Potentiometric study of binary complexes of methyl 2-pyridyl ketone oxime, phenyl 2-pyridyl ketone oxime and diacetyl monooxime with some transition and heavy metal ions in aqueous solution

The complexation reaction between some oximes including methyl-2-pyridylketone oxime (MPKO), phenyl-2-pyridylketone oxime (PPKO) and diacetyl monooxime (DMO) with some transition and heavy metal ions Co2+, Ni2+, Zn2+, Pb2+, Fe2+, Fe3+, Cr3+ and La3+ has been studied potentiometrically in aqueous solution at 25+/-0.1 degrees C and ionic strength (mu) of 0.1M supported by KCl. The overall stability constants logbeta's of respective species were obtained by computer refinement of pH-volume data using BEST program. The best model among the several proposed models was selected according to the lowest sigma(fit) value. The main species in binary systems are ML, ML2, MLH, MLH2, ML2H, ML2H2, MOHL, M(OH)2L, M(OH)L2 and M(OH)2L2 (L = MPKO or PPKO or DMO).     

Determination of Cu,Fe, Pb and Zn by Flame‐AAS after Preconcentration Using Sodium Dodecyl Sulfate Coated Alumina Modified with Complexing Agent

A sensitive and simple method for the simultaneous preconcentration of trace transition and heavy metal ions is reported. The method is based on the adsorption of Cu, Fe, Pb and Zn on N,N′‐Diacetyl‐4‐bromo‐2,6‐di(aminomethyl)anisole (DABDAMA) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal content on the complexes are eluted using 6 mL of 2 mol l⁻¹ nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied for these metals content evaluation in samples including soil, blood and vegetable samples.     

Application of Cloud Point Extraction for Copper,Nickel, Zinc and Iron Ions in Environmental Samples

A cloud point extraction procedure was presented for the preconcentration of copper, nickel, zinc and iron ions in various samples. After complexation by 2‐(6‐(1H‐benzo[d]imidazol‐2‐yl)pyridin‐2‐yl)‐1H‐benzo[d]Imidazole (BIYPYBI), analyte ions are quantitatively extracted in Triton X‐114 following centrifugation. 1.0 mol L^?1 HNO₃ nitric acid in methanol was added to the surfactant‐rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for BIYPYBI, Triton X‐114 and HNO₃ and bath temperature, centrifuge rate and time were optimized. Detection limits for Cu²⁺, Fe³⁺, Zn²⁺ and Ni²⁺ ions was 1.4, 2.2, 1.0 and 1.9 ng mL^?1, respectively. The preconcentration factors for all ions was 30, while the enrichment factor of Cu²⁺, Fe³⁺, Zn²⁺ and Ni²⁺ ions was 35, 25, 39 and 30, respectively. The proposed procedure was applied to the analysis of real samples.     

Synthesis, characterization, crystal structures, and solution studies of Ni(II), Cu(II) and Zn(II) complexes obtained from pyridine-2,6-dicarboxylic acid and 2,9-Dimethyl-1,10-Phenanthroline

The homonuclear water-soluble and air stable compounds (dmpH) (H₅O₂) au][M(pydc)₂].0.5H₂O (M = Ni(II) (1), Cu(II) (2), Zn(II) (3); pydcH₂ = pyridine-2,6-dicarboxylic acid, dipicolinic acid, dmp = 2,9-dimethyl-1,10-phenanthroline) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, ¹H NMR, ¹³C NMR, elemental analysis and X-ray diffraction single crystal analyses for 1, 2 and 3. The complexes 1–3 represent the isostructural features. Extensive hydrogen bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the complex units by linking them to form three dimensional polymeric networks. The stoichiometry and stability of the all three complexes in aqueous solution were investigated by potentiometric pH titration.     

Synthesis and crystal structure of Mn(II) and Hg(II) compounds and solution studies of Mn(II), Zn(II), Cd(II) and Hg(II) compounds based on piperazinediium pyridine-2,3-dicarboxylate

Novel metal organic frameworks including {(pipzH₂)[Mn(py-2,3-dc)₂]·7.75H₂O}_n, 1, {(pipzH₂)[Zn(py-2,3-dc)₂]·4H₂O}_n, 2, [Cd(py-2,3-dc)(H₂O)₃]_n, 3 and {(pipzH₂)[Hg₄Cl₁₀]}_n, 4, in which pipz is piperazine and py-2,3-dcH₂ is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e. (pipzH₂)(py-2,3-dcH)₂ and corresponding metallic salts and studied by IR, ¹H NMR, ¹³C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P2₁/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) Å, b = 19.910(2) Å, c = 12.997(1) Å, β = 94.354(2)° for 1 and a = 15.940(1) Å, b = 11.2690(9) Å, c = 11.1307(9) Å, β = 90.685(2)° for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although Zn^II, Cd^II and Hg^II were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H?O, N-H?O, C-H?O, N-H…Cl and C-H?Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1–4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn²⁺, Zn²⁺, Cd²⁺ and Hg²⁺ ions in aqueous solution were investigated by potentiometric pH titrations.     

