RU2601333C1 - Method for deposition of heavy nonferrous metals from industrial solutions and/or wastes - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used in nonferrous metallurgy for neutralizing of acidic industrial solutions. Method involves treatment of solutions and/or wastes with complex reagent - precipitation agent, containing calcium carbonate, iron, silicon oxides and magnesium in weight ratio CaCo₃:F_AGG:SiO₂:MgO = 100:0.7-9.5:1.3-4.8:2.5-6.5, at active mixing to produce in pulp of pH 5.0-5.5, and subsequent maintenance of pulp at active mixing 0.5-2 hours, filtering and washing of precipitate. Obtained precipitate is calcined at 720-770 °C for 1-2 hours. As precipitation agent is used industrial water slurries of thermal power plants, containing calcium carbonate, iron, silicon and magnesium oxides, at reaching of their composition to the specified ratio.

EFFECT: method provides higher efficiency and cost effectiveness of treatment of industrial solutions and/or wastes, containing heavy non-ferrous metals and iron, as well as obtaining from them a compound of sediment, which is suitable for extraction of metals, and involvement of the obtained concentrates in recycling, which enables to eliminate discharge of toxic wastes into the environment.

3 cl, 5 tbl, 4 ex

Description

The invention relates to methods designed to neutralize acidic industrial solutions and / or by precipitation from them of valuable components - heavy non-ferrous metals.

The proposed method can be used at non-ferrous metallurgy enterprises for the neutralization and separation of metals from solutions obtained, for example, as a result of underground leaching of copper, zinc and other metals by sulfuric acid, as well as waste waste solutions or man-made acidic waters containing not only non-ferrous metals, but also iron in both the divalent and trivalent state.

Such solutions also include mine and subsurface waters associated with the development of copper-zinc deposits, for example, water from the technogenic lake of the Levikhinsky mine (Sverdlovsk region), containing, g / l: 0.165 Cu; 0.413 Zn; 0.730 Fe, and having a pH of 2.80. This is also the basement water of the Sak-Elga River (Chelyabinsk Region) with a pH of 2.4-4.0, containing, in g / l, up to 0.038 Cu; 0.150 Zn and from 0.001 to 0.250 Fe, moreover, iron can be in both divalent and trivalent states. In addition, waste solutions and effluents from plants processing ore and concentrates containing them, as well as poor solutions resulting from underground sulfuric acid leaching of poor ores are neutralized and precipitated from them by heavy non-ferrous metals.

These solutions are characterized by very large volumes, a low concentration of metals in them (less than 1 g / l), an unstable content of these metals, and high acidity (pH up to 2.4). In addition, as a rule, these metals are accompanied by iron ions in the bivalent and trivalent state, the deposition of which takes place at pH up to 7.2 and pH 1.7-4.3 (respectively).

A known method designed for the treatment of industrial effluents (US patent US 4025430), including in the first stage, the neutralization of acidic wastewater with pH = 1.4 hydrated lime (5-20% CaO) to pH = 8.5-9.5 and sedimentation draft. At the second stage, the clarified mother liquor is treated with a solution of sodium silicate (Na ₂ SiO ₃ ) in an amount of 5-30 stoichiometries, which are necessary for more complete metal precipitation, and a flocculant, for example polyacrylamide, is added to increase the rate of settling (clarification) of the solutions. Precipitation formed at stages 1 and 2 is sent to the settling pond.

The disadvantages of this method:

- a complex technological scheme (two stages of processing and filtration, the circulation of solutions, the addition of flocculants during sedimentation, etc.);

- high water consumption - the use of water for the preparation of lime mortar (5-20% CaO), a solution of sodium silicate, flocculant;

- the use of a significant amount of expensive reagents CaO, Na ₂ SiO ₃ and coagulants (for example, polyacrylamide) and high consumption of the main active substance CaO due to the high pH = 8.5-9.5 in the first stage of processing;

- low sedimentation sedimentation rate, which requires the introduction of a coagulant;

- discharge of sediments into a settling pond for its storage, which requires alienation of land areas, expenses for arrangement and maintenance of a toxic sediment storage.

The closest in technical essence to the proposed method is the "Method of wastewater treatment from heavy metal ions" (RU 2191750), including the treatment of man-made solutions with a pH of 4.5 calcium-containing reagent by draining wastewater containing copper and zinc through a layer of crushed calcium carbonate - limestone fineness (minus) -3 + 0 mm at a rate of 100 ml / day at a pH of 6.4-6.5.

The disadvantages of this method include the following:

- low productivity of the process (100 ml / day), which makes it difficult and unsuitable to use it for the treatment of large volumes of industrial wastes and / or solutions. Carrying out the process in diffusion mode through the stage of gypsum precipitate formation CaSO ₄ · 2H ₂ O, which facilitates the deposition of, for example, copper due to the formation of basic deviline sulfates CaSO ₄ · CuSO ₄ · 3Cu (OH) ₂ or langite CaSO ₄ · 3Cu (OH) ₂ . The rate of the deposition process can also be reduced due to iron ions, which accompany zinc, copper and other non-ferrous metals in spent solutions of hydrometallurgical processing of polymetallic ores, solutions of their underground leaching, basement and other effluents. In addition, iron (II) and (III), precipitated at a pH of 6.4-6.5 together with gypsum and copper and zinc compounds increases diffusion difficulties in the processing of the initial solutions;

- low efficiency of the process due to the high consumption of the main active substance CaO, which is part of the limestone, due to the deposition process at pH 6.4-6.5 and the formation of gypsum both in the free state and in the composition of the compounds providing heavy color deposition metals;

- loss of valuable heavy non-ferrous metals with an excess of limestone, which does not ensure their recycling - the use of sludge for subsequent extraction of metals.

The objective of the invention is the creation of a high-performance and economical method of intensive processing of industrial solutions and / or effluents containing heavy non-ferrous metals and iron, to obtain a complex precipitate from them, suitable for subsequent extraction at existing enterprises of non-ferrous metallurgy by known methods.

The technical results to which the present invention is directed is to increase the productivity and economy of the method for intensive processing of industrial solutions and / or effluents containing heavy non-ferrous metals and iron, as well as obtaining from these solutions and / or effluents a complex precipitate of heavy non-ferrous metals suitable for their subsequent extraction at existing non-ferrous metallurgy enterprises by known methods, and the involvement of the obtained complex concentrates of heavy non-ferrous meta lows in recycling, which eliminates the discharge of toxic waste into the environment.

An additional technical result is to obtain an enriched complex concentrate of precipitated metals by removing hydrated moisture and carbon monoxide from precipitated metal carