Adsorbed state of p-mercaptobenzoic acid on silver nanoparticles

To exploit a gap mode plasmon in flocculates of metal nanoparticles most efficiently, the interaction between adsorbed chemical species and metal nanostructures were adjusted. We successfully formed flocculates of Ag nanoparticles (AgNPs) using electrostatic interaction between dissociated p-mercaptobenzoic acid (PMBA), protonated p-aminothiophenol (PATP) and their counter ions (Mⁿ⁺, X^m−), as well as van der Waals force between neutral PMBA, PATP and AgNPs. Detailed adsorbed state of PMBA and PATP in addition to trapped counter ions was characterized using enormous SERS enhancement in a flocculation method.     

Material and Method Developments for Developing and Lifting Latent Finger Mark from Wet Polymer‐Coated Metal Surfaces

We have developed two strategies to develop finger mark images when powdering methods are no longer effective. One strategy is based on flocculation‐on‐demand colloidal chemistry. An example of this strategy is to apply a suspension of titanium dioxide, water, and chitosan polymer onto the finger mark after the surface is pretreated with a dilute solution of sodium dodecyl sulfate. Pigmented titanium dioxide particles get flocculated and deposited to the finger mark surface when the suspension becomes unstable as the cationic polymer (chitosan) electrostatically interacts with the anionic surfactant (sodium dodecyl sulfate) at the interface. The second strategy is based on the differential adsorptions of pigmented particles on background versus the finger mark surface. By choosing proper pigment–surfactant combinations, particles can be oriented such that the surfactant molecules will attract the pigment particles on the finger mark surfaces but not on the background. An example of this strategy is a suspension made of titanium dioxide particles and a fluorocarbon–hydrocarbon amine oxide surfactant. Differential adsorption results in clear finger mark images, which can be lifted off using various sol–gel chemistries.     

Flocculation kinetics of an ochre suspension in salt(NaCl)-containing aqueous media in the presence of anionic and cationic acrylamide copolymers

The sedimentation kinetics of an ochre suspension in salt (NaCl)-containing aqueous media was studied in the presence of ionogenic (anionic, A, and cationic, C) acrylamide copolymers with high molecular weight (M > 2 × 10⁶) using a VT–0.5 torsion balance. The ionic strength of the dispersion medium varied in the wide range from 0.001 N to 0.4 N. The flocculation proceeded predominantly by a `bridge' mechanism, and the fraction of macromolecules inactive in the acts of floccule formation was significantly higher for C copolymer as compared with A copolymer. A drastic fall in the flocculating activities of A and C copolymers when passing from salt-free to salt-containing media is caused mainly by two following events: 1. The change in the conformational state of macromolecules, primarily, in their effective dimensions 2. The participation of a certain part of electrolyte in the formation and modification of an electrical double layer around disperse phase particles After introducing binary compositions of A and C flocculants into salt-containing media their resultant flocculating effect depends on the introduction mode of polymeric components. A strong difference in the magnitudes of the flocculating effect for A and C copolymers is observed in water. In the region of high ionic strengths (0.1–0.4 N) this difference becomes far less distinct. The flocculating activities of A and C copolymers were compared when introduced as the first (λ_A and λ_C) and the second (λ_A ^′ and λ_C ^′) additives. It was shown that λ_A/λ_A ^′>1 and λ_C/λ_C ^′>1. Such relationship between λ_A and λ_A ^′, λ_C and λ_C ^′ indicates that selective interactions between A and C copolymers play an essential role in the flocculation processes. The last statement was indirectly confirmed in the present work by the data of electrochemical and viscosimetric studies. When using C copolymer as the second additive in the region of low ionic strengths its main function undergoes reversal, and the copolymer begins to operate not as a flocculant, but as a stabilizer of disperse phase particles (λ_C< 0). Received: 14 April 2000 Accepted: 4 August 2000     

硫酸根型阴离子交换树脂法改善PAC絮凝性能的研究

体系以聚合氯化铝溶液为原料，以硫酸型强碱性阴离子交换树脂为载体，进行离子交换反应。结果表明，在保持氧化铝含量基本不变的情况下，能有效地提高聚合铝的碱化度。同时生成含ＳＯ４＾２－的聚合氯化铝，实验证明它的絮凝效果优于了聚合氯化铝。     

Effect of high voltage electrical discharges on filtration properties of Saccharomyces cerevisiae yeast suspensions

In the present work the dead-end filtration of Saccharomyces cerevisiae yeast suspensions disrupted by high voltage electrical discharges (HVED treatment) was investigated. The efficiency of disruption was evaluated using conductivity disintegration index of suspension Z (Z = 0–1) and absorbance spectra of supernatant solutions. The electronic microscopy study, particle sizing and measuring of ζ-potential and turbidity were used to characterize variation of the colloidal properties of a yeast suspension during disruption. The HVED treatment was found to cause an effective disruption of yeast cells and extraction of intracellular proteins and other bio-products. The study of filtration revealed suspension filterability deterioration after disruption. It was shown that filtration behaviour of the HVED-processed suspensions was governed by cake formation, the filtrate volume decreased and the cake resistance increased with increase of Z. For high levels of disruption (Z > 0.99), filtration was governed by membrane fouling. The optimal dosage of polycationic flocculant promoted the formation of flocks and accelerated filtration. However, selected flocculant (poly(diallyldimethylammonium chloride)) provoked binding of bio-product and was inappropriate for using as an agent enhancing extraction from disrupted yeast cells.     

