Wet processes for the extraction of nickel from its ores

Wet processes are used in some cases to extract nickel from speiss and matte containing nickel, cobalt, and copper; but whilst several methods have been suggested for extracting nickel directly from its ores, none seems to have been established as an economic success. It is cheaper to concentrate the nickel to a speiss or matte in the dry way, and particularly so with sulphide and arsenide ores. When a sulphide or arsenide ore is to be treated by a wet process, it is roasted before being submitted to the action of solvents. H. C. Mabee and A. E. Smaill proposed to smelt the nickeliferous pyrrhotitic ore with an alkali flux under non-oxidizing conditions to obtain a low- grade matte containing all the copper, nickel, and precious metals. This matte, on exposure to the air, disintegrates into a fine powder, which is roasted in a two- stage mechanically-rabbled furnace, in the first stage of which the temperature is maintained at 400° and in the second stage at 600°. The product is mixed with 10 per cent, of its weight of sodium chloride, damped with water, and again roasted at 400°, the issuing vapours being absorbed in water. This water is then used to leach the roasted product, and leaching is continued with 10 per cent, sulphuric acid. The residue contains practically all the iron and the greater part of the nickel, but only a small proportion of copper and sulphur, and is amenable to direct smelting for the production of nickel steel. The leach liquor is electrolysed for the recovery of copper, then treated for the removal of iron, and again electrolysed to recover the nickel. Over 90 per cent, of the copper and 40 per cent, of the nickel are said to be obtained as pure metals.

S. H. Emmens suggested dissolving the nickel from pyrrhotite ores by the solvent action of a soln. of ferric sulphate, but the solvent action is more rapid with the roasted ore. Nickel is precipitated from the soln. as hydrate. In the most favourable cases it was found that only one-third the amount of nickel and two-thirds the amount of copper in the ore are dissolved by the soln. of ferric sulphate. H. L. Herrenschmidt heated the ore with a soln. of ferric chloride, and precipitated cobalt and nickel from the soln. by manganese sulphide or hydroxide. C. W. B. Natusch, and W. Schoneis extracted the roasted ore with a soln. of ferric chloride, evaporated the soln. to dryness, and heated it until the iron chloride was decomposed. On extracting the soln. with water, nickel, cobalt, copper, gold, silver, and zinc chlorides pass into soln. T. Macfarlane subjected the partially roasted ore to a chloridizing roast with common salt, at a low red-heat; and to the extract in hot water added a little sodium hydroxide to precipitate any iron, sodium sulphide to precipitate any copper, and the sodium hydroxide to precipitate the nickel as hydroxide. A. Drouin digested the ore, roasted at a low temp., with an acidified 20 to 25 per cent. soln. of sodium chloride. The lead was precipitated as chloride by cooling the soln., the copper was precipitated by iron, the iron by calcium carbonate, and the nickel by lime-water. P. de P. Ricketts dissolved the nickel and copper with dil. sulphuric acid, and precipitated the nickel as a basic sulphate by alkalies and alkali sulphates. The basic sulphate is converted into oxide by calcination, and the copper is precipitated from the soln. electrolytically. C. G. Richardson dissolved the copper and nickel in hydrochloric acid, and separated the two salts by fractional distillation in hydrochloric acid. H. Grosse- Bohle precipitated the cobalt and nickel from their hot soln. in hydrochloric or sulphuric acid by means of zinc. The copper was first precipitated from the soln. by iron. C. Perron digested the ore in an ammoniacal soln. of ammonium sulphide, and precipitated the nickel from the soln. in the usual manner. The Metals Extraction Corporation extracted the nickel by means of a soln. of magnesium chloride at 250°. D. Lance found that when the soln. in a soln. of ammonia or an amine is heated, the metals are precipitated in the order: Zinc, cadmium, cobalt, nickel, copper, and silver. G. Schreiber treated the soln. with calcium carbonate to precipitate iron, aluminium, and arsenic; with hydrogen sulphide to precipitate copper; with soln. of alkalies or alkaline earths, say milk of lime, to precipitate cobalt and nickel, and lastly manganese. A. Seigle digested the ore with hydrochloric acid, chlorine water, and potassium cyanide. E. Gunther and R. Franke devised a process for extracting nickel from the anode slimes obtained in the refining of copper. E. R. Thews discussed the re-melting and refining of scrap nickel.