Gold Nanoparticles Loaded on Activated Carbon as Novel Adsorbent for Kinetic and Isotherm Studies of Methyl Orange and Sunset Yellow Adsorption

In this research, a novel adsorbent gold nanoparticle loaded on activated carbon (Au-NP-AC) was synthesized by a low cost in a routine protocol. Subsequently, this novel material characterization and identification are followed by different techniques such as th eBruner–Emmet–Teller (BET) theory, scanning electron microcopy, and transmission electron microscopy analysis. Unique properties such as high BET surface area (>1229.55 m²/g) and low pore size (<22.46 Å) and average particle size lower than 48.798 Å in addition to high reactive atom and presence of various functional groups make it possible for efficient removal of sunset yellow (SY) and methyl orange (MO). Generally, the influence of variables including amount of adsorbent, initial dyes concentration, contact time, temperature on dyes removal percentage has great effect on removal percentage that their influence was optimized. The kinetic of proposed adsorption processes efficiently followed, pseudo-second-order and intra-particle diffusion approach. The equilibrium data of the removal strongly follow the Langmuir monolayer adsorption with high adsorption capacity in a short amount of time. This novel adsorbent by small amount (0.01 g) really is applicable for removal of high amount of both dyes (MO and SY) in short time (<18 minutes). Equilibrium data fitted well with the Langmuir model at all amount of adsorbent, while maximum adsorption capacity for MO 161.29 mg g^?1 and for SY 227.27 for 0.005 g of Au-NP-AC.     

Use of metal composite MOF‐5‐Ag2O‐NPs as an adsorbent for the removal of Auramine O dye under ultrasound energy conditions

In this work, MOF‐5 composited with Ag₂O nanoparticles was prepared and characterized via X‐ray diffraction, field emission‐scanning electron microscopy, energy‐dispersive spectroscopy and FT‐IR analysis. This new material was subsequently employed for removing basic yellow dye [Auramine O (AO)] from aqueous solution under ultrasound irradiation. Several experiments were designed by central composite design in which operational parameters such as such as pH, MOF‐5‐Ag₂O mass and initial concentration of AO involved in the process were optimized. The significance of individual parameters and their possible interactions were investigated using analysis of variance (anova ). The optimum values of 6, 0.025 g and 6 mg l^?1 were obtained for the pH, MOF‐5‐Ag₂O‐NPs mass and the initial concentrations of AO, respectively, with desirability of 1.0. At such conditions, the efficiency for the removal of AO was found to be 89.45%. Various isotherm models for fitting the experimental equilibrium data were studied, and it was found that the Langmuir model has the highest efficiency for correlation of experimental equilibrium data, so that the monolayer adsorption capacity of MOF‐5‐Ag₂O for successful removal of AO was 260.70 mg g^?1 at optimal conditions.     

Magnetic molecularly imprinted polymer for the efficient and selective preconcentration of diazinon before its determination by high‐performance liquid chromatography

A molecularly imprinted polymer was selectively applied for solid‐phase extraction and diazinon residues enrichment before high‐performance liquid chromatography. Diazinon was thermally copolymerized with Fe₃O₄@polyethyleneglycol nanoparticles, methacrylic acid (functional monomer), 2‐hydroxyethyl methacrylate (co‐monomer), and ethylene glycol dimethacrylate (cross‐linking monomer) in the presence of acetonitrile (porogen) and 2,2‐azobisisobutyronitrile (initiator). Then, the imprinted diazinon was reproducibly eluted with methanol/acetic acid (9:1, v/v). The sorbent particles were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The comprehensive study of variables through experimental design showed that the maximum performance was achieved under these conditions: pH 7, 10 mL sample volume, 15 mg sorbent, 10 min vortex time, 5 min ultrasonic time, 200 μL methanol/acetic acid (9:1, v/v) as eluent, and 5 min desorption time. Under optimized conditions, the molecularly imprinted polymer solid‐phase extraction method demonstrated a linear range (0.02–5 g/mL), a correlation coefficient of 0.997, and 0.005 g/mL detection limit.     

Selective and sensitized spectrophotometric determination of trace amounts of Ni(II) ion using alpha-benzyl dioxime in surfactant media

Highly sensitive and interference-free sensitized spectrophotometric method for the determination of Ni(II) ions is described. The method is based on the reaction between Ni(II) ion and benzyl dioxime in micellar media in the presence of sodium dodecyl sulfate (SDS). The absorbance is linear from 0.1 up to 25.0 microg mL-1 in aqueous solution with repeatability (RSD) of 1.0% at a concentration of 1 microg mL-1 and a detection limit of 0.12 ng mL-1 and molar absorption coefficient of 68,600L mol-1 cm-1. The influence of reaction variables including type and amount of surfactant, pH, and amount of ligand and complexation time and the effect of interfering ions are investigated. The proposed procedure was applied to the determination of trace amounts of Ni(II) ion in tap water, river water, chocolate and vegetable without separation or organic solvent extraction.