Sulphur extractants

Fig. 9.6 Interference by elemental sulphur. Extract of sewage sludge sample treated with 7% fuming sulphuric acid(a) and also treated with cyanide (b).

Abstract The sodium sulphide-induced collectorless flotation of several minerals are first introduced in this chapter. The results obtained are that sodium sulphide-induced collectorless flotation of sulphide minerals is strong for pyrite while galena, jamesonite and chalcopyrite have no sodium sulphide-induced collectorless flotability. And the nature of hydrophobic entity is then determined through J h-pH diagram and cyclic voltammogram, which is element sulphur. It is further proved widi the results of surface analysis and sulphur-extract. In the end, the self-induced and sodium sulphide-induced collectorless flotations are compared. And it is found that the order is just reverse in sodium sulphide-induced flotation to the one in self-induced collectorless flotation. 

Figure 3.11 Effects of HS" concentration on the adsorption, the amount of neutral sulphur extracted fiom pyrite surface and collectorless flotation of pyrite at pH = 11.0 (Sun et al., 1993a)...

A factory in which soda ash is made is called an alkali works. A works using the Leblanc process is divided into several departments (1) The acid works where sulphuric acid is made (2) Salt-cake works (3) Black-ash works and lixiviation (4) White-ash (soda ash) works or caustic soda works (5) Bleaching powder works where the hydrogen chloride from the salt-cake works is converted into chlorine, and the latter converted into bleaching powder and (6) Sulphur extraction from tank-waste. The following is a diagrammatic representation of the Leblanc process ... 

The flame from the burner must be moderate, otherwise the sulphur (extract) will be scorched and lose its efficacy. This is shown by a dark rim in the distilling flask (bulb). 

Extraction with Organic solvents Extraction with carbon Sulphur extraction Desorbate treatment by... 

Extraction with Organic solvents Caustic soda solution Supercritical gases Exiiaetion with earbon disulfide or other solvents Percolation with eaustie soda e.g. extraction with supercritical CO2 Sulphur extraction Sulfosorbon process Phenol-loads activated earbon Organic compounds Desorbate treatment by distillation, steam desorption of solvent Phenol separation with subsequent purging S aration of C02/or-ganic compounds... 

In the next step (1993) we concentrated on mixed nitrogen/sulphur extractants (aliphatic shift bases) which had two nitrogen and two sulphur donor atoms in the molecule. But also with these compounds no tendency was found to distinguish between for instance Am (III) and Eu (III). 

Toxic substances sometimes handled In OCS operations include hydrogen sulfide (H2S), chlorine (CI2), and ammonia (NH3). The following are examples of facilities other than oil, gas, and sulphur extraction facilities to which this recommended practice also may be applicable ... 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

Edeleanu process An extraction process utilizing liquid sulphur dioxide for the removal of aromatic hydrocarbons and polar molecules from petroleum fractions. 

Beryllium is added to copper to produce an alloy with greatly increased wear resistance it is used for current-carrying springs and non-sparking safety tools. It is also used as a neutron moderator and reflector in nuclear reactors. Much magnesium is used to prepare light nieial allo>s. other uses include the extraction of titanium (p. 370) and in the removal of oxygen and sulphur from steels calcium finds a similar use. 

Carbon disulphide is an excellent solvent for fats, oils, rubber, sulphur, bromine and iodine, and is used industrially as a solvent for extraction. It is also used in the production of viscose silk, when added to wood cellulose impregnated with sodium hydroxide solution, a viscous solution of cellulose xanthate is formed, and this can be extruded through a fine nozzle into acid, which decomposes the xanthate to give a glossy thread of cellulose. 

In America, the sulphur deposits (mostly in Louisiana and Texas) are dome-shaped layers about 30 cm thick, between limestone above and anhydrite below. From these, the sulphur is extracted by the Frasch process. A metal tube, about 15 cm diameter and containing two concentric inner tubes (Figure 10.1) is sunk into the top of the deposit. Water, superheated to 450 K, is forced... 

This reaction is also used on a large scale, to obtain iodine from seaweed. The ash from burnt seaweed ( kelp ) is extracted with water, concentrated, and the salts other than iodides (sulphates and chlorides) crystallise out. The more soluble iodides remain and the liquor is mixed with sulphuric acid and manganese dioxide added the evolved iodine distils off and is condensed. 

Addition of an oxidising agent to a solution of an iodide (for example concentrated sulphuric acid, hydrogen peroxide, potassium dichromate) yields iodine the iodine can be recognised by extracting the solution with carbon tetrachloride which gives a purple solution of iodine. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

It occurs chiefly as cinnabar, the red sulphide HgS, from which it is readily extracted either by roasting (to give the metal and sulphur dioxide) or by heating with calcium oxide the metal distils off and can be purified by vacuum distillation. 

Add cautiously 15 ml. of concentrated sulphuric acid to 50 ml. of water in a 100 ml. distilling-flask, and then add 10 g. of pinacol hydrate. Distil the solution slowly. When about 40 ml. of distillate (consisting of pinacolone and water) have been collected, and no more pinacolone comes over, extract the distillate with ether. Dry the extract over sodium sulphate. Distil the dry filtered extract carefully, with the normal precautions for ether distillation (p. 164). When the ether has been removed, continue the distillation slowly, rejecting any fraction coming over below 100 . Collect the pinacolone, b.p. 106 , as a colourless liquid having a peppermint odour. Yield, 4 5-5 o g. A small quantity of higher-boiling material remains in the flask. 

Place the distillate in a separating-funnel and extract the benzonitrile twice, using about 30 ml. of ether for each extraction. Return the united ethereal extracts to the funnel and shake with 10% sodium hydroxide solution to eliminate traces of phenol formed by decomposition of the benzenediazonium chloride. Then run off the lower aqueous layer, and shake the ethereal solution with about an equal volume of dilute sulphuric acid to remove traces of foul-smelling phenyl isocyanide (CaHjNC) which are always present. Finally separate the sulphuric acid as completely as possible, and shake the ether with water to ensure absence of acid. Run off the water and dry the benzonitrile solution over granular calcium chloride for about 20 minutes. 

Now grind up the mixture of solution and glass in the mortar to ensure extraction of the sodium salts, and then filter. Divide the filtrate into three portions, reserving two portions for testing for halogens and sulphur. 

This type of extraction depends upon the use of a reagent which reacts chemically with the compound to be extracted, and is generally employed either to remove small amounts of impurities in an organic compound or to separate the components of a mixture. Examples of such reagents include dilute (5 per cent.) aqueous sodium or potassium hydroxide solution, 5 or 10 per cent, sodium carbonate solution, saturated sodium bicarbonate solution (ca. 5 per cent.), dilute hydrochloric or sulphuric acid, and concentrated sulphuric acid. 

Dilute hydrochloric or sulphuric acid finds application in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base e.g., ammonia, amines, etc.) into a water-soluble salt e.g., ammonium chloride, amine hydrochloride). Thus traces of aniline may be separated from impure acetanilide by shaking with dilute hydrochloric acid the aniline is converted into the soluble salt (aniline hydrochloride) whilst the acetanilide remains unaffected. 

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