Surface Of Primary Particles Research Articles

Effects of Macromolecular Conformation upon Solid-Liquid Separation and Water Treatment Plant Residuals

The efficiency of solid-liquid separation in coagulation -sedimentation processes depends greatly upon the performance of the coagulant with respect to the production of suitable floc properties. When high-molecular weight polymers (that function primarily by bridging between proximate primary particles) are used as coagulant-aids, the dynamic processes of polymer adsorption and macromolecular rearrangement figure prominently in the success of floc formation. Ideally, one would like to have the macromolecule adsorb quickly upon the primary particle surface in an extended, rod-like conformation; this configuration should persist throughout the collisional process to produce rapid floc growth. A period of macromolecular relaxation would then ensue, with the formation of additional affiliations between functional groups and surface sites. Recently, there have been speculations that the relative speeds of these processes may not necessarily conform to the common perception that sorption is quick and that the ...

Flow induced phase inversion agglomeration: Fundamentals and batch processing

AbstractA novel agglomeration technique, based on flow induced phase inversion (FIPI) is described and applied to the batch preparation of polyethylene‐bound abrasive calcite agglomerates. Water soluble polymers are used to agglomerate the needle‐like crystals of tetraacetylethylene diamine and also sodium chloride crystals. In a typical isothermal FIPI agglomeration process primary particles are dispersed in the molten binder, which is subsequently inverted by the addition of sufficient amount of primary particles, which also defines the critical filler concentration at phase inversion, Cc. Agglomerate particle size is primarily a function of Cp – Cc where Cp is the mean concentration of filler. Cc decreases with increasing binder molecular weight and primary particle surface area. Agglomerate size distribution is affected by processing, mainly by the mixing time after phase inversion. For the non‐isothermal FIPI agglomeration process, phase inversion is induced locally, by the addition of fine particles in the molten binder. Phase inversion is then propagated by cooling the dispersion during mixing. Agglomerate characteristics such as particle size, particle size distribution, binder concentration distribution in each agglomerate size range, agglomerate topology, binder morphology in the agglomerates, agglomerate strength, and agglomerate dissolution rate in water were evaluated. These agglomerate characteristics are related to the binder and filler properties as well as to the processing conditions.

Effects of Diols on Surface Area and Pore Radius of Alkoxy-Derived Silica Gels

The effects of diols on specific surface area and pore size distribution of alkoxy-derived silica gels were investigated. The specific surface area of dried gels decreased and the fractional pore volume of large pores increased with an increase of chain length of diols used in starting solutions. These results were explained in terms of inhibition of coalescence among primary particles caused by the formation of chemical bonds between silicon or oxygen atoms on the surface of primary particles and hydroxy groups of diols.

Whisker formation from jet of supercritical fluid solution

The growth mechanism of a whisker of stigmasterol particles deposited by rapid expansion from supercritical CO 2 solutions has been investigated by scanning electron microscope. Amorphous fine particles were found to be under relatively low pre-expansion pressures while whisker-like crystals were observed under relatively high pre-expansion pressures. The turning point was about 13 MPa at 373 K. It was found that the secondary products grew on a screen in the expansion jet after deposition of primary particles of about 10-nm diameter. The morphology of secondary products was found to strongly depend on the surface condition of the primary particle. Because of the temperature decrease caused by the rapid expansion, the pre-expansion pressure plays an important role in determining the thermal roughening degree on the surface of primary particles, and consequently the morphology of the secondary products.

Characterization of X-ray amorphous material in a Scottish soil by selective chemical techniques

AbstractMixed SiO2-Al2O3-Fe2O3 gel systems are a feature of many Scottish soils. They are usually associated with the surface of primary soil particles and consequently when present even in small amounts can have an effect on soil properties incommensurate with the proportion present. Currently, chemical dissolution methods provide the most satisfactory means of assessment. A range of chemical techniques, including dissolution by alkali, dithionite, acid oxalate and pyrophosphate, trimethylsilylation and fluoride exchange, have been used to examine the inorganic gel in a Scottish brown forest soil developed on glacial till derived from epidiorite. The reactivity of the gel, as determined by fluoride exchange, is similar to that reported for Japanese and New Zealand allophanic soils.

The Characterization of the Hydroxyl Surface of Silica Gel

Abstract The properties of silica gel were studied as a function of the hydrothermal treatment of hydrogel by means of the nitrogen-adsorption isotherm, the mechanical strength, thermodilatometry, and infrared spectroscopy. As a result, the number of contact points between primary particles of silica was found to decrease, and closed pores were found to be produced, by this treatment. The analysis of the infrared absorption spectra of the OH groups of this material showed that there are three kinds of OH groups in silica gel; (1) free OH groups on the outer surface of primary particles, which can adsorb molecules easily, (2) weakly perturbed OH groups inside closed pores, and (3) strongly hydrogen-bonded OH groups on the surface around the contact points. The relative concentration of these OH groups changes drastically upon the hydrothermal treatment; this is in accord with the change in the macroscopic properties mentioned above.