医疗机构废水处理研究与应用

文章通过对南昌市某医疗机构废水处理工程运行特性进行研究,工程运行结果表明:采用水解酸化+生物接触氧化+ClO2消毒工艺对医疗废水进行处理,工艺运行稳定,出水水质可以达到《医疗机构水污染物排放标准》(GB18466-2005)中的浓度限值,吨水处理费用仅为1.35元。     

Ethylcellulose microparticles containing chitosan and gelatin: pH-dependent release caused by complex coacervation

Ethylcellulose microparticles containing chitosan and gelatin were prepared by spray drying water-in-oil (W/O) emulsion. Water phase was chitosan:gelatin solution in distilled water, and oil phase was ethylcellulose solution in dichloromethane. FITC-dextran was included in water phase as a fluorescence dye. The maximum coacervation was observed at pH 6.0 when the ratio of chitosan to gelatin was 1:15. Microparticles containing chitosan and gelatin in the ratio showed a higher release under acidic condition (e.g. pH 4.0) and neutral condition (e.g. pH 7.0), but a lower release at pH 5.0 and pH 6.0. The complex coacervate composed of chitosan and gelatin was efficiently formed at those pHs, and the formation of coacervate would be responsible for the lower release.     

Analysis of mono-sugars obtained by acid hydrolysis of algae-based polysaccharides

Fossil fuel reserves are limited and global warming is emerging as a serious problem. To solve these problems, efforts to develop alternative energy sources are underway. In recent years the chemical industry based on the environmentally sound and sustainable biomass has been developing. Algae is regarded as important raw material of biomass. Polysaccharides such as cellulose and galactan obtained from the biomass can be converted to simple mono-saccharides by acid hydrolysis reactions. The formed monosaccharides are analyzed quantitatively and qualitatively by using liquid chromatography, ion chromatography and gas chromatography. By using acids to hydrolyze polysaccharides, monosaccharides can be formed as the structure of close form and/or open form. In this study, analysis methods of monosaccharides formed by acid saccharification are investigated to distinguish between close form and open form.     

Effect of functional groups of carbon nanotubes on the cyclization mechanism of polyacrylonitrile (PAN)

The cyclization mechanism of polyacrylonitrile (PAN) in PAN/functionalized carbon nanotube (CNT) composites was examined. The surface functionalization of CNTs was carried out by using diazonium reagents with 4-substituted aniline. The results strongly suggest that the type of functional groups on the CNTs strongly influences the cyclization mechanism of PAN during the stabilization process. The nitrile of PAN in F–Ph–CNT/PAN composite was cyclized through the free radical reaction during thermal stabilization whereas nitrile of PAN in COOH–Ph–CNT/PAN composite underwent cyclization via the ionic reaction due to the acid groups on the surfaces of the CNTs. The fluoro functional groups on the CNTs can act as effective external initiators for nitrile cyclization in homo PAN, in contrast to acid functional groups. Consequently, a lower cyclization temperature (265 °C) and enthalpy value (688 J/g) of F–Ph–CNT were shown compared to those of homo PAN.     

An effective oxidation approach for luminescence enhancement in CdS quantum dots by H2O2

The effects of surface passivation on the photoluminescence (PL) properties of CdS nanoparticles oxidized by straightforward H₂O₂ injection were examined. Compared to pristine cadmium sulfide nanocrystals (quantum efficiency ≅ 0.1%), the surface-passivated CdS nanoparticles showed significantly enhanced luminescence properties (quantum efficiency ≅ 20%). The surface passivation by H₂O₂ injection was characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and time-resolved PL. The photoluminescence enhancement is due to the two-order increase in the radiative recombination rate by the sulfate passivation layer.     

