DE2733727A1 - Leaching sulphide cpds. - under oxidising conditions and by adding nitrogen mon:oxide and/or di:oxide - Google Patents

Abstract

Leaching of metals and metal compds. in water or aq. soln. under oxidising conditions is carried out in the presence of NO and/or NO2. NO or NO2 is used either alone or together with a carrier gas, or in the form of a cpd. Used for leaching metal sulphides, sulphide ores, Cu cpds. including anode sludge of Cu electrolysis, alloys, intermediate- and by-prods. of metallurgical processes. The method does not require the use of an autoclave and high pressure in order to obtain a rapid reaction between the components. It is partic. applied to extn. of metals from e.g. Cu sulphide, Zn sulphide concentrates, As sulphide deposits, NiS, CoS, ZnS, sludges, slags, sublimates, partic. anode sludge contg. Se, Ag, Te, Bi, Au, Pt, Pd, Pb, apart from Cu.

Description

Leaching process

Oxidative leaching processes that involve soluble metal compounds by simple extraction from hard-to-separate metal compounds, ores or sludges can be isolated are because of the slow reaction rate at the oxidative leaching of the metal or the metal compound can only be used to a limited extent, since the diffusion resp.

Dissolution rate of the gas in the solution in general for the leaching is rate-determining.

For faster leaching, it has therefore already been proposed that Reaction in the autoclave under pressure and at high temperatures of e.g. 85 to 1400C or with vigorous stirring. However, these methods require high pressure resistant Reaction vessel with good corrosion resistance at high temperature. Other Processes in which stirring with vibrations with frequencies of more than 15 Hz takes place, or in which there is a circulation of the oxygen gas through the ore suspension is enforced (e.g. according to DT-PS 888 929; DT-AS 1 038 762), are also too expensive.

All of these known processes are based on leaching only by changing the reaction conditions and increasing the contact between gas and to promote liquid phase, but not on a change in mechanism the oxidizing reaction. Accordingly, these known methods are in their effect severely limited and because of the slow response rate as well as in terms of the outlay on equipment and inadequate on the energy side. Other leaching processes, those who work with oxidizing ferric sulfate also show a slow reaction and result in undesirable iron contamination.

The invention has set itself the task of eliminating these disadvantages.

A leaching process is therefore proposed to solve this problem, in which, according to the invention, the leaching in the presence of nitrogen monoxide and / or Nitrogen dioxide is carried out.

It is surprising that such a process in which the reaction sequence between the oxygen and the metal or the metal compound in the leachate Material is made by means of a catalytic process, to significantly better effects leads, with the material to be leached selectively and with high purity is leached and also the leaching and ore scraps for further treatment are in suitable condition. It is particularly surprising that you can use the According to the method according to the invention, also copper from copper compounds or copper starting material can leach out much better selectively, especially since the separation of copper has so far was considered particularly difficult.

In the oxidizing leaching of metal sulfides, the reaction proceeds, for example, according to the following general formula: This reaction proceeds only slowly under normal conditions, as experiment D of Example 4 shows. In the presence of NO or NO2, however, the conversion is much faster, since the NO or NO2 activates the dissolved or diffused oxygen. The activation mechanism is presumably based on the fact that the NO gas is converted into NO2 by reacting with oxygen and that the NO2 dissolves in the suspension, so that the NO2 reacts with the metal sulfide, leaches it in an oxidizing manner and in turn converts itself back to NO. This NO is again oxidized to NO2 by O2, whereupon the above process is repeated. If only N02 is initially added, the same processes take place with the exception of the first step. Accordingly, NO and NO 2 are always present in the reaction system even if only one of these substances is used alone at the beginning. Due to these reaction mechanisms, NO and NO2 are practically not consumed, but only the oxygen, so that NO or NO2 has a catalytic effect during the oxidation by O2. In the presence of sulfur, this new reaction mechanism takes place according to the following general formulas, the activated state being indicated by an *.

Presumably, the oxidation of NO proceeds according to formula (a) and the Oxidation of the metal compound according to formula (b) at the same time. The sulfur that results from the sulfide according to formula (b), leaves the reaction system so that the reaction is extremely stable and the concentrations e.g. of sulfur in the solution or allow the pH values to be adjusted very easily.

The nitrogen oxides can either be pure, as a mixture, together with a third gas or in the form of a compound that NO or N02 results. Such connections are for example nitrites like NaN02, KN02 or

NH4NO2. These compounds can also be used as an aqueous solution will.

The total amount of NO and N02 can be 0.005 to 0.5 chemical equivalents of the metal component to be leached, but can also with higher NO or. N02 concentrations are worked to speed up the reaction even more.

A feed of NO and N02 is usually not necessary, since these are not consumed.

Oxygen can be used as pure oxygen, as an oxygen-containing gas such as used as air or as air enriched with oxygen even in situ generation of oxygen is not excluded.

The oxygen is either continuously supplied or depending on consumption used in excess in the system from the start.

