RU2363661C2 - Method for reprocessing of nickel-containing and metal admixtures containing solutions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used for reprocessing of waste nickel-containing acid solutions generated at electrochemical treatment of the copper. The method for reprocessing of water solutions containing the nickel sulphate, sulphuric acid and admixtures includes the three-stage neutralisation with calcium compounds e.g. lime milk and chalk. The first stage of neutraliszation is carried out at pH 1.8-2.0, the second one - at pH 5-6, and the third - at pH more than 8.5.

EFFECT: invention allows to simplify the marketable products obtaining from waste nickel-containing acid solutions.

3 cl, 1 dwg, 3 tbl, 14 ex

Description

The present invention relates to the field of non-ferrous metallurgy, and more particularly to a method for processing spent nickel-containing acidic solutions of copper electrolyte plants.

It is known that electrolytic refining of copper produces waste solutions containing nickel sulfate, sulfuric acid, a small amount of copper sulfate, iron and trace elements of lead, zinc, cadmium, bismuth, antimony and tin. A typical solution contains about 200 g / l of sulfuric acid, 14-15 g / l of Ni, about 3 g / l of zinc, less than 2 g / l of iron and trace amounts of other metals. The solutions are processed to produce nickel sulfate by multi-stage evaporation, separation of intermediate precipitates, recrystallization, purification of solutions from impurities and return of sulfuric acid concentrated to a content of 1200 g / l to electrolysis of copper (Pozin M.E. Mineral salt technology. T.1, M. : Chemistry, 1974, p. 735-736). This process is energy-intensive and complex, and at some enterprises it has been replaced by treating the spent solutions with milk of lime with the precipitation of a mixture of gypsum and nickel hydroxide (up to 4% in Ni) used in metallurgical industries. A known variation of this method (patent US 4009101), used in nickel plating, in which a part of the solution is neutralized with alkali, the resulting nickel hydroxide is added to the remaining part of the solution to neutralize it. The method allows to increase the concentration of the solution and thus somewhat reduce the cost of evaporation. However, in this case, it is not a satisfactory solution to the problem because of the need for separation of sulfates during multi-stage evaporation.

It is also well known to obtain nickel hydroxide from solutions containing nickel sulfate by introducing alkali, for example, patents No. RF 2208585, RF 2191160, RF 2177447, DE 19846093, EP 0908258, US 5498403. However, due to impurities contained in the initial solution, obtaining the ready-to-use product is complicated by this method, and the production of intermediates due to the use of alkali is economically disadvantageous.

A variation of this method, leading to the production of a marketable product, is a two-stage alkali deposition according to JP 59056590 with precipitation of impurities in the first stage and nickel hydroxide in the second. To reduce alkali consumption, separation of part of the acid by dialysis is used, and for better purification from impurities, the addition of hydrogen peroxide is used.

A known method of two-stage neutralization of acidic solutions of Nickel sulfate with magnesium hydroxide (patent US 4006215), with the receipt of Nickel hydroxide and other hydroxides, applied to solutions containing Nickel, cobalt, iron, namely, solutions of sulfuric acid opening of laterite ores. The use of magnesium hydroxide (with its subsequent regeneration by precipitation after adding lime at an elevated temperature and separation of the gypsum and magnesium hydroxide fractions) complicates the process, and the composition of the solutions for dissecting laterite ores is significantly different from the composition of the solutions of spent nickel-containing acid solutions of copper electrolyte plants. The patent specification also mentions the fact of filing an application for a similar invention using calcium hydroxide.

Closest to the claimed method is a three-stage precipitation of nickel sulfate from a solution of iron and zinc impurities (patent JP 2003095660) by adding lime while feeding air as an oxidizing agent, at the corresponding pH of the stages: the first 3.0-4.0, the second 5.5-5.85 and the third 5.9 -6.1. The purified nickel sulfate solution is then processed by conventional methods.

The technical task of processing is to obtain a marketable product or products containing nickel from spent nickel-containing acidic solutions, for example, solutions of copper electrolyte plants, in the most economical and technologically advanced way.

