The efficacy of nitrosonaphthol functionalized XAD-16 resin for the preconcentration/sorption of Ni(II) and Cu(II) ions

Amberlite XAD-16 resin has been functionalized using nitrosonaphthol as a ligand and characterized employing elemental, thermogravimetric analysis and FT-IR spectroscopy. The sorption of Ni(II) and Cu(II) ions onto this functionalized resin is investigated and optimized with respect to the sorptive medium (pH), shaking speed and equilibration time between liquid and solid phases. The monitoring of the influence of diverse ions on the sorption of metal ions has revealed that phosphate, bicarbonate and citrate reduce the sorption up to 10–14%. The sorption data followed Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherms. The Freundlich parameters computed are 1/n = 0.56 ± 0.03 and 0.49 ± 0.05, A = 9.54 ± 1.5 and 6.0 ± 0.5 mmol g⁻¹ for Ni(II) and Cu(II) ions, respectively. D–R isotherm yields the values of X_m = 0.87 ± 0.07 and 0.35 ± 0.05 mmol g⁻¹ and of E = 9.5 ± 0.23 and 12.3 ± 0.6 kJ mol⁻¹ for Ni(II) and Cu(II) ions, respectively. Langmuir characteristic constants estimated are Q = 0.082 ± 0.005 and 0.063 ± 0.003 mmol g⁻¹, b = (4.7 ± 0.2) × 10⁴ and (7.31 ± 0.11) × 10⁴ l mol⁻¹ for Ni(II) and Cu(II) ions, respectively. The variation of sorption with temperature gives thermodynamic quantities of ΔH = −58.9 ± 0.12 and −40.38 ± 0.11 kJ mol⁻¹, ΔS = −183 ± 10 and −130 ± 8 J mol⁻¹ K⁻¹ and ΔG = −4.4 ± 0.09 and −2.06 ± 0.08 kJ mol⁻¹ at 298 K for Ni(II) and Cu(II) ions, respectively. Using kinetic equations, values of intraparticle transport and of first order rate constant have been computed for both the metal ions. The sorption procedure is utilized to preconcentrate these ions prior to their determination in tea, vegetable oil, hydrogenated oil (ghee) and palm oil by atomic absorption spectrometry using direct and standard addition methods.     

Amberlite XAD-2 functionalized with 2-aminothiophenol as a new sorbent for on-line preconcentration of cadmium and copper

A new functionalized resin has been applied in an on-line preconcentration system for copper and cadmium determination. Amberlite XAD-2 was functionalized by coupling it to 2-aminothiophenol (AT-XAD) by means of an NN spacer. This resin was packed in a minicolumn and used as sorbent in the on-line system. Metal ions were sorbed in the minicolumn, from which it could be eluted directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Elution of Cd(II) and Cu(II) from minicolumn can be made with 0.50 mol l⁻¹ HCl or HNO₃. The enrichment factors obtained were 28 (Cd) and 14 (Cu), for 60 s preconcentration time, and 74 (Cd) and 35 (Cu), if used 180 s preconcentration time. The proposed procedure allowed the determination of cadmium and copper with detection limits of 0.14 and 0.54 μg l⁻¹, respectively, when used preconcentration periods of 180 s. The effects of foreign ions on the adsorption of these metal ions are reported. The validation of the procedure was carried out by analysis of certified reference material. This procedure was applied to cadmium and copper determination in natural, drink and tap water samples.     

Preconcentration of mercury(II) using a thiol-functionalized metal-organic framework nanocomposite as a sorbent

A novel type of porous metal-organic framework (MOF) was obtained from thiol-modified silica nanoparticles and the copper(II) complex of trimesic acid. It is shown that this nanocomposite is well suitable for the preconcentration of Hg(II) ions. The nanocomposite was characterized by Fourier transfer infrared spectroscopy, X-ray powder diffraction, energy-dispersive X-ray diffraction and scanning electron microscopy. The effects of pH value, sorption time, elution time, the volume and concentration of eluent were investigated. Equilibrium isotherms were studied, and four models were applied to analyze the equilibrium adsorption data. The results revealed that the adsorption process obeyed the Langmuir model. The maximum monolayer capacity and the Langmuir constant are 210 mg g^?1 and 0.273 L mg^?1, respectively. The new MOF-based nanocomposite is shown to be an efficient and selective sorbent for Hg(II). Under the optimal conditions, the limit of detection is 20 pg mL^?1 of Hg(II), and the relative standard deviation is <7.2 % (for n?=?3). The sorbent was successfully applied to the rapid extraction of Hg(II) ions from fish, sediment, and water samples.

Highly selective determination of palladium(II) after preconcentration using Pd(II)-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A novel Pd(II)-imprinted amino-functionalized silica gel sorbent was prepared with the help of a surface-imprinting technique for the preconcentration and separation of Pd(II) prior to its determination by inductively coupled plasma atomic emission spectrometry. Compared to the traditional solid sorbents and non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had a higher adsorption capacity and selectivity for Pd(II). The maximum static adsorption capacity of the imprinted and non-imprinted sorbent for Pd(II) was 26.71 mg g⁻¹ and 10.13 mg g⁻¹, respectively. The relative selectivity factor (α_r) of Pd(II)/Zn(II), Pd(II)/Au(III), Pd(II)/Ru(III), Pd(II)/Rh(III), Pd(II)/Pt(IV), Pd(II)/Ir(III), Pd(II)/Fe(III) and Pd(II)/Zn(II) is 39.0, 60.2, 92.0, 85.0, 50.0, 58.0 and 45.0, respectively. The detection limit (3σ) of the method is 0.36 μg L⁻¹. The relative standard deviation was 3.2% for eight replicate determinations of 10 μg of Pd²⁺ in 200 mL water sample. The method was validated by analyzing a standard reference material, and the results obtained were in good agreement with the standard values. The method was also applied to the determination of trace palladium in geological samples with satisfactory results.     

Speciation analysis of inorganic Sb(III) and Sb(V) ions by using mini column filled with Amberlite XAD-8 resin

The speciation of inorganic Sb(III) and Sb(V) ions in aqueous solution was studied. The adsorption behavior of Sb(III) and Sb(V) ions were investigated as iodo and ammonium pyrollidine dithiocarbamate (APDC) complexes on a column filled with Amberlite XAD-8 resin. Sb(III) and Sb(V) ions were recovered quantitatively and simultaneously from a solution containing 0.8 M NaI and 0.2 M H₂SO₄ by the XAD-8 column. Sb(III) ions were also adsorbed quantitatively as an APDC complex, but the recovery of the Sb(V)-APDC complex was found to be <10% at pH 5. According to these data, the concentrations of total antimony as Sb(III)+Sb(V) ions and Sb(III) ion were determined with XAD-8/NaI+H₂SO₄ and XAD-8/APDC systems, respectively. The Sb(V) ion concentration was calculated by subtracting the Sb(III) concentration found with XAD-8/APDC system from the total antimony concentration found with XAD-8/NaI+H₂SO₄ system. The developed method was applied to determine Sb(III) and Sb(V) ions in samples of artificial seawater and wastewater.     

Atomic absorption spectrometric determination of Cd(II), Mn(II), Ni(II), Pb(II) and Zn(II) ions in water,fertilizer and tea samples after preconcentration on Amberlite XAD-1180 resin loaded with l-(2-pyridylazo)-2-naphthol

A new chelating resin, 1-(2-pyridylazo)-2-naphthol (PAN) coated Amberlite XAD-1180 (AXAD-1180), was prepared and used for the preconcentration of Cd(II), Mn(II), Ni(II), Pb(II) and Zn(II) ions prior to their determination by flame atomic absorption spectrometry (FAAS). The optimum pH for simultaneous retention of the elements and the best elution means for their simultaneous elution were pH 9.5 and 3 M HNO₃, respectively. The sorption capacity of the resin was found to be 5.3 mg/g for Cd and 3.7 mg/g for Ni. The detection limits for Cd(II), Mn(II), Ni(II), Pb(II) and Zn(II) were 0.7, 10, 3.1, 29 and 0.8 μg/L, respectively. The effects of interfering ions for quantitative sorption of the metal ions were investigated. The preconcentration factors of the method were in the range of 10–30. The recoveries obtained were quantitative (≥95%). The standard reference material (GBW07605 Tea sample) was analysed for accuracy of the described method. The proposed method was successfully applied to the analysis of various water, urea fertilizer and tea samples. The article is published in the original.     

Use of an o-aminobenzoic acid-functionalized XAD-4 copolymer resin for the separation and preconcentration of heavy metal(II) ions

XAD copolymer resins may be functionalized with heavy metal ion-selective ligands either by covalent linkage to the polymer backbone or by impregnation. These resins may be tailored to be specific for certain heavy metals by adjusting the adsorption and elution parameters, thereby enabling simple and cost-effective spectrophotometric and flame atomic absorption spectrometry (FAAS) determinations of these metals without requiring the more sophisticated coupled instrumental techniques. For the synthesis of o-aminobenzoic acid (ABA)-immobilized XAD-4 copolymer resin that is expected to preconcentrate a number of transition and heavy metals, the azo-linkage method was chosen. For this purpose the copolymer was nitrated, reduced to the corresponding amine, converted to the diazonium salt with nitrite, and reacted with o-aminobenzoic acid to produce the XAD-ABA sorbent. This sorbent was capable of preconcentrating Pb(II), Cd(II), Ni(II), Co(II) and Zn(II) from weakly acidic or neutral aqueous solution. The retained metals were eluted with 1.0 M HNO₃ from the resin column, and were subsequently determinated with by flame atomic absorption spectrometry. The developed resin preconcentration and determination method was successfully applied to the analysis of a synthetic metal mixture solution, a certified reference material (CRM) of coal sample, and brackish lake water.     

Removal of Pb(II) ions from aqueous systems using thiol-functionalized cobalt-ferrite magnetic nanoparticles

We have investigated the removal of Pb²⁺ ions from water using thiol-functionalized, cobalt-ferrite, magnetic nanoparticles. These magnetic nanoparticles were prepared using the co-precipitation method and their surfaces were modified with tetraethoxy silane and 3-mercaptopropyl trimethoxysilane in order to provide a sufficient surface concentration of the thiol (–SH) functional groups. The adsorption of the Pb²⁺ ions from the aqueous solutions onto the thiol-functionalized, cobalt-ferrite, magnetic nanoparticles was studied. The investigated parameters include the pH value of the model water, the concentration of the adsorbent, the contact time and the temperature of adsorption. The removal of the Pb²⁺ was found to be greater at the higher pH values and increasing the temperature was also found to increase the removal of Pb²⁺ ions.     

Determination of Pb(II), Cu(II) and Fe(III) with capillary electrophoresis using ethylenediaminetetraacetic acid as a complexing agent and vancomycin as a complex selector.

The simultaneous determination of metal ions using ethylenediaminetetraacetic acid (EDTA) as a complexing agent and vancomycin as a complex selector was successfully studied by capillary electrophoresis with the U-shaped cell. The partial filling method (counter current mode) was used in order to gain selectivity of the separation, and also to increase the detection sensitivity. The effect of the vancomycin concentration on the separation behavior of free EDTA and metal products, and the effect of the EDTA concentration on the stability of metal-EDTA products were considered. Under the optimal condition, the reproducibilities (RSD) of the migration time and the peak area were less than 3.39% and 9.61%, respectively. With the high sensitivity of the method, Pb(II), Cu(II) and Fe(III) in tap water were successfully determined, and the recoveries were 99 - 105%. The concentrations of these metal ions found in tap water did not exceed the maximum allowed concentrations regulated by the U.S. Environmental Protection Agency.     

Amorphous and ordered organosilicas functionalized with amine groups as sorbents of platinum (II) ions

Two groups of amine-functionalized organosilicas have been synthesized: amorphous polysiloxane xerogels (APX) and ordered mesoporous organosilicas (OMO) by co-condensation of tetraethoxysilane and appropriate alkoxysilanes: aminopropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine. The obtained materials were characterized by sorption measurements, X-ray diffractometry, elemental analysis, transmission electron microscopy, and scanning electron microscopy. The OMO samples have well developed porous structure—the values of specific surface area are in the range 740–840 m²/g. While the APX samples are less porous having the corresponding values in the range 280–520 m²/g. The sizes of the ordered mesopores of OMO are in the range 5.9–6.5 nm while for the APX they are 2.9–12.1 nm indicating structural differences between both groups of the samples. All samples were tested as the sorbents of Pt(II) ions. The influence of various parameters such as pH, contact time, equilibrium concentration on Pt(II) adsorption ability onto prepared adsorbents was studied in detail. Additionally, the effect of chloride concentration on Pt(II) adsorption was investigated. The values of static sorption capacities were in the range of 32–102 mg_Pt(II)/g and 20–139 mg_Pt(II)/g for OMO and APX series, respectively.     

