Decomposition of Carboxylic Acids in Water by O3, O3/H2O2, and O3/Catalyst

This paper studies the decomposition of formic, oxalic and maleic acids by O₃, O₃/catalyst, and O₃/H₂O₂. The catalytic effect of Co²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Cr³⁺, and Fe²⁺ ions is investigated. The results showed that—Co²⁺ and Mn²⁺ have the highest catalytic activity for the decomposition of oxalic acid while the catalytic effect of the studied ions is insignificant on the rate of decomposition of formic acid. Maleic acid decomposes by ozone into formic acid and glyoxylic acid, which subsequently oxidizes to oxalic acid. Though the studied ions have no effect on the decomposition of maleic acid, they have a significant effect on the produced oxalic and glyoxylic acids. In the presence of Cu²⁺ ions glyoxylic acid is mainly transformed into formic acid and traces of oxalic acid. In such case, a complete decomposition of maleic acid and its degradation products is achieved within 45 min. The results also show that combining H₂O₂ with O₃ results in an increase in the rate of decomposition of oxalic acid. However, O₃/H₂O₂ system is less active than O₃/Co²⁺ or O₃/Mn²⁺.     

Transition metal complexes with Girard reagent-based ligands. Part V. Synthesis,characterization and crystal structure of pentagonal-bipyramidal manganese(II) complex with 2,6-diacetylpyridine bis(Girard-T hydrazone)

The article describes the synthesis and crystal structure of the Mn(II) complex with 2,6-diacetylpyridine bis(Girard-T hydrazone), (H₂dap(GT)₂)²⁺, of the formula [Mn(H₂dap(GT)₂)(NCS)₂](NCS)₂·MeOH. The complex has a pentagonal-bipyramidal coordination geometry, with pentadentate N₃O₂ ligand in the equatorial plane and two isothiocyanato groups in the axial positions. Both the ligand and the complex are characterized by their FT-IR spectra and thermal data.     

Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions

Aminoalkyl celluloses (AmACs) were prepared from 6-chlorodeoxycellulose and aliphatic diamines H₂N(CH₂)_mNH₂ (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺ and their mixtures were also investigated in detail. Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu²⁺ > Ni²⁺ > Co²⁺ > Mn²⁺. Accordingly, their behavior followed the Irving-Williams series and Cu²⁺ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.     

Reduction electrocatalytique de l'oxygene sur electrodes solides d'oxydes mixtes contenant des ions manganese. II. Rôle du couple Mn3+-Mn4+en sites octaédriques

Résumé On montre, en étudiant la réduction électrochimique de l'oxygène sur les manganites de nickel dopés en cuivre, Ni_1-x Cu _x Mn₂O₄, que lélectrocatalyse se produit par adsorption sur des sites actifs constitués par des ions Mn⁴⁺ associés, en sites octaédriques, à des ions Mn³⁺.

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It is demonstrated through the example of the electrochemical reduction of oxygen on nickel manganites doped with copper, Ni_1-x Cu _x Mn₂O₄, that the electrocatalysis occurs through adsorption on active sites formed by Mn⁴⁺ ions associated, in octahedral sites, with Mn³⁺ ions.

     

A single‐phase,thermally stable and color-tunable white light emitting Na2Ca1-x-yCexMnyP2O7 phosphors for white light emitting diodes via energy transfer

The solid-state reaction method was used to develop a series of Na₂Ca_1-x-yCe_xMn_yP₂O₇ phosphors in an H₂–N₂ environment. The crystal structure of the pyrophosphate host, valence state of dopants (Ce, Mn), emission behavior of dopants, energy transfer mechanism, and thermal quenching behavior were thoroughly examined. Doping with Ce³⁺ and Mn²⁺ ions enhanced the photoluminescence characteristics of Na₂Ca_1-x-yCe_xMn_yP₂O₇ while having negligible effect on the host's phase purity. Under 365 nm UV light irradiation, the addition of Ce³⁺ ion in the Na₂CaP₂O₇ host revealed an asymmetric band with the typical blue emission around 415 nm and a shoulder around 455 nm. To obtain white light, Mn²⁺ ion was supplementarily substituted to the present system. When the Mn²⁺ ions concentration was elevated in the Na₂CaP₂O₇ host, the emission intensity of 560 nm peak corresponding to Mn²⁺ transition enhanced significantly at the cost of Ce³⁺ emission of 415 nm. The systematic decrease of Ce³⁺ emission intensity and corresponding increase in the Mn²⁺ intensity with the increase in Mn²⁺ concentration indicated the possibility of effective energy transfer from Ce³⁺ to Mn²⁺ ions. The obtained results indicated that energy transfer from the Ce³⁺ to Mn²⁺ ions governed by dipole-quadrupole interaction. Because of the efficient energy transfer, the blue emission from Ce³⁺ and the orange red emission of Mn²⁺ provide white light from a single host along with high value of activation energy and low thermal quenching behaviour make the present phosphors to be suitable for high-power LEDs.     

