Filtration, contact

Sodium silicate solution [1344-09-8] pKj 9.51, pKj 11.77 (for silicic acid, H4Si04) Purified by contact filtration with activated charcoal. 

Solvent-refined and dewaxed lube oil stocks can be further refined by clay or acid treatment to remove color-forming and other undesirable materials. Continuous contact filtration, in which an oil-clay slurry is heated and the oil removed by vacuum filtration, is the most widely used... 

Water treatment by either direct or contact filtration has become common practice for raw water with low turbidity [<3NTU] and low colour. Simple metal salts such as alum or ferric chloride are added to plant inlet water. Hydrolysis takes place with the formation of hydroxylated species, which adsorb, reducing or neutralizing the charge on the colloidal particles in the raw water, promoting their collision and the formation of floes that settle or can be filtered out. 

Fig. 10.8 Flow diagram for the single-stage contact filtration unit.

Adsorption can be carried out by stagewise or continuous-contacting methods. The stagewise operation of adsorption is called contact filtration because the liquid and the solid are contacted in a mixer and then the solid is separated from the solution by filtration. 

Single-Stage Adsorption Contact filtration can be carried out as a single-stage operation (Figure 10.8) either in a batch or a continuous mode. If we assume that the amount of liquid retained with the solid is negligible, the material balance for a solute gives... 

The total amount of adsorbent is 6.7g which is significantly less than what was calculated for single-stage contact filtration. It should be noted that the minimum amount of adsorbent usage is realized when a larger amount of the adsorbent is fed to the first stage followed by the smaller amount to the second stage. 

Contact filtration a process in which finely divided adsorbent clay is used to remove color bodies from petroleum products. 

Continuous contact filtration a process to finish lubricants, waxes, or special oils after acid treating, solvent extraction, or distillation. 

Purified by contact filtration with activated charcoal. 

Iron Fe+2 (ferrous) Fe+3 (ferric) Discolors water on precipitation source of deposits in water lines, boilers, etc. interferes with dyeing, tanning, paper mfr., etc. Aeration, coagulation and filtration, lime softening, cation exchange, contact filtration, surface active agents for iron retention... 

FIGURE 15.12 Batch contact filtration. Schematic arrangement for single-stage batch sorption, (a) Agitated batch contacting tank (b) filter press (c) filtrate storage tank. 

Liquid solutions, where the solute to be removed is adsorbed relatively strongly compared with the remainder of the solution, are treated in batch, semicontinuous, or continuous operations in a maimer analogous to the mixer-settler operations of liquid extraction (contact filtration). Continuous countercurrent cascades can be simulated or actually realized by use of such techniques as fluidized beds. 

A solution of washed, raw cane sugar, 48% sucrose by weight, is colored by the presence of small quantities of impurities. It is to be decolorized at 80 C by treatment with an adsorptive carbon in a contact filtration plant. The data for an equihbrium adsorption isotherm were obtained by adding various amounts of the carbon to separate batches of the original solution and observing the equilibrium color reached in each case. The data, with the quanti of carbon caressed on the basis of the sugar content of the solution, are as follows ... 

Prove that for crosscurrent two-stage treatment of liquid solutions by contact filtration, when the adsorption isotherm is linear, the least total adsorbent results if the amounts used in each stage are equal. 

Aeration coagulation and filtration lime softening cation exchange contact filtration surface-active agents for iron retention... 

Figure 10-14 illustrates the general process of contact filtration, and Fig. 10-15 shows the use of a rotary-type filter. In Fig. 10-14 the naphtha is introduced after contacting, but some refiners add naphtha before the acid treatment. 

Fig. 10-15. Arrangement of equipment for the Oliver precoat method of contact filtration. Oliver United Filters, Inc.)...

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