Study on complexation adsorption behavior of dibenzo-18-crown-6 immobilized on CPVA microspheres for metal ions

Dibenzo-18-crown-6 (DBC) was immobilized on crosslinked polyvinyl alcohol (CPVA) microspheres, resulting in polymer-supported crown ether DBC–CPVA. The complexation adsorption behaviors of DBC–CPVA microspheres towards diverse metal ions were investigated. The experimental results show that among alkali metal ions, the complexation adsorption ability of DBC–CPVA for K⁺ ion is the strongest, and crown ether-metal complex in 1:1 ratio is formed, exhibiting a high adsorption capacity. The adsorption capacities of alkali metal ions on DBC–CPVA are in the order: K⁺ ? Na⁺ > LI⁺ > Rb⁺ > Cs⁺. Among several divalent metal ions, DBC–CPVA exhibits stronger adsorption ability towards Zn²⁺ and Co²⁺ ions, and a “sandwich”-type complex is formed probably in a molar ratio of 2:1 between the immobilized DBC and Zn²⁺ ion as well as between the immobilized DBC and Co²⁺ ion. The adsorption capacities of the several divalent metal ions on DBC–CPVA are in the order: Zn²⁺ > Co²⁺ ? Cd²⁺ > Cu²⁺ > Ni²⁺ > Pb²⁺. The complexation adsorption is exothermic physical physisorption process, and raising temperature leads to the decrease of the adsorption capacity. At the same time, the entropy during the complexation adsorption decreases, so the adsorption process is driven by the decrease of enthalpy.     

Thermodynamic characteristics of ion-exchange sorption of Co2+ cations on Na-vermiculite

The exchange of Na⁺ ions of vermiculite for Co²⁺ cations is measured by sorption-analytical and microcalorimetric methods. The previously revealed growth of the equilibrium constant with a rise in the degree of filling θ of vermiculite exchange sites with Co²⁺ cations is confirmed. This result is explained by the segregation of Co²⁺ and Na⁺ cations being exchanged in separate interlayer regions of vermiculite. The negative heats of exchange of Na⁺ cations for Co²⁺ cations are associated with the energy consumption for the rearrangement of the segregated interlayer regions in vermiculite. The positive entropy changes resulting from the exchange indicate the formation of a more disordered Co-Na-layered “cake” in comparison with the initial Na-form vermiculite. A decrease in the integral molal free-energy change ΔG _m of the mixed form of the mineral is determined by the entropy factor. It is shown that, as θ increases, the ΔG _m(θ) dependence passes from a positive to a negative range of values. This pattern of the curve may be interpreted as a gradual phase transition from the Na-form to the mixed Co-Na-segregated form. The first derivatives of the enthalpy and entropy changes with respect to the degree of filling θ exhibit distinct maxima at θ ～ 0.20 as a result of the transition from the ideal mixing of Co²⁺ and Na⁺ cations being exchanged to their segregation.     

Behavior of manganese dioxide electrodes in a system containing a solid protonic electrolyte

The behavior of manganese dioxide electrodes containing powders of graphite and titanium as electroconducting additives is studied in a system with a solid protonic hydrated electrolyte (SPHE). The MnO2 reduction is accompanied by ion exchange between formed Mn²⁺ ions and structural protons of SPHE. The open-circuit potentials drift in the anodic direction and stabilize when the MnO² composition at a boundary with SPHE is close to stoichiometric. The drift is due to conjugated reactions of the MnO₂ reduction and the graphite oxidation process that decays with time. With increasing cathodic current density, the solid-phase reduction of MnO₂ via an electronic-protonic mechanism becomes predominant. At low polarizing-current densities, the open-circuit and steady-state potentials remain passably stable until the exchange capacity of SPHE by protons is exhausted or MnO₂ near the interface with SPHE is spent. The feasibility of using MnO₂-SPHE-based amperometric sensors for assaying components whose oxidation in a gas medium yields protons is considered     