Catalytic behaviour of metal ions located at different sites of heteropolycompounds

It was discovered experimentally that heteropolymolybdophosphoric acids (HPA) with Keggin and Dawson structure are inactive for H₂O₂-decomposition, while their salts (Fe³⁺, Cu²⁺, Co²⁺ and Mn²⁺) all possess more activity. It could be concluded that the active species is the countercation of these kinds of heteropolymolybdates. The molybdenum ions in the polyanions are not active. If the molybdenum ions in the polyanions of these acids are substituted partly by vanadium ion (HPA-n), then not only does the catalytic activity increase regularly with the number of vanadium ions substituted (n) but the kinetic curve is also different from that of the salt, characterized by an S-shape, indicating the formation of an active intermediate as a result of the reaction between the polyanion of HPA-n and the substrate.     

Gaseous Elemental Mercury Removal Using Combined Metal Ions and Heat Activated Peroxymonosulfate/H2O2 Solutions

Several novel oxidation removal processes of elemental mercury (Hg⁰) from flue gas using combined Fe²⁺/Mn²⁺ and heat activated peroxymonosulfate (PMS)/H₂O₂ solutions in a bubbling reactor were proposed. The operating parameters (e.g., PMS/H₂O₂ concentration, Fe²⁺/Mn²⁺ concentration, solution pH, activation temperature, and Hg⁰/NO/SO₂/O₂/CO₂ concentration), mechanism and mass transfer-reaction kinetics of Hg⁰ removal were investigated. The results show that heat and Fe²⁺/Mn²⁺ have significant synergistic effect for activating PMS and PMS/H₂O₂ to produce free radicals to oxidize Hg⁰. Hg⁰ removal is strongly affected by PMS/H₂O₂ concentration, Fe²⁺/Mn²⁺ concentration, activation temperature, and solution pH. · and ·OH produced from combined heat and Fe²⁺/Mn²⁺ activated PMS/H₂O₂ play a leading role in Hg⁰ removal. Under optimized experimental conditions, Hg⁰ removal efficiencies reach 100, 94.9, 66.9, and 58.9% in heat/Fe²⁺/PMS/H₂O₂, heat/Mn²⁺/PMS/H₂O₂, heat/Fe²⁺/PMS, and heat/Mn²⁺/PMS systems, respectively. Hg⁰ removal processes in four systems belong to fast reaction and were controlled by mass transfer under optimized experimental conditions. © 2018 American Institute of Chemical Engineers AIChE J, 65: 161–174, 2019     

Synthesis of a novolac‐based 3‐aminopropylsiloxane resin and its application for the removal of Cu2+, Cr3+, and Ni2+ from electroplating wastewater

Novolac resin was modified with 3‐aminopropyltrimthoxysilane to obtain phenol‐formaldehyde‐aminopropylsiloxane resin (PF‐APS). Fourier transformation infra‐red spectra, thermogravimetric analysis, elemental analysis, and pH‐metric titration were used to characterize PF‐APS. Its chemical formula was suggested to be C₁₄H_12.49N_0.1O₂Si_0.1. The resin shows high experimental metal ions uptake capacity within short time of equilibration. The metal capacity was determined by atomic absorption spectrometry to be 0.787 mEq Cu/g. Maximum separation efficiencies of Cu²⁺, Cr³⁺, and Ni²⁺ from aqueous solutions on PF‐APS were at pH 8.0 and time of stirring 60 min; 94.0%, 90.8%, 83.2%, respectively. No significant interference from the background ions Na⁺, Cl^?, and was observed on the separation process. The heavy metal ions were eluted using 0.01 mol L^?1 EDTA at 65°C releasing >94% of the separated metal ions. The method of separation was applied successfully to remove the heavy metal ions Cu²⁺, Cr³⁺, and Ni²⁺ from electroplating wastewater from Dekirnis, Dakahlia Governorate, Egypt. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40993.     