Selective extraction and preconcentration of ultra-trace amounts of arsenic(V) ions using carbon nanotubes as a novel sorbent

In the present study, multiwalled carbon nanotubes (MWCNTs) as solid phase extraction sorbent were developed for preconcentration of arsenic(V) species prior to graphite furnace atomic absorption spectrometry (GFAAS) determination. Arsenic(V) was selectively sorbed on the packed column with MWCNTs within a pH 9.5 in the presence of 2-(5-bromo-2-pyridylazo)-5-diethyl amino phenol (5-Br-PADAP). The adsorbed species was then desorbed with 1 mL of 2.0 M HNO₃. Experimental parameters including pH, sample volume and flow rate, type, volume and concentration of eluent that influence the recovery of the arsenic(V) species were optimised. Under the optimised conditions, the calibration curve was linear in the range of 0.2–10.0 µg L^?1 with detection limit of 0.016 µg L^?1. The relative standard deviations (RSD) for seven replicate determinations at 1.0 µg L^?1 level of arsenic was 6.69%. The proposed method was successfully applied to the determination of arsenic in water samples and certified reference material (NIST RSM 1643e).     

Sorption isotherms of Nickel(II), Cobalt(II), Mercury(II), and Lead(II) ions on a phosphorus-containing polymeric sorbent

The influence of the concentration of a complexing ion on the sorption recovery of nickel, cobalt, mercury, and lead ions from aqueous solutions by a phosphorus-containing polymeric polybutadiene-based sorbent was studied. Sorption isotherms of the studied metal ions were processed by the Langmuir and Freindlich models. The affinity of metal ions to the functional groups of a sorbent and the stability of complexes were established to decrease in the order Hg(II) > Pb(II) > Co(II) > Ni(II).     

Amberlite XAD-2 functionalized with o-aminophenol: synthesis and applications as extractant for copper(II), cobalt(II), cadmium(II), nickel(II), zinc(II) and lead(II)

A stable chelating resin matrix was synthesized by covalently linking o-aminophenol (o-AP) with the benzene ring of the polystyrene–divinylbenzene resin, Amberlite XAD-2, through a –N=N– group. Elemental analyses, thermogravimetric analysis (TGA) and infrared spectra have characterized the resulting chelating resin. It has been used to preconcentrate Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Pb²⁺, prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption of Cu, Cd, Co, Ni, Zn and Pb are 6.2–7.4, 5.6–7.2, 5.6–9.0, 6.0–9.0, 5.7–7.0 and 5.0–6.0, respectively. These metals are desorbed (recovery 91–98%) with 4 mol dm⁻³ HNO₃. The sorption capacity of the resin is 3.37, 3.42, 3.29, 3.24, 2.94 and 3.32 mg of metal g⁻¹ of resin, respectively, for Cu, Cd, Co, Ni, Zn and Pb. The effect of NaF, NaCl, NaNO₃, Na₂SO₄, and Na₃PO₄ on the sorption of these metal ions has been investigated. These electrolytes are tolerable up to 0.01 mol dm⁻³ in case of all the metal ions, except Cl⁻ which is tolerable even up to 0.1 mol dm⁻³ for Zn and 1.0 mol dm⁻³ for Pb. The preconcentration factor for Cu, Cd, Co, Ni, Zn and Pb are 50, 50, 100, 65, 40 and 40 (concentration level 10–25 μg dm⁻³) respectively. Simultaneous enrichment of the six metals is possible. The method has been applied to determine Cu, Cd, Co, Ni, Zn and Pb content in well water samples (RSD≤8%).     

A metal organic framework prepared from benzene-1,3,5-tricarboxylic acid and copper(II), and functionalized with various polysulfides as a sorbent for selective sorption of trace amounts of heavy metal ions

