Liquid filtration carbon treatment

With powder activated earbon, in most cases, the carbon is dosed into the liquid, mixed and then removed by a filtration process. In some cases, two or more mixing steps are used to optimise the use of powder carbon. Powder activated carbon is used in a wide range of liquid phase applications and some specific gas phase applications such as Incinerator flue gas treatment and where it is bonded into filters sueh as fabrics for personnel protection. 

Potable Water Treatment. Treatment of drinking water accounts for about 24% of the total activated carbon used in liquid-phase applications (74). Rivers, lakes, and groundwater from wells, the most common drinking water sources, are often contaminated with bacteria, viruses, natural vegetation decay products, halogenated materials, and volatile organic compounds. Normal water disinfection and filtration treatment steps remove or destroy the bulk of these materials (75). However, treatment by activated carbon is an important additional step in many plants to remove toxic and other organic materials (76—78) for safety and palatability. 

Pentathionic Acid, HaS508.—This is present in Wackenroder s solution 1 (p. 220), and can be separated by removing the sulphuric acid by treatment with a little barium carbonate, the remaining acid liquid after filtration being capable of concentration to a specific gravity of 1-3 by evaporation on a water-bath and to 1-6 by evaporation in a vacuum at the ordinary temperature.2 The solution contains also tetrathionic acid, which may be eliminated by the method described on p. 219. 

Isopropoxydimethylsilyl)methyl chloride2 is readily prepared from (chlorodimethylsilyl)methyl chloride by treatment with isopropyl alcohol (1.1 equiv) and triethylamine (1.1 equiv) in diethyl ether at room temperature (0.5 hr) and then at reflux temperature (0.5 hr). After filtration of the white salt, the filtrate is washed successively once with water, twice with 0.1 N hydrochloric acid, once with an aqueous 10% solution of sodium hydrogen carbonate and once with water, then dried over sodium sulfate. Filtration and distillation give the product in 80% yield, bp 65-67°C/50 mm, as an air-stable, colorless liquid. The checkers used commercially available material purchased from Aldrich Chemical Company, Inc. 

Selenic Acid.—Selenic Acid, H2Se04, is also a il colourless syrupy liquid it can be produced by direct oxidation of selenium by chlorine water, but on concentra-I tion the resulting hydrochloric acid reduces the selenic acid I to selenious acid, as hydriodic acid reduces sulphuric acid. It is best prepared by addition of copper carbonate to the mixture of selenic and hydrochloric acids obtained in that way selenate and chloride of copper are formed the 1 mixture is evaporated to dryness, and the copper chloride is dissolved out with alcohol, leaving the insoluble selenate 1 behind. The selenate is dissolved in water, and on treatment with sulphuretted hydrogen, copper sulphide is precipitated, and removed by filtration the selenic acid is then concentrated if it contains a trace of water, it is a heavy liquid 5 but if quite anhydrous, it forms a solid, melting at 58°. 

In order to avoid these extremely dangerous phenomena, methods of treatment of PO with adsorbents (active carbon, charcoal, attapulgite, diatomaceous earth) were devised. By the treatment at room temperature of PO with these adsorbents (0.1-1% adsorbent in liquid PO), after a short contact time of about 15 minutes the high MW polyether is almost quantitatively retained by adsorption. The PO resulting after the filtration of the solid adsorbent is practically free of high MW polymers, and the polyethers obtained with the treated PO can be used to manufacture resilient flexible foams which will not collapse, with high rise and free of blow hole formation. 

Features to be considered in the selection of carbon to be used are discussed in Chapters 7, 13—15, but at this time we should call attention to the distinction between the roles of powdered and granular carbons. Powdered carbons are applied in a so-called batch-contact treatment in this, measured amounts of carbon and the substance to be treated are mixed and subsequently separated by filtration. With granular carbons, the gas or liquid to be purified is passed continuously through a bed of carbon. Formerly, granular carbons were used primarily in vapor-phase adsorption, but in recent years the use has been extended to liquid-phase applications. 

The quantity of carbon to be added varies from 2-50 pounds per 1,000 gallons. Generally, the carbon is made into a thin slurry which is added to the wine in the treatment tank. The mixing should be gentle to avoid aeration. After several hours of contact, a clarifier, such as gelatin or bentonite, can be added and when the solids have settled, the liquid is filtered. An alternative method is to filter immediately after treatment, in which case, double filtration should be provided. 

The treatment of liquids with higli flow rates and/or high concentrations of contaminants requires a frequent replacement of carbon adsorbent. In such cases pulsed (Fig. 5.) or moving bed systems are installed. In this technological solution the purified water enters the filtration column from the bottom and flows upward. At the same time, GAC is dosed downward from the top and it is removed continuously or in pulses at the bottom of the filtration column. Thus, the filter with moving or pulsed bed can be maintained with no downtimes. 

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