Theoretical Study of NO2 Adsorption on a Transition-Metal Zeolite Model

Calculations for the study of NO₂ adsorption on a transition-metal-exchanged zeolite (M=Zn, Cu, Ni, Co, Fe) were carried out using an ab initio density functional theory and pseudopotential approaches. A tritetrahedral model (T3) was used to represent the structure of the zeolite. The density functional calculations predict that the bonding energy follows the order Zn>Ni>Cu>Fe>Co. Analysis of the electronic properties shows that only in the case of Cu and Ni ions does the d¹⁰-s¹d⁹ promotion favor interaction between the NO₂ molecule and the metallic center. The optimization results show that there is a charge transfer from the metallic ion to the NO₂ molecule, which produces a weakening of the N–O bond.     

Removal of Heavy Metals and Other Cations from Wastewater Using Zeolites

Abstract

Zeolites from abundant natural deposits were investigated by the Bureau of Mines for efficiently cleaning up mining industry wastewaters. Twenty-two zeolites were analyzed by X-ray diffraction and inductively coupled plasma analysis (ICP). These included clinoptilolite, mordenite, chabazite, erionite, and phillipsite. The zeolites were primarily in the sodium or calcium form, but potassium and magnesium counter ions were also present. Bulk densities of a sized fraction (minus 40, plus 65 mesh) varied from 0.48 to 0.93 g/cc. Heavy metal ion exchange loading values on two clinoptilolites ranged from 1.6 meq/g for lead to 0 meq/g for mercury in single ion tests. The selectivity series was determined to be Pb>Cd>Cs>Cu(II)>Co(II)>Cr(III)>Zn>Ni(II)>Hg(II). Sodium was the most effective exchangeable ion for ion exchange of heavy metals. Wastewater from an abandoned copper mine in Nevada was used to test the effectiveness of clinoptilolite for treating a multiion wastewater. Aluminum, Fe(III), Cu(II), and Zn in the copper mine wastewater were removed to below drinking water standards, but Mn(II) and Ni(II) were not. Calcium and NH₄ were absorbed preferentially to all heavy metal cations except Pb. Adsorbed heavy metals were eluted from zeolites with 3-pct NaCl solution. Heavy metals were concentrated in the eluates up to 30-fold relative to the waste solution. Anions were not adsorbed by the zeolites.     

Ferrite process of electroplating sludge and enrichment of copper by hydrothermal reaction

In this paper, ferrite process of electroplating sludge and enrichment of copper by hydrothermal reaction was investigated. By the hydrothermal treatment, Zn, Ni, Cu, Cr-bearing electroplating sludge can be transformed into high value-added Ni–Zn–Cr ferrite by adding iron source (FeCl₃·6H₂O) and precipitator. The most optimum reaction conditions were explored: 1.57 g/g dry sludge as the dosage of FeCl₃·6H₂O, pH 8.5 of the slurry adjusted by ammonia, 4 h as the reaction time, and 200 °C as the reaction temperature. Under these conditions, the purer Ni–Zn–Cr ferrite could be prepared, and Cu was extracted to the range from 76 wt% to nearly 84 wt%, when ammonia was selected as the precipitator. Leaching toxicity of heavy metals from Ni–Zn–Cr ferrite prepared with additional iron source and precipitator, was much lower than the regulated limit of Toxicity Characteristic Leaching Procedure (TCLP), indicating that Ni–Zn–Cr ferrite synthesized hydrothermally from electroplating sludge had a better chemical stability. Therefore, the ferrite process by hydrothermal reaction is a feasible method with respect to the reuse and self-purification of electroplating sludge.     

Adsorption of Metal Ions on A Novel Amine-Type Chelating Resin

Distribution equilibria were investigated for the adsorption of metal ions and acids on Sumichelate MC-10 resin, a polyethylene polyamine type of novel chelating resin. The total exchange capacities for HCl and HNO₃ were evaluated as 5.6 and 6.3 mol/kg dry resin, respectively. Adsorption of various divalent transition metals and precious metals was investigated from HCl on the chloride form of the resin. The adsorption of transition metals took place in the sequence Cd>Zn>Cu>Co>Mn. The adsorption of Pt(IV) was only slightly selective over Pd(II); however, the latter was selectively eluted with high concentrations of HCl. Adsorption of Ag(I), Zn(II) and Cu(II) was investigated from 1 mol/dm³ NH₄NO₃ on the free base form of the resin. It took place in the sequence Cu>Ag>Zn. The mechanism of the adsorption of metal ions mentioned above was qualitatively discussed.     