Porosity and interior structure analysis of pellet-flocs

Pellet-flocs are the result of modified flocculation performance. They are spherically shaped and can reach several millimeters in size. Since pellet-floc aggregates are created from macroflocs and these from microflocs and these, in turn, from primary solid particles, it can be expected that the total porosity is composed of porosities resulting from spaces between all these sub-elements. Accordingly, micro- and macroporosity can be distinguished in the interior structure of pellet-flocs.

Although considerable attention has been given to total aggregate porosity measurement, no reports can be found about the full morphological characteristics of different types of pores. Moreover, there is no single reliable method that can accurately obtain values for the respective fractions of pore volume (microporosity, macroporosity) within a relatively big floc aggregate.

This work is an approach to probe the porosity within pellet-flocs at different size levels by combining the outcomes from different examination methods.

Pellet-floc aggregates were investigated using the following techniques: free settling, light microscopy of resin-embedded microtome slices and scanning electron microscopy (SEM).

The results confirmed that the biggest portion of porosity is composed of micropores in the size range of a few microns, which were first visible by SEM image analysis. Light microscopy of resin-embedded microtome slices is an accurate method to obtain so called macroporosity of a whole agglomerate with equivalent pore diameter above 50 μm. The study of free settling data revealed satisfactorily the total porosity of pellet-flocs. Finally, a multilevel porosity model of pellet-flocs could be obtained.     

Saturated hydraulic conductivity of a volcanic ash soil affected by repulsive potential energy in a multivalent anionic system

Acid rain is supposed to influence soil structures, because soils have pH-dependent charges. The adverse effects of acid rain on soils must be assessed. Although repulsive potential energy among soil clay particles generates swelling and dispersion, thereby changing the soil’s hydraulic conductivity, the relationship between hydraulic conductivity and repulsive potential energy has not been evaluated. Moreover, research into repulsive potential energy in multivalent counterionic systems has been rare. In this paper, repulsive potential energies for a volcanic ash soil (allophanic Andisol), which is characterized by a number of pH-dependent charges, were evaluated in a multivalent counterionic system. Changes in saturated hydraulic conductivity (K) of volcanic ash soil during dilute acid leaching and their relationship with the repulsive potential energies were examined. When nitric acid at pH 3 or 4 was leached, K decreased rapidly. On the other hand, the decrease in K attenuated as the proportion of sulfate in the dilute acid increased. Electrophoretic mobilities were measured and the zeta potentials were estimated. From the zeta potentials and the calculation of repulsive potential energies between the clay particles in the NO₃–SO₄ system, we concluded that the decrease in K for an acid solution with a high proportion of nitrate was due to swelling and dispersion of the soil induced by electrostatic repulsive potential energy. Because sulfate formed complexes on the clay surface, the repulsive potential energy decreased as the proportion of sulfate in the dilute acid increased. Then, the flocculation of the soil was maintained, thereby inhibiting the decrease in K.     

添加剂对TiO2/水分散体流变性的影响

研究了TiO₂生产中有关助剂对其流变性能的影响,得到了TiO₂/水分散体的流变性能与三乙醇胺用量之间的关系,并找到了最佳用量.实验发现,六偏磷酸钠为分散剂时,其使用效果有时间依赖性;碳酸铵作絮凝剂时则对分散体的流变性能和形成的絮凝体有影响.     

阳离子聚电解质对油污泥的絮凝作用机理

用高密度电荷阳离子聚电解质处理油污泥［１,２］,依靠其与粘土颗粒间的静电作用压缩污泥中固相颗粒的表面双电层,中和ζ电位,使其颗粒间斥力减小,引力增大,油污泥化学脱稳,致使粘土颗粒聚集絮凝成团块,油颗粒聚集,实现油、水、泥渣的三相分离．１　实验部分１．１　样品制备　现场采集的油污泥中油品含量１９％,固含量８％,体系漏斗粘度３７ｓ,密度１．０９ｇ／ｃｍ３．阳离子聚电解质（ＣＦ）、聚丙烯酰胺－丙烯酸β－羟基丙酯基三甲基氯化铵按文献［２,３］方法制备,平均分子量２．６０×１０６,阳离子电荷度４５％．阴离…     

Adsorption and flocculation by polymers and polymer mixtures

Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including ‘electrostatic patch’ attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of ‘site blocking’.