The technical problem is solved by three-stage neutralization of aqueous solutions containing Nickel sulfate, sulfuric acid and impurities, calcium compounds such as milk of lime and chalk, characterized in that the first stage of neutralization is carried out at pH 1.8-2.0, the second stage of neutralization is at a pH of 5-6, and a third at a pH of more than 8.5. The peripheral speed of rotation of the mixer during neutralization is at least 4 m / s. The filtrate after the third precipitation step is used as recycled water in the copper refining process.

The advantage of the method compared to the closest analogues of JP 59056590 and US 4006215 is the use of a cheaper reagent (milk of lime) and a simpler technological scheme (simple three-stage deposition, without the use of oxidizing agents and regeneration of reagents), which reduces both capital and operating costs. In addition, the method is essentially waste-free, since both the main product and by-products can be used in industry, and the filtrate after the last stage of neutralization can be used as recycled water in the production cycle of copper electrolyte plants.

The first stage of neutralization is carried out at pH 1.8 ÷ 2.0. At pH greater than 2, precipitation of metal compounds contaminating gypsum begins. At a pH of less than 1.8, precipitation does not occur completely. At this stage of neutralization, chalk can be used instead of milk of lime.

The second stage of neutralization is carried out to obtain a gypsum precipitate containing 0.4-1% nickel and impurities - basic copper sulfate, zinc hydroxide, iron hydroxide. This precipitate is then used in the metallurgical industry or processed to obtain non-ferrous metal concentrates and, again, pure gypsum. The second stage of neutralization is carried out at pH 5 ÷ 6. At pH less than 5, part of the impurities remains in the filtrate and contaminates a rich nickel concentrate. At pH greater than 6, a larger percentage of nickel precipitates, reducing the nickel content in the concentrate.

The third stage of neutralization is carried out at a pH of not less than 8.5, preferably up to a pH of 9.5. In this case, almost complete precipitation of nickel in the form of nickel hydroxide occurs, together with gypsum. The resulting concentrate contains at least 15% nickel and can be used in metallurgy. At a pH of less than 8.5, a sufficiently complete deposition of nickel is not achieved, and it is lost with the solution. At a pH of more than 9.5, a further increase in nickel recovery is not observed, and the consumption of milk of lime increases.

Thus, with the proposed three-stage neutralization, in addition to solving the main task of nickel extraction, two concomitant advantages are achieved: obtaining pure gypsum in the first stage of neutralization for use in the production of building materials and obtaining a non-ferrous metal concentrate suitable for their extraction in the second stage of neutralization.

The peripheral speed of the mixer (frame or impeller) to ensure efficient mixing should be at least 4 m / s, preferably at least 6 m / s. At a peripheral speed of less than 4 m / s, the characteristics of the deposition process are degraded. At a speed of more than 6 m / s, no further improvement is observed.

Each stage of neutralization is accompanied by filtration with the separation of sediment. The filtrate of the third stage of neutralization is returned to the copper electrolyte production as a circulating solution, thereby achieving a non-waste technology. For economic reasons, the process is carried out under normal conditions (atmospheric pressure and temperature, which increases during neutralization due to the fact that the neutralization reaction is exothermic).

The scheme of processing solutions is shown in the drawing.

The implementation of the method can be demonstrated by the following examples.

Example 1a and 1b.

Two samples of 600 ml of electrolyte of the following composition are taken (samples a) and b) in table 1):

Table 1 Substance Sample a) Sample b) Sulfuric acid, g / l 216 218 Cu, g / l 0.51 0.50 Re, g / l 1.51 1,52 Ni, g / l 14.5 13.8 Zn, g / l 3.04 3.10 As, mg / l 10.13 10.11 Bi, mg / l 0.66 0.70 Pb, mg / l 5.58 5.47 Sn, mg / L 117.3 112.6

In option 1A, after the first neutralization with milk of lime with a pH of 1.9 and filtration, pure two-water gypsum is obtained.

In option 1b, after the first neutralization with powdered chalk with a pH of 1.9 and filtration, pure two-water gypsum is obtained.

After the second stage of neutralization with milk of lime to pH 5.5 and filtration, a nickel-poor gypsum precipitate is obtained for options 1a and 1b.

