Wyniki wyszukiwania - Biblioteka Nauki

1

On the advantages of using prehydrolysed aluminum coagulants

100%

Rak M. , Świderska-Bróż M.

Environment Protection Engineering

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2001

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tom vol. 27, nr 3-4

5-17

EN

The advantages of polyaluminum chlorides (i.e. prehydrolyzed aluminum coagulants differing in basicity) are specified. Expts. were carried out on riverine water samples (from the Odra and its tributary, the Olawa) which varied in temp. and pollution level. Polyaluminum chlorides yielded a greater destabilization of colloids and their efficiency in the removal of water pollutants was higher compared with conventional Al sulfate coagulant. They were of greater utility than Al sulfate because of a lower residual Al concn. and a smaller increase in water corrosivity. The increase in the basicity of the prehydrolyzed coagulants exerted a favorable influence on their efficiency and allowed redn. of their doses.

PL

Omówiono zalety wstępnie zhydrolizowanych koagulantów glinowych o różnej alkaliczności, tzw. chlorków poliglinu. Badano próbki wody z Odry i Oławy różniące się temperaturą i poziomem zanieczyszczenia. Chlorki poliglinu zapewniły większą destabilizację koloidów oraz efektywniejsze usuwanie zanieczyszczeń niż tradycyjne stosowany siarczan glinu. Okazały się też bardziej przydatne z uwagi na mniejsze stężenie glinu pozostałego i intensyfikację korozyjności oczyszczanych wód. Stwierdzono zarówno dodatni wpływ zwiększającej się alkaliczności koagulantów wstępnie zhydrolizowanych na ich efektywność, jak i zmniejszenie wymaganej dawki koagulantu.

2

Electrostatic interactions of colloid particles in mixed electrolytes

84%

Warszyński P. , Adamczyk Z.

Bulletin of the Polish Academy of Sciences. Chemistry

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2001

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tom Vol. 49, No. 1

101-114

EN

Electrostatic interactions of two spherical particles immersed in an electrolyte mixture were analyzed theoretically. A numerical scheme was developed for solving the governing Poisson-Boltzmann equation expressed in the bispherical co-ordinate system. The method was based on the alternating direction over-relaxation procedure using the Newton-Raphson iteration. The novelty of the algorithm consists in using the grid transforming functions enabling a more uniform distribution of mesh points in regions characterized by strong electric field. Using the numerical method, electric potential distribution (within and outside the sphere) was calculated which allowed one to determine the effective surface potential of a spherical particle immersed in a mixture of electrolytes. The interaction energy of particles as a function of their separation was also determined numerically for various amounts of a 2:1 electrolyte added to a 1:1 electrolyte. These energy profiles were compared with analytical approximations derived using the linear superposition approach (LSA) exploiting the effective potential determined previously. It was demonstrated that the LSA can be used as a good estimate of the potential distribution and interaction energy for distances between particles exceeding the double-layer thickness. It was also shown that a small addition of the 2:1 electrolyte decreased significantly the interaction energy between particles, which has implications for colloid stability.

3

Colloid silica viscosity determined by the particle sedimentation method

84%

Adamczyk Z. , Siwek B. , Zembala M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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tom Vol. 48, No. 3

231-242

EN

Viscosity of colloid silica was determined as a function of the volume fraction varied between 0 and 0.37. A new method of viscosity measurements was applied, based on determination of particle sedimentation velocity. The sedimentation velocity was calcu-lated from the kinetics of irreversible adsorption (deposition) of melamine latex particles (particle size 1.7 and 3.6 pirn) at silanized mica. Deposition kinetics was determined in the sedimentation cell using the direct microscope observation technique. This method is significantly more accurate, especially in the region of low shear rates, than the classical viscosity measurements exploiting commercial viscometers. It was found that colloid silica viscosity increased more rapidly with increased volume fraction than predicted by the classical Batchalor and Dougherty-Krieger models. The deviation has been attributed to the secondary electroviscous effect stemming from the electrostatic interactions among sil-ica colloid particle. This has quantitatively been interpreted in terms of the effective hard particle concept used previously to describe densities of particle mono-layers. Explicit de-pendence of the effective particle volume on the double-layer thickness has also been given.

4

Fennosil 515 - poprawa retencji koloidalnej i wydajności

67%

Sień D. , Gaziński J. , Fabrykowski P. , Karczewski M. , Strengell K.

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2008

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tom R. 64, nr 1

34-38

EN

Arguably the most important factor in the wet end of your papermachine is Colloidal Retention. Colloidal trash can create problems with runnability and sheet quality. It doesn't let your retention system or additives work well, and it leads to deposits, holes, breaks, and overall papermaking chaos. Retaining this extremely small material in the sheet while it's still small is the only way to efficiently purge your papermachine wet end of this potential problem child. Anchor it on the fibers, in the sheet, to the reel, and out the doors the only way to be sure it's gone. Don't use dispersants that only try to push them back into the water, until they eventually saturate the wet end and deposit out somewhere, anywhere, everywhere! This type of chemistry just creates a Vicious Cycle where low colloidal retention creates foam from non-retained size, which prompts for increased defoamer dosage, which in turn hurts sizing and begs for more size addition; while the dispersant added to stop the forming deposits only hurts sizing even more, and back to the beginning of the cycle. Dispersants and detacktifiers don't work. Microparticle colloidal silica is highly recommended as part of your machine retention system to assure the best colloidal retention and amid these problems. Microparticle silica and cationic wet end starch together form a team, a net that fishes out this small material and holds it strongly onto the fiber. Silica has proven itself over the last 20 plus years. And now more than ever, where Sizing products depend so much on starch for emulsification and retention, it makes sense that the silica that works best together with starch will help sizing while it stops the Vicious Cycle from ever starting. Here we review the details of the mechanism; and a few case studies.