混凝改善超滤膜过滤性能的研究

研究有机物的特性如亲、疏水性以及相对分子质量的大小对超滤膜通量的影响.着重考察混凝对有机物特性的影响以及改善超滤膜通量的效果.试验表明,超滤膜直接过滤原水时,主要截留疏水性有机物,从而造成膜通量的下降.投加硫酸铝25 mg/L和100 mg/L时,虽然TOC去除率仅为18.4%和48.2%,但明显提高了膜通量,这是由于混凝有效地去除小分子疏水性有机物的缘故.研究表明,膜通量的下降与膜截留疏水性有机物的多少有密切关系.     

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime Over Rare Earth Pyrophosphates

A new application of rare earth pyrophosphates in vapor phase Beckmann rearrangement of cyclohexanone oxime was investigated. The rare earth phosphates were characterized by means of XRD, FT-IR, NH₃-TPD and water contact angle measurement. It was found that the weak surface acidity and appropriate surface hydrophobicity should be two key factors in the excellent performance of these catalysts.     

Hydrophobic Flocculation Flotation for Beneficiating Fine Coal and Minerals

ABSTRACT

It is shown that hydrophobic flocculation flotation (HFF) is an effective process to treat finely ground ores and slimes so as to concentrate coal and mineral values at a fine size range. The process is based on first dispersing the fine particles suspension, followed by flocculation of fine mineral values or coal in the form of hydrophobic surfaces either induced by specifically adsorbed surfactants or from nature at the conditioning of the slurry with the shear field of sufficient magnitude. The flocculation is intensified by the addition of a small amount of nonpolar oil. Finely ground coals, ilmenite slimes, and gold finely disseminated in a slag have been treated by this process. Results are presented indicating that cleaned coal with low ash and sulfur remaining and high Btu recovery can be obtained, and the refractory ores of ilmenite slimes and fine gold-bearing slag can be reasonably concentrated, leading to better beneficiation results than other separation techniques. In addition, the main operating parameters affecting the HFF process are discussed.     

Copper based hydrophobic ceramic nanocoating

A mechanism for the development of nanocoatings for the tiles industry by using copper nanoparticles has been proposed. A standard processing procedure in which ceramics were fast-firing at 1200 °C in air atmosphere simulating an industrial process was followed. The ceramic nanocoating was multifunctional having shine metallic aspect and hydrophobic characteristics. The surface crystallizations were studied by X-ray diffraction and corresponded to copper oxide nanocrystals. The hydrophobic response was based in the nanoroughness of the surface and correlated with the Cu⁺/Cu²⁺ ratio as determined by XANES. The cellular nano microstructure look biomimetic with the one of hydrophobic leafs. The development of the cellular nano microstructure was based on the Rayleigh-Bernard cells of a saturated glass during cooling in which thermal convection currents allow the crystallization of nanoparticles at the surface of the glass.     

Picosecond Laser Surface Texturing of a Stavax Steel Substrate for Wettability Control

In this investigation, a picosecond laser was employed to fabricate surface textures on a Stavax steel substrate, which is a key material for mold fabrication in the manufacturing of various polymer products. Three main types of surface textures were fabricated on a Stavax steel substrate: periodic ripples, a two-scale hierarchical two-dimensional array of micro-bumps, and a micro-pits array with nano-ripples. The wettability of the laser-textured Stavax steel surface was converted from its original hydrophilicity into hydrophobicity and even super-hydrophobicity after exposure to air. The results clearly show that this super-hydrophobicity is mainly due to the surface textures. The ultrafast laser-induced catalytic effect may play a secondary role in modifying the surface chemistry so as to lower the surface energy. The laser-induced surface textures on the metal mold substrates were then replicated onto polypropylene substrates via the polymer injection molding process. The surface wettability of the molded polypropylene was found to be changed from the original hydrophilicity to super-hydrophobicity. This developed process holds the potential to improve the performance of fabricated plastic products in terms of wettability control and easy cleaning.     

