The sorption behavior of a nickel-insolubilized humic acid system in a column arrangement

The sorption characteristics of insolubilized humic acid (IHA) were investigated for Ni (II) in a column arrangement. The sodium form of the IHA (INaA) was used as a solid phase. Column operations were performed with five steps and all of them were monitored continuously by a flowthrough cell-adapted UV-Vis spectrophotometer. Thus, all solid-phase extraction (SPE) steps were visualized by breakthrough curves and analyses progress were evaluated. However, all calculations and evaluations were focused on the atomic absorption spectrophotometric (AAS) analyses of the solutions collected during the stripping steps. There was a high correlation (r(2), 0.972) between peak area and AAS data of stripping steps. The effect of concentration and pH of the loading solution onto sorption of Ni (II) by INaA was investigated. Sorption characteristics were evaluated by using Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) adsorption isotherms, as well as by Scatchard plot analysis. Multilayer sorption was found to be agreeable for Ni (II). From the D-R isotherm the mean free energy of sorption (E) was calculated (6.65 kJ mol(-1)) and attributed to the multilayer sorption. Finally, the sorption characteristic of the INaA-Ni (II) system was compared with that of the INaA-Cu (II) system, and possible separation of two ions in a binary mixture system is discussed.     

Thermodynamics and kinetics of adsorption of Cu(II) from aqueous solutions onto a new cation exchanger derived from tamarind fruit shell

A novel cation exchanger (TFS-CE) having carboxylate functionality was prepared through graft copolymerization of hydroxyethylmethacrylate onto tamarind fruit shell (TFS) in the presence of N,N′-methylenebisacrylamide as a cross-linking agent using K₂S₂O₈/Na₂S₂O₃ initiator system, followed by functionalisation. The TFS-CE was used for the removal of Cu(II) from aqueous solutions. At fixed solid/solution ratio the various factors affecting adsorption such as pH, initial concentration, contact time, and temperature were investigated. Kinetic experiments showed that the amount of Cu(II) adsorbed increased with increase in Cu(II) concentration and equilibrium was attained at 1 h. The kinetics of adsorption follows pseudo-second-order model and the rate constant increases with increase in temperature indicating endothermic nature of adsorption. The Arrhenius and Eyring equations were used to obtain the kinetic parameters such as activation energy (E_a) and enthalpy (ΔH^#), entropy (ΔS^#) and free energy (ΔG^#) of activation for the adsorption process. The value of E_a for adsorption was found to be 10.84 kJ · mol^?1 and the adsorption involves diffusion controlled process. The equilibrium data were well fitted to the Langmuir isotherm. The maximum adsorption capacity for Cu(II) was 64 · 10 mg · g^?1 at T = 303 K. The thermodynamic parameters such as changes in free energy (ΔG^°), enthalpy (ΔH^°), and entropy (ΔS^°) were derived to predict the nature of adsorption process. The isosteric heat of adsorption increases with increase in surface loading indicating some lateral interactions between the adsorbed metal ions.     

Removal of Cu(II), Cd(II) and Cr(III) ions from aqueous solution by dam silt

The removal of heavy metals, such as Cu(II), Cd(II) and Cr(III) from aqueous solution was studied using Chorfa silt material (Mascara, Algeria). The main constituents of silt sediment are quartz, calcite and mixture of clays. The experimental data were described using Freundlich, Langmuir, Dubinin–Radushkevich (D–R) and Langmuir–Freundlich models. The adsorbed amounts of chromium and copper ions were very high (95% and 94% of the total concentration of the metal ions), whereas cadmium ion was adsorbed in smaller (55%) amounts. The Langmuir–Freundlich isotherm model was the best to describe the experimental data. The maximum sorption capacity was found to be 26.30, 11.76 and 0.35 mg/g for Cr³⁺, Cu²⁺ and Cd²⁺, respectively. The results of mean sorption energy, E (kJ/mol) calculated from D–R equation, confirmed that the adsorption of copper, chromium and cadmium on silt is physical in nature.     

