Uptake of Cu, Cd and Pb on Zn–Al layered double hydroxide intercalated with edta

Hydrotalcite-like compound [Zn₂Al(OH)₆]₂edta·nH₂O(ZnAl-edta) was obtained from the precursor [Zn₂Al(OH)₆]NO₃·nH₂O (ZnAl-NO₃), by the anion exchange method, with the aim of uptake Cu²⁺, Cd²⁺ and Pb²⁺ from the aqueous solutions by chelating process between edta and metal cations. The amount of Cu²⁺, Cd²⁺ and Pb²⁺ adsorbed was monitorized by atomic absorption technique at different contact time, pH and metal concentrations. The results indicate the very fast adsorption of the metal cations by ZnAl-edta reaching the equilibrium of the uptake reaction in two hours for Cu and Pb and 24 h for Cd. The shape of the adsorption isotherms suggests specific interaction and high host–guest affinity. At pH 5.5 and initial concentration C_i = 10 mM, the amount adsorbed was C_s = 1117, 375 and 871 μmol/g for Cu²⁺, Cd²⁺ and Pb²⁺, respectively.     

Adsorption of Cu2+, Cd2+ and Pb2+ ions by layered double hydroxides intercalated with the chelating agents diethylenetriaminepentaacetate and meso-2,3-dimercaptosuccinate

The hydrotalcite-like compound [Zn₂Al(OH)₆]NO₃·nH₂O (ZnAl-NO₃) was intercalated with the chelating agents diethylenetriaminepentaacetic acid (dtpa) and meso-2,3-dimercaptosuccinic acid (dmsa) by anion-exchange to uptake Cu²⁺, Cd²⁺ and Pb²⁺ from aqueous solutions. The amounts of heavy metals adsorbed at variable contact times and metal concentration were determined by atomic absorption spectrometry. The amounts removed of the three metal cations by both adsorbents were high. The shape of the adsorption isotherms obtained indicated specific interactions and a high host–guest affinity. However, the metal ions were removed from solution not only by chelation, but also by precipitation or even by isomorphic substitution of Zn²⁺ by another metal ions in the brucite-like layer.     

Synthesis and characterization of new bis(crown ether)s of Schiff base type containing recognition sites for sodium and nickel guest cations

New bis(crown ether) ligands of Schiff base type ( 2 – 4 ) containing recognition sites for sodium and nickel guest cations have been synthesized by the condensation of two equivalents of 4′-formyl-5′-hydroxy(benzo-15-crown-5) ( 1 ) with diamines, H₂N–(CH₂)_n–NH₂(n = 2–4). Homonuclear ditopic crystalline 2 : 1 (Na⁺ : ligand) complexes ( 2a – 4a , 2b – 4b ) of the ligands with NaSCN and NaClO₄ have been prepared. The NaClO₄ complexes of 3 and 4 ( 3b and 4b ) form heteronuclear tritopic crystalline complexes with Ni²⁺ cations of stoichiometry 2 : 1 : 1 (Na⁺ : Ni²⁺ : ligand). A homonuclear monotopic Ni²⁺ complex has also been prepared by the reaction with Ni(CH₃COO)₂ · 6H_2O. The UV-VIS spectra of 2 – 4 and their NaClO₄ complexes ( 2b – 4b ) are studied in different solvents including acidic and basic media. In polar solvents, tautomeric equilibria (phenol–imine, O–H…︁N and ketoamine, O…︁H–N forms) are present, as supported by the UV-VIS data.     

Effect of cations in solution on the oxidation of methanol on the surface of platinum electrode

The effect of metal cations in solution on the oxidation of methanol on the electrode surface of platinum is a neglected aspect to direct methanol fuel cell (DMFC). In this paper, a smooth platinum electrode absorbing metal cations as the working electrode was applied to investigate the methanol oxidation with the cyclic voltammetry (CV) in 1.0 mol L⁻¹ H₂SO₄. From the analysis of experiment, it is found that the cations, Li⁺, Ce⁴⁺, Mn²⁺, Ni²⁺, Cu²⁺, have some negative effect on the catalytic oxidation of methanol on the surface of platinum. The degree of the effect from different cations was analyzed.     