After the third stage of neutralization with milk of lime to pH 9.5 and filtration, a nickel-rich gypsum precipitate is obtained for options 1a and 1b.

The results of the process by mass and composition of sediment are shown below in table 2.

table 2 Process stages Content and masses of substances Example 1a Example 16 First neutralization The percentage of impurities in two-water gypsum 0,101 0.104 Second neutralization The mass of sediment, g 5.52 5.60 The content of Ni,% 4.36 4.28 Cu content,% 1.84 1.85 The content of Zn,% 10.95 11.02 Fe content,% 5.45 5.40 Third neutralization The mass of sediment, g 52.6 49.8 The content of Ni,% 16,0 15.9 Cu content,% 0.014 0.013 The content of Zn,% 0.17 0.16

Thus, over 95% went into the precipitate rich in nickel, and less than 5% nickel in both cases turned into poor.

The filtrate after the third precipitation step in Example 1a contained Ni 5.11 mg / L, Fe less than 0.0025 mg / L, Cu 0.095 mg / L, Zn 0.008 mg / L, which allows the use of such a solution as circulating water in copper electrolyte production .

Examples 2-14.

The stock solution was treated in a similar manner to that described in Example 1a at various precipitation pHs. The table below shows the conditions and main results of the three-stage deposition (table 3). From these examples it is seen that the optimal pH of the deposition of stages 1-3 are, respectively, 1.8-2.0, 5-6, 8.5-9.5. The above examples demonstrate the possibility of obtaining a marketable product (nickel concentrate with a nickel content of more than 15%) by three-stage neutralization of aqueous solutions containing nickel sulfate, sulfuric acid and impurities using lime milk or, in the first stage of neutralization, chalk.

Table 3 No. p / p Name of sediment The peripheral speed of rotation of the mixer, m / s pH in stages Recovery% one 2 3 Ni Cu Fe Zn 3 Gypsum sediment 1.7 5.5 9.5 0.01 0.001 0.01 0.01 2 1.8 5.5 9.5 0.01 0.001 0.01 0.01 one four 1.9 5.5 9.5 0.01 0.001 0,03 0.04 four 2.0 5.5 9.5 0.01 0.001 0.1 0.1 5 2.2 5.5 9.5 0.01 0.001 60 thirty 6 Precipitation of non-ferrous metal hydroxides 1.9 4.8 9.0 5 60 one hundred thirty 7 1.9 5,0 9.0 5 74 one hundred 46 3 6 1.9 5.5 9.0 5 90 one hundred 70 8 1.9 6.0 9.0 5 96 one hundred 92 9 1.9 6.2 9.0 fifteen one hundred one hundred one hundred 10 Nickel-rich gypsum sediment 1.9 5.5 8.2 90 four 0.001 8 eleven 1.9 5.5 8.5 95 four 0.001 8 3 6 1.9 5.5 9.0 95 four 0.001 8 12 1.9 5.5 9.5 95 four 0.001 8 13 1.9 5.5 9.8 95 four 0.001 8

During the process, nickel is almost completely precipitated as nickel hydroxide. The precipitate of the second stage of deposition, containing 0.5-5.0% nickel, significant amounts of zinc and copper, can also be used in metallurgy or to extract non-ferrous metals from it. Pure gypsum obtained in the first stage of deposition of the three-stage method can be used, for example, in the production of building materials. The filtrate after the third stage of precipitation, as can be seen from example 1A, can be used as recycled water.

Claims (3)

1. The method of processing aqueous solutions containing Nickel sulfate, sulfuric acid and impurities, including a three-stage neutralization of solutions with calcium compounds, such as milk of lime and chalk, characterized in that the first stage of neutralization is carried out at pH 1.8-2.0, the second the stage of neutralization is carried out at a pH of 5-6, and the third at a pH of more than 8.5. 2. The method according to claim 1, characterized in that the peripheral speed of rotation of the mixer during neutralization is at least 4 m / s. 3. The method according to claim 2, characterized in that the filtrate after the third stage of deposition is used as recycled water in the process of refining copper.

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