and Gray lowland soils under eight crop groups (Type A: paddy rice, Type B: winter crops, Type C: vegetables 1, Type D: vegetables 2, Type E: vegetables and forages, Type F: legume crops, Type G: orchard, and Type H: grass). In the vegetable group (Type C) and the orchard group (Type G), which required large amounts of fertilizer and frequent top-dressing, NO₃–N concentrations in the soil pore water were extremely high. In these agricultural lands, it was clear that the inorganic nitrogen produced by nitrification in surface soil was dominantly discharged from a depth of 90 cm in July to September. The descending order of the amount of discharge of NO₃–N (N-discharge) was Type C > G > D > E > F > B > H > A for the Andosol, and Type G > C > F > D > E > B > H > A for the Gray lowland soil. If fertilization of the vegetables and orchard was performed based on the standard application amount, the annual average NO₃–N concentration at a depth of 90 cm exceeds 10 mg L^?1. To reduce the risk of groundwater contamination by NO₃–N, we calculated the annual cumulative water flux density and annual cumulative NO₃–N flux density. We examined the calculated fertilizer amount and proposed reduced fertilizer application amounts so that the annual average concentration of NO₃–N in soil pore water would not exceed 10 mg L^?1. The standard application amount of nitrogen fertilizer for vegetables should be reduced by 65.8 and 30.8 kg ha^?1 in the Andosol and the Gray lowland soil, respectively. We also proposed that the standard application amount of nitrogen fertilizer be reduced by 59.9 and 40.7 kg ha^?1 in Andosol orchards and Gray lowland soil orchards, respectively.     

Studies on Permeation of Nd (III) through Supported Liquid Membrane Using DNPPA + TOPO as Carrier

The transport behavior of Nd (III) through a supported liquid membrane (SLM) containing PTFE as support with organophosphorus extractant dinonyl phenyl phosphoric acid (DNPPA) carrier has been studied. The effect of neutral donors such as TOPO (tri-n-octyl phosphine oxide) TBP (tri-n-butyl phosphate), TEHP (tris 2-ethylhexyl phosphate) and Cyanex 923 (a mixture of four trialkyl phosphine oxides) in combination with DNPPA on transport of Nd (III) from HCl across SLM has been examined and the following trend was observed: TOPO > Cyanex 923 > TBP > TEHP. The effect of experimental variables such as feed acidity (0.5 to 5 M HCl), neodymium metal ion concentration (6.94 × 10^?4 to 6.94 × 10^?3 M), DNPPA concentration (0.2 to 0.6 M), stripping reagents in the receiving phase on Nd (III) transport across SLM were investigated. The percentage transport of Nd (III) was 97% after 6 hr run with 0.6 MDNPPA + 0.13 MTOPO as carrier. The permeability of Nd (III) decreased with increase in HCl and Nd (III) concentration in the feed solution. The transport of Nd (III) decreased with increase in membrane thickness as well as with decrease in pore size. Under optimized conditions transport behavior of other rare earths was also investigated independently, the trend observed was: La > Pr ≥ Nd > Sm > Eu > Gd > Tb > Dy > Ho > Er > Tm > Lu ≥ Y.     

Recovery of 137Cs from Laboratory Waste using Solvent Extraction with Sodium Tetraphenylboron (TPB)

The paper describes a method for the recovery of ¹³⁷Cs from an aqueous radioactive laboratory waste solution containing ¹³⁷Cs (2 µg/mL) in the presence of high concentration of Na⁺ using solvent extraction technique. The method comprises of adjustment of pH to the acidic range (pH = 2), contacting the aqueous radioactive solution with sodium tetraphenylboron (TPB) in nitrobenzene, whereby ¹³⁷Cs binds with tetraphenylboron anions and gets separated. Results of this investigation indicate that ¹³⁷Cs could be efficiently and selectively extracted from an aqueous solution media containing high concentration of Na⁺ under mildly acidic pH into an organic phase and back extracted with small volume of 3 M HNO₃, thus enabling concentration. The proposed method was successfully applied in real samples.