Intensifying graft-polymerization in the process of modifying polycaproamide fibres

Conclusions -- The kinetics of the graft polymerization of dimethylaminoethyl methacrylate to polycaproamide fibre initiated by the redox systems Fe²⁺ - H₂O₂, Cu²⁺ - H₂O₂, and by an ROC containing a complex copper compound (Cu _c ²⁺ - H₂O₂) has been studied.-- An increase in the rate of graft polymerization, in the amount of grafted component, and the degree of useful conversion of the monomer has been found when the reaction is initiated by the ROS Cu _c ²⁺ - H₂O₂.Moscow Textile Academy. Translated from Khimicheskie Volokna, No. 3, pp. 11–12, May–June, 1992.     

Entropy-stabilized metal-CeOx solid solutions for catalytic combustion of volatile organic compounds

Doped Ceria with abundant oxygen vacancies exhibits enhanced performance in heterogeneous oxidation. In principle, doping 50 mol% divalent cations (such as: Cu²⁺, Zn²⁺, and Mg²⁺) into CeO₂ lattice would produce an exceptional catalyst with maximum active oxygen species. However, the huge size gap between Ce (IV) and divalent metal cations obstructs its synthesis. Here, we utilize the theory of increasing configurational entropy with five metal dopants to lower the Gibbs-free energy, and successfully incorporate 50 mol% divalent metal cations into CeO₂ lattice. This unique doping environment endows Ce_0.5Zn_0.1Co_0.1Mg_0.1Ni_0.1Cu_0.1O_x two features: (a) Abundant active oxygen species for excellent performance in volatile organic compounds catalytic oxidation; (b) Bring multi reactive sites, which enable the simultaneous combustion of carbon monoxide, propylene and toluene. Moreover, the increased entropy value makes Ce_0.5Zn_0.1Co_0.1Mg_0.1Ni_0.1Cu_0.1O_x an ultra-stable catalyst in both thermal and hydrothermal conditions (e.g., Working >200 hr in water-resistance experiment).     

Hydroxylation of phenol with H2O2 over transition metal containing nano-sized hollow core mesoporous shell carbon catalyst

The catalytic performance of transition metal (Fe²⁺ or Cu²⁺) containing nano-sized hol low core mesoporous shell carbon (HCMSC) heterogeneous catalysts for the hydroxylation of phenol with hydrogen peroxide (H₂O₂) in water was investigated in a batch reactor. The metal-containing HCMSC catalyst showed higher activity than the same metal ion-exchanged zeolites. The nature of the metal and its content in the HCMSC had remarkable influence on the reaction results under the typical reaction conditions (PhOH/H₂O₂=3, reaction temperature=60 ‡C). Fe²⁺ containing HCMSC catalyst showed high catalytic activity with phenol conversion of 29%, selectivity to catechol (CAT) and hydroquinone (HQ) about 85%, H₂O₂ effective conversion about 70% and selectivity to benzoquinone (BQ) below 1% in the batch system.     

Charge states of atoms in ceramic superconductors HgBa2Ca n − 1Cu n O2n + 2, Tl2Ba2Ca n − 1Cu n O2n + 4, and Bi2Sr2Ca n − 1Cu n O2n + 4 (n = 1–3)

The parameters of the electric-field-gradient tensor for copper sites in the HgBa₂Ca _{n ? 1}Cu _n O_{2n + 2}, Tl₂Ba₂Ca _{n ? 1}Cu _n O_{2n + 4}, and Bi₂Sr₂Ca _{n ? 1}Cu _n O_{2n + 4} (n = 1–3) lattices have been determined using ⁶⁷Cu(⁶⁷Zn) Mössbauer emission spectroscopy and calculated in the framework of the point-charge approximation. The agreement between the experimental and calculated parameters has been achieved under the assumption that the holes formed as a result of the decrease in the oxidation state of a part of the mercury, thallium, or bismuth atoms are distributed over the oxygen sites in the Cu-O or adjacent planes. It has been demonstrated that the oxidation state of cations can be controlled in high-temperature superconducting ceramic materials.     

Preparation and characterisation of a poly(acrylamidoglycolic acid-co-acrylamide) hydrogel for selective binding of Cu and application to diffusive gradients in thin films measurements