Catalytic Ozonation of m-Dinitrobenzene

The efficiency of catalytic ozonation with homogeneous (containing dissolved ions of Fe²⁺, Mn²⁺, Cu²⁺, Ni²⁺, Co²⁺, V⁵⁺, Cr³⁺, Mo⁶⁺) and heterogeneous (MnO₂, Ni₂O_3, Fe₂O₃, CuO, Al₂O₃, CoO, V₂O₅, Cr₂O₃, MoO₃, TiO₂) catalysts and non-accompanied ozonation was compared for degradation of m-dinitrobenzene (m-DNB). Several transition metals in homogeneous and heterogeneous form improved significantly the ozone performance for degradation of m-DNB. This improvement was found to be due to supplementary formation of reactive species (hydroxyl radicals) and better ozone utilization. The effects observed were found to be strongly dependent on the treatment conditions.     

Solvent-induced assembly of two supramolecular isomers of Mn thiophenedicarboxylate coordination polymers

Two supramolecular isomers of Mn^II thiophenedicarboxylate coordination polymers, namely, [Mn₂(tdc)₂(dmf)₂]_n (1) and [Mn₃(tdc)₃(dmf)₃]_n (2) (H₂tdc = 2,5-thiophenedicarboxylic acid, dmf = N,N-dimethylformamide), were synthesized with solvent-induced assembly method and the antiferromagnetic interactions between the Mn^II ions in their solid phase were measured.     

Polymer pendant ligand chemistry, 4. Recovery of precious metal ions from strongly acidic solution with a polymer-supported o-phenylenediamine hydrochloride ligand

We report on the synthesis and reactivity of a polymer-supported o-phenylenediamine hydrochloride ligand, PS-PDHC, using macroporous 6% crosslinked polystyrene-divinylbenzene beads. The PS-PDHC ligand was found to be highly selective to AuCl₄⁻ ions in strongly acidic solutions in the presence of other precious metal ions, PdCl₄²⁻, PtCl₄²⁻, RhCl₆³⁻, and RuCl₅²⁻ (selectivity values: 2.5, Au/Pd; 7.5, Au/Pt; 7, Au/Rh; 2.2, Au/Ru) as well as other transition metal ions, Fe ³⁺, Cr³⁺, CU²⁺, Nit+, and Mn²⁺. The sorption capacity, selectivity, kinetics of removal and recovery, and solution isotherms have been determined for AuCl₄⁻ ions in competition with the above-mentioned metal ions. The relative ease of formation of the anionic complex in 0.5 M HCI, AuCl₄⁻ was thought to be the primary reason for its selective ability to bind to the PS-PDHC ligand by an anion-exchange mechanism. Therefore, the effect of the HCI concentration on the kinetics of AuCl₄⁻ ion removal from solution was also investigated to clearly show that raising the pH from 0 to 5 caused a dramatic decrease in rate. The AuCl₄⁻ ion can be recovered quantitatively from the PS-PDHC beads using a 5% thiourea solution in 0.1 M HCl, allowing the polymer-supported ligand to be reused.     

Magnesium ferrite nanoparticles as a magnetic sorbent for the removal of Mn2+, Co2+, Ni2+ and Cu2+ from aqueous solution

The aim of this research was to prepare magnesium ferrite (MgFe₂O₄) magnetic nanoparticles and to investigate their sorption characteristics towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions in aqueous solution. MgFe₂O₄ was synthesized by glycine-nitrate combustion method and was characterized by low crystallinity with crystallite size of 8.2?nm, particle aggregates of 13–25?nm, BET surface area of 14?m²/g and pore size of 8.0?nm. Sorption properties of MgFe₂O₄ towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions were studied using one-component model solutions and found to be dependent on metal ions concentration, contact time, pH and conditions of regeneration experiment. The highest sorption capacity of MgFe₂O₄ was detected towards Co²⁺ (2.30?mmol?g¹) and Mn²⁺ (1.56?mmol?g^?1) and the lowest towards Ni²⁺ (0.89?mmol?g^?1) and Cu²⁺ (0.46?mmol?g^?1). It was observed that sorption equilibrium occurs very quickly within 20–60?min. The pH_zpc of sorbent was calculated to be 6.58. At studied pH interval (3.0–7.0) the sorption capacity of MgFe₂O₄ was not significantly affected. Regeneration study showed that the metal loaded sorbent could be regenerated by aqueous solution of 10^?3 M MgCl₂ at pH 6.0 within 120?min of contact time. Regeneration test suggested that MgFe₂O₄ magnetic sorbent can be efficiently used at least for four adsorption-desorption cycles. The high sorption properties and kinetics of toxic metal ion sorption indicates good prospects of developed sorbent in practice for wastewater treatment.     