A novel ion-imprinted nanocomposite for selective separation of Pb2+ ions

In this study, the ion-imprinting method has been integrated to develop a novel composite material for the selective separation of Pb²⁺ ions. Also, Pb²⁺ ion binding ability of the organosmectite based inorganic-organic composite incorporation of bicyclic C18 organic compound into smectite layers was conducted to draw a projection its potential use as a solid phase exchanger which is quite selective toward Pb²⁺ ions. The ion-imprinted nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), swelling tests, and elemental analyses. After that, maximum binding capacity, pH, and equilibrium binding time were also been optimized. In order to show the selectivity of the composite synthesized, non-imprinted composites were also synthesized in absence of Pb²⁺ ions during polymerization. In this step, Ni²⁺, Co²⁺, Al³⁺, Zn²⁺, and Cu²⁺ ions were used as competitors under batch adsorption conditions. The relative selectivity coefficients of imprinted composite were calculated as 28.5, 156.5, 69.3, 24.8 and 131.6 for Pb²⁺/Co²⁺, Pb²⁺/Cu²⁺, Pb²⁺/Al³⁺, Pb²⁺/Zn²⁺, Pb²⁺/Ni²⁺ binary solutions, respectively. Finally, reusability of the composites was evaluated to show its cost-efficiency by repeating adsorption-desorption experiments ten-times. The adsorption capacity of the imprinted composites did not change significantly whereas that of non-imprinted version reduced dramatically.     

Synthesis of a Dithiocarbamate Chelate Resin and Its Oxidized form and Their Adsorption Properties for Heavy Metal Ions

A series of macroporous dithiocarbamate chelate resins, III and V, and an oxidized resin, VI, with high adsorption capacity were prepared. The influence of various reaction conditions of amination, dithiocarboxylation, and oxidation were examined. The structure and the conversion of functional groups of resins were confirmed by IR spectra and elemental analysis. The adsorption capacities of Resin II for Hg²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ are 4.40, 2.44, 1.77, and 1.36 mmol/g, respectively. The adsorption capacities of Resins V and VI for Cu²⁺. Zn²⁺, Ni²⁺, Co³⁺, Ag⁺, Hg²⁺, Cd²⁺, Pb²⁺, and Au³⁺ are 4.07–0.51 and 3.81–0.59 meq ion/g, respectively. The adsorption rate and the influence of pH on the adsorption percentage of the resins for metal ions were examined. Noble metal, transitional metal, and heavy metal ions can be quantitatively adsorbed by the resins. The adsorbed Cu²⁺, Pb²⁺, Cd²⁺, Co³⁺, and Ni²⁺ can be quantitatively eluted with 5N HNO₃, and the presence of large amounts of Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺ did not interfere.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

Spectroscopic identification of adsorption properties of Zn2+ ions at cationic positions of high-silica zeolites with distant placing of aluminium ions

For Zn²⁺ cations in ZnZSM-5 zeolite unusual type of cationic positions, formed by two distantly placed framework aluminium atoms, is considered. Some extent of structural destabilization of cations in these cationic positions in comparison with traditional localization should result in promoted Lewis activity and adsorption activity of these sites. The last ones are manifested in the significantly increased IR low frequency shifts for adsorbed molecules and in their ability for heterolytic dissociation at elevating temperature. DFT cluster quantum chemical modeling of light alkane adsorption on Zn²⁺ in ZnZSM-5 zeolites confirms these conjectures in full agreement with recent experiments. Similar to the previously considered dihydrogen and methane molecule adsorption, we present here the calculations of ethane molecular and dissociative adsorption on these sites. It is shown that the unusually large ethane IR frequency shift recently observed in ZnZSM-5 zeolite can result from adsorptive interaction of C₂H₆ with Zn²⁺ stabilized in a cationic position with distantly placed aluminium ions. The dissociative adsorption of ethane molecules with the formation of bridged hydroxyl group and Zn–C₂H₅ structure is considered and an activation energy of ethylene formation from the alkyl fragment is evaluated.     

