Characteristics and formation of [AlO4Al12(OH)24(H2O)12]7+ in electrolysis process

[AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ (Al₁₃) formation in electrolysis process is studied. The results detected by²⁷Al NMR spectroscopy show that high content of Al₁₃ polymer is formed in the partially hydrolyzed aluminum solution prepared by controlled electrolysis process. In the produced electrolyte of total Al concentration ([Al_T]) 2.0 mol · L⁻¹ with a basicity (B = OH/Al molar ratios) of 2.0, the content of Al₁₃ polymer is over 60% of total Al. Dynamic light scattering shows that the size distribution of the final electrolyte solutions ([Al_T] = 2.0 mol · L⁻¹) is trimodal with B = 2.0 and bimodal with B = 2.5. The aggregates of Al₁₃ complexes increase the particle size of partially hydrolyzed aluminum solution.     

On the stability of Al<Subscript>13</Subscript> Keggin cation in aqueous hydrogen peroxide solutions

We report the first attempt to study the behavior of the [AlO₄Al1₂(OH)₂₅(H₂O)₁₁]⁶⁺ (Al₁₃) Keggin cation (KC) in water–peroxide solutions. Addition of hydrogen peroxide into an aqueous solution containing the Al₁₃ KC reduces pH due to the acidity of hydrogen peroxide. According to the ²⁷Al NMR studies of water–peroxide solutions prepared just before the NMR experiment, with their pH adjusted to the initial value of 5.5 with aqueous NaOH, the Al₁₃ KC concentration decreases immediately once hydrogen peroxide is added to the initial system. Addition of 18.2 wt % hydrogen peroxide to the initial 0.88 mM Al₁₃ solution gives rise to a fourfold decline in Al₁₃ polyoxo cation concentration to 0.22 mM. Then, the KC concentration in the test system remains unchanged for 1 week. Large hydrogen peroxide amounts (27.9 wt % or higher) added to the initial system almost completely degrade the KC. Sodium sulfate added to the initial water–peroxide solution of Al₁₃ chloride where the hydrogen peroxide concentration is 5.5 wt % precipitates the earlier described Al₁₃ sulfate [AlO₄Al₁₂(OH)₂₅(H₂O)₁₁](SO₄)₃ · 16H₂O, where the aluminum polyoxo cation does not contain coordinated hydrogen peroxide molecules, peroxo or hydroperoxo groups as shown by X-ray diffraction.     

Investigations of Polyoxometalates in Aqueous Solutions. I. The Formation of Al13(OH)7+ 31 Cation

Abstract

The formation of polyhydroxo aluminum(III) complexes has been investigated at 30°C and in a 3 M (K)Cl ionic medium by p[H] measurements. The uncommon “integral titration” technique employed has enabled measurements of oversaturated solutions up to OH^? to Al(III) ratios as large as 2.65. This has allowed the detection of the undescribed species Al₁₃(OH)⁴⁺ ₃₅. The data can very satisfactorily be explained by assuming the species Al₂(OH)⁴⁺ ₂, Al₃(OH)³⁺ ₆, Al₁₃(OH)⁷⁺ ₃₂, and Al₁₃(OH)⁴⁺ ₃₅. The Al(III) concentration has been changed from ≈0.0025 to ≈ 0.040 M and the spacings of the titration curves at different aluminum levels are a clear and direct evidence for the formation of Al₁₃(OH)⁷⁺ ₃₂, which dominates the hydrolysis products. The data presented in this paper are best accounted for if the trimer Al₃(OH)³⁺ ₆ is substituted for Al₃(OH)⁵⁺ ₄ which is frequently reported. The formation of the “13” cations may result from the reaction of four Al₃(OH)³⁺ ₆ with a transient Al(OH)^? ₄ species which is formed, upon addition of a rather concentrated basic solution, owing to a local excess of OH^?.     

AlCl<Subscript>3</Subscript>/amide ionic liquids for electrodeposition of aluminum

AlCl₃/amide (acetamide, propionamide, butyramide) ionic liquids were used as the electrolytes to study the electrodeposition behavior of aluminum on a tungsten electrode. Cyclic voltammograms on the tungsten electrode indicate that Al(III) ions can be reduced to aluminum only within the molar ratio range of 1.1 to 1.5 and the reduction potentials of Al(III) ions strongly depend on the molar ratio of AlCl₃/amide. Raman spectra results reveal that the electroactive specie of AlCl₃/amide ionic liquids is Al₂Cl₇ ^?. Aluminum coatings were prepared at ?0.25 V (vs. Al/Al³⁺) and at 313 K in AlCl₃/amide ionic liquids with the molar ratio of 1.3. The SEM and cross-sectional SEM images show that all the obtained aluminum films are silver-colored, thick, and adherent. The EDS and XRD analysis confirm that the obtained deposits are pure aluminum. The present results can provide a new route for aluminum electrodeposition under ambient conditions.     

