Separation Of Metal Ions Research Articles

Elimination of toxic metal ion by means of poly m-phenylene (isophthalamide) ultra filtration membranes

Poly m-phenylene (Isophthalamide) (PMIA) Ultrafiltration membranes were synthesized by Non-solvent induced phase inversion technique using Lithium Chloride (LiCl) with various compositions of Poly ethylene glycol (PEG-600) and N-methyl pyrrolidone (NMP) solvent. The effects of compositions of PEG-600, pure water flux and percentage water content of the membranes were studied. The application of PMIA membranes in separation of toxic heavy metal ions from solutions was also attempted and the results were discussed.

D2EHPA is a potential extractant for extraction of europium and samarium from chloride medium

Europium and samarium, the most valuable rare earth metals are broadly used in different areas such as fluorescent, medical materials and samarium-cobalt permanent magnet in the industrial community. Solvent extraction is an extensively applied separation process for collection of high purity rare earth metal ions. Due to the congruent physical and chemical properties of rare earth metal ions, the separation of specific elements from the mixture is ambiguous. In such places solvent extraction process is most efficient because of their ease in terms of the equipment and conditions associated with them. Solvent extraction, using di-2-ethylhexylphosphoric acid (D2EHPA) is the most frequently used industrial extractant for the extraction and separation of rare earth metal ions compared with other extractants. Present report deal with the studies on solvent extraction of europium (III) and samarium (III) from chloride medium using D2EHPA diluted in kerosene. Utmost extraction such as 96.65% Eu(III) and 86% Sm(III) happened at 0.001 mol/L hydrogen ion concentration in the aqueous medium. 100% extraction of Eu (III) and Sm(III) has been noticed with 0.07 mol/L and 0.08 mol/L D2EHPA, respectively. The separation factors of Eu/Co and Sm/Co are 1844.44 and 1556, respectively.

Study on Development and Evaluation of Metal Ion Separation Systems Based on Complexation and Liquid-liquid Transfer

著者はこれまで金属イオンの溶媒抽出分離について，新規抽出剤としての多座配位子の開発と分離機能解析，および新たな抽出溶媒としてのイオン液体（IL）の機能解析を中心に研究を行ってきた。本稿では，ペンダントアーム型多座配位子とスルホンアミド型多座配位子の抽出試薬としての機能解析，ILキレート抽出における抽出種の荷電状態評価，IL三相抽出系の開発，抽出試薬としての分離機能解析，および塩析相分離剤としての親水性ILの利用について，著者らの研究成果の一部を概説する。

Synthesis and Adsorption Study of some Chitosan Acid Derivatives as Dispersants for Ceramic Alumina Powders

The different functionality nature of Chitosan adds to its application as a preferable natural polymer not only for the recovery, separation, and concentration of metal ions, but for the fabrication of a wide spectrum of efficient materials, and opens a new window to act as a dispersant for ceramic particles in an aqueous medium; this is why the current study focused on getting Chitosan from chitin extracted from shrimp shells by known and modified chemical methods to obtain a high Degree of Deacetylation (DD) reached 93% to increase its solubility in dilute acidic aqueous medium. Three acid Chitosan derivatives were synthesized by grafting Chitosan chains with Glutaric, Pimelic, and Sebacic acids. The grafting process was checked by FTIR, which confirmed the compositions of the acid derivatives prepared as well as Chitosan... The ability of Chitosan and its derivatives to act as a dispersant for alumina ceramics powder was assessed by sedimentation and rheological techniques. The results showed that they have good power for deflocculating alumina particles, this implies that they may be good dispersant for ceramic processing in aqueous media which is the priority for ceramic manufacturers. The quantity of adsorbed dispersants, qe (mg/g), was determined by thermal gravimetric analysis, and hence the remaining concentration in equilibrium Ce (mg/L), four different types of adsorption isotherm models were determined and evaluated by calculating the variables and constants for each type and studying the behavior of polymers prepared toward each model. The S-shape curve was obtained from plotting qe vs Ce referring to that the adsorption follows BET isotherm of multi-layer where each layer obeys Langmuir-Freundlich isotherm.