Synergistic Effect in Selective Reduction of NO by Alkanes over Mechanically Mixed Oxide Catalysts

The process of selective catalytic reduction of nitrogen oxides by propane in the presence of O₂, as well as in the presence or absence of CO, was studied over series of commercial oxide catalysts used in petrochemical processes. For the first time synergistic effect was observed for catalytic systems consisting of mechanical mixtures of Cu–Zn–Ni–Al (catalyst I) + Fe–Cr (catalyst II) and Cu–Zn–Ni–Al (catalyst I) + Ni–Cr (catalyst III). The activity of these mixtures in nitrogen oxides reduction by propane was greater than that of individual components in each case. The worked-out catalytical systems showed high effectivity in the process of simultaneous removal of several toxic components: NO _x , CO, hydrocarbons – from model gas mixtures, as well as from real exhausts of automotive transport.     

Highly salicylate-selective membrane electrode based on a new thiomacrocyclic Schiff base complex of binuclear copper(II) as neutral carrier

New binuclear metallic complexes of thiomacrocyclic Schiff base, 3,9,13,19 -tetraphenyl-6,16-dithione-1,11-dithio-4,5,7,8,14,15,17,18-octaazacycloeicosa-3,8,13,18-tetraene binuclear metal(II) [M(II)₂-TDDOCT] (M = Cu, Co, Ni), were synthesized and their anion response characteristics were investigated. The performances of the electrodes are considerably influenced by the nature of the central metals. The Cu(II) complex-based electrode exhibited a good selectivity to salicylate anion with an anti-Hofmeister selectivity pattern: Sal⁻ > ClO₄⁻ > SCN⁻ > I⁻ > Benzoate > B_r⁻ > Acetate > F⁻ > SO₃²⁻ > NO₂⁻ > Cl⁻ > NO₃⁻ > SO₄²⁻ > H₂PO₄⁻. The electrode had an excellent linear response to Sal⁻ from 9.0 × 10^− 7 to 1.0 × 10^− 1 M with a slope of − 59.3 mV per decade,a detection limit of 5.0 × 10^− 7 M, and a fast response time within 15 s over the entire concentration series in phosphate buffer solutions of pH 5.0 at 25 °C. Spectroscopic techniques and the influence of lipophilic charged additives on the electrode behavior were used to investigate the response mechanism to Sal⁻. The electrode can be applied to the direct determination of salicylate in human urine and pharmaceutical samples and the results obtained are in accord with the results from a standard method.     

Effects of specific adsorption of copper (II) ion on charge transfer reaction at the thin film LiMn2O4 electrode/aqueous electrolyte interface

This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn₂O₄ thin film electrode/aqueous solution (1 mol dm⁻³ LiNO₃) interface. The zeta potential of LiMn₂O₄ particles showed a negative value in 1 × 10⁻² mol dm⁻³ LiNO₃ aqueous solution, while it was measured as positive in the presence of 1 × 10⁻² mol dm⁻³ Cu(NO₃)₂ in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO₃)₂ was estimated to be 35 kJ mol⁻¹, which was ca. 10 kJ mol⁻¹ larger than that observed in the solution without Cu(NO₃)₂. These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction.     

Trace elements in Turkish biomass fuels: Ashes of wheat straw, olive bagasse and hazelnut shell

Ash contents of wheat straw, olive bagasse and hazelnut shells were 7.9%, 3.9%, 1.2%, respectively, which seemed to be within the average values of ash of biomass. The microstructure of ashes included smooth, polygonal, granular and molten drop structures. A large percentage of particles present in ashes are commonly ∼1-20 μm in size. SEM/EDS analyses performed on the major ash forming elements in different ashes indicated that Si, Ca, K and Mg and P were generally the most abundant species. Trace element levels in ash samples of various biomass types such as hazelnut shell, wheat straw, olive bagasse were analysed using ICP spectroscopy. The elements determined were some of those considered being of great environmental concern such as, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb. In all of the ashes studied Fe had the highest concentration among other trace elements, Mn was the second element that exhibited higher concentrations. The order of concentration of elements in the ashes from the highest to the lowest values was as follows: Fe > Mn > Zn > Cu > Ni > Cr > Pb > Co.     