The Redox Chemistry of Manganese(III) and -(IV) Complexes

The oxidation-reduction thermodynamics for the manganese(III), -(IV), and -(II) ions, and their various complexes, are reviewed for both aqueous and aprotic media. In aqueous solutions the reduction potential for the manganese(III)/(II) couple has values that range from +1.51 V vs. NHE (hydrate at pH 0) to −0.95 V (glucarate complex at pH 13.5). The Mn(IV)/(III) couple has values that range from +1.0 V (solid Mn^IVO₃ at pH 0) to −0.04 V (tris gluconate complex at pH 13.5). With anhydrous media the propensity for the Mn(III) ion to disproportionate to solid Mn^IVO₂ and Mn(II) ion is avoided. For aprotic systems the range of redox potentials for various manganese complexes is from +2.01 V and +1.30 for the Mn(IV)/(III) and Mn(III)/(II) couples (bis terpyridyl tri-N-oxide complex in MeCN), respectively, to −0.96 V for the Mn(IV)/(III) couple (tris 3,5,-di-tert-butylcatecholate complex in Me₂SO). The redox reactions between manganese complexes and dioxygen species (O₂, O₂, and H₂O₂) also are reviewed.     

Photoluminescence properties of Ce3+/Mn2+ doped calcium zirconium silicate phosphors with energy transfer for white LEDs

A series of Ce³⁺ doped and Ce³⁺/Mn²⁺ co-doped calcium zirconium silicate CaZrSi₂O₇ (CZS) phosphors have been synthesized via conventional high temperature solid state reactions. The luminescence properties, energy transfer between Ce³⁺ and Mn²⁺ have been investigated systematically. Under 320 nm excitation, the phosphor CZS: 0.05Ce³⁺ exhibit strong blue emission ranging from 330 nm to 500 nm, attributed to the spin-allowed 5d-4f transitions of Ce³⁺ ions. There are two different emission centers of Ce³⁺ ions, Ce³⁺(I) and Ce³⁺(II). The emission spectra of Ce³⁺, Mn²⁺ co-doped phosphors shows a broad emission around 550 nm corresponding to the ⁴T₁(⁴G)-⁶A₁(⁶S) spin-forbidden transition of Mn²⁺. The energy transfer between Ce³⁺ and Mn²⁺ is detected and the transfer efficiency of Ce³⁺(II) to Mn²⁺ is faster than that of Ce³⁺(I) to Mn²⁺. The resonant type is identified via dipole-dipole mechanism. Additionally, a blue-shift emission of Ce³⁺ and a red-shift emission of Mn²⁺ have been observed following the increase of Mn²⁺ content in relation to the energy transfer. Thermal quenching has been investigated and the emission spectra show a blue-shift with the temperature increases, which have been discussed in details. CZS: 0.05Ce³⁺, yMn²⁺ phosphors can be tuned from blue to white and even to yellow by adjusting the Mn²⁺ content. All the results indicate that CZS: Ce³⁺, Mn²⁺ phosphor have a potential application for near-UV LEDs.     

Tunable Multicolor Emission and Energy Transfer of Sb3+/Mn2+ Codoped Phosphate Glasses by Design

In this work, the luminescent properties of Sb³⁺/Mn²⁺ codoped 60P₂O₅–40MgO glass are presented. White light photoluminescence combining blue and orange‐red light was observed under ultraviolet light excitation. The emission spectra showed that the blue emission intensity of Sb³⁺ decreased significantly whereas the red emission intensity of Mn²⁺ increased with the increasing concentration of Mn²⁺ ions. Meanwhile, by maintaining the concentration of MnO (2.0 mol%) and increasing concentration of Sb₂O₃, both the blue emission and red emission were enhanced remarkably. The energy transfer from Sb³⁺ to Mn²⁺ ions via the dipole–quadrupole interaction was confirmed.     

Syntheses and Characterization of 1D, 2D and 3D Organotin Polymers with Benzimidazole-5,6-dicarboxylic Acid and Trimethyltin Chloride

Three types of di- and trimethyltin(IV) polymers [Me₂Sn(C₉H₄N₂O₄)]_n · 4H₂O 1, [(Me₃Sn)₂(C₉H₄N₂O₄)]_n · H₂O 2 and [(Me₃Sn)₂(C₉H₄N₂O₄)]_n · CH₃OH 3 have been synthesized by the reaction of trimethyltin chloride with benzimidazole-5,6-dicarboxylic acid under three different experimental conditions. All the complexes were characterized by elemental analysis, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and X-ray crystallography diffraction analysis. The structure analyses reveal that complex 1 has a 1D helical chain in which benzimidazole-5,6-dicarboxylic acid act as a tetradentate (O,O-chelation) ligand coordinating to dimethyltin (IV) ions, two water molecules take part in the coordination giving seven-coordinated tin centers in the component. Complex 2 and 3 are 2D and 3D corrugated polymers in which the deprotoned acid as tetradentate ligand affords by three oxygen atoms and a nitrogen atom.     