Maximizing the zinc ions removal by organic ligand-stabilized conjugate polysterene macronet material

Non-ionogenic cross-linked polystyrene-divinylbenzene resin (PAD-600) is modified with two different organic ligands: 2-amino-1-methylbenzimidazole (MAB) and diethyldithiophosphoric acid (DEDTP). The PAD600-MAB and PAD600-DEDTP have a porous microstructure, and the impregnated MAB and DEDTP molecules are homogenously distributed on the surface of PAD-600 via the hydrophobic part of organic ligands and van der Waals interactions. The sorption capacity and kinetics for Zn2+ removal are studied by a batch method. The Zn2+ sorption followed the Freundlich model (Kf = 1.11 for PAD600, Kf = 2.09 for PAD600-DEDTP, and Kf = 1.45 for PAD600-MAB) and pseudo-second order (k2 = 33.13 g∙mmol∙min–1 for PAD600, k2 = 0.35 g∙mmol∙min–1 for PAD600-DEDTP, and k2 = 3.45 g∙mmol∙min–1 for PAD600-MAB). The interaction of MAB and DEDTP with Zn2+ on the surface of PAD-600 can maximize the sorption of Zn2+ and change the morphology from homogenous porous to heterogeneous low-porous state. The FTIR spectra reveal the impregnation efficiency and the formation of zinc complexes after Zn2+ sorption. The equilibrium and maximum sorption are reached after 1 h at pH = 6. The effects of pH and temperature on Zn2+ sorption are also explored. PAD600-MAB exhibits a lower sorption capacity at higher temperature than PAD600-DEDTP due to the formation of stable zinc dialkyldithiophosphate on the surface. The computer modeling confirms the contribution of electrostatic and van der Waals forces to the solid stability for adsorption process, and the direct interactions of organic ligands with Zn2+ are highly dependent on complex formation. As inexpensive and green sorbents, the PAD600-MAB and PAD600-DiPDTP can be used for selective concentration and separation of various metal ions.

Solvent Extraction of Metal Ions from Sulfate Solutions Obtained in Leaching of Spent Ni-MH Batteries

Abstract The nickel metal hydride batteries (Ni-MH) are used in many electronic equipment, like cell phones, computers, cameras as well as hybrid cars. Spent batteries can be a rich source of many metals, especially rare earth elements (REE), such as lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), samarium (Sm), gadolinium (Gd). Ni-MH batteries also contain iron (Fe) as well as non-ferrous metals, i.e. nickel (Ni), cobalt (Co), zinc (Zn), manganese (Mn), etc. Leaching of such waste with sulfuric acid solutions is one among many methods recovering of useful metals in hydrometallurgical processes. The main aim of this work was separation of metal ions from pregnant leach liquor (PLL) by solvent extraction using phosphorous compounds and ionic liquids (ILs). The initial pH of the aqueous solution was 0.1. Di (2-ethylhexyl) phosphoric acid (D2EHPA), bis (2,2,4-trimethylpentyl) phosphinic acid (Cyanex 272), and phosphoniumionic liquid – trihexyl (tetradecyl) phosphonium bis (2,4,4-trimethylpentyl) phosphinate (Cyphos IL 104) were used as the selective extractants. The initial concentration of the extractants in an organic phase was equal to 0.1 mol∙dm−3. The obtained results show that the highest extraction efficiency was obtained for Fe(III) and Zn(II) in extraction experiments with 0.1 M D2EHPA at pH of 0.1. Ni(II), Co(II) and REE remained in the aqueous solutions. In the next stage, REE were extracted with the mixture of 0.1 M Cyanex 272 and 0.1 M Cyphos IL 104 at pH equal to 3.8. Finally, Ni(II) and Co(II) ions were efficiently removed from the aqueous phase using 0.1 M solution of Cyphos IL 104 at pH around 5.4.

Comparison of some magnetic nanoparticles based on iron oxide for separation and determination of cadmium metal ion by atomic spectrometry in seawater, wastewater and urine samples

ABSTRACT Magnetic nanoparticles based on iron oxide can be synthesised easily and separated with a magnetic bar. To determine heavy and dangerous metal of cadmium, for the first time, five types of magnetic nanoparticles based on iron oxide were used for separation and measurement of heavy and dangerous metal ion of cadmium. To obtain the high specific surface area for nanocomposite, the silicate nanoparticles were used and TAR ligand was used for adsorption of the cadmium metal to the nanocomposite. The used complex ligand was 4-(2ʹ–thiazolylazo) – resorcinol which has a thiol group with a high tendency to silver and gold ion metals. To increase the specific surface, absorption and extraction of cadmium ion, the magnetic silica nanoparticles were used. To obtain more accuracy and precision for ion determination, the optimisation of the effective parameter is important. In this research, MINITAB software was used for the performance of response surface modelling (RSM) optimisation method. To determine the heavy metal ion of cadmium, the flame atomic absorption spectrometry was used. Under the optimum conditions (pH = 4.1, the concentration of ligand = 1.5 mM, temperature = 27ºC) and using the magnetic nanoparticle with high specific surface, a preconcentration factor of 180, the linear range 0.4–110 (µg L−1), recovery (98%), limit of quantification of 0.34 µg L−1 and a limit of detection of 0.11 µg L−1 for cadmium ion were obtained. To obtain the precision of the method, each measurement was repeated 5 times, and the relative standard deviation value for cadmium ion concentration of 8.0 µg L−1 was obtained to be 3.1%. Finally, to evaluate the suggested method, the detection and measurement of cadmium ion in seawater, wastewater and urine sample were performed.