Reactivity of sugar cane bagasse as a natural solid phase extractor for selective removal of Fe(III) and heavy-metal ions from natural water samples

This work introduces the feasibility of using sugar cane bagasse (SCB) – a sugar cane industry waste – as a selective solid phase extractor for Fe(III). The order of metal uptake capacities in μmol g^?1 for the extraction of six tested metal ions from aqueous solution using static technique is Fe(III) > Cu(II) > Pb(II) > Zn(II) > Cd(II) > Co(II). Since SCB exhibits remarkable binding characteristics for Fe(III), special interest was devoted for optimizing its uptake and studying its selectivity properties under static and dynamic conditions. In this respect, batch experiments were carried out at the pH range 1.0–4.0, initial concentration of metal ion (10–100 μmol), weight of phase (25, 50, 75, 100, 125 and 150 mg) and shaking time (10, 30, 45, 60, 90, 120 and 150 min). FT-IR spectra of SCB before and after uptake of Fe(III) were recorded to explore the nature of the functional groups responsible for binding of Fe(III) onto the studied natural biosorbent. The equilibrium data were better fitted with Langmuir model (r² = 0.985) than Freundlich model (r² = 0.934). Moreover, Fe(III) sorption was fast and completed within 60 min. The adsorption kinetics data were best fitted with the pseudo-second-order type. As a view to find a suitable application of SCB based on its unique property as a benign sorbent, it was found that, Fe(III) spiked natural water samples such as doubly distilled water (DDW), drinking tap water (DTW), natural drinking water (NDW), ground water (GW) and Nile River water (NRW) was quantitatively recovered (>95.0%) using batch and column experiments, with no matrix interferences.     

Preconcentration procedure trace amounts of palladium using modified multiwalled carbon nanotubes sorbent prior to flame atomic absorption spectrometry: 1st Nano Update

A method for preconcentration of palladium at trace level on modified multiwalled carbon nanotubes columns and determination by flame atomic absorption spectrometry (FAAS) has been developed. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO₃ and the oxidized multiwalled carbon nanotubes were modified with 5-(4′-dimethylamino benzyliden)-rhodanine, and then were used as a solid sorbent for preconcentration of Pd(II) ions. Factors influencing sorption and desorption of Pd(II) ions were investigated. The sorption of Pd(II) ions was quantitative in the pH range of 1.0–4.5, whereas quantitative desorption occurs with 3.0 mL 0.4 mol L^?1 thiourea. The amount of eluted palladium was measured using flame atomic absorption spectrometry. The effects of experimental parameters, including sample flow rate, eluent flow rate, and eluent concentration were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 200). The relative standard deviation of the method was ±2.73% (for eight replicate determination of 2.0 μg mL^?1 of Pd(II)) and the limit of detection was 0.3 ng mL^?1. The method was applied to the determination of Pd(II) in water, road dust, and standard samples.     

Thermodynamics of the Cu(II) adsorption on thin vanillin-modified chitosan membranes

In this work, low-density vanillin-modified thin chitosan membranes were synthesized and characterized. The membranes were utilized as adsorbent for the removal of Cu(II) from aqueous solutions. The experimental data obtained in batch experiments at different temperatures were fitted to the Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. The adsorption equilibrium data fitted well with the Langmuir model (average R² > 0.99). Interactions thermodynamic parameters (Δ_intH, Δ_intG, and Δ_intS), as well as the interaction thermal effects (Q_int) were determined from T = (298 to 333) K. The thermodynamic parameters, the Dubinin–Radushkevick equation and the comparative values of Δ_intH for some Cu(II)–adsorbent interactions suggested that the adsorption of Cu(II) ions to vanillin-chitosan membranes show average results for both the diffusional (endothermic) and chemical bonding (exothermic) processes in relation to the temperature range studied.     