Electrodeposition behavior of zinc–nickel–iron alloys from sulfate bath

The present work is directed at collecting the properties of Zn–Ni and Zn–Fe alloys in one alloy via the electrodeposition of Zn–Ni–Fe ternary alloy. Electrodeposition of ternary Zn–Ni–Fe alloy was investigated and compared with the characteristics of Zn–Ni electrodeposits. The electrodeposition was performed from a sulfate bath onto a steel substrate. Structural analysis by X-ray diffraction (XRD) method revealed that the Zn–Ni–Fe alloys consisted of a mixture of zinc, and (γ-Ni₂Zn₁₁) and (Fe₃Ni₂) phases. The study was carried out using electrochemical methods such as cyclic voltammetry and galvanostatic for electrodeposition, while anodic linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Surface morphology and chemical composition of the deposits were also examined by using scanning electron microscopy and atomic absorption spectroscopy, respectively. It was found that the obtained Zn–Ni–Fe alloy exhibited more preferred surface appearance and better corrosion resistance without adding any organic brighteners to the plating bath in comparison to Zn–Ni alloy that electrodeposited at similar conditions. Results obtained revealed that the increase in corrosion resistance of ternary deposits is not only attributed to the formation of (γ-Ni₂Zn₁₁) phase, but also to iron codeposition and formation of (Fe₃Ni₂) phase.     

Electrochemical reforming of CH4−CO2 mixed gas using porous Gd-doped ceria electrolyte with Cu electrode

This paper reports on the composition and flow rate of outlet gas and current density during the reforming of CH₄ with CO₂ using three different electrochemical cells: cell A, with Ni−GDC (Gd-doped ceria: Ce_0.8Gd_0.2O_1.9) cathode/porous GDC electrolyte/Cu−GDC anode, cell B, with Cu−GDC cathode/ porous GDC electrolyte/Cu−GDC anode and cell C, with Ru−GDC cathode/ porous GDC electrolyte/ Cu−GDC anode. In the cathode, CO₂ reacts with supplied electrons to form CO fuel and O²⁻ ions (CO₂+2e⁻→CO+O²⁻). Too low affinity of Cu cathode to CO₂ in cell B reduced the reactivity of the CO₂ with electrons. The CO fuel, O²⁻ ions and CH₄ gas were transported to the anode through the porous GDC mixed conductor of O²⁻ ions and electrons. In the anode, CH₄ reacts with O²⁻ ions to produce CO and H₂ fuels (CH₄+O²⁻→2 H₂+CO+2e⁻). The reforming efficiency at 700−800 °C was lowest in cell B and highest in cell A. The Cu anode in cells A and C worked well to oxidize CH₄ with O²⁻ ions (2Cu+O²⁻→Cu₂O+2e⁻, Cu₂O+CH₄→2Cu+CO+2H₂). However, a blockage of the outlet gas occurred in all the cells at 700−800 °C. The gas flow is inhibited due to a reduction in pore size in the cermet cathode, as well as sintering and grain growth of Cu metal in the anode during the reforming.     

Landfill gas (LFG) processing via adsorption and alkanolamine absorption

Landfill gas (LFG) was upgraded to pure methane using the adsorption and absorption processes. Different toxic compounds like aromatics and chlorinated compounds were removed using granular activated carbon. The activated carbon adsorbed toxic trace components in the following order: carbon tetrachloride > toluene > chloroform > xylene > ethylbenzene > benzene > trichloroethylene ≈ tetrachloroethylene. After removing all trace components, the gas was fed to absorption apparatus for the removal of carbon dioxide (CO₂). Two alkanolamines, monoethanol amine (MEA) and diethanol amine (DEA) were used for the removal of CO₂ from LFG. The maximum CO₂ loading is obtained for 30 wt.% MEA which is around 2.9 mol L^− 1 of absorbent solution whereas for same concentration of DEA it is around 1.66 mol L ^− 1 of solution. 30 wt% MEA displayed a higher absorption rate of around 6.64 × 10^− 5 mol L^− 1 min^− 1. DEA displayed a higher desorption rate and a better cyclic capacity as compared to MEA. Methane obtained from this process can be further used in the natural gas network for city.     

Biosorption of chromium, copper and zinc on rice wine processing waste sludge in fixed bed

Wine processing waste sludge (WPWS) has shown effective removal of heavy metals in batch studies, but the adsorption in a fixed-bed WPWS column has not been examined and the mass transport in this column remains unclear. This study aimed to investigate: (1) the retardation factor (R) and the dispersion coefficient (D) of WPWS, employing one-dimensional convective–dispersive model with breakthrough curve (BTC) and using chromium, copper and zinc as the adsorbates; and (2) explore the adsorption mechanism of WPWS column for heavy metals. The retardation factor for various metal treatments is shown in the following order: Cr(18.3) > Cu(13.0) > Zn(7.2), indicating their binding affinity toward WPWS. The dispersion coefficients were calculated to be 2.36 × 10⁻⁶, 5.89 × 10⁻⁷ and 6.83 × 10⁻⁷ m² s⁻¹ for Cr, Cu and Zn treatments, respectively. The high charge density for Cr³⁺ ion makes it longer for the Cr column to attain exhaustion state, about 4.0 and 8.2 times the time required for the Cr and Zn columns. However, the least retardation and adsorption amount for Zn can be attributed to its full orbital in electronic configuration.     