Ion beam engineered graphene oxide membranes for mono-/di-valent metal ions separation

Graphene oxide (GO) membranes with precisely controlled nanopores are promising for selectively ionic separation. Here, an ion beam was used to efficiently and simply post-modify GO membranes, creating nanopores in a controllable manner. We compared the influence of GO membrane thickness and ion fluence on the GO structure and the consequent mono-/di-valent metal ion separation performance. Experimental results indicate all GO membranes exhibited improved K+ selectivity with respect to other ions after ion beam irradiation. Moreover, the K+ ion permeability of the optimal membranes is up to 1.4 × 10−3 mol m−2 h−1 and the membrane shows extremely high K+ separation factor to di-valent ions. Remarkably, this method could be used as an in-situ post-treatment for pre-assembled GO membranes. We believe that this strategy offers novel insights into fabricating nanoporous membranes constructed by two-dimensional nanomaterials for a variety of fields including energy, desalination and biomedical applications.

Polymer Inclusion Membranes (PIMs) Doped with Alkylimidazole and their Application in the Separation of Non-Ferrous Metal Ions.

The study involved the transport of zinc(II), cadmium(II), and nickel(II) ions from acidic aqueous solutions using polymer inclusion membranes (PIMs). PIMs consisted of cellulose triacetate (CTA) as a support; o-nitrophenyl pentyl ether (o-NPPE) as a plasticizer; and 1-octylimidazole (1), 1-octyl-2-methylimidazole (2), 1-octyl-4-methylimidazole (3), or 1-octyl-2,4-dimethylimidazole (4) as ion carriers. The membranes were characterized by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that Zn(II) and Cd(II) are effectively transported across PIMs, while Ni(II) transport is not effective. The rate of transport of metal ions across PIMs is determined by the diffusion rate of the M(II)–carrier complex across the membrane. The best result achieved for Zn(II) removal after 24 h was 95.5% for the ternary Zn(II)–Cd(II)–Ni(II) solution for PIM doped (4). For this membrane, the separation coefficients for Zn(II)/Cd(II), Zn(II)/Ni(II), and Cd(II)/Ni(II) were 2.8, 104.5, and 23.5, respectively. Additionally, the influence of basicity and structure of carrier molecules on transport kinetics was discussed.

Separation and preconcentration of arsenite and other heavy metal ions using graphene oxide laminated with protein molecules

The graphene oxide surface was laminated with bovine serum albumin (BSA) followed by the directional flow through a membrane to prepare a free-standing PLGO (protein laminated GO) composite. BSA immobilization increased the interlayer spacing of GO and led to the formation of capillaries. The column packed with PLGO adsorbent permeated water faster as much as ca. 5 fold as compared to only GO packed column. The PLGO composite was used to develop a solid phase extraction method for the selective preconcentration of As(III) in the presence of As(V), prior to their determination. As(III) binding to sulfhydryl groups of BSA in PLGO plays a key role in the speciation. The coexisting heavy metal ions did not hinder the recovery of trace As(III). The method was advantageously employed for the preconcentration of As(III), Pb(II), Cd(II), Zn(II), Cu(II) and Ni(II) from water and food samples. A 3 mL of 1 M hydrochloric acid would be adequate for the complete desorption (recovery > 99%) of the adsorbed metal ions. The preconcentration limit achieved for As(III), Pb(II), Cd(II), Zn(II), Cu(II) and Ni(II) were 1.7, 2.0, 2.0, 2.0, 1.8 and 2.0 μg L−1 respectively, with an optimized sample flow rate of 10 mL min−1.