Synthesis and spectroscopic characterization of new tetradentate Schiff base and its coordination compounds of NOON donor atoms and their antibacterial and antifungal activity

New Schiff base (H₂L) ligand is prepared via condensation of o-phthaldehyde and 2-aminobenzoic acid in 1:2 ratio. Metal complexes are prepared and characterized using elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, ¹H NMR, ESR and thermal analysis (TGA). From the elemental analyses data, the complexes were proposed to have the general formulae [MCl(L)(H₂O)]·2H₂O (where M = Cr(III) and Fe(III)); [M(L)]·yH₂O (where M = Mn(II), Ni(II), Cu(II) and Zn(II), y = 1–2) and [M(L)(H₂O)_n]·yH₂O (where M = Co(II) (n = y = 2), Co(II) (n = y = 1), Ni(II) (n = 2, y = 1). The molar conductance data reveal that all the metal chelates were non-electrolytes. IR spectra show that H₂L is coordinated to the metal ions in a bi-negative tetradentate manner with NOON donor sites of the azomethine-N and carboxylate-O. The ¹H NMR spectral data indicate that the two carboxylate protons are also displaced during complexation. From the magnetic and solid reflectance spectra, it was found that the geometrical structure of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II)), square planar (Cu(II)), trigonal bipyramidal (Co(II)) and tetrahedral (Mn(II), Ni(II) and Zn(II)). The thermal behaviour of these chelates showed that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the ligand molecule in the subsequent steps. The biological activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species.     

Thermodynamic and isotherm studies of the biosorption of Cu(II), Pb(II), and Zn(II) by leaves of saltbush (Atriplex canescens)

The Freundlich and Langmuir isotherms were used to describe the biosorption of Cu(II), Pb(II), and Zn(II) onto the saltbush leaves biomass at 297 K and pH 5.0. The correlation coefficients (R²) obtained from the Freundlich model were 0.9798, 0.9575, and 0.9963 for Cu, Pb, and Zn, respectively, while for the Langmuir model the R² values for the same metals were 0.0001, 0.1380, and 0.0088, respectively. This suggests that saltbush leaves biomass sorbed the three metals following the Freundlich model (R² > 0.9575). The K_F values obtained from the Freundlich model (175.5 · 10⁻², 10.5 · 10⁻², and 6.32 · 10⁻² mol · g⁻¹ for Pb, Zn, and Cu, respectively), suggest that the metal binding affinity was in the order Pb > Zn > Cu. The experimental values of the maximal adsorption capacities of saltbush leaves biomass were 0.13 · 10⁻², 0.05 · 10⁻², and 0.107 · 10⁻² mol · g⁻¹ for Pb, Zn, and Cu, respectively. The negative ΔG^∘ values for Pb and the positive values for Cu and Zn indicate that the Pb biosorption by saltbush biomass was a spontaneous process.     

Facilitated kinetic transport of Cu(II) through a supported liquid membrane with calix[4]arene as a carrrier

In the present investigation, p-morpholinomethylcalix[4]arene (1) has been examined as a carrier in supported liquid membrane (SLM) for Cu(II) transport. The influence of different parameters, such as solvent, membrane dipping time, support membrane, co-anions, donor and acceptor pH, and carrier concentration on Cu(II) transport, was checked. The permeability values were calculated by using Danesi mass transfer model. Higher Cu(II) permeability was observed in diphenyl ether, with 1 h dipping time, Celgard 2500 and Cl^? as co-anion. The optimum pH for donor phase was 2 and that for acceptor phase was neutral at 10^?3 M carrier concentration. Diffusion coefficients were calculated using Reinhoudt's model, lag time measurements as well as by Wilke–Chang relation and compared. The transport was found to be diffusion-controlled in the membrane phase and the diffusion coefficient was calculated to be 1.54 × 10^?10 m/s whereas the extraction constant was calculated to be 1.19 × 10^?5 m/s.     

Evaluation of Acacia nilotica as a non conventional low cost biosorbent for the elimination of Pb(II) and Cd(II) ions from aqueous solutions

In the present study a biomass derived from the leaves of Acacia nilotica was used as an adsorbent material for the removal of cadmium and lead from aqueous solution. The effect of various operating variables, viz., adsorbent dosage, contact time, pH and temperature on the removal of cadmium and lead has been studied. Maximum adsorption of cadmium and lead arises at a concentration of 2 g/50 ml and 3 g/50 ml and at a pH value of 5 and 4, respectively. The sorption data favored the pseudo-second-order kinetic model. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherm of the metal ions by A. nilotica biomass. Based on regression coefficient, the equilibrium data found were fitted well to the Langmuir equilibrium model than other models. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) have been calculated, respectively revealed the spontaneous, endothermic and feasible nature of adsorption process. The activation energy of the biosorption (Ea) was estimated as 9.34 kJ mol⁻¹ for Pb and 3.47 kJ mol⁻¹ for Cd from Arrhenius plot at different temperatures.     