聚合Al13晶体的制备及表征

近几十年来 , 环境污染的日益严重使人们对健康问题和全球生态系统越来越关注 ?由于一个元素的生物可给性在很大程度上取决于它存在的物理化学形态和浓度 , 准确测定环境和生物体系中的痕量元素的不同形态是研究这些元素的生物毒性 ? 生物有效性和传输机理的关键 ?形态分析成了     

Hydrothermal synthesis and thermodynamic properties of 2CaO·3B<Subscript>2</Subscript>O<Subscript>3</Subscript>·H<Subscript>2</Subscript>O

2CaO·3B₂O₃·H₂O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B₂O₃·H₂O in HCl·54.572H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HCl·54.501H₂O and of CaO in (HCl+H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol⁻¹ of 2CaO·3B₂O₃·H₂O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

Interaction of Aluminium(III) with Uranyl Ions in the Course of Joint Hydrolysis

Interaction of U(VI) with Al(III) in solutions at pH 2 and in precipitates obtained at pH 5 was studied using spectrophotometry, luminescence, and IR spectroscopy. It was shown that in the range of pH 3–4, hydrolyzed forms of uranyl and of aluminium come into interaction. The mixed hydroxoaqua complexes (H₂O)₃UO₂(-OH)₂Al(H₂O)³⁺ ₄,(H₂O)₃UO₂(-OH)₂Al(OH)(H₂O)²⁺ ₃, or (H₂O)₄UO₂OAl(OH)(H₂O)²⁺ ₄are likely to form in the solution. With an increase in pH, mixed polymers of a large size (oligomers) can form which further take part in the precipitate formation. The reaction between U(VI) and Al(III) in precipitates is confirmed by the data of IR spectroscopy and by the changes in the physico-chemical properties of these precipitates as compared with the properties of a mechanical mixture of separately precipitated uranium and aluminium. The important role of the oligomeric mixed forms in the formation of precipitate remains at pH levels varying from 5 to 14.     

Interaction of Aluminium (III) with the f-Family Ions Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) in the Course of Simultaneous Hydrolysis

The interaction of Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) with Al(III) in solutions at pH 0–4 was studied by the spectrophotometric method. It was shown that, in the range of pH 3–4, the hydrolyzed forms of neptunyl and plutonyl react with the hydrolyzed forms of aluminium. In the case of Pu(VI), the mixed hydroxoaqua complexes (H₂O)₃PuO₂(-OH)₂Al(OH)(H₂O)₃ ²⁺ or (H₂O)₄PuO₂OAl(OH)(H₂O)₄ ²⁺ are formed at the first stage of hydrolysis. Np(VI) also forms similar hydroxoaqua complexes with Al(III). The formation of the mixed hydroxoaqua complexes was also observed when Np(IV) or Pu(IV) was simultaneously hydrolyzed with Al(III) at pH 1.5–2.5. The Np(IV) complex with Al(III) has, most likely, the formula (H₂O) _n (OH)Np(-OH)₂Al(OH)(H₂O)₃ ³⁺. At pH from 2 to 4.1 (when aluminium hydroxide precipitates), the Np(V) or Nd(III) ions exist in solutions with or without Al(III) in similar forms. When pH is increased to 5–5.5, these ions are almost not captured by the aluminium hydroxide precipitate.     

Study of Aqueous Al2(SO4)3 Solution under Hydrothermal Conditions: Sulfate Ion Pairing, Hydrolysis, and Formation of Hydronium Alunite

Raman spectra have been measured for aqueous Al₂(SO₄)₃ solutions from 25 to hydrothermal conditions at 184°C under steam saturation. The Raman spectrum at 184°C contained four polarized bands in the S–O stretching wavenumber range, which suggest that a new sulfato complex, where sulfate acts as a bridging ligand (possibly bidentate or tridentate), is formed in solution, in addition to a 1:1 aluminium(III) sulfato complex, where sulfate is monodentate, which is the only ion pair identified at room temperature. Under hydrothermal conditions, it was possible to observe the hydrolysis of aluminium(III) aqua ion by measuring the relative intensity of bands due to SO^2? ₄ and HSO₄ ^?, according to the coupled equilibrium reaction [Al(OH₂)₆]³⁺ + SO₄ ^2? ? [Al(OH₂)₅OH]²⁺ + HSO₄ ^?. The precipitate in equilibrium with the solution at 184°C could be characterized as a hydronium alunite, (H₃O)Al₃(SO₄)₂(OH)₆, by chemical analysis, X-ray diffraction, and Raman and infrared spectroscopy.     