Many wet methods have been proposed for extracting the nickel from ores of the type of garnierite, rewdanskite, etc. Methods were described by E. Andre, A. Badoureau, F. R. Bode, B. Bogitch, A. Cahen, J. J. Hissink, F. O. Kichline, H. C. Mabee and A. E. Smaill, W. A. Dixon, R. Lake, and H. Parkes.

R. Hermann dissolved rewdanskite in sulphuric acid, and evaporated the soln. until acid began to vaporize; the mass was then lixiviated with water, the iron in the soln. oxidized with salt and nitre, and then precipitated by calcium carbonate. The nickel was precipitated by sodium sulphide. J. P. Laroche and J. P. Pratt treated garnierite with sulphuric acid; added to the soln. an amount of ammonium sulphate equivalent to the proportion of nickel present to precipitate ammonium nickel sulphate; and added sodium carbonate to the soln. of ammonium nickel sulphate in boiling water to precipitate nickel carbonate. In place of ammonium sulphate, an alkali oxalate can be added to precipitate nickel oxalate, and the oxalate furnishes nickel carbonate when boiled with a soln. of sodium carbonate. G. Rousseau treated the hydrochloric acid soln. with bleaching powder to oxidize the iron, and precipitated the iron with calcium carbonate; then precipitated the nickel with milk of magnesia. I. Kamiensky oxidized the iron in a hydrochloric acid soln. by chlorine, and precipitated it with magnesium carbonate; nickel was precipitated from the decanted soln. by sodium carbonate. M. Araud heated in retorts a paste made of the ore with 'hydrochloric acid so as to volatilize the chlorides which were condensed in water. The iron was precipitated from the soln. by calcium carbonate, and the nickel by milk of lime. M. Sebillot crystallized ammonium nickel sulphate from a sulphuric acid soln. of the ore to which ammonium sulphate had been added. In a second process, the ore was heated with sulphuric acid in a reverberatory furnace; the solid mass was leached with water; iron was precipitated from the soln. by calcium carbonate after oxidation with bleaching powder; magnesium was precipitated by sodium phosphate; and nickel sulphate was crystallized from the mother-liquor. G. Urazoff and M. M. Romanoff treated the washed ore with sulphur dioxide or sulphurous acid as solvent, and obtained good yields with ore having 0.9 to 5.08 per cent, of nickel. A. H. Allen treated the ore with a mixture of sulphuric acid and sodium nitrate; heated the mass to redness; lixiviated with water; precipitated from the soln. the chromium and iron by calcined magnesia, and the nickel by hydrogen sulphide. P. Christofle suggested several processes, (i) The hydrochloric acid soln. of the ore was treated with calcium carbonate or hydroxide to precipitate iron, and with milk of lime to precipitate the nickel; (ii) the ore was heated with a conc. soln. of oxalic acid, the nickel remained undissolved, and the residue reduced for nickel; (iii) a hot, conc. hydrochloric acid soln. of the ore when cold was treated with bleaching powder, and nickel oxalate precipitated by oxalic acid; or the iron and aluminium were precipitated by calcium carbonate, and the nickel by lime water and bleaching powder. H. L. Herrenschmidt treated the ore with a soln. of ferrous sulphate to dissolve manganese, cobalt, and nickel as sulphates whilst ferric oxide remains as a residue. The addition of sodium sulphides precipitates cobalt and nickel as sulphides, and any manganese sulphide in the residue is removed by treatment with a soln. of ferric chloride. The manganese is recovered as calcium manganite. The mixed sulphides of cobalt and nickel are roasted to sulphates, and the cobalt and nickel are separated from the soln. of the sulphates in hot water. In another process, H. L. Herrenschmidt precipitated the iron from the soln. by copper carbonate, and the copper by nickel hydroxide or carbonate, and the remaining soln. of nickel and cobalt sulphate was treated for cobalt and nickel. T. Storer digested the garnierite with a soln. of ferric chloride at 187° in an autoclave; the nickel passes into soln. as chloride, whilst the iron is left as oxide.