A poly(acrylamidoglycolic acid-co-acrylamide) [poly(AAGA-co-AAm)] hydrogel was prepared by copolymerising 2-acrylamidoglycolic acid (AAGA) with acrylamide (AAm). The copolymer hydrogel composition and structure was characterised by FTIR spectroscopy and elemental microanalysis and found to contain 3.5 AAGA monomer units for each AAm monomer unit. This was similar to the monomer ratios used in the synthesis. The metal ion binding properties of the hydrogel were characterised for a range of metal ions (Cu²⁺, Cd²⁺, K⁺, Na⁺, Mg²⁺ and Ca²⁺) under varying conditions of pH, ionic strength, metal concentration and time. The hydrogel was shown to bind Cu²⁺ and Cd²⁺ strongly under non-competitive binding conditions, with binding capacities of 5.3 and 5.1 μmol cm⁻², respectively. The binding capacity of each metal decreased, under competitive binding conditions (with a range of metal ions present at 17.8 μN), to 1.3 and 0.17 μmol cm⁻², respectively, indicating stronger selectivity for Cu²⁺. The metal ions were readily recovered (>94%) by eluting with 2 M nitric acid solution for 24 h. The binding capacities for Cu²⁺ and Cd²⁺ were also found to decrease with increasing ionic strength and at pH values <5. The copolymer was found to have an equilibrium swelling ratio (q_w) of over 500 at a maxima of pH 5.4 and at low ionic strengths. Finally, the copolymer hydrogel was tested as a binding phase with the diffusive gradients in thin films technique. A linear mass vs. time relationship was observed for Cu²⁺ in synthetic Windermere water with a recovery of approximately 100%.     

Synthesis and characterization of cellulose ion exchangers. I. Polymerization of glycidyl methacrylate,dimethylaminoethyl methacrylate,and acrylic acid with cotton cellulose using thiocarbonate-H2O2 redox system

Polymerization of glycidyl methacrylate (GMA), dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid (AA) with cotton fabric using a cellulose thiocarbonate-hydrogen peroxide redox system as an initiator was investigated under different conditions. This includes the nature and concentration of the initiator and monomer, polymerization time and temperature, and liquor ratio. The percent of polymer add-on is generally favored by increasing monomer and H₂O₂ concentration, as well as duration and temperature of the polymerization, but with the certainty that the percent of polymer add-on follows the following order: GMA > DMAEMA > AA. On the other hand, the percent of polymer add-on increases by decreasing the liquor ratio. Incorporation of Fe²⁺ or Cu²⁺ ion in the polymerization system enhances the percent of polymer add-on significantly. Replacing the H₂O₂ by other oxidants such as Cr⁶⁺ or Mn⁴⁺ is made, and the capability of such cations to expedite polymerization of the said monomers with cotton cellulose is studied. Also studied is the synthesis of cation exchanger via reaction of poly(GMA)-cellulose copolymer with hexamethylene tetramine. Furthermore, the ion exchange characteristics of the cellulosic copolymers obtained with this as well as with other monomers are reported. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1029–1037, 1997     

Synthesis,characterization, metal sorption,and biological activity of poly(N‐heterocylic acrylamide)

N‐heterocyclic acrylamide monomers were prepared and then transferred to the corresponding polymers to be used as an efficient chelating agent. Polymers reacted with metal nitrate salts (Cu²⁺, Pb²⁺_, Mg²⁺, Cd²⁺, Ni²⁺, Co²⁺_, Fe²⁺) at 150°C to give metal‐polymer complexes. The selectivity of the metal ions using prepared polymers from an aqueous mixture containing different metal ion sreflected that the polymer having thiazolyl moiety more selective than that containing imidazolyl or pyridinyl moieties. Ion selectivity of poly[N‐(benzo[d]thiazol‐2‐yl)acrylamide] showed higher selectivity to many ions e.g. Fe³⁺, Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺. While, that of poly[N‐(pyridin‐4‐yl)acrylamide] is found to be high selective to Fe³⁺ and Cu²⁺ only. Energy dispersive spectroscopy measurements, morphology of the polymers and their metallopolymer complexes, thermal analysis and antimicrobial activity were studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42712.     

Wet oxidation of acetic acid by H2O2 catalyzed by transition metal-exchanged NaY zeolites

During the wet oxidation of contaminated wastewaters, the destruction of low molecular weight carboxylic acid intermediates such as acetic, glyoxalic, and oxalic acids is often the rate-controlling step. Oxidation of acetic acid, a very recalcitrant intermediate, requires compelling treatment severity. Heterogeneous catalytic wet oxidation of model acetic acid aqueous solutions was conducted under mild conditions (below the normal boiling point of water) using hydrogen peroxide over various transition metal-exchanged NaY zeolites. Treatment of Cu²⁺–NaY with oxalic acid [OA] led to a catalyst, Cu²⁺–NaY [OA], with significantly improved properties in terms of total organic carbon (TOC) removal efficiency and catalyst stability against leaching. This catalyst outperformed homogeneous Cu²⁺ by a factor of 2–2·5 times. Continuous feeding of H₂O₂ reduced its undesirable decomposition. Improvement of the TOC-degradation performance by Cu²⁺–NaY [OA] was tentatively attributed to the removal of sodium and possibly aluminium in the zeolite. © 1998 Society of Chemical Industry     