It is sufficient to fill the reaction vessel with oxygen, with neither an overpressure of oxygen still a special measure for the contact between Gas and solution are required. Still, you can get a faster response rate achieve when working with a higher oxygen partial pressure. Preferably the suspension of the material to be leached is circulated or stirred.

The water or the aqueous solution in which the leaching takes place Depending on the material to be leached, it is neutral, weakly or strongly acidic. As a leaching liquid For example, sulfuric acid can be used.

The leaching is preferably carried out at temperatures between room temperature and 850C; In contrast to the known processes, higher temperatures are not used preferred because the solubility of NO and NO2 in the leaching liquid is reduced will. The reaction slows down noticeably at temperatures below room temperature. A temperature between 40 and 650C is preferred.

The process according to the invention works particularly well with metal sulfides perform, for example with sulphide ores such as copper sulphide or zinc sulphide concentrate, Arsenic sulfide precipitate, also sulfide mixtures containing NiS, CoS, ZnS and the like, such as Lech or stone from non-ferrous metallurgical processes; can also Metals and metal compounds such as alloys and also intermediates or By-products from metallurgical processes are used such as, for example Sludge, slag, dust, sublimate, precipitate and the like. These metal compounds are suspended with water or with aqueous solutions such as Pochschlamm and the Exposed to leaching.

Furthermore, the oxidizing leaching can be carried out using the method according to the invention in the case of copper, take place from the anode sludge that occurs during copper electrolysis. A such anode sludge contains copper, selenium, silver, tellurium, bismuth, Gold, platinum, palladium, lead and the like; it is with the invention Method possible and expedient, the copper alone selectively from this anode sludge to remove, because the residue of the material to be leached is easier to further treat leaves. The selective leaching is carried out by suspending the anode sludge in water Sulfuric acid with a concentration of 20 to 150 g / l, the copper being copper sulfate is leached out.

In the case of anode slurries containing selenium, the temperature should be set during leaching between 20 and 80 ° C, since selenium dissolves at a higher temperature. the other reaction conditions correspond to those of sulphide leaching. Hardly anything like that Selenium-containing final liquors with copper sulphate can be used again directly in the copper electrolysis can be used.

The residue from the leaching is then used to extract silver, gold, Tellurium and the like are processed further, with the selenium being carried out from the residue prior evaporation can be isolated.

The invention is explained in more detail below with the aid of examples will.

Example 1 125 g of a sulphide mixture containing 39% Ni, 15% Co, 1.6% Cu and 35% S as well as 1000 ml of water and 5 g of concentrated sulfuric acid were made into a leach pound and placed in a 2 liter beaker given, which is provided with a stirrer and sealed by a lid. Oxygen is supplied through the cover by means of separate lines from a pressure bottle, the supply of NO or NO2; there is also a on the lid Manometer attached. The beaker is filled with oxygen in a thermostat, whereupon the Pochschlamm stirred vigorously at 45 0C and 43 ml of a 200 g NaN02 per liter containing solution is supplied.

The leaching was carried out for two hours with a constant supply of oxygen carried out, the oxygen pressure corresponding to 180 mm H20. After leaching the contents were filtered and the residue rinsed with water. There were 1150 ml of filtrate and 5.50 g of residue are obtained. The filtrate contained 40.7 g of Ni per liter and 15.5 g Co, giving a leaching coefficient of 95.9% for nickel and 95.1 % Corresponded to cobalt.

In a comparison test without the addition of NO or NO2 while maintaining the same Hardly any reaction was found to the working conditions.

Example 2 Analogously to Example 1, a punching sludge made from 50 g of zinc sulfide was produced (Grain size <150 mesh, Zn 46.7%, Fe 9.75%, S 29.9%, Pb 0.1%), 500 ml of water and 40 g of sulfuric acid and prepared analogously to Example 1 for three hours at 60.degree treated with the addition of 28.5 ml of the NaNO2 solution, after rinsing the residue 600 ml of filtrate and 22.5 g of dry residue were obtained. The filtrate contained 31.0 g zinc and 5.6 g iron per liter at a pH of 0.35. The coefficient of leaching for tin is 78% and for iron is 75%. The residue contained 23.3% Zn, 5.42 % Fe and 66.1% S, which is a large excess of sulfur compared to the metals Zn and represents Fe.

Example 3 200 g of an arsenic sulfide precipitate (As 6.12%, Cu 0.34 %, S 10.3%, H 2 O 78%) were suspended in water, the pH being adjusted with 4 g of sulfuric acid was set to 2.0. The leaching was carried out as in Example 1 at one temperature of 400C with the addition of 12.3 ml of the NaNO2 solution (0.15 equivalents) for two hours carried out, with the oxygen pressure now at 100 mm H20 column. After filtering and rinsing, 1200 ml of filtrate and 21.0 g of residue were obtained after drying at 45.degree. The filtrate contained 10.0 g arsenic, 0.56 g copper, 3.5 g SO4 per liter at a pH value from 1.8. Of the Leaching coefficient for As is 98%. The residue consisted mainly of monoclinic crystalline sulfur, 98%.