Optical absorption and EPR studies on tenorite mineral

Optical absorption and EPR studies of the mineral tenorite, a cupric oxide which originated from Mexico and contains 54.40 wt% of CuO. EPR spectral results indicate two Cu(II) closely interacting ions to give a d² type structure. The calculated spin Hamiltonian at room temperature and liquid nitrogen temperature is g = 2.160 and D = 125 G. The intensity of resonance line is not the same in low and high field regions. The optical absorption spectrum is due to Cu(II) in which three sets of energies indicating Cu(II) in two independent tetragonal C_4v symmetry, in addition to d² structure of octahedral coordination. The octahedral and tetragonal field parameters are compared with those reported for several other copper containing minerals.     

Study on a novel manufacturing process of membrane electrode assemblies for solid polymer electrolyte water electrolysis

A novel manufacturing process for catalyst coated membrane (CCM) was utilized to fabricate the membrane electrode assemblies (MEA) for solid polymer electrolyte (SPE) water electrolysis. The properties and performance of the modified CCM were analyzed and evaluated by SEM, electrochemistry impedance spectroscopy (EIS) and I–V curves. The characterizations reveal that the sprayed Nafion layers are very effective for increasing the reaction interface between SPE and the electrode catalyst layer. The test experiments show that the SPE water electrolyzer with new MEA structure can lower about 0.1 V of water electrolysis voltage at atmosphere pressure and 2 A cm⁻².     

Synthesis of polyacrylamide-bound hydroquinone via a homolytic pathway: Application to the removal of heavy metals

Polyacrylamide (PAAm) was chemically modified with hydroquinone (HQ) via a homolytic route. A degree of modification of approximately 58% was obtained under optimal reaction conditions: time of 6 h, and [modifier]/[acrylamide] molar ratio of 5. PAAm and its modified form HQ–PAAm were characterized by UV–visible spectroscopy, FT–IR spectroscopy, ¹³C NMR spectroscopy, DSC, TGA, XRD, and SEM. A relatively lower molecular weight of the corresponding hydroquinone-functionalized form was measured. The glass transition temperature of the modified polymeric material was lower than that of the pristine one: 78.82 °C for HQ–PAAm versus 161.19 °C for PAAm. A study of Cu(II) adsorption by the cross-linked PAAm and HQ–PAAm resins was conducted by varying the following parameters: pH, time, temperature, ionic strength, sorbent mass, and initial Cu(II) concentration. The adsorption capacity of Pb(II) and Cd(II) by the different resins and their corresponding extents of desorption were estimated. The optimal conditions for metal ion uptake by polyacrylamide and its modified resin were: pH = 5.4, time = 120 min, temperature = 45 °C. The sorption extent by the modified resin was in the order Pb(II) > Cu(II) > Cd(II). The desorption of the experimented metallic ions from the resins exceeded 97%. A new way of cross-linking PAAm and its modified form is described herein.     

Development of efficient SPE–TLC method and evaluation of biological interactions of contraceptives with progesterone receptors

TLC–SPE methodologies were developed to ascertain biological interactions of norethindrone acetate and dydrogesterone contraceptives with plasma progesterone receptor proteins. TLC solvent system for plain and Cu(II) impregnated silica gel plates was n-hexane-n-butanol (90:10, v/v), which took 20 min to run up to 10.0 cm. The best separation was on Cu(II) impregnated plates due to maximum difference in R_f values and compact spots. The optimized SPE conditions were pH 2.0 and 3.0 of phosphate buffer (50 mM) for norethindrone acetate and dydrogesterone, respectively. The flow rate of plasma and eluting solvent (methanol) through C₁₈ cartridge was 0.10 mL/min. The interactions of these contraceptives with progesterone receptor proteins were analysed by TLC–SPE results, which were supported by modelling using PyMOL and Autodoc4 softwares. The dydrogesterone was found to be bound strongly than norethindrone acetate. Attempts have been made to discuss the drugs’ interactions at chemo-supramolecular level.     

