Colour removal, activated carbon

The raw material has to be washed to remove impurities. Diluted sodium hydroxide allows the removal of phenols and benzonitrile, and diluted sulphuric acid reacts with pyridine bases. The resulting material is distilled to concentrate the unsaturated compounds (raw feedstock for coumarone-indene resin production), and separate and recover interesting non-polymerizable compounds (naphthalene, benzene, toluene, xylenes). Once the unsaturated compounds are distilled, they are treated with small amounts of sulphuric acid to improve their colour activated carbons or clays can be also used. The resulting material is subjected to polymerization. It is important to avoid long storage time of the feedstock because oxidation processes can easily occur, affecting the polymerization reaction and the colour of the coumarone-indene resins. 

Again, there are several choices of extractant, and the preferred one depends mainly on the type of soil under test. One of the most widely used procedures is the Olsen method (Olsen ef al., 1954), which was developed in the USA to correlate crop response to fertilizer on calcareous soils. The amount of P extracted will vary with temperature (increases by 0.43 mg P kg- per degree rise between 20°C and 30°C) and shaking speed, so conditions should be standardized. The extractant is 0.5 M sodium bicarbonate adjusted to pH 8.5. The bicarbonate competes with phosphate on the adsorption sites extracts, and removes most, but not all of it, together with some soluble calcium phosphate. Addition of phosphate-free activated carbon before shaking is necessary if coloured soil extracts are obtained, and then they will require filtration. 

Treating milk fat with adsorbents (e.g., carbon, activated carbon, carbon impregnated with metal salts, porous glass, impregnated or chemically-bonded porous glass) can reduce the cholesterol content of milk fat (Keen, 1991). These adsorbents also remove colours and flavors, but these may be added back into the butterfat. 

These pollutants are not removed by conventional methods of water treatment. The chlorination and the ozonization also is not always effective because is accompa-ined by formation of secondary compaunds, frequently harmful. Even the low concentration of these substances also influences organoleptic properties (taste, colour, odour) of water negatively and it is toxic and carcinogenic for human organisms. It was stated, that the removal of these substances from water may be achieved by means of adsorption on activated carbons [9—11 ]. 

The most common method for purifying ILs involves the use of sorbents such as activated carbon, silica and alumina. These sorbents are especially useful for the removal of coloured impurities. Many different methods for the use of sorbents have appeared in the literature, below are three popular examples ... 

How does activated carbon help in removing the dirty colour of the product during the process of recrystallization ... 

Active carbon filter for removal of organics, odours, colouration etc. 

Another, similar, application of activated carbons is in the treatment of edible oils and fats to remove undesirable components. Here, they are used in conjunction with certain bleaching clays. Activated carbon are also used in treating wines and spirits to remove any traces of fusel oil. In the production of brandies, they are used to remove undesirable flavours and to reduce the amount of aldehydes in the raw distillate. In the case of beers, activated carbons are used to improve their colour, and to remove flavours attributed to phenol and colouring matter. 

Carbonaceous materials have long been known to provide adsorptive properties. The earliest applications may date back centuries with the discovery that charred materials could be used to remove tastes, colours and odours from water. Now activated carbons are used widely in industrial applications which include decolourizing sugar solutions,... 

Bacteria and viruses may be eliminated from water by ultraflltration membrane separations, or just bacteria by using microflltration. On the small, local scale membrane Alter units are ideal for treating drinking water, especially if coupled with an activated carbon element to remove colour and unpleasant taste. 

Olsen s extractant has a minor disadvantage it tends to dissolve organic matter resulting in coloured extracts which interferes in colorimetric estimation. Thus activated charcoal is used with the soils to adsorb soluble organic matter. The charcoal must be phosphate free totally. Also carbon dioxide bubbles are formed during colour development which must be completely removed by allowing time or else the COg bubbles interfere with colorimetry. 

Much of the colour produced during sulphonation is contained in the spent acid. The upper layer in the separator, which contains around 90% alkylbenzene sulphonic acid (the remainder being primarily dissolved sulphuric acid) is also removed from the separator and neutralised with sodium hydroxide solution or with sodium carbonate solution to yield the active paste. When sodium hydroxide is used a considerable amount of heat must be removed. This is done in the third loop reactor of this process, the neutralisation heat exchanger (also known as the neutraliser). If sodium carbonate solution is used, the neutralisation is much less exothermic and no heat exchanger is needed at this stage. 

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