Treatment of wastewater to remove ammonium ions by precipitation

The process of wastewater treatment to remove ammonium ions by precipitation in the form of ammonium magnesium phosphate was studied. The fundamental aspects of the chemical precipitation process were examined. The effect of various factors on the efficiency of wastewater treatment was experimentally analyzed.     

Substituted and fused spiro[benzo-2-azepine-3,1′-cyclohexanes]

5-Methyl-4,5-dihydro-3H-spiro[benzo-2-azepine-3,1-cyclohexane] N-oxide was rear- ranged into 5-methyl-1-oxo-1,2,4,5-tetrahydro-3H-spiro[benzo-2-azepine-3,1-cyclohexane]. The latter was used for the synthesis of spiro{triazolo[3,4-a]- and-tetrazolo[5,1-a]benzo-2- azepinecyclohexanes}.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1647–1651, August, 2004.     

A geometrically constraining bis(benzimidazole) ligand and its nearly tetrahedral complexes with Fe(II) and Mn(II)

2,2'-Bis[2-(1-propylbenzimidazol-2-yl)]biphenyl), 4, and its bis complexes with Fe(II) and Mn(II) have been prepared and characterized structurally and spectroscopically. Ligand 4 adopts an open, "trans" conformation in the solid state with the benzimidazole (BzIm) groups on opposite sides of the biphenyl unit. In its complexes with metal ions, a "cis" conformation is observed, and 4 behaves as a geometrically constraining bidentate ligand with four planar groups connected by three "hinges". Reaction of 4 with Fe(II) or Mn(II) yielded isomorphous crystals (space group Pnn2) of Fe(II)(4)2.(ClO4)2 and Mn(II)(4)2.(ClO4)2, in which the M(II)(4)2 cations exhibit distorted-tetrahedral coordination geometries (N-M-N angles, 109 +/- 11 degrees ) enforced by rigid, chiral nine-membered M(4) rings in the twist-boat-boat conformation. Individually, the cations show R,R or S,S stereochemistry, and the crystals are racemates. Mn(II)(4)2.(ClO4)2 exhibits a quasi-reversible Mn(II) --> Mn(III) oxidation at E(1/2) = 0.64 V; the corresponding Fe(II) --> Fe(III) oxidation occurs at E(1/2) = 1.76 V. The electrochemical stability of the Fe(III) oxidation state in this system suggests the possibility of isolating an unusual pseudotetrahedral Fe(III)N(BzIm)(4) species. Ultraviolet spectra of the iron and manganese complexes are dominated by absorptions of the ligand 4 blue-shifted by approximately 2000-3000 cm(-1). Ligand-field absorptions were observed for the Fe(II) complex; those for the Mn(II) complex were obscured by tailing ultraviolet absorptions. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-spin Mn(II) complex, while for the Fe(II) complex, the falloff of the magnetic moment with decreasing temperature is indicative of zero-field splitting with D approximately 4 cm(-1).     

The Structure of o-Hydroxyaryloxy-bis-(o-arylenedioxy)-phosphoranes and their Acid-Base Properties

Abstract

The crystalline phosphoranes have been obtained. IR-, UV- and NMR spectra of phosphoranes (Ia,b) and their interaction products with nitrogen bases have been investigated. It was determined that phosphoranes have structure (I) with pentacoordinate phosphorus and phenolic hydroxy group, while their products of interactions with nitrogen bases have the ionic structure (II) with hexacoordinate phosphorus (II). The X-ray difraction approves the structure (I) for phosphorane Ib.     

Laser photolysis study of the triplet states of phthalocyanines on the surface of silica nanoparticles in aqueous solutions

Aluminum and zinc phthalocyanines (AlPc and ZnPc, respectively) adsorbed on the surface of silica nanoparticles (60 nm in diameter) in aqueous solutions have been found to form H-aggregates, which possess characteristic absorption spectra with bands (having a maximum at 640 nm) in a shorter wavelength region with respect to the main Q-band of the monomer (having a maximum at 670 nm). For AlPc on the surface, J-aggregates of two types (long-wavelength bands with maximums at 740 and 770 nm) are also observed. Using nanosecond laser photolysis (with the excitation wavelength of 337 nm) in deoxygenated solutions of AlPc on the surface, the formation of the triplet electronically excited states of J-aggregates has been detected, which are characterized by a broad absorption spectrum in the region of 400–800 nm and a lifetime of 360 μs. No intermediate products have been detected during the photolysis of H-aggregates of ZnPc on the surface.     

TOF-SIMS 5 instrument sensitivity to matrix elements in GeSi Layers: Analysis based on recording of complex secondary ions

Ge _x Si_{1 − x} layers are investigated by means of secondary ion mass spectrometry (SIMS). Experimental results obtained with the use of a TOF-SIMS 5 instrument are presented. To surmount the so-called matrix effect, SIMS analysis is performed by using complex secondary ions: Ge₂⁻, CsGe⁺, and Cs₂Ge⁺.     

Mechanical Properties of a Basalt-Fiber-Reinforced Plastic Rod Used in Composite High-Voltage Wires in Torsion and Three-Point Bending

Mechanics of Composite Materials - Results of experimental investigations into a unidirectional composite of basalt fibers and epoxy resin used as part of high-voltage electric wires are presented....     

Energy spectrum and optical transitions in C80 fullerene isomers

The energy spectra of all isomers of the C₈₀ fullerene have been calculated in terms of the Schubin-Wonsowskii-Hubbard model. On this basis, their optical absorption spectra have also been calculated. The optical absorption spectra calculated for the endohedral Ca@C₈₀, Ba@C₈₀, and Sr@C₈₀ fullerenes with the I _h symmetry agree well with the experimental data. This circumstance allows us to conclude that the optical absorption spectra of other isomers (for which experimental data are unavailable) obtained in this work can be used for their identification.     

Crystal chemistry of lanthanide oxochlorotungstates

Crystal chemical properties of lanthanide oxochlorotungstates of composition LnWO₄Cl (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) are reported. The unit cell parameters a, b, c, c′, and V of the LnWO₄Cl compounds are correlated with lanthanide ionic radii from different radius systems and with the lanthanide atomic number. The ionic radius systems most suitable for describing the crystal chemical properties of the lanthanide oxochlorotungstates are determined.