Wet methods have been suggested for the treatment of the nickel copper mattes. The matte is soluble in acids. With unroasted mattes, some copper sulphide contaminated with cobalt and nickel remains as a residue whilst the iron and most of nickel and cobalt pass into soln. The residue thus requires another special treatment for these two metals. It is therefore preferable to roast the matte before it is treated with acids - sulphuric or hydrochloric acid. With a successful roasting very little iron dissolves in either acid. Any arsenic present remains in the residue as ferric or copper arsenate. The treatment of the matte was described by C. Schnabel, H. Lundberg, A. Badoureau, L. Knab, and J. de Coppet; of speiss, by C. Schnabel, A. Badoureau, W. A. Dixon, and J. A. Phillips; and of slags, by C. Schnabel, M. Herter, and H. H. Vivian. T. Tatebe reduced the garnierite ore with carbon monoxide and hydrogen at 800° to 850°, and leached the product concurrently with aq. ammonia and a soln. of ammonium carbonate in air or oxygen. The nickel dissolved as NiCO₃(NH₃)_n. Calcination of the solid furnishes ammonia, carbon dioxide, and nickel oxide.

The older chemists obtained their nickel from copper-nickel-cobalt speiss which was usually " opened up " by roasting it at a gentle heat to prevent caking, and to volatilize the greater portion of the arsenic. Since some of the arsenic formed a nickel arsenate during the roasting, it was found advisable to mix the roasted ore with charcoal and roast the mixture. The operation was repeated as long as the vapour of arsenic was evolved. O. L. Erdmann recommended keeping the roasted speiss moist in a cellar until it is hydrated, when it is more quickly attacked by the acid. A. Laugier, R. Tupputi, W. F. Wackenroder, P. Berthier, E. F. Anthon, J. Berzelius, and O. L. Erdmann dissolved the roasted speiss in nitric acid, or in aqua regia; J. Berzelius, O. L. Erdmann, and S. Cloez dissolved the roasted speiss in hydrochloric acid; A. Patera, O. L. Erdmann, R. Hermann, J. L. Proust, and T. Thomson used sulphuric acid. J. von Liebig heated the roasted speiss with 1 part of fluorspar and 3.5 parts of sulphuric acid above 100°; F. Wohler fused the unroasted speiss with 3 parts of potassium carbonate and 3 parts of sulphur, and extracted the product with water. S. F. Hermstadt fused the speiss with 3 parts of nitre; P. Berthier used 1 part of speiss with 1.6 parts of nitre and 2 parts of potassium carbonate; and R. Wagner, 5 per cent, of sodium nitrate and 10 per cent, of anhydrous sodium carbonate. C. R. Hayward described a process involving an oxidation roasting followed by leaching, etc.; A. B. Baghdasarain, and F. L. Duffield, a process involving a chloridizing roast of the sulphides, or oxides; P. Louyet described a process in use at a works in Birmingham in which the material was fused with chalk and calcium fluoride, and the resulting regulus roasted and taken up with hydrochloric acid. L. Thompson also used a somewhat similar process, and he dissolved the regulus in sulphuric acid. P. Berthier opened up the unroasted speiss by fusing it with 2 parts of lead oxide, and dissolving the product in nitric acid or in aqua regia. M. I. Gutman and A. D. Mayantz studied the precipitation of nickel hydroxide by magnesia or magnesium carbonate.