Leach liquors chloride

Rice, N. M. Gibson, R. W. Solvent extraction with Cyanex 301 and 302 for the upgrading of chloride leach liquors from lateritic nickel ores. Value Adding through Solvent Extraction, [Papers presented at ISEC 96], Melbourne, Mar. 19-23, 1996, 1, 715-720. 

Nickel and Cobalt. Often present with copper in sulfuric acid leach liquors are nickel and cobalt. In the case of chloride leach liquors, separation of cohall front nickel is inherently simpler because cobalt, unlike nickel, has a strong tendency to form anionic chlnro-complcxes. Thus coball can be separated by amine extractants, provided the chloride content of the aqueous phase is carefully controlled. A successful example of this approach is the Falconhridge process developed in Norway. 

Copper Recovery from Chloride Leach Liquors.155... 

In a process variant (Enhanced Acid Regeneration System EARS process), the ilmenite is roasted to convert the titanium component into the insoluble rutile form and to condition the iron component for leaching. The product is then rapidly leached at atmospheric pressure in hydrochloric acid to remove the iron, leaving rutile crystals in the former ilmenite grain. This synthetic rutile (typically 96-98% Ti02) is then washed, filtered, and calcined. The iron chloride leach liquors are processed to regenerate the acid, and the iron oxide pellets can be sold for use by the steel or cement industries. 

The chlorides of most metals have a very good water solubility, though there are exceptions in the case of some metals. A typical example of the latter is silver which can be very efficiently separated by forming insoluble silver chlorides. Although, the separation of silver as the chloride is rarely used as a method for bulk precipitation, it is certainly useful for the removal of relatively small amounts of the metal when present as a minor constituent In the case of cuprous and cupric chlorides, the former has a low solubility in water hence, if the leach liquor contains cupric chloride, a suitable reducing agent such as sulfur dioxide can be introduced to convert cupric chloride to cuprous chloride so that precipitation occurs. 

The separation of impurities such as calcium, barium and radium can be effected by the precipitation of their sulfates. In the case of sulfuric acid leaching of uraninite ore, the leach liquor contains radium which is removed if barium chloride is added since barium sulfate acts as a carrier for radium sulfate. 

Vanadium usually is recovered from its ores by one of two processes, (1) leaching raw mineral with hot dilute sulfuric acid, and (2) roasting ore with common salt to convert vanadium into water soluble sodium vanadates. In the sulfuric acid leaching process, vanadium is extracted from acid leach liquors by solvent extraction with an aliphatic amine or an alkyl phosphoric acid in kerosene. The organic solvent extract then is treated with an aqueous solution of ammonia in the presence of ammonium chloride to convert vanadium into ammonium metavanadate. Alternatively, the organic extract is treated with dilute sulfuric acid or an aqueous solution of soda ash under controlled conditions of pH. Vanadium is precipitated from this solution as a red cake of sodium polyvanadate. 

Amine salts represent the only commercially important class of extractants of the anion-exchange type. Their most widespread use is in the extraction of uranium from sulfate leach liquors, but they have found application in the recovery of cobalt, zinc and copper from chloride solutions, as well as in the extraction of metals that readily form oxyanions, such as vanadium, molybdenum and tungsten. 

Molybdenum can also be recovered economically from some uranium leach liquors, particularly those of the USA. When uranium is stripped from amine extractants by solutions of sodium chloride, any molybdenum present remains in the organic phase, and can be subsequently recovered by being stripped into a solution of sodium carbonate. A process has been operated in which the strip liquor is acidified to a pH value of 4.5 and the molybdenum is reextracted into a solution of quaternary amine chloride in kerosene.218 The extracted metal is stripped into a solution containing sodium hydroxide and sodium chloride to produce liquors containing 30-40 g of molybdenum per litre, from which calcium molybdate can be precipitated by the addition of calcium chloride. 

The mineral boronatrocalcite i. e. double borate of sodium and oaloium Na20. 2 CaO. 5 B203.16 H20, is found mainly in Chile and Peru. It is decomposed with diluted hydroohloric acid in wooden vats and boric acid is obtained by crystallizing from dear leach liquor. In a similar way is also treated the mineral boraroite whioh is mainly magnesium borate and chloride MgCl2. 

Under certain conditions, there are definite advantages in using hydrochloric, nitric, or other acids to carry out a dissolution step. In their evaluation of proposed processes for the recovery of alumina, Peters ei al. (P8) cited earlier experimental work which showed that both hydrochloric and sulfuric acid are equally good in extracting alumina from calcined clay (TIO). In the separation of the leach liquor from the silica residue by filtration, the chloride solution rapidly separated, while the sulfate solution did not separate easily. In addition to ease of filtration, the hydrochloric acid leach also made the later removal of iron easier. The insolubility of titanium dioxide in hydrochloric acid also eliminated another separation problem. Under this particular situation, hydrochloric acid was the natural choice. As in most large leaching operations, the acid would be recovered and recycled. 

In the various solvent-extraction circuits employed in this process, use is made of a solution of D2EHPA in kerosene as the extractant. The selective recovery of the various metals is achieved by careful control of the equiUbrium pH value of the aqueous phases in the multistage extraction and stripping operations. After the leach liquor has passed through two separate circuits, each of which comprises five stages of extraction and four of stripping, the europium product is obtained initially as a solution of europium(III) chloride. Further purification of the product is accomplished by reduction with amalgamated zinc to Eu +, which is by far the most stable of the divalent lanthanide ions with respect to the reduction of water cf. the redox potentials of the Eu /Eu and Sm /Sm + couples, which are —0.43 and —1.55 V respectively ). Sulfuric acid is added to the... 

In the ion exchange process the leach liquor is passed through a bed of anion exchange resin beads which are loaded with chloride or in some cases nitrate. The resin will normally be a polymer carrying quaternary amine functions and having the generalized formula Pol(NR3)x+Cl, where Pol represents a polymer chain such as styrene-divinylbenzene copolymer, R = alkyl and... 

The Goro process (Figure 5.14) developed by INCO (now CVRD-lnco) for the treatment of a nickel laterite deposit in New Caledonia (Bacon and Mihaylov 2002 Mihaylov et al. 2000 Mihaylov et al. 1995) also treats the laterite leach liquor directly but uses a completely different approach. The flow sheet involves the coextraction of nickel and cobalt by SX with the sulfnr-snbstitnted organophosphinic acid, CYANEX 301, followed by their separation in chloride medinm by SX using an amine extract. 

The leach liquors are then poured through ion-exchanger beds or columns. The resins employed for these processes are typically of the sulfonate variety. Uranium is removed from the resin by elution with solutions containing high concentrations of chloride or nitrate ions after which the uranium is recovered by precipitation through addition of ammonia. 

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