Efficient stripping voltammetric detection of organophosphate pesticides using NanoPt intercalated Ni/Al layered double hydroxides as solid-phase extraction

We developed a simple strategy for designing a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs) based on solid-phase extraction (SPE) using nanosized Pt intercalated Ni/Al layered double hydroxides (labeled as NanoPt-LDHs). By assembling NanoPt with LDHs together, the resulting NanoPt-LDHs are highly efficient to capture OPs. It dramatically facilitates the enrichment of OPs onto their surface and realizes the sensitive stripping voltammetric detection of methyl parathion (MP) as a model of OPs. The stripping analysis shows highly linear over MP concentration ranges of 0.001–0.15 and 0.3–1.0 μg mL^? 1 with a detection limit of 0.6 ng mL^–1 (S/N = 3). The combination of NanoPt, LDHs, SPE, and square-wave voltammetry (SWV) provides a fast, simple, and sensitive electrochemical method for OPs.     

Thermochemistry of Cu(II) and Ni(II) complexes with N,N-di-n-butyl-N′-thenoylthiourea and N,N-di-iso-butyl-N′-thenoylthiourea

Two substituted N-acylthioureas and the respective Ni(II) and Cu(II) complexes were synthesized, namely: N,N-di-n-butyl-N′-thenoylthiourea (Hnbtu); N,N-di-iso-butyl-N′-thenoylthiourea (Hibtu); bis[N,N-di-n-butyl-N′-thenoylthioureato]nickel(II), [Ni(nbtu)₂]; bis[N,N-di-n-butyl-N′-thenoylthioureato]copper(II), [Cu(nbtu)₂]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]nickel(II), [Ni(ibtu)₂]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]copper(II), [Cu(ibtu)₂]. The standard (p^° = 0.1 MPa) molar enthalpies of formation and sublimation of the two N-acylthioureas were measured, at T = 298.15 K, by rotating-bomb combustion calorimetry and Calvet microcalorimetry, respectively. The standard (p^° = 0.1 MPa) molar enthalpies of formation of the Ni(II) and Cu(II) complexes were determined, at T = 298.15 K, by high precision solution–reaction calorimetry. From the results obtained, the enthalpies of hypothetical metal–ligand and metal–metal exchange reactions, in the gaseous phase, were derived, thus allowing a discussion of the gaseous phase energetic difference between the complexation of Ni(II) and Cu(II) to 1,3-ligand systems with (S,O) ligator atoms.     

Equilibrium and kinetics studies on adsorption of Cu(II) from aqueous solutions onto a graft copolymer of cross-linked starch/acrylonitrile (CLSAGCP)

A synthetic graft copolymer of cross-linked starch/acrylonitrile was used as an adsorbent for the removal of Cu(II) ions from an aqueous solution of copper nitrate hexahydrate Cu(NO₃)₂ · 6H₂O at different temperatures and fixed pH. The amount adsorbed increased with increasing concentration of Cu(II) ions and decreasing temperature. The length of time taken to reach equilibrium of the adsorption of Cu(II) ions was the same at all temperatures tested. Kinetics studies showed that the adsorption process obeyed first-order reversible kinetics and the adsorption isotherms followed the Freundlich model. Furthermore, the thermodynamic parameters, i.e. standard free energy (ΔG^∘), standard enthalpy (ΔH^∘), and standard entropy (ΔS^∘), of the adsorption process were calculated and the results are discussed in detail.     