Über die Hydrolyse von Eisen(III)Salzlösungen. I. Die Hydrolyse der Lösungen von Eisen(III)chlorid

When a very diluted iron(III)chloride solution is slowly alkalified by a weak base, the deprotonation of [Fe(H₂O)₆]³⁺ proceeds in a first stage to form mono- and dinuclear hydroxoaquo-complexes. In a second stage 4 dimers condense around a chloride ion to form an eight membered ring, an embryon, which grows fast to very small crystals of the composition Fe₄O₃(OH)₅Cl and the structure of the β-FeOOH. These crystalline micells remain colloidally dissolved. If the pH is raised above approximately 3.4 the Cl^?- are exchanged against OH^?-ions and flocculation occurs. This shows that Pauli, assuming the micells of such sols to be polynuclear complex ions, is basically correct, and it follows that micells can also be micro-crystals. When an iron(III)chloride solution is neutralized fast with a strong base, an ‘amorphous’ precipitation is obtained which gives with MoK_α-X-rays only two broad reflections, showing that the iron oxide hydroxide octahedra are condensed in a highly disordered way. The coherently scattering areas of this precipitate are probably tetramers. Small amounts of primarily formed amorphous iron(III)hydroxide are transformed into β-FeOOH.     

Direct preparation of Al-substituted α-Ni(OH)2 from Al-containing salt solution by immersing method

The present study attempts to prepare Al-substituted α-Ni(OH)₂ and Al-substituted α-Ni(OH)₂ with modified interlayer anions by directly immersing pure α-Ni(OH)₂ into AlCl₃-containing solutions. XRD and FT-IR analysis demonstrated Al-substituted α-Ni(OH)₂ can be prepared directly by soaking pure α-Ni(OH)₂ into AlCl₃ solution. Al-substituted α-Ni(OH)₂ with S₂O₃^2? as the primary anion in the interlayer can be obtained by immersing pure α-Ni(OH)₂ into AlCl₃-Na₂S₂O₃ solution. The analysis of Al content in samples demonstrated the Al content in the Al-substituted α-Ni(OH)₂ was regulated by adjusting the molar ratio of pure α-Ni(OH)₂ soaked in the solution and Al³⁺ dissolved in the solution. The Al element entered the lattice of pure α-Ni(OH)₂ through a process of pure α-Ni(OH)₂ dissolved followed by the precipitation of Al³⁺, Ni²⁺ and OH^?. The S₂O₃^2? entered the interlayer of Al-substituted α-Ni(OH)₂ through the formation process of the Al-substituted α-Ni(OH)₂ or though ion exchange with the intercalated Cl^?. The strongly alkaline solution soaking results demonstrated that Al-substituted α-Ni(OH)₂ prepared by soaking pure α-Ni(OH)₂ into AlCl₃-containing solutions could preliminary get stabilized in the strongly alkaline solution.     

Synthesis and Characterization of Al(OH)<Subscript>3</Subscript>, Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles and Polymeric Nanocomposites

Applying of the most toxic halogenated and aromatic flame retardants is limited with respect to the environmental requirements. Nontoxic Al(OH)₃ nanoparticles were synthesized via a simple surfactant-free precipitation reaction at room temperature. The effect of various precipitation-agents on the morphology of the products was investigated. Al(OH)₃ nanoparticles were added to the polysulfone and poly styrene (PS) matrices. Electron microscope images show excellent dispersion of aluminium hydroxide in PS matrix. Nanoparticles appropriately enhanced both thermal stability and flame retardant property of the polymeric matrices. The enhancement of flame retardancy is due to endothermic decomposition of Al(OH)₃ that absorbs heat and simultaneously releases of water (makes combustible gases diluted and cold). Dispersed nanoparticles play the role of a barrier layer against flame, oxygen and polymer volatilization. Al(OH)₃ was converted to Al₂O₃ and its photo-catalyst property in degradation three different organic dyes as pollutants was investigated.     