Effect of UV Radiation on the Removal of Carboxylic Acids from Water by H2O2 and O3 in the Presence of Metallic Ions

The effect of UV radiation on the removal of formic, oxalic and maleic acids from water by metallic ion (Fe²⁺ or Cu²⁺)/H₂O₂ and metallic ion/O₃ was studied and compared. The results showed that metallic ion/O₃/UV has higher efficiency than metallic ion/H₂O₂/UV for oxalic acid removal. UV radiation significantly increases the efficiency of metallic ion/H₂O₂ for formic and maleic acids removal while its effect on the efficiency of metallic ion/O₃ for formic acid removal is minor_. However, at pH 2, O₃ alone showed higher efficiency than metallic ion/H₂O₂/UV for formic acid removal. Contrary to the relative efficiency of metallic ions in the previous systems, Cu²⁺ exhibited higher rate than Fe²⁺ for the removal of the degradation products of maleic acid by O₃. UV radiation exhibited a minor effect on the efficiency of Cu²⁺/O₃, while it exhibited a large effect on the efficiency of Fe²⁺/O₃ for the removal of the degradation products of maleic acid.     

Redox polymerisation—kinetics of polymerisation of acrylamide initiated by the Mn3+-citric acid redox system

The kinetics and mechanism of polymerisation of acrylamide initiated by manganese(III) acetate-citric acid (CA) redox system in aqueous acetic acid and sulphuric acid medium were studied over the temperature range 30-50° C. The overall rates of polymerisation (R_p), disappearance of manganic ion (—R_m), and degree of polymerisation (X?_n) were measured with variation in [monomer], [Mn³⁺], [CA], [H⁺], μ and temperature. The polymerisation is initiated by the organic free radical arising from the Mn³⁺-CA reaction and the termination is by metal ions. The various rate parameters were evaluated and discussed.     

Alkane oxidation on isolated Cu2+ ions in zeolitic matrix: a relation between catalytic activity and Cu2+-site local topography

Catalytic ethane oxidation, with O₂, using H-ZSM-5 and H-mordenite containing different discrete types of isolated Cu(II) cations was studied. An ESR spectroscopic study was carried out on copper ion coordination in zeolites. It was shown that the intrinsic activity of Cu(II) ion depends strongly on the Cu²⁺-site local topography. Covalent-bonded Cu(II) cations in the most coordinatively unsaturated square-planar coordination in H-ZSM-5 demonstrated the highest activity in C₂H₆ complete oxidation.     

Synthesis and photophysical behavior of a water-soluble fluorescein-bearing polymer for Fe<Superscript>3+</Superscript> ion sensing

An acrylic monomer bearing xanthene group, acryloylfluorescein (Ac-Flu) was synthesized from fluorescein and acryloyl chloride in the presence of triethylamine in dry dichloromethane (CH₂Cl₂) at room temperature. The synthesized Ac-Flu was identified by IR, MS and ¹HNMR spectra. Copolymer of Ac-Flu and acrylamide (AM) was synthesized with thermal initiator and it was characterized by the method of IR, UV–Vis and DSC. The photophysical behaviors of Ac-Flu and its copolymer were explored by recording the fluorescence spectra in solution, solid state and film in detail. In addition, the ability of the copolymer to detect different metal cations (Mn²⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) in aqueous solution was investigated. The results showed that poly(Ac-Flu-co-AM) had a good linear response between the logarithm of concentration of Fe³⁺ (lg[Fe³⁺]) against the relative fluorescence intensity for Fe³⁺ concentration. The results suggest that this copolymer may offer potential as a reusable polymer sensor for Fe³⁺ ion in aqueous solution.     