Example 4 100 g of an arsenic sulfide precipitate analogous to Example 3 and 500 ml of water were mixed with 2 g of sulfuric acid at pH adjusted to 2.0 suspended. Three such suspensions A, B and C were opposed with NO gas in Air of various concentrations with an air supply of 600 ml / min. treated, wherein the air was violently introduced into an open container and for Agitation contributed, while the NO gas was supplied from a separate reservoir became. The leaching coefficients were examined every hour. In the case of a further control suspension D, the leaching was carried out without the addition of NO gas carried out. The values are given in Table 1 below.

Table 1 Experiment leaching conditions As Suction - supply of NO leaching - duration equivalent NO conc. coefficient Std. TO As vol. percent 1 | | | 36 A 2 0.46 0.60 75 3 99 1 26 B 2 0.42 0.53 56 3 85 1 20 C 2 0.19 0.24 39 3 58 D 2 0 0 - 3 | | | 4.5 Table 1 clearly shows that NO also has a catalytic effect in a leaching process when the NO gas is mixed with the air or blown in together in an open reaction vessel.

Example 5 50 g of an anode sludge from copper electrolysis (H2O 25%, Cu 11.8%, Se 12.7%, Te 2.8%, Ag 12.2%, Pb 10.6%) and 50 g 98% ige Sulfuric acid and 500 ml of water were in a 2000 ml beaker suspended and the leaching carried out analogously to Example 1, with 5.6 ml of the NaNO2 solution was added with strong magnetic stirring at a temperature of 75 ° C became. The oxygen pressure was 180 mm H20. A total of 0.175 chemical Equivalents of NO or NO2, based on the amount of copper, added.

After one hour of leaching, the mixture was filtered as before, with 650 ml of filtrate and 29.0 g of residue were obtained. The filtrate contained per liter 8.7 g Cu, 0.029 g Se, less than 0.01 g Ag, giving leaching coefficient of 95.8 % for Cu, 0.3% for Se and <0.1 for Ag. The residue sludge dried at 400C contained 0.87% Cu, 21.83% Se and 21.4% Ag.

Example 6 Analogously to Example 5, 25 g of sulfuric acid were now added 50 g of the copper sludge and 500 ml of water suspended, with the leaching at 450C with 11.2 ml of the NaN02 solution for three hours under a pressure of 180 mm H2O Oxygen was carried out with a constant supply of oxygen. The NO or.

The amount of NO2 corresponds to 0.35 chemical equivalents compared to the im System existing copper. 630 ml of filtrate and 29 g of residue were obtained, the filtrate containing 9.05 g of copper and 0.035 g of selenium per liter, during the Anode sludge residue contained 0.65% copper.

Example 7 Analogously to Example 5, 50 g of the anode sludge were added 1000 ml of a sulfuric acid solution with a concentration of 50 g sulfuric acid suspended per liter and at 750C with the addition of 0.35 equivalents of NaNO2 Copper leached for one hour at 180 mm H20 oxygen pressure. The coefficient of leaching was 94.7% for copper and 0.60% for selenium.

Comparative experiment 1 The procedure was analogous to Example 7, but without the addition of NaN02. After three hours of leaching, the leaching coefficients were for copper 44.6% and for selenium 1.0%.

Comparative experiment 2 The procedure was analogous to Example 7, but with the sulfuric acid concentration was now 200 g / l and 300 g / l. The leaching coefficients were 99.0 and 99.1% for copper and for selenium at 95.6 and 99.0%, respectively.

Claims (7)

Claims 1. Leaching process in the metals or metal compounds leached in the presence of water or aqueous solutions and oxygen, characterized in that the leaching in the presence of nitric oxide and / or Nitrogen dioxide is carried out. 2. leaching method according to claim 1, characterized in that the nitrogen monoxide or nitrogen dioxide, as a pure gas, together with a Carrier gas or as these nitrogen oxides evolving compound is used. 3. Leaching method according to claim 1 to 2, characterized in that that the oxygen is supplied as pure oxygen or as an oxygen-containing gas will. 4. leaching process according to claim 1 to 3, characterized in that that the sum of nitric oxide and nitrogen dioxide is 1/200 to 1/2 chemical Equivalents of the metal component to be leached. 5. leaching process according to claim 1 to 4, characterized in that that the water or the aqueous solution, depending on the material to be leached, is acidic or is neutral. 6. leaching process according to claim 1 to 5, characterized in that that the temperature of the water or the aqueous solution is kept between 20 and 850C will. 7. leaching process according to claim 1 to 6, characterized in that that as leachable material metal sulfides, sulfide ores, including copper compounds Anode sludge from copper electrolysis, alloys, intermediate or by-products from metallurgical processes and their mixtures are used.