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Fennosil 515 - poprawa retencji koloidalnej i wydajności

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

Przegląd Papierniczy

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2008

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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.

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Phenomenon of vortex rings in method of production nanosuspension metallic

Laskowski S.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2003

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Vol. 39, nr 14

74-80

EN

Nanosuspension was made using wire explosion in the liquid. Providing that silver and copper proportions are right, the liquid could be strongly sterile. Suspension which contains only silver particles has also antibacterial properties. We can control dimensions of metal in water by varying voltage, current and capacity of pulse generator. The experiments let us conclude that the increase of energy (over define limits) does not lead to crumbling in the suspension. It has been confirmed by microscope observations and sedimentation test in different conditions. Different types of wire dezintegration process have been observed and documented thanks to a high speed digital video camera and still photography. It was also possible to notice vortex ring process.

3

Kinetics of random sequential adsorption of interacting particles on partially covered surfaces

Weroński P.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 3-4

221-239

EN

The random sequential adsorption (RSA) approach was used to analyse adsorption kinetics of charged spheres at charged surfaces precovered with smaller sized, likely charged particles. The algorithm of M. R. Oberholzer et al. [20] was exploited to simulate adsorption allowing electrostatic interaction in three dimensions, that is, particle-particle and particle-surface interactions during the approach of a particle to the substrate. The calculation of interaction energies in the model was achieved with the aid of a many-body superposition approximation. The effective hard particle approximation was used for determination of corresponding simpler systems of particles, namely: the system of hard spheres, the system of particles with perfect sink model of particle-interface interaction, and the system of hard discs at equilibrium. Numerical simulations were performed to determine adsorption kinetics of larger particles for various surface concentration of smaller particles. It was found that in the limit of low surface coverage the numerical results were in a reasonable agreement with the formula stemming from the scaled particle theory with the modifications for the sphere-sphere geometry and electrostatic interaction. The results indicate that large particle-substrate attractive interaction significantly reduces the kinetic barrier to the large, charged particle adsorption at a surface precovered with small, likely charged particles.

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Irreversible adsorption of colloids and proteins at heterogeneous surfaces

Adamczyk Z., Weroński P., Musiał E.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 2

175-187

EN

Irreversible adsorption of colloid particles at heterogeneous surfaces was studied theoretically. In contrast to previous models, the dimension of the adsorption sites having the shape of circular discs, was comparable with the size of adsorbing spheres. Adsorption was assumed to occur if the sphere contacted the disc only. Numerical simulation of the Monte-Carlo type enabled one to determine particle flux, adsorption kinetics and jamming coverage as a function of the site density (coverage) and the size ratio particle/site, denoted by lambda . It was demonstrated that adsorption kinetics and the jamming coverage increased significantly, at a fixed site density, when lambda increased, i.e., for larger particle to site size ratio. It was also proven that the results derived from previous model elaborated for negligible site dimensions are valid only if lambda > 10.

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Colloid adsorption at heterogeneous surfaces

Adamczyk Z., Siwek B., Jachimska B., Kowal A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 3

347-357

EN

Irreversible adsorption of colloid particles at heterogeneous surfaces was studied experimentally. The substrate of controlled heterogeneity was produced by covering mica sheets by colloid iron oxide (hematite) particles to a desired concentration. The particles of averaged diameter of 70 nm were produced by forced hydrolysis of FeCls solutions followed by a hydrothermal ageing. The coverage of colloid hematite particles (heterogeneity degree) was determined by electron microscopy and atomic force microscopy (AFM). Adsorption kinetics of polystyrene latex (averaged diameter 0.87Mim) at heterogeneous surfaces was studied by using the direct optical microscope observations in the impinging-jet cell. It was demonstrated that the initial adsorption rate attained the limiting value pertinent to homogeneous surfaces for heterogeneity degree of a few per cent. This behaviour was quantitatively interpreted in terms of the theoretical model considering the coupling between surface and bulk transport of particles. Similarly, the experimental results obtained for higher surface coverage of latex (long adsorption times) were in a good agreement with the random sequential adsorption (RSA) model.

6

On the advantages of using prehydrolysed aluminum coagulants

Rak M., Świderska-Bróż M.

Environment Protection Engineering

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2001

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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.

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Electrostatic interactions of colloid particles in mixed electrolytes

Warszyński P., Adamczyk Z.

Bulletin of the Polish Academy of Sciences. Chemistry

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2001

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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.

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Colloid silica viscosity determined by the particle sedimentation method

Adamczyk Z., Siwek B., Zembala M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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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.