Removal of concentrated heavy metal ions from aqueous solutions using polymers with enriched amidoxime groups

Particulate and fibrous adsorbents with enriched amidoxime groups were synthesized by using a novel monomer N,N′‐dipropionitrile acrylamide. The adsorption properties of amidoximated poly(N,N′‐dipropionitrile acrylamide) [poly(DPAAm)] particles and a nonwoven fabric grafted with the same for UO₂²⁺, Pb²⁺, Cu²⁺, and Co²⁺ at high concentrations were investigated by batch process. Metal ion adsorption studies were conducted from metal ion solutions with different initial concentrations (100–1500 ppm). It was shown that particulated amidoximated poly(DPAAm) has higher adsorption capacity than amidoximated nonwoven fabrics for all metal ions, especially for uranyl ions. The results of the adsorption studies showed that the interaction between UO₂²⁺ and amidoximated groups agree with the Langmuir‐type isotherm. From the Langmuir equation, the adsorption capacities were found as 400 mg UO₂²⁺/g dry amidoximated poly(DPAAm) and 250 mg UO₂²⁺/g dry amidoximated graft polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1705–1710, 2004     

Fe2+–Thioureadioxide–H2O2-induced polymerization of glycidyl methacrylate and its mixtures with acrylamide,acrylonitrile, butylmethacrylate,or styrene with cotton fabric

Fe²⁺–thioureadioxide-H₂O₂-induced polymerization of glycidyl methacrylate (GMA) and its mixtures with acrylamide (Aam), acrylonitrile (AN), butylmethacrylate (BMA), or styrene was investigated at different temperatures (50–95°C), for different periods of time (5–130 min) using different concentrations of Fe²⁺-thioureadioxide and H₂O₂. The add-on increased by increasing the thioureadioxide concentration up to 0.05% then decreased. H₂O₂ concentration of 0.005% constituted the optimal for GMA and GMA/Aam mixtures, and 0.02% H₂O₂ for GMA/AN, GMA/BMA and GMA/styrene mixtures. Increasing the concentration of GMA either alone or in admixtures resulted in improved add-ons; the magnitude of this improvement relied on the nature of the monomer used along with GMA. The polymerization reaction was characterized by an initial fast rate followed by a slower one irrespective of monomer or monomer mixtures used. Presence of Aam along with GMA offset the fast termination observed with the latter at higher temperatures (above 60°C). GMA/Aam mixtures produced higher add-ons than Aam alone irrespective of their rations in the mixtures, indicating activation of Aam with GMA. On the other hand, Aam deactivated GMA. Similar situation was encountered when styrene or acrylonitrile was used instead of Aam except that the percent add-ons obtained with GMA/AN mixtures decreased upon raising the polymerization temperature above 80°C. Contribution of GMA in the add-ons obtained with the different mixtures was also examined. For instance, the add-on was composed mainly of poly(GMA) when GMA/Aam at a ratio of 8:2 was used. On the other hand, using GMA/Aam at a ratio of 2:8 brought about add-ons of poly(GMA/Aam) in which the concentration of GMA and Aam were roughly equal.     

A novel two-dimensional network self-assembled by the narrowest ladder cations [Cu(CH3COO)(bpe)(H2O)]nn+ containing the Cu2(μ-O)2 cores and the dimeric anions [Cu2(nta)2(bpe)]2− through hydrogen-bonding interaction

A novel complex [Cu(CH₃COO)(bpe)(H₂O)]_n·n/2[Cu₂(nta)₂(bpe)] ·6nH₂O) (bpe=trans-1,2-bis(4-pyridyl)ethylene) was synthesized and characterized. The molecule structure shows that it is composed of the ladder-like double chain cations [Cu(CH₃COO)(bpe)(H₂O)]_nⁿ⁺ and the dimeric anions [Cu₂(nta)₂(bpe)]²⁻. Through bridging oxygen atom of the acetate, the Cu₂ (μ-O)₂ core is formed. The ladder-like chain cation is the narrowest ladder [3.422(3) Å]. Two-dimensional undulating network is constructed by the cations and the dimeric anions through hydrogen-bonding interactions.     

Structural and dielectric properties of CuCl2 and ZnCl2 doped polyaniline

This article addresses the synthesis and characterization of polyaniline (PANI) both in pure and doped forms with various levels of CuCl₂ and ZnCl₂ in HCl medium where ammonium persulphate was used as an oxidant. Synthesized polymeric materials were characterized spectroscopically (UV‐visible spectroscopy, Fourier transform infrared spectroscopy, and Atomic absorption spectroscopy), thermally (Differential scanning calorimetry), and morphologically (Scanning electron microscopy). Free adsorption energy was calculated via Langmuir adsorption isotherm based on the quantities of Cu²⁺ and Zn²⁺ cations in both pre‐ and post‐ polymerization process where it was found that Cu²⁺ and Zn²⁺ are adsorbed physically on PANI surface. The dielectric measurements as a function of frequency and temperature showed that conductivity decreased with increasing doping levels of metal cations at high temperatures. POLYM. COMPOS., 31:1862–1868, 2010. © 2010 Society of Plastics Engineers.