Efficient removal of Hg (II) ions from waste water by a new nano-composite poly-o-toluidine tin-zirconium (IV) molybdophosphate

ABSTRACT A new nano-composite cation exchanger poly-o-toluidine tin-zirconium (IV) molybdophosphate (PTD-SnZrMoP) was synthesised by incorporating conducting polymer poly-o-toluidine into a novel four-component inorganic cation exchanger tin-zirconium (IV) molybdophosphate with two cations and two anions. The nano-composite was characterised by FTIR, FESEM, TEM, XRD and TGA/DTA techniques. The ion exchange capacity of the nano-composite ion exchanger (2.40 meq/g) was observed to be higher as compared to that of its inorganic counterpart (1.95meq/g). The nanocomposite was found to be thermally stable, and retained 60.4% of its ion exchange capacity up to a temperature of 400°C. Elution behaviour, thermal stability, chemical stability, distribution studies and quantitative separations of metal ions from synthetic binary mixtures as well as real life effluent samples from a thermal power plant on poly-o-toluidine tin-zirconium (IV) molybdophosphate nano-composite exchanger were also investigated. The nano-composite was employed for the quantitative separation of Hg (II) ions from thermal power plant effluents.

Ferrous sulfide and carboxyl-functionalized ferroferric oxide incorporated PVDF-based nanocomposite membranes for simultaneous removal of highly toxic heavy-metal ions from industrial ground water

The deterioration of the aquatic environment by the heavy metal ions contamination causes serious threat to environment and human beings. However, the treatment of complex industrial wastewater by simultaneous removal of multiple heavy metal ions via a one-step method is still extremely challenging. To this end, we synthesize ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide (CFFO) nanoparticles, which were introduced into polyvinylidene fluoride (PVDF) matrix (individually/mixed together in an optimum ratio) through phase inversion technique. Three types of mixed matrix membranes (MMMs) were developed, viz. FeS/PVDF, CFFO/PVDF and FeS/CFFO/PVDF. The prepared membranes were characterized by SEM, TEM, AFM, FTIR, XRD, BET, and XPS techniques. The properties of the membranes were also examined for pure water flux, hydrophilicity, water uptake capacity, mechanical and thermal property, salt separation and simultaneous separation of toxic heavy metal ions such as lead, (Pb), cadmium (Cd), and chromium (Cr) from industrial ground water. The resultant membranes exhibited relatively high water flux (340–1266 L/m2h) than the unmodified PVDF membrane, due to changes in the porosity and hydrophilicity of the membranes. FeS/CFFO/PVDF membrane showed that it could effectively treat Pb, Cd, Cr and As contaminated industrial ground water, simultaneously with a high removal efficiency of about 88% for Cr(VI), 99% for Cd2+, 99% for Pb2+ and 95% for As in a single filtration process. In addition, the developed membranes conspicuously reduce their concentrations below the maximum contaminant level of WHO and BIS (India). The probable mechanism of separation of heavy metal ions through MMMs could be understood through FTIR and XPS techniques. The results of this study inferred that FeS/CFFO/PVDF membrane is a potential candidate for the simultaneous separation of Pb, Cd, Cr, and As.

Separation of valuable metals in spent LiNi0.46Co0.2Mn0.34O2 battery by shear induced dissociation coupling with ultrafiltration

There are valuable metals in spent ternary lithium-ion batteries. A method for selective separation of Al (III), Fe (III), Li (I), Mn (II), Co (II), Ni (II) and Cu (II) from acid leaching of spent LiNi0.46Co0.2Mn0.34O2 battery was proposed. Al (III) and Fe (III) are firstly separated by chemical precipitation, and other metal ions are formed polymer-metal complexes by adding polyacrylate sodium (PAAS) as complexing agent. According to the difference of shear stabilities of PAA-metal complexes, selective separation of metal ions was fulfilled by shear induced dissociation coupling with ultrafiltration using rotating disk membrane (RDM). The shear induced dissociation mechanism of polymer-metal complex was studied. Compared with the traditional separation methods, such as acidification and extraction, shear induced dissociation coupling with ultrafiltration without the consumption of acid and alkali, is green and environmentally friendly effective method for the recovery of metal ions.