Biosorption of metal ions with Penicillium chrysogenum

Biosorption of metal ions with Penicillium chrysogenum mycelium is described in this article. Alkaline pretreatment was used to remove proteins and nucleic acids from cells, and this treatment increased the adsorption capacities, for Cr³⁺ from 18.6 mg g⁻¹ to 27.2 mg g⁻¹, for Ni²⁺ from 13.2 mg g⁻¹ to 19.2 mg g⁻¹, for Zn²⁺ from 6.8 mg g⁻¹ to 24.5 mg g⁻¹. The adsorption of metal ions was strongly pH dependent. The mycelium could beused for large-scale removal of Cr³⁺ from tannery wastewater. The results show that this inexpensive mycelium adsorbent has potential in industry because of its high adsorption capacity. The main chelating sites are amino groups (−NH₂) of chitosan in the mycelium. A new model is established, which describes the relation of adsorption of metal ions on pH according to amino group chelating with metal ions and H⁺. The relative errors of simulation for Cu²⁺, Ni²⁺, Zn²⁺, and Cr³⁺ are 4.66%, 5.45%, 11.55%, and 1.69%, respectively.     

Conversion of porous PbO2 layers through galvanic displacement reaction with Mn2 + ions

The galvanic exchange between Mn^2 + ions and electrodeposited porous PbO₂ was studied to produce a porous oxide whose lower conductivity prevented its direct oxygen bubble-templated anodic deposition. Immersion of PbO₂ layers in acid acetate solutions of Mn^2 + led to the formation of amorphous MnO_x shell onto PbO₂. Due to its amorphous nature, MnO_x could not be proved to be MnO₂ by XRD. However, MnO_x was cathodically stripped at the same potential as MnO₂. The deposition of the MnO_x shell onto PbO₂ enhanced the capacity of the porous electrodes.     

用MnO_2离子筛吸附剂从溶液中提取锂(英文)

研究了MnO2离子筛的制备、表征及其提锂性能。通过控制低温水热合成反应条件制备了4种不同晶相的一维纳米MnO2,进一步用浸渍法制备了Li-Mn-O三元氧化物前驱体,并经酸处理后得到对Li+具有特殊选择性的离子筛。用XRD、吸附等温线、吸附动力学及pH滴定等手段对产物的晶相结构和Li+吸附性能进行了研究。结果表明,SMO-b和SMO-d离子筛的Li+平衡吸附量符合Freundlich吸附等温方程。反应物浓度对MnO2不同晶面的生长速率有不同的影响,但(NH4)2SO4对吸附容量并无提高。吸附速率方程符合一级动力学Lagergren方程。MnO2离子筛Li+的吸附量远远高于Na+。     

Vibrational and scanning electron microscopy study of the mordenite modified by Mn, Co, Ni, Cu, Zn and Cd

The mordenite samples loaded with divalent nitrates of Mn, Co, Ni, Cu, Zn and Cd were investigated using FTIR and scanning electron microscopy (SEM) methods. It was found from FTIR spectra that in 3000-4000 cm⁻¹ region of mordenite samples with similar water concentration ions, Mn²⁺, Co²⁺, Cu²⁺, and Zn²⁺ tend to break hydrogen bonds formed between water molecules and zeolite framework, whereas Ni²⁺ and Cd²⁺ accommodate to hydrogen bonds. From SEM results it was concluded, that ions Mn²⁺, Co²⁺, Zn²⁺ form innersphere complexes with oxygens from Brönsted acid sites, whereas Ni²⁺ and Cd²⁺ associate with Brönsted acid sites without exchange of protons.     

Highly selective fluorescent recognition of Zn2+ based on naphthalene macrocyclic derivative

A new macrocyclic chemosensor containing two naphthalene fluorophores has been synthesized. The fluorescent properties of this receptor has been studied in the presence of various metal ions such as Na⁺, Ag⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺. When increasing concentrations of Zn²⁺ ions were introduced, the emission of L was drastically increased (EFE = 4.34). This special change was not observed when other metal ions were used; such highly selective fluorescent response indicates that this receptor can easily discriminate Zn²⁺ ions from other similar species. Model calculations at DFT level further suggest the possible interaction mode, and relatively steric position between the host and guest also influence the optical response.     