Promotion of Fe3O4/Cr2O3 high temperature water gas shift catalyst

The promotion of Fe₃O₄/Cr₂O₃ high temperature water gas shift catalysts is described and discussed. Catalysts containing 2 wt% B, Cu, Ba, Pb, Hg and Ag are prepared by co-precipitation. B is found to poison the activity slightly whereas the other additives did increase the activity, with the relative order being Hg>Ag,Ba>Cu>Pb>unpromoted>B. The promoters decrease the activation energy of the catalyst, but the data give a linear relationship for the Constable–Cremer plot and it is concluded that CO adsorption is an important factor controlling activity.     

Leaching characterisation and geochemical modelling of minor and trace elements released from recycled concrete aggregates

The pH dependent release of Cd, Cr, Cu, Mn, Mo, Ni, Pb, V and Zn from different recycled concrete aggregate samples was determined. Geochemical speciation modelling was applied on the concentrations of Cu, Cr, Mo and Ni in the leachates in order to predict the measured concentrations and the specific release mechanisms. The model was able to reproduce the characteristic pH dependent release patterns for these elements and reasonable to sometimes excellent matches between the predicted and measured concentrations were achieved. Binding of Mo and Cr as oxyanions (MoO₄²⁻ and CrO₄²⁻) to ettringite was modelled with fair agreement for Cr only. For Cu and Ni, the predicted and measured concentrations agreed well for the partly carbonated sample at high alkaline pH (11–13). The importance of complexation to humic substances was also shown in samples derived from construction debris.     

Preparation of alkaline PVA-based polymer electrolytes for Ni–MH and Zn–air batteries

Alkaline PVA polymer electrolyte with high ionic conductivity of about 0.047 S cm^–1 at room temperature was obtained by a solution casting method. The PVA polymer electrolytes, blended with KOH and H₂O, were studied by DSC, TGA, cyclic voltammetric and a.c. impedance methods. The PVA polymer electrolytes show good mechanical strength and high ionic conductivity. The electrochemical stability window at the metal–electrolyte interface is ±1.2 V for stainless steel. Ni–MH and Zn–air batteries with PVA polymer electrolytes were assembled and tested. Experimental results show good electrochemical performances of the PVA-based Ni–MH and Zn–air batteries.     

The impedance properties of the oxide film on the Ni–Cr–Mo Alloy-22 in neutral concentrated sodium chloride solution

The oxide film properties on Alloy-22 in the applied potential (E) range −600 mV to 600 mV (vs. saturated KCl, Ag/AgCl reference electrode) were characterized by Electrochemical Impedance Spectroscopy (EIS) in near neutral pH, 5 M NaCl solutions, at 30 °C. The impedance properties of the film were compared to the chromium content of the film determined by X-ray photoelectron spectroscopy (XPS). The oxide film properties on Alloy-22 may be divided into three applied potential (E) ranges: −600 mV ≤ E < −300 mV, −300 mV ≤ E ≤ 300 mV, and E > 300 mV. For the range −600 mV ≤ E < −300 mV the film resistance (R_film) increases with potential accompanied by an increase in Cr₂O₃ content; in the range −300 mV ≤ E ≤ 300 mV, R_film values and the Cr₂O₃ content of the oxide film achieve their maximum values; for E > 300 mV, a decrease in both R_film and Cr₂O₃ is observed accompanied by a significant increase in Cr(OH)₃. Comparison of the impedance properties for Alloy-22 to those of Ni–Cr alloys indicate that the barrier layer oxide on Alloy-22 contains a lower number of less mobile defects, most likely Cr interstitials. Destruction of the barrier layer for E > 300 mV leads to the formation of a thicker, less protective bilayer, which is high in Mo content.     

Transparent Al–In–Zn–O Oxide semiconducting films with various in composition for thin-film transistor applications

Al–In–Zn–O thin-film transistors were fabricated. To examine the effect of In composition, we adopted a co-sputtering method using Al–Zn–O and In₂O₃ targets. The sputtering power of In₂O₃ was varied to 200, 150, and 50 W. The mobility and turn-on voltage of each device were 27.8 cm²V⁻¹ s⁻¹ and −4.2 V, 4.5 cm²V⁻¹ s⁻¹ and −3.5 V, 0.7 cm²V⁻¹ s⁻¹ and −3 V, respectively. We also investigated instabilities under negative gate bias stress (NBS) and negative bias illumination stress (NBIS). While the NBS was not influenced by the In contents, the NBIS characteristics were optimized for the device with In₂O₃ sputtering at 150 W.     