Reusable hydroxamate immobilized silica adsorbent for dispersive solid phase extraction and separation of rare earth metal ions

Silica gel with covalently immobilized N-Benzoyl-N-phenylhydroxylamine fragments (SiO2-BPHA) has been successfully prepared using surface assembling approach. The SiO2-BPHA is characterized by FTIR, high-resolution X-ray photoelectron spectroscopy, by SEM and BET measurements, and by elemental and thermogravimetric analysis. It has been demonstrated that SiO2-BPHA can be successfully used as an adsorbent for dispersive solid-phase extraction (DSPE) and separation of Rare Earth Elements (REE) from aqueous solution. The adsorbent capacities toward La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+, and Y3+ ions have been determined from the adsorption isotherms. Adsorption kinetics and competitive adsorption of REEs from multielement solution have been studied as a function of pH. Sharp changes of REEs recovery on SiO2-BPHA have been observed in the pH range 3.3–5.0 with more than 95% of the metal adsorption at pH ≥ 5.0. The complete desorption of all REEs from SiO2-BPHA can an in 0.1 mol L−1 of HNO3. Reusability test has demonstrated that SiO2-BPHA can be used for quantitative adsorption of almost all (average adsorption of Ce and Pr ions is about 90%) REEs from multielement solution with pH = 5.0, without loss in adsorption capacity and selectivity for at least ten consecutive cycles. It has been found that essential (more than 100 times) growth of distribution coefficient in respect to the atomic number of REE is observed for multielement solution analyzed. In optimal conditions, the selectivity factor is about 80 for Lu/La and Yb/La pairs and takes about 60 for Tm/La pair, which serves as an evidence of the high potential of SiO2-BPHA in REEs separation.

Separation of Tb(III) and Dy(III) from Chloride Solution by Extraction and Scrubbing with Ionic Liquid Prepared with Cyanex 272 and Aliquat 336

Terbium and dysprosium are rare earth elements which are employed in the manufacture of advanced materials. Separating Tb(III) and Dy(III) is very complicated because their chemical properties are similar. In order to develop a separation process based on solvent extraction, extraction and scrubbing experiments were conducted using weak hydrochloric solutions containing Tb(III) and Dy(III). In this work, three kinds of Cyanex 272, namely, single Cyanex 272, a mixture with Alamine 336 and an ionic liquid prepared with Aliquat 336 were employed. In the initial pH range between 1.5 and 5, the extraction behavior of both Tb(III) and Dy(III) was very similar using these extractants, resulting in low separation factor. In terms of extraction percentage and separation factor, the ionic liquid showed better performance than both single Cyanex 272 and the mixture. Scrubbing experiments were conducted using the loaded ionic liquid, employing a Dy(III) scrubbing solution. The optimum concentration of Dy(III) in the scrubbing solution was determined. A McCabe-Thiele diagram for the scrubbing of Tb(III) in the loaded ionic liquid with Dy(III) solution was constructed. In order to verify the separation of both metal ions, batch simulation cross-current scrubbing experiments were performed. After 6 cross-current scrubbing stages, the purity of Dy(III) in the loaded ionic liquid increased from 50% to 99%. By utilizing the data reported in this work, a process can be developed for the separation of Tb(III) and Dy(III) by solvent extraction. Key words: terbium(III), dysprosium(III), solvent extraction, scrubbing, separation

Elaboration and Characterization of New Polymeric Membrane Based on Poly (N, N‐Diethyl Aminoethyl Methacrylate), Cellulose Triacetate, and Polysulfone

Polymerinclusion membranes used for selective transport and separation of metallic ions have emerged in recent times. Their expansion depends on the method of preparation and the study of their structure. In this paper, an improvement of a novel category of thin films for performing ion separation was reported. The membranes were elaborated using a mixture of polymers: cellulose triacetate (CTA), polysulfone (PSu) and poly (N, N‐diethyl aminoethyl methacrylate) (PDEAEM), 2‐nitrophenyl pentyl‐ether (NPPE) was used as plasticizer, 15‐crown‐ether‐5 (15‐C‐5) was incorporated into the polymers as a metal ion carrier. The membranes (polymers − plasticizer − carrier) were synthesized using a new method and characterized by various techniques including Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The CTA membranes exhibited well‐defined pores completely filled with the other polymers and plasticizer (NPPE). The surfaces of all synthesized membranes were found to be smooth. Overall, our results showed that the addition of plasticizer with polymers resulted in homogeneous and hydrophobic membranes. As application, quality parameters including electric conductivity, chlorides, bicarbonates and heavy metal (Pb2+) were determined before and after treatment of real wastewater using the synthesized polymeric membranes.

Phosphonate-Decorated Covalent Organic Frameworks for Actinide Extraction: A Breakthrough Under Highly Acidic Conditions

Although solid-phase extraction is a useful approach for metal ion separation from aqueous solutions, existing sorbents suffer from low extraction efficiencies and/or instability when in contact wi...