Two color up-conversion emissions of Er<Superscript>3+</Superscript>-doped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanopowders prepared by non-aqueous sol-gel method

Er³⁺-doped Al₂O₃ nanopowders have been prepared by the non-aqueous sol-gel method using the aluminum isopropoxide as precursor, acetylacetone as a chelating agent, nitric acid as a catalyzer, and hydrated erbium nitrate as a dopant under isopropanol environment. The different phase structure, including three crystalline types of (Al, Er)₂O₃ phases, α, γ, θ, and an Er–Al–O stoichiometric compound phase, Al₁₀Er₆O₂₄, was observed for the 0.01–0.5 mol% Er³⁺-doped Al₂O₃ nanopowders at the sintering temperature of 1,000 °C. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the ²H_11/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺, were detected by a 978 nm semiconductor laser diodes excitation. With increasing Er³⁺ doping concentration from 0.01 to 0.1 mol%, the intensity of the green and red emissions increased with a decrease of the intensity ratio of the green to red emission. When the Er³⁺ doping concentration rose to 5 mol%, the intensity of the green and red emissions decreased with an increase of their intensity ratio. The maximum intensity of both the green and red emissions with the minimum of intensity ratio was obtained, respectively, for the 0.1 mol% Er³⁺-doped Al₂O₃ nanopowders composed of a single α-(Al,Er)₂O₃ phase. The intensity ratio of the green emission at 523 and 545 nm increased monotonously for all Er³⁺ doping concentrations. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er³⁺-doped Al₂O₃ nanopowders.     

Thermal decomposition of zinc and cadmium zirconyl oxalates

The enthalpy of formation at 298.15 K of the polymer Al₁₃O₄(OH)₂₈(H₂O)³⁺₈ and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔH_f “Al₁₃” (298.15 K) = ? 602 ± 60.2 kJ mole^?1 and ΔH_f Al(OH)₃ (298.15 K) = ? 51 ± 5 kJ mole^?1. Using theoretical values of ΔG_R “Al₁₃” and ΔG_R Al(OH)₃, we calculated ΔG_f “Al₁₃” (298.15 K) = ? 13282 kJ mole^?1; ΔS_f “Al₁₃” (298.15 K) = + 42.2 kJ mole^?1; ΔG_f Al(OH)₃ (298.15 K) = ? 782.5 kJ mole^?1; and ΔS_f Al(OH)₃ (298.15 K) = + 2.4 kJ mole^?1.     

Reflections upon and recent insight into the mechanism of formation of hydroxyaluminosilicates and the therapeutic potential of silicic acid

The chemistry of mono or ortho silicic acid (Si(OH)₄) is barely considered in most chemistry texts. Mention is usually only made of its autocondensation in forming hydrated amorphous silica and its reaction with ammonium molybdate in forming the molybdosilicic acid complex. Reference should now be made to its unique inorganic chemistry with aluminium (Al) and specifically aluminium hydroxide (Al(OH)_3(s)) in forming hydroxyaluminosilicates (HAS_(s)). The competitive condensation or substitution of Si(OH)₄ into a framework of Al(OH)_3(s) results in the formation of either HAS_A or HAS_B. Which type of HAS_(s) predominates depends upon the ratio of Si:Al in preparative solutions with the formation of HAS_B requiring a two-fold excess of Si(OH)₄ over Al. The Si:Al ratio of HAS_A is 0.5 and the existence of HAS_A is a prerequisite to the formation of HAS_B in which the ratio of Si:Al is 1.0. HAS_A is composed of only octahedrally co-ordinated Al, Al^VI, whereas HAS_B is composed of equal quantities of Al^VI and tetrahedrally coordinated Al, Al^IV, and is formed by a Si(OH)₄-fuelled dehydroxylation reaction. HAS_(s) are significantly more ‘kinetically’ stable than Al(OH)_3(amorphous) with HAS_B predicted to predominate at pH > 4.0 and [Si(OH)₄] > 0.1 mmol/L. HAS_(s) are critical secondary mineral phases in the biogeochemical cycle of Al and Si(OH)₄ and the formation of HAS_(s) have played a major role in precluding Al³⁺_(aq) from biochemical evolution. In the future Si(OH)₄ and the formation of HAS_(s) are predicted to be of significant importance in providing protection for humans against a potentially burgeoning exposure to biologically available Al.     

Kinetic model of coherent synchronized ethylene monooxidation by hydrogen peroxide on a biomimetic catalyst,per-FTPhPFe<Superscript>3+</Superscript>OH/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A kinetic model that fits the experimental data is studied on the basis of the most probable mechanism of ethylene oxidation by hydrogen peroxide over a biomimetic catalyst, perfluorinated iron (III) tetraphenylporphyrin, deposited on aluminum oxide (per-FTPhPFe³⁺OH/Al₂O₃). Effective rate constants for the catalase and oxygenase reactions and their effective activation energies are found.     