Retaining60Co2+ ions from residual water on zeolites

The ion exchange between⁶⁰Co²⁺ ions contained in residual radioactive water and zeolites of the NaA, NaX and CaA types was studied. The more advanced retaining of⁶⁰Co²⁺ ions occurs for the NaA zeolite with the higher exchange capacity, as compared to NaX. With the CaA zeolite, a very weak ion exchange with⁶⁰Co²⁺ ions was observed.     

IR Spectroscopic Study of the Interaction of Transition Metal Ions with Hydroxyapatite Modified by Potassium Ferrocyanide

IR spectroscopy was used to study the modification of hydroxyapatite by potassium ferrocyanide and the interaction of transition metal ions with the modified adsorbent. The structural changes of hydroxyapatite upon the adsorption of Zn²⁺ ions were studied by X-ray phase analysis. Potassium ferrocyanide was found to interact with the surface hydroxyl groups of hydroxyapatite through the nitrogen unshared electron pair. Co²⁺, Ni²⁺, and Zn²⁺ ions were found to eliminate outer-sphere K⁺ ions of adsorbed ferrocyanide to give Fe²⁺— CN—M²⁺— NC—Fe²⁺ bridging structures. Zn²⁺ cations additionally eliminate a part of the Ca²⁺ ions from structural positions of hydroxyapatite, which leads to the appearance of a two-phase hydroxyapatite–sholzite system with heterogeneous distribution of the Ca²⁺ ions in the mot her mineral phase, while the Zr²⁺ ions are found in the new sholzite phase.     

Kinetics of the exchange between MnO or Mn3O4 and some divalent cations in aqueous solution

The kinetics of the exchange between MnO or Mn₃O₄ and Co²⁺, Cu²⁺, Ni²⁺, or Zn²⁺ ions in solution, was determined by measuring the γ-activity of⁵⁶Mn acquired by the solution after shaking with the neutron irradiated solid. The results indicated a fast exchange followed by a slower apparently diffusion-controlled exchange. The exchange capacity increased in the series: Co²⁺<Ni²⁺<Cu²⁺=Zn²⁺ for MnO and Ni²⁺<Co²⁺<Zn²⁺<Cu²⁺ for Mn₃O₄. The trends could not be satisfactorily explained by the ionic radii or crystal field stabilisation-energies. In the case of MnO, the results were discussed in terms of the estimated standard enthalpy change of the exchange reaction.     

Novel nanostructured dendrimer based on 1,3-bis(4,6-dichloro-1,3,5-triazine-2-yl)urea as an excellent adsorbent for Pb2+, Ni2+, Co2+ and Zn2+ metal ions

Human health is seriously harmed by the consumption of poor-quality water. Due to high toxicity and water solubility, heavy metals are present in wastewater discharged from numerous industries. In the environmental realm, metal-containing water must be treated before being released. A dendrimer is a superior adsorbent for the removal of heavy metal ions due to its nanostructure and hydrophilic end group. In this work, a novel triazine-based hydroxy-terminated dendrimer up to generation three is designed employing a carbamide core. The dendrimer's structure was explored using FT-IR and ¹H NMR studies. Full generation dendrimers UG1.0, UG2.0, and UG3.0 were utilized as an adsorbent for Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ion removal from water in a series of tests. The ability of dendrimers to uptake Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions was investigated under various pH, time interval and dendrimer generation parameters. The presence of metal in the dendrimer was confirmed by FT-IR studies of dendrimer-metal complexes. The overall results show that Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions uptake increases with the generation, time, and pH.     