Copper removal from aqueous solution using biochar: Effect of chemical activation

The main aim of this study was to test the efficiency of biochar for Cu removal from synthetic and soil solutions, respectively.The biochar was produced from brewers draff via pyrolysis. Additionally, the prepared biochar was also activated using 2 M KOH to enhance its sorption efficiency to remove Cu from both solutions. Two different aqueous solutions were prepared for these experiments: (i) a synthetic using Cu-nitrate salt with 0.01 M NaNO₃ and (ii) soil solution obtained from a Cu-contaminated soil using 0.01 M CaCl₂ leaching procedure. Batch sorption and column experiments were used to evaluate the efficiency of both biochar (BC) and activated biochar (BC_act) to remove Cu from the solutions.Results showed that both biochar samples are pure amorphous carbon and the Cu sorption is thus mainly a result of physical sorption on the biochar surface. Next, chemical activation, using 2 M KOH, significantly increased the total volume of all pores in biochar (from 0.01 ± 0.002 to 8.74 ± 0.18 mL g⁻¹). On the other hand, the BET surface area was similar for both sorbents (BC = 9.80 ± 0.62 m² g⁻¹ and BC_act = 11.6 ± 0.4 m² g⁻¹). Results also demonstrate enhanced sorption efficiency of the BC_act (10.3 mg g⁻¹) in comparison with the BC (8.77 mg g⁻¹). Additionally, enhanced Cu removal during column retention test was observed for the BC_act in both synthetic and soil solutions, respectively.In summary, the results showed that biochar prepared from brewers draff was able to remove Cu from both aqueous solutions.     

Highly selective solid-phase extraction of trace Pd(II) by murexide functionalized halloysite nanotubes

The originality on the high efficiency of murexide modified halloysite nanotubes as a new adsorbent of solid phase extraction has been reported to preconcentrate and separate Pd(II) in solution samples. The new adsorbent was confirmed by Fourier transformed infrared spectra, X-ray diffraction, scanning electron microscope, transmission electron microscope and N₂ adsorption–desorption isotherms. Effective preconcentration conditions of analyte were examined using column procedures prior to detection by inductively coupled plasma-optical emission spectrometry (ICP-OES). The effects of pH, the amount of adsorbent, the sample flow rate and volume, the elution condition and the interfering ions were optimized in detail. Under the optimized conditions, Pd(II) could be retained on the column at pH 1.0 and quantitatively eluted by 2.5 mL of 0.01 mol L^?1 HCl–3% thiourea solution at a flow rate of 2.0 mL min^?1. The analysis time was 5 min. An enrichment factor of 120 was accomplished. Common interfering ions did not interfere in both separation and determination. The maximum adsorption capacity of the adsorbent at optimum conditions was found to be 42.86 mg g^?1 for Pd(II).The detection limit (3σ) of the method was 0.29 ng mL^?1, and the relative standard deviation (RSD) was 3.1% (n = 11). The method was validated using certified reference material, and has been applied for the determination of trace Pd(II) in actual samples with satisfactory results.     

An insight to the filtration mechanism of Pb(II) at the surface of a clay ceramic membrane through its preconcentration at the surface of a graphite/clay composite working electrode

The use of cyclic voltammetry (CV) and linear scan anodic stripping voltammetry (LSASV) to predict the selectivity of microfiltration ceramic membranes made from a lump of local clay towards Pb(II) ions filtration is described. The membranes were characterized by different techniques followed by CV analysis of the Fe(CN)₆^3-/Fe(CN)₆^4- redox couple and Pb(II) on bare graphite, raw clay, and clay-modified carbon paste electrode (clay-modified CPE). The effect of clay loading in the range of 1–10 % (w/w) on the electrodes is studied, where an enhanced peak current is observed for 5 % w/w clay. Moreover, a decrease in the peak current can be seen for bare graphite electrodes, suggesting that the clay mineral had played a substantial role in the sieving of heavy metal ions through the ceramic membrane. The electroactive surface area of 5% w/w raw clay towards Fe(II) ions was found to be in the order of 3.07 × 10^-2 cm² and higher than 5% w/w clay sintered to 1000 °C and bare graphite. CV analysis shows that both, 5 % w/w raw clay and 5 % w/w clay sintered to 1000 °C exhibited high peak currents towards Pb(II) ions. The mobility of the Pb(II) ions is found to increase when 5% w/w clay sintered to 1000 °C is utilized as membrane/electrode, leading to an increase in the amount of reduced Pb(II) ions on the surfaces of the clay membranes/electrodes. The study suggests successful filtration of Pb(II) ions through the proposed membrane/electrode and a much better accumulation than Fe(II) at the surface of the membrane/electrode before being subjected to filtration.