Separation performance of a nanofiltration membrane influenced by species and concentration of ions

Nanofiltration (NF), which has been largely developed over the past decade, is a promising technology for the treatment of organic and inorganic pollutants in surface and ground waters. The ESNA 1 membrane from the Nitto Denko Corporation of Japan is made of aromatic polyamide, which provides salt rejection from 50% to 90%. In this paper permeation experiments of aqueous solutions of five chlorides (NH₄Cl, NaCl, KCl, MgCl₂ and CaCl₂), three nitrates (NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂), and three sulfates (NH₄)₂SO₄, Na₂SO₄ and MgSO₄) were carried out. The effects of species and concentration of salts on the separation performance of the ESNA 1 membrane were investigated. The experimental results showed that the rejection to most salts by the ESNA 1 membrane decreased with the growth of the concentration. Then, the reflection coefficient and solute permeability of ESNA 1 membrane were calculated by the Spiegler-Kedem equation from experimental data. The reflection coefficients of the ESNA 1 membrane to salts are all above 0.95. The salt permeabilities, except for magnesium and calcium salts, increased with the growth of concentration. The sequence of rejection to anions by the ESNA 1 membrane is R(SO²⁻₄) > R(Cl⁻) > R(NO⁻₃) at the same concentration which ranges from 10 mol/m³ to 100 mol/m³. The sequence of rejection to anions by the ESNA 1 membrane can be written as follows: R(Na⁺) > R(K⁺) > R(Mg²⁺) > R(Ca²⁺) at 10 mol/m³ concentration and R(Mg²⁺) > R(Ca²⁺) > R(Na⁺) > R(K⁺) at 100 mol/m³ concentration.     

The influence of chlorine on the dispersion of Cu particles on Cu/ZnO(0001) model catalysts

One of the ways in which chlorine is thought to poison metal catalysts on oxide supports is by altering their dispersion. The effect of chlorine on Cu/ZnO(0001) model catalysts was studied by vapor‐depositing Cu onto Zn‐terminated ZnO(0001), both with and without preadsorbed Cl₂, using XPS, ion scattering spectroscopy (ISS), temperature‐programmed desorption (TPD), work function, and band bending measurements. A disordered, but nearly close‐packed overlayer of Cl adatoms forms at saturation with ∼0.30 Cl adatoms per Zn site. Without Cl, vapor‐deposited Cu grows in two‐dimensional islands that cover ∼33% of the ZnO, after which these islands thicken (i.e., as 3D Cu particles) while the clean ZnO between these Cu islands gets covered with Cu only very slowly. Preadsorbed Cl decreases the fraction of the surface that is covered by Cu islands by a factor of three, so Cl(a) either decreases the number of 2D Cu islands or their critical area before thickening. Both are consistent with weaker binding of Cu to the Cl‐covered surface than to the clean ZnO. The TPD features for formate decomposition after HCOOH adsorption onto Cu/ZnO(0001) were suppressed with preadsorbed Cl, but the CO₂ : CO selectivity increased. When Cu was deposited onto Cl‐presaturated ZnO, neither the Zn‐ nor Cu‐formate peaks were observed, showing that Cl covers both the Zn sites and the growing Cu islands, as suggested by ISS also. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inhibitory effect of tungstate, molybdate and nitrite ions on the carbon steel pitting corrosion in alkaline formation water containing Cl ion

The pitting corrosion of carbon steel in carbonate-formation water solution in the presence of chloride ions and the effect of addition WO₄²⁻, MoO₄²⁻ and NO₂⁻ anions on the pitting corrosion were studied using cyclic voltammetry and potentiostatic current-time measurements and complemented by scan electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) investigations. Cyclic voltammograms of carbon steel in the presence of chloride ions in carbonate-formation water solution show one anodic peak, corresponding to the formation green rust carbonate and the two cathodic peaks. As the addition of Cl⁻ ions concentration increases, the anodic peak current density increases and pitting potential E_pit shifts to more negative potential. It is shown that the rate of pit initiation () decreases and the pitting potential E_pit moves to more positive direction upon the addition of inorganic anions. It was found that pitting inhibition of carbon steel increases in the sequence: (WO₄)²⁻ > (MoO₄)²⁻ > (NO₂)⁻.