Response of Two-Dimensional Polymeric Cadmium Ferrocenyl Disulfonates to Heavy Metal Ions

A sandwich-like 2D infinite framework of {[Cd(pbbm)₂(SO₃FcSO₃)]·(CH₃OH)₂·(H₂O)₆} _n (1) with nanosized porous structure [Fc(SO₃)₂Na₂ = ferrocene-1,1′-disulphonate, pbbm = 1,1′-(1,3-propylene)-bis-1H-benzimidazole] was prepared by combining d ¹⁰ Cd²⁺ ions with highly conjugated pbbm and disodium ferrocene-1,1′-disulfonate. Experimental results show that 1 could serve as a new fluorescent probe for the detection of many divalent metal ions in water, such as Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺ and Pb²⁺, and trace organic solvents, including acetone, toluene, methylene chloride, ether, tetrahydrofuran, and methanol. The main product was very different from previous chemosensory materials that only identify one or two metal ions. The powdery multipurpose chemosensory materials proposed here could also sequester dangerous heavy metal ions, especially Pb²⁺. A computational study of ferrocene-1,1′-disulfonate and 1 gave insight into the process of ion exchange and sorption. This study introduces a promising new field of fluorescent chemosensors based on nanoporous coordination polymers with free functional groups.     

Mechanism-based tuning of room-temperature ferromagnetism in Mn-doped β-Ga2O3 by annealing atmosphere

Mn-doped β-Ga₂O₃ (GMO) films with room-temperature ferromagnetism (RTFM) are synthesized by polymer-assisted deposition, and the effects of annealing atmosphere (air or pure O₂ gas) on their structures and physical properties are investigated. The characterizations show that the concentrations of vacancy defects and Mn dopants in various valence states and lattice constants of the samples are all modulated by the annealing atmosphere. Notably, the samples annealed in air (GMO–air) exhibit a saturation magnetization as strong as 170% times that of the samples annealed in pure O₂ gas (GMO–O₂), which can be quantitatively explained by oxygen vacancy (V_O)-controlled ferromagnetism due to bound magnetic polarons established between delocalized hydrogenic electrons of V_Os and local magnetic moments of Mn²⁺, Mn³⁺, and Mn⁴⁺ ions in the samples. Our results provide insights into mechanism-based tuning of RTFM in Ga₂O₃ and may be useful for design, fabrication, and application of related spintronic materials.     

Synthesis of polyamidoxime chelating ligand from polymer‐grafted corn‐cob cellulose for metal extraction

A conventional free‐radical initiating process was used to prepare graft copolymers from acrylonitrile (AN) with corn‐cob cellulose with ceric ammonium nitrate (CAN) as an initiator. The optimum grafting was achieved with corn‐cob cellulose (anhydroglucose unit, AGU), mineral acid (H₂SO₄), CAN, and AN at concentrations of 0.133, 0.081, 0.0145, and 1.056 mol/L, respectively. Furthermore, the nitrile functional groups of the grafted copolymers were converted to amidoxime ligands with hydroxylamine under basic conditions of pH 11 with 4 h of stirring at 70°C. The purified acrylic polymer‐grafted cellulose and polyamidoxime ligand were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy analysis. The ligand showed an excellent copper binding capacity (4.14 mmol/g) with a faster rate of adsorption (average exchange rate = 7 min), and it showed a good adsorption capacity for other metal ions as well. The metal‐ion adsorption capacities of the ligand were pH‐dependent in the following order: Cu²⁺ > Co²⁺ > Mn²⁺ > Cr³⁺ > Fe³⁺ > Zn²⁺ > Ni²⁺. The metal‐ion removal efficiency was very high; up to 99% was removed from the aqueous media at a low concentration. These new polymeric chelating ligands could be used to remove aforementioned toxic metal ions from industrial wastewater. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40833.     

The mechanism of electrodeposition of acrylic resin on aluminium

A mechanism for the electrodeposition of acrylic resin on aluminium is proposed, based on experimental studies of acid value, anodic gas evaluation and anodic film resistance. The mechanism can be expressed as Alf Al³⁺ + 3e 2Al³⁺ + 3H₂Of Al₂O₃ + 6H⁺ 2Al³⁺ + 6H₂Of 2Al(OH)₃ + 6H⁺ H⁺ + RCOC^– f RCOOH. This is different from the mechanism for zinc and steel, where it is metal ions from anodic dissolution which neutralize the macro-ions and cause a deposit on the anode surface.