Equilibrium deposition filtration

An alternative method used for preparing supported catalysts is the Equilibrium Deposition Filtration (EDF) technique, otherwise called equilibrium adsorption. Following this technique the support is immersed in a large volume of a dilute aqueous solution of the TMIS, ideally at fixed pH and ionic strength. Equilibration of the suspension follows for several hours under stirring. During equilibration the TMIS are deposited at the interface developed between the support surface and the aqueous solution. We call this mode of deposition interfacial deposition. In the filtration step the interfacially deposited TMIS are practically separated from the non-deposited ones. 

In contrast, employing equilibrium deposition-filtration or homogeneous deposition-precipitation the deposition takes place during the equilibration step (Figure 2.1) inside the interface developed between the surface of the support particles and the impregnating solution. This results in relatively small supported nanoparticles. The small size of the supported nanoparticles is largely imposed by the relatively small size of the interface (Figure 2.3). 

Preparation of Supported Catalysts by Equilibrium Deposition - Filtration A. Lycourghiotis... 

The subject of the present lecture is the preparation of supported catalysts using the method of Equilibrium Deposition - Filtration for which we propose the term EOF. We propose the following structure for the lecture ... 

Deposition of active elements on industrial supports using Equilibrium Deposition-Filtration (EDF)... 

The general conclusion that may be drawn from the previous results is that Equilibrium Deposition - Filtration is a simple and attractive method for preparing supported catalysts with relatively high active surface and quite good physicochemical and catalytic properties. 

The hydrodynamic forces acting on the suspended colloids determine the rate of cake buildup and therefore the fluid loss rate. A simple model has been proposed in literature [907] that predicts a power law relationship between the filtration rate and the shear stress at the cake surface. The model shows that the cake formed will be inhomogeneous with smaller and smaller particles being deposited as the filtration proceeds. An equilibrium cake thickness is achieved when no particles small enough to be deposited are available in the suspension. The cake thickness as a function of time can be computed from the model. 

As indicated above, there is a relationship between particle concentration, equilibrium factor and the amount of highly mobile radioactive particles. Removal of the accumulation mode particles may decrease the decay product exposure, but increase the dose because of the high effectiveness of the "unattached activity in dose deposition. Thus, air cleaning may not succeed in lower risk unless both factors are taken into account. Jonassen explores electrostatic filtration in this context. Finally, design considerations are presented for a possible alternative control system using activated carbon in an alternating bed system. 

The effect of a given process such as plateout, filtration or field deposition on the PAEC is, however, better expressed by the ratio of the PAEC at a process level, r, to the PAEC at a process level of r =0. This quantity, which like the equilibrium factor is independent of the radon concentration, can adequately be named the ERF (energy- (or exposure) reduction factor)... 

After equilibrium, filtration, and pH adjustment, the residual calcium ion concentration was then titrated by EDTA solution. A higher residual calcium ion concentration indicates better inhibition activity and, therefore, more effectiveness in controlling calcium carbonate deposition in the treated water. As shown in Table III, at dosages of 1 to 5 ppm, the polyacrylic acid was more effective than the acrylic acid/N-(hydroxyalkyl)-acrylamide copolymers. 

The addition of proteolytic enzymes to the beer gives an unquestioned result from the point of view of stability, but (he mechanism of the action is yet to be elucidated. Beers, treated or not treated, have after filtration practically the same nitrogen content moreover, the deposits contain only an insignificant trace of nitrogen. We may then say that the albuminoid substance does not intervene directly in the formation of turbidity, as is often believed. It is probable that the peptonization produced by the enzyme added serves to kc ei) in equilibrium certain organic and inorganic substances, which under ordinary conditions are precipitated. 

The bracketed term in Equation (2.32) contains only constants in the case of incompressible filtration, and the medium resistance term includes a contribution to the flow resistance due to the layers of cake deposited prior to increasing the filtration pressure. Some time should be allowed before judging the parallel nature of the lines shown on Figures 2.12, to allow for equilibrium to be established. 

The efforts that can be made to restrict the amount of flux decline, i.e. to establish an equilibrium flux rate, can be split into two categories, dependent largely on the scale of operation stirred cells and crossflow filtration. The former is of use in the laboratory for small-scale separations, the latter is more appropriate for process applications. Both stirring and crossflow enq>loy the same princ le hi ear at the sur ce of the deport. Further techniques to restrict deposit thickness, minimise fouling or regenerate flux are discussed in Section. 10.7. All the main membrane arrangements are illustrated in Figure 10.4. 

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