A novel negative dielectric constant material based on phosphoric acid doped poly(benzimidazole)

Metamaterials or artificial negative index materials (NIMs) have generated great attention because of their unique electromagnetic properties. The main challenge in current NIM development is creating a homogenous NIM without the need of complex geometric architectures consisting of capacitors and inductors or aggregated fillers, but possessing a tunable plasma frequency. A natural material that can exhibit negative values for permittivity and permeability simultaneously has not been found, or discovered. If one can design a negative dielectric constant material with a tunable plasma frequency of interest, implementing negative permeability into the material or system would be much more readily achievable to create a metamaterial. In this regard, a novel negative dielectric constant material, which is an essential key to creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at frequencies of kHz to MHz because of its reduced plasma frequency and an induction effect. As temperature increased, the dielectric spectrum changed from a relaxation to a resonance behavior and exhibited a larger magnitude of negative dielectric constant at a lower frequency. The conductivity of the doped PBI measured as a function of both temperature and frequency followed the same trend as the dielectric constant. With respect to the dielectric constant and the conductivity data, it can be assumed that the origin of the negative dielectric constant is attributed to the resonance behavior of the highly mobile ions at elevated temperatures and high frequencies. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of grain size on the mechanical properties and crack formation of HPFRCC containing deformed steel fibers

This research investigated the influence of sand grain size on the behavior of high-performance fiber-reinforced cementitious composites (HPFRCC). Four types of sand with different grain sizes were investigated using the same matrix composition containing 2.0% hooked and twisted fibers by volume. The compressive strength was significantly greater for the finer sand grains, despite little difference in the packing density. The better compressive strength was mainly due to the denser calcium silicate hydrate (CSH) resulting from an intensive pozzolanic reaction with the finer silica sand, rather than to an improvement in packing density. The interfacial bond strength of those fibers was notably improved, having favorable effects on the mechanical properties and multiple crack formation of HPFRCCs. Although both fibers showed superior properties in mortars with a finer sand grain, twisted fiber produced more sensitive behavior according to the sand grain size.     

Investigation of the stereodefect distribution and conformational behavior of isotactic polypropylene polymerized with different Ziegler–Natta catalysts

Two isotactic polypropylene (iPP) samples (PP-A and PP-B) were obtained by utilizing two different heterogeneous Ziegler–Natta catalysts in a given polymerization system. The molecular structure and conformational behavior of the samples were studied. The results of determination of xylene soluble material (XS) and ¹³C NMR showed that the average isotacticity of the samples were nearly same. However, the results of high-resolution high-temperature ¹³C NMR (HRHT ¹³C NMR) and successive self-nucleation and annealing (SSA) fractionation revealed that the amount of high isotacticity of PP-B was lower than that of PP-A, and the amount of relative medium and low isotacticity of PP-B was higher than PP-A, indicating that the stereodefect distribution of PP-B was more uniform than PP-A. The calculation of average meso sequence length from SSA was found to be in good agreement with that calculated from the results of HRHT ¹³C NMR. Moreover, Fourier transformation infrared was utilized to study the influence of stereodefect distribution on the conformational behavior of iPP. The result suggested that the molecular conformation of the PP-B was more disordered than PP-A, the regularity of molecular structure for PP-B was lower than that of PP-A. The related action mechanism and the influences of which on crystallization behavior were discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characteristics of Ag-doped BaTiO3 nanopowders prepared by spray pyrolysis

Pure and Ag-doped BaTiO₃ nanopowders were prepared by spray pyrolysis. Precursor powders, prepared from a spray solution with citric acid and ethylenediaminetetraacetic acid (EDTA) as chelating agents, had large, hollow particles irrespective of Ag doping. Both pure and Ag-doped powders had partially aggregated particles after post-treatment at 900 °C that could be easily milled to nanoparticles. The mean sizes of the pure and Ag-doped BaTiO₃ particles were 75 and 91 nm, respectively. The Ag-doped particles were mainly of cubic BaTiO₃ crystal structure, with small Ag phases observed. High-density BaTiO₃ pellets were formed by sintering the powders at the low temperature of 1000 °C. The silver was uniformly distributed in a tetragonal BaTiO₃ phase without phase separation in the doped pellet. The dielectric constants of the pellets formed from the pure and Ag-doped BaTiO₃ powders were 1826 and 2400, respectively.