Tunable Wettability by Clicking Counterions Into Polyelectrolyte Brushes

Polymer brushes have recently emerged as an extremely versatile way to modify surface properties in a robust and controlled way. The introduction of responsive polymers and block copolymers in polymer‐brush systems has also opened up new routes to ‘smart' surfaces with switchable surface properties. Here, the use of polyelectrolyte brushes as a supramolecular platform for the immobilization of a wide range of species, leading to a tunable wettability of substrates, is presented.     

Low temperature preparation of TiO2 nanodot film on substrates

Herein, we report a photoinduced transition of hydrophobicity to high hydrophilicity of TiO₂ nanodot films in applications of cell sheet engineering. A phase-separation-induced self-assembly process was adopted to prepare a TiO₂ nanodot gel film on a substrate. Subsequently, a hydrothermal treatment (with ethanol/water at 140 °C for 2 h) was used to convert the nanodot gel film to TiO₂ nanodot solid film. The resulting TiO₂ dots were amorphous with adjustable size and density. The amorphous TiO₂ nanodot film showed a conversion from a good hydrophobic surface, with a water contact angle (WCA) of 67.6 ± 2.0°, to a highly hydrophilic one, with a WCA of 5.3 ± 2.0° (i.e. almost superhydrophilic) after UV irradiation. A good reversibility was also observed.     

磁控溅射法制备防水透湿织物的性能研究

介绍子利用磁控溅射法制备透湿织物的基本原理及方法，通过对防水透湿织物憎水性及透湿性的测试分析，发现溅射后织物的憎水性明显提高，且憎水性随溅射功能的增大而减小，随压力的增大而增在，而溅射前后的透湿性受功率和压力的影响不大。     

Bioflocculation of mesophilic and thermophilic activated sludge

Thermophilic activated sludge treatment is often hampered by a turbid effluent. Reasons for this phenomenon are so far unknown. Here, the hypothesis of the temperature dependency of the hydrophobic interaction as a possible cause for diminished thermophilic activated sludge bioflocculation was tested. Adsorption of wastewater colloidal particles was monitored on different flat surfaces as a function of temperature. Adsorption on a hydrophobic surface varied with temperature between 20 and 60 degrees C and no upward or downward trend could be observed. This makes the hydrophobic interaction hypothesis unlikely in explaining the differences in mesophilic and thermophilic activated sludge bioflocculation. Both mesophilic and thermophilic biomass did not flocculate with wastewater colloidal particles under anaerobic conditions. Only in the presence of oxygen, with biologically active bacteria, the differences in bioflocculation behavior became evident. Bioflocculation was shown only to occur with the combination of wastewater and viable mesophilic biomass at 30 degrees C, in the presence of oxygen. Bioflocculation did not occur in case the biomass was inactivated or when oxygen was absent. Thermophilic activated sludge hardly showed any bioflocculation, also under mesophilic conditions. Despite the differences in bioflocculation behavior, sludge hydrophobicity and sludge zetapotentials were almost similar. Theoretical calculations using the DLVO (Derjaguin, Landau, Verweij and Overbeek) theory showed that flocculation is unlikely in all cases due to long-range electrostatic forces. These calculations, combined with the fact that bioflocculation actually did occur at 30 degrees C and the unlikelyness of the hydrophobic interaction, point in the direction of bacterial exo-polymers governing bridging flocculation. Polymer interactions are not included in the DLVO theory and may vary as a function of temperature.     

Influence of mixing characteristics for water encapsulation by self-assembling hydrophobic silica nanoparticles

Water encapsulation using silica nanoparticles was assessed using two different types of single step mixing processes. The influential mixing characteristics have been determined. Direct mixing at high rotational speed requires high shear and vigorous stirring properties. Progressive water atomisation using gentle mixing process requires high atomisation pressure and rapid surface refreshing of the mixed material. Mechanisms of powder formation were also proposed. Encapsulation of micrometric water droplets in shell-like structure is respectively obtained by either progressive size reduction of macroscopic particulates or direct coating of pre-formed microscopic droplets. These mechanisms resulting from the interactions between a solid particle and a liquid highly depend on parameters such as particle's hydrophobicity, surface tension or kinetic energy.