Effect of metal substitution for cobalt on the oxygen adsorption properties of YBaCo<Subscript>4</Subscript>O<Subscript>7</Subscript>

YBaCo₄O₇ compound is capable to intake and release a large amount of oxygen in the temperature range of 200–400°C. In the present study, the effect of Zn, Ga and Fe substitution for Co on the oxygen adsorption/desorption properties of YBaCo₄O₇ were investigated by thermogravimetry (TG) method. Due to fixed oxidation state of Zn2+ ions, the substitution of Zn²⁺ for Co²⁺ suppresses the oxygen adsorption of YBaCo_4−xZn_xO₇. The substitution of Ga³⁺ for Co³⁺ also decreases the oxygen absorption capacity of YBaCo_4−xGa_xO₇. This can be explained by the strong affinity of Ga³⁺ ions towards the GaO₄ tetrahedron. Compared with Zn- and Ga-substituted samples, the drop of oxygen adsorption capacity is smallest for Fe-substituted samples because of the similar changeability of oxidation states of Co and Fe ions.     

Interfering influence of silver on the voltammetric behaviour of Cd2+ and Zn2+ ions on hmde in supporting electrolytes containing nitrates

A new kind of secondarily formed peaks was found in cyclic and stripping voltammetry in neutral sulphate, perchlorate and nitrate supporting electrolytes containing some divalent cations and a substance (for example O₂), the reduction of which gives as a by-product OH^? ions. The hydroxides deposited in the vicinity of the mercury electrode, in the course of a cathodic scan, react during the anodic scan according to the reaction Hg+Me(OH)₂=Hg(OH)₂+Me²⁺+2e forming a new, separate anodic peak.It was found that silver exerts a catalytic effect on the reduction of NO₃^? ions on the mercury electrode. In neutral nitrate supporting electrolyte containing Ag⁺ ions the hydroxides of some cations (Cd²⁺, Zn²⁺, Mn²⁺, Co²⁺ and Ni²⁺) were deposited during the cathodic scan or during the preelectrolysis. Afterwards, in the course of the anodic scan, a new peak, of the kind described above, was observed. The same effect was formerly interpreted, for Zn²⁺ and Cd²⁺, as evidence for the formation of intermetallic compounds, AgZn and AgCd.     

Metal Complexes with Macrocyclic Ligands,V. Formation and dissociation kinetics of the pentaco-ordinated Ni2+, Cu2+, Co2+ and Zn2+ complexes with 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane

The formation and dissociation kinetics of the pentaco-ordinated Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ complexes with 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4-MeCyclam-14) was studied by pH-stat techniques and spectrophotometrically. The rates of the reactions between 4-MeCyclam-14 and each of the four metal ions, although slower than normal complexations by a factor of 10³?10⁴, closely follow the order Cu²⁺ > Zn²⁺ > Co²⁺ > Ni²⁺, found for the rate of water exchange. This implies that beside water exchange an other constant factor plays an important role in the rate determing step. The dissociation of the pentaco-ordinated 4-MeCyclam-14 complexes is acid catalyzed. The limiting rate for acid dissociation is not reached even in 2.5M HNO₃ in the case of Ni(4-MeCyclam-14)²⁺. From the formation and dissociation rates stability constants have been calculated, which do not show any macrocyclic effect.     

ESR spectra and magnetic constants of α-Al2O3:Co2+,H+ and α-Al2O3 :Co2+,X+

New anisotropic ESR spectra of Co²⁺ doped sapphire, different from hitherto known, are reported. The new spectra which are observed, beside the well-known spectra of α-Al₂O₃:Co²⁺, are shown to form two sets, each one consisting of six spectra (1–6) and (7–12). The spectra of both sets are proven to be interrelated by B_3a symmetry. g and A tensors for each set will be given. Evidence is given that the two sets are to be assigned to the defects α-Al₂O₃:Co²⁺,H⁺ and α-Al₂O₃:Co²⁺,X⁺. The former is concluded to consists of a Co²⁺ ion at the substitutional site (c) and a proton located in a potential minimum along a straight line between O^2- ions situated in O²⁺ triangles above and below the CO²⁺ ion. The potential function for the proton has been calculated by quantum-chemical calculations to clucidate the geometrical structure of the paramagnetic center. The α-Al₂O₃:Co²⁺,X⁺ could not be fully analyzed but some evidence is presented, that X⁺ might be alkali ions.