Determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process

Polymer enhanced ultrafiltration (PEUF) is a newly developed method for the removal of heavy metals from aqueous solutions. This method was applied for the removal of mercury and cadmium with the presence of polyethyleneimine (PEI) as a water soluble polymer. After ultrafiltration experiments for metal–polymer mixtures, two separate streams, namely, retentate and permeate, former of which contains mainly metal–polymer complex and free polymer molecules while latter of which mainly contains free metal ions, were obtained. At the end of PEUF experiments, performance of operation was determined by concentration analyses which was achieved by atomic absorption spectroscopy (AAS) applied in a different way for permeate and retentate streams considering the effect of presence of polymer. For mercury analysis, cold vapor AAS was applied. It was observed that the presence of PEI did not affect the atomic absorption signal when 10% HCl was added to the sample solutions. For calcium and cadmium, flame AAS was used. It was observed that change in PEI concentration results in change in measured concentration of calcium and cadmium. Therefore, two new approaches were developed for accurate measurement of concentrations of calcium and cadmium. It was also observed that presence of other metals did not affect the accuracy of the measurement of a particular metal in the concentration range studied.     

Thermal decomposition of transition metal carboxylates

Thermal solid-phase decomposition of anhydrous copper(ii) formate has been studied at 120–180 ° The rate of gas evolution during the decomposition depends on the depth of conversion and can be presented as the sum of first-order reaction rates and the rate of the autocatalytic process (a second-order reaction). The evolution of the solid phase during thermolysis has been observed by optical microscopy. The decomposition of copper formate is a complex topochemical process, a combination of homogeneous and heterogeneous transformations and dispersion of large crystals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. l, pp. 72–76, January, 1996.     

Effect of aryl ligands on the chemical hardness of arylmercury cations

¹⁹F NMR spectroscopy was used to study the exchange reactions involving 4-fluorothiophenoxides, 4-nitrophenoxides, chlorides, and acetates of arylmercury and triphenylphosphinegold. The analysis of the data on equilibrium constants allows one to obtain information on the comparative chemical hardness of ArHg⁺ and Ph₃PAu⁺ cations. The increase in the electron-donating ability of aryl ligands enhances the chemical hardness of ArHg⁺ cations, their influence being best described by ⁰ constants of substituted phenyl groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1255–1260, May, 1996.     

Reaction of 2,6-dibenzylidenecyclohexanone with phosphorus pentachloride: Triple functionalization of the isosemiquinoid system

The reaction of 2,6-dibenzylidenecyclohexanone with PCl₅ occursvia the sequential stages of desoxychlorination and substitutional phosphorylation to form (after oxidation, methoxylation, and hydrolysis on the surface of the chromatographic SiO₂ adsorbent) organophosphorus products of the 1-(a-chloro-, a-hydroxy-, or -alkoxy)benzyl-2-chloro-3-(-(dimethylphosphoryl)benzylidene)cyclobex-1-ene series.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 441–443, February, 1996.     

High-temperature TG/DSC/QMS applications in environmental protection

The decomposition reactions of polystyrene, phenolic resin and a protective undercoating material for automobiles which contains PVC were tested using a new type of thermal analysis — mass spectrometry coupling system for measurements to 1500C or 2000C, which is based on the principle of a two-step skimmer orifice system. The results will be presented, with particular emphasis on the detection sensitivity of the new system for the products of decomposition.The capability of this coupling system to detect even heavy metals such as lead and silver in the waste gases from decomposition or after evaporation at high temperatures will also be demonstrated.     

不共轴光学系统自动优化中的有关问题

描述不共轴光学系统计算机优化中坐标变换与逆变换、“入瞳”与光线坐标、像面基准与质量函数定义的一致性问题。     

Surface modified precipitated calcium carbonates at a high degree of dispersion

Calcium carbonates of different degrees of surface hydrophobicity were obtained when sorbic acid or polyoxyethylene glycol were present during the precipitation. In the presence of trace amounts of divalent cations carbonates with high surface hydrophilicity and improved monodisperse character are obtained. Surface modification of the calcium carbonates by several proadhesive compounds can markedly improve the chemical affinity of the carbonates to polymers. Very effective are isostearoyl titanate and two polyoxyethylene compounds. Precipitated calcium carbonates modified with 2 to 3 percent (wt/wt) of isostearoyl titanate increased the tensile strenght of butadiene-styrene rubber by approximately 100%. Polyurethane is only strengthened when 30 wt/wt of a filler are introduced independently of the type proadhesive compounds. The best strength and hysteresis of polyurethanes are obtained with calcium carbonate modified with 2 percent (wt/wt) of polyoxyethylene glycol.     

Carbon Nanotubes Grown on Sepiolite as Catalyst Carrier

Multi-walled carbon nanotubes were synthesized by the catalytic decomposition of acetylene at 750℃ over sepiolite powder,which was treated with aqueous cobalt nitrate. It is expected that the composite with high specific area will have high capacity of hydrogen storage.     

Identification of formylglycine in sulfatases by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

C(alpha)-Formylglycine, the catalytic amino acid residue in the active site of sulfatases, is generated by post-translational modification of a cysteine or serine residue. We describe a highly sensitive procedure for the detection of C(alpha)-formylglycine-containing peptides in tryptic digests of sulfatase proteins. The protocol is based on the formation of hydrazone derivatives of C(alpha)-formylglycine-containing peptides when using dinitrophenylhydrazine as a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The hydrazone derivatives desorb and ionize with high efficiency and can be detected in the sub-femtomole range. The presence of C(alpha)-formylglycine is indicated by a mass increment of 180.13 u, corresponding to the hydrazone moiety, and also by a unique C-terminal fragment ion, characteristic of sulfatases, that becomes prominent in MALDI post-source decay mass spectra of the hydrazone derivatives.     

The theoretical basis of column chromatography in multicomponent separations. Part 2: Peak capacity. Column systems with good selectivity

The selectivity of a column system, S, defined by equation 28, includes a variation coefficient (β) of plate number with capacity ratio which has a large influence on the peak capacity, as shown in Fig. 18. Some typical chromatograms are given. In order to predict S for a column system from Kovat's Index, equations 40 and 41 are given to calculate the constant of the carbon number rule for squalane at different temperatures or for different stationary phases. The specific retention value of heptane on squalane at different temperatures can be calculated from equation 42. The nonpolarity index, defined by equation 43, was used to calculate the retention value of heptane on various stationary phases. In liquid chromatography, the order of elution may be reversed by changing the composition of the eluent on the same chemically bonded silica (manufactured in China). The linear relations between the log retention values of different kinds of solutes or of a single solute on the silicas of different surface areas when using the same eluent are given.