Novel composites were obtained via direct assembly of polysulfides (S_x^2?, X?=?3, 4, 6) on the surface of a metal organic framework (MOF; type benzene-1,3,5-tricarboxylic/Cu(II). They are referred to as S_x-MOFs and were used for highly selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions. The structure of the S_x-MOFs was characterized by Raman spectroscopy, FT-IR, X-ray diffraction, and scanning electron microscopy. The Raman spectra of S_x-MOF is similar to the bare MOF and shows the MOFs structure to be well retained after S_x functionalization. The selective interaction of S_x with soft metal ions and the high surface area of MOFs resulted in excellent affinity and selectivity for ions such as Hg(II). The S_x-MOFs of type S₄-MOF had the highest distribution coefficient K_d value (~10⁷) and best extraction recovery (~100%) for Hg(II). The S₄-MOF also has high selectivity in the following order: Hg(II) >?>?Pb(II)?>?Zn(II)?>?Ni(II)?>?Co(II). The binding process of the metals occurs via M–S bonding. The ions were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). The detection limit for Hg(II) is 0.13 μg L^?1. The S₄-MOF was applied to the extraction of trace metal ions from natural and contaminated waters and data were compared with other sorbets. The results revealed that S₄-MOF is an excellent adsorbent for sorption of heavy metal ions even in the presence of the relatively high concentration of other ions.

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Graphical abstract A composite was synthesized via direct assembly of polysulfides (S_x^2?, X?=?3, 4, 6) on surface of the metal organic framework (S_x-MOF) and was used for selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions.

     

Synthesis of pyridin-3-yl-functionalized silica as a chelating sorbent for solid-phase adsorption of Hg(II), Pb(II), Zn(II), and Cd(II) from water

Silica gel modified with 3-aminopropyltrimethoxysilane was anchored with nicotinaldehyde to prepare a new chelating surface (or matrix). It was synthesized and characterized by elemental analysis, cross-polarization magic-angle spinning ¹³C nuclear magnetic resonance (NMR) spectroscopy, diffuse reflectance infrared Fourier-transform spectroscopy, nitrogen adsorption–desorption isotherm, Brunauer–Emmett–Teller surface area, and Barrett–Joyner–Halenda pore sizes. The new surface exhibits good chemical and thermal stability as determined by thermogravimetry curves. This new organic–inorganic material was used for preconcentration of Hg(II), Pb(II), Zn(II), and Cd(II) from water prior to their determination by inductively coupled plasma atomic emission spectrometry. The optimum pH for quantitative sorption of these metal ions is in the range of 6–8, and the sorption capacity is in range of 486–1,449 μmol/g. By batch method, 95 % extraction takes ≤30 min. All the metals could be desorbed with a solution of hydrochloric acid (6 N) without loss of the expensive ligand. Solutions of the metal ions were prepared by dissolution of the nitrate solution.     

Adsorption characteristics of as(III) and as(V) with titanium dioxide loaded Amberlite XAD-7 resin.

The adsorption characteristics of As(V) and As(III) on titanium dioxide loaded Amberlite XAD-7 resin have been studied. The resin was prepared by impregnation of Ti(OC2H5)4 followed by hydrolysis with ammonium hydroxide. Batch adsorption experiments were carried out as a function of the pH, shaking time and the concentration of As(V) and As(III) ions. The resin showed a strong adsorption for As(V) from pH 1 to 5 and for As(III) from pH 5 to 10. The adsorption isotherm data for As(V) at pH 4 fitted well to a Langmuir equation with a binding constant of 59 dm3 mol(-1) and a capacity constant of 0.063 mmol g(-1). The data for As(III) at pH 7 also fitted well to a Langmuir equation with a binding constant of 5.4 dm3 mol(-1) and a capacity constant of 0.13 mmol g(-1). The effect of diverse ions on the adsorption of arsenic was also studied. Column adsorption experiments showed that the adsorption of As(III) is more favorable compared to As(V), due to both the faster adsorption and larger capacity for As(III) than As(V).     

Selective solid-phase extraction of nickel(II) using a surface-imprinted silica gel sorbent

A new Ni(II)-imprinted amino-functionalized silica gel sorbent with excellent selectivity for nickel(II) was prepared by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction (SPE) of trace Ni(II) in water samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Ni(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Ni(II) was 12.61 and 4.25 mg g⁻¹, respectively. The relatively selective factor (α_r) values of Ni(II)/Cu(II), Ni(II)/Co(II), Ni(II)/Zn(II) and Ni(II)/Pd(II) were 45.99, 32.83, 43.79 and 28.36, which were greater than 1. The distribution ratio (D) values of Ni(II)-imprinted polymers for Ni(II) were greatly larger than that for Cu(II), Co(II), Zn(II) and Pd(II). The detection limit (3σ) was 0.16 ng mL⁻¹. The relative standard deviation of the method was 1.48% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08618 and GBW 08402), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace nickel in plants and water samples with satisfactory results.