Physical insights into kinetic models of adsorption

The pseudo first- (PFO) and second-order (PSO) kinetic models have been extensively applied to study the kinetics of interfacial processes, for example, separation or removal of toxic metal ions from aqueous solution by adsorption. However, the two models were used without any specialization of operating conditions and their theoretical origin is not well understood. The aim of the present study is to provide clear physical understanding on the relationships of the Langmuir kinetics with the two models. The conditions under which the Langmuir kinetics can be reduced to the simplified models and their explicit dependence on operating conditions and isotherm parameters are provided. We adopt the square root method to obtain two roots of the differential Langmuir rate equation at equilibrium, then prove that one root is the surface coverage fraction and the other is the reciprocal of adsorption efficiency at equilibrium, and show that the root ratio is a critical factor in assessing the applicability of the PFO and PSO models. This critical factor solely depends on the ratio of available adsorbate to adsorbent capacity and the product of the Langmuir equilibrium constant and adsorbent capacity. The reduction of the Langmuir kinetics to the PFO and PSO models can be valid only under extreme conditions. The system with too high or too low available adsorbate relative to the maximum adsorbent capacity or with too small adsorption rate constant multiplied by the maximum adsorbent capacity relative to the desorption rate constant might be approximately described by the PFO model. On the other extreme that available adsorbent capacity matches available adsorbate and desorption rate constant is negligible compared with the adsorption rate constant multiply by the maximum adsorbent capacity, the PSO model could replace the Langmuir kinetics. As such, the desorption part in the Langmuir rate equation disappears and the reversible Langmuir kinetics is reduced to irreversible process. Obviously, this is hardly encountered in reality. The present study offers physical insights into the relationships between the Langmuir kinetics with the PFO and PSO models in terms of operating conditions and isotherm parameters.

Graphene Oxide/Carbon Nanotube Membranes for Highly Efficient Removal of Metal Ions from Water.

Graphene oxide (GO) has an excellent adsorption capacity toward metal ions. Therefore, it is widely recognized as an auspicious material for fabrication of membranes applied in metal ion separation. However, GO membranes are not stable in aqueous solution because of electrostatic repulsion between GO nanosheets which are negatively charged. This paper shows that stable GO membranes can be easily obtained by the noncovalent interaction of GO with oxidized carbon nanotubes (CNTs). The experiment also shows that the GO/CNTs membranes can be used for the effective adsorption of metal ions. The kinetic data, adsorption isotherms, competitive adsorption experiment, and X-ray photoelectron spectroscopy indicate that the adsorption of metal ions is based on chemisorption. The membranes are remarkably durable in acidic, neutral, and basic solutions. Although the significant stabilization of the membranes by CNTs is observed, they strongly influence the adsorption process. Our study reveals that even a small amount of CNTs (GO/CNTs in the ratio 8:1) significantly reduces adsorption capacities of the membranes which were as follows: 37, 40, 50, 42, 48, and 98 mg g-1 for Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The reduction of the membrane adsorption capacities results from the creation of micro- and nanochannels formed by entangled CNTs. Durability and adsorptive properties of studied membranes indicate their potential use for the removal of metals from water.

Carrier-mediated liquid membrane systems for lead (II) ion separations

Liquid membranes (LMs), such as bulk liquid membrane (BLM), supported liquid membrane (SLM), emulsion liquid membrane, and polymer inclusion membrane (PIM) coupled with variety of carriers such as crown ethers, organo-phosphorous compounds, carboxylic acids and calixarenes, have been investigated for the transport of Pb(II) ions from different aqueous media. The effects of the chemical compositions and LM configurations on the transport selectivity and the recovery yield of Pb(II) ions have been reviewed in this paper. The comparison among the selectivities of these carriers showed that crown ether-mediated LMs can be efficiently used in analytical laboratories for high selective preconcentration of trace amounts of Pb(II) ions. On the other hand, D2EHPA-mediated LMs could be the mostly suitable for simultaneous removal and recovery of the other heavy metal ions including Pb(II) ions from wastewater. For the potential applicability of the existing LM configurations in the areas of metal ion separation processes, it seems that BLM, SLM, and PIM are sufficient enough on the laboratory scale at high selective preconcentration step. The other configurations such as hollow fiber or emulsion LMs would be the most suitable to apply on large scale of heavy metal ions removal from wastewater.