Study of Equilibria in the Aluminium(III)-Glycine and -Alanine Systems

The formation of various hydrolytic and mixed hydrolytic complexes of the aluminium(III) ion in the presence of glycine and L-alanine, has been studied in 0.5 mol dm^?3 (Na)NO₃ medium at 25deg;C, by emf method. The concentration ratios of amine acids to aluminium(III) were varied from 1 : 1 to 10 : 1. The least-squares treatment of the data obtained, in the absence of the amino acids, indicates the formation of the dimer, [Al₂(OH)₂]⁴⁺, and monomer, [AlOH]²⁺, with the stability constants log β₂₂ = ?7.03 ± 0.03 and log β₁₁ = ?5.65 ± 0.09, respectively. At pH values higher then ～4.0 formation of the trimer [Al₃(OH)₄]⁵⁺ (log β₃₄ = ?12.60 ± 0.08) becomes significant. In the presence of amino acids the evidence has been found for the formation of [Al₂(OH)₄]²⁺ (log β₂₄ = ?15.65 ± 0.09). Besides the formation of the pure hydrolytic complexes, equilibria in the title systems can be explained by assuming the main reaction products to have the compositions [Al(OH)₃Gly] (log β₁₃₁ = ?7.53 ± 0.04), [Al₂(OH)₂(Gly)₂] (log β₂₂₂ = 6.56 ± 0.09) and [Al(OH)₃Ala] (log β₁₃₁ = ?7.70 ± 0.03), [Al₂(OH)₂Ala₂] (log β₂₂₂ = 7.23 ± 0.07).     

Microwave‐Assisted Hydrothermal Synthesis of [Al(OH)(1,4‐NDC)] Membranes with Superior Separation Performances

In this study, we report a facile ligand‐assisted in situ hydrothermal approach for preparation of compact [Al(OH)(1,4‐NDC)] (1,4‐NDC=1,4‐naphthalenedicarboxylate) MOF membranes on porous γ‐Al₂O₃ substrates, which also served as the Al³⁺ source of MOF membranes. Simultaneously, it was observed that the heating mode exerted significant influence on the final microstructure and separation performance of [Al(OH)(1,4‐NDC)] membranes. Compared with the conventional hydrothermal method, the employment of microwave heating led to the formation of [Al(OH)(1,4‐NDC)] membranes composed of closely packed nanorods with superior H₂/CH₄ selectivity.     

Supramolecular microrods can be prepared by mixing aqueous Ru(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>Cl<Subscript>3</Subscript> and K<Subscript>3</Subscript>Fe(CN)<Subscript>6</Subscript> solutions at room temperature

This paper describes the ionic self-assembly method to fabricate supramolecular one-dimensional microrods in solution. Such microrods were formed in a one-step process through the mixing aqueous Ru(NH₃)₆Cl₃ and K₃Fe(CN)₃ solutions at room temperature. Chemical composition of the resulting structures, which are composed of from Fe(CN)₆⁴⁻ and Ru(NH₃)₆³⁺, was determined by energy-dispersed spectroscopy. The data show that the formation of microrods depends on the molar ratio and concentration of the reactants.     

Mechano-hydrothermal preparation of Li-Al-OH layered double hydroxides

A mechano-hydrothermal (MHT) method was used to synthesize Li-Al-OH layered double hydroxides (LDHs) from LiOH·H₂O, Al(OH)₃ and H₂O as starting materials. A two-step synthesis was conducted, that is, Al(OH)₃ was milled for 1 h, followed by hydrothermal treatment with LiOH·H₂O solution. Effects of the LiOH/Al(OH)₃ molar ratio (R_Li/Al) and hydrothermal temperature (T_ht) on the crystallinity, morphology, and composition of the product were examined. The resulting LDHs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared, and elemental analyses. The results showed that pre-milling plays a key role in the LDH formation during subsequent hydrothermal treatment. The Li/Al molar ratio of the obtained LDHs keeps constant at 0.5, independent from theR_Li/Al (0.5–5.0) in the starting materials. An increase in the T_ht (20–80 °C) can enhance the crystallinity and morphology regularity of the products. The so-obtained Li-Al-OH LDHs exhibit high crystallinity and well-dispersity, which may have wider applications than the aggregate ones obtained using conventional mechanochemical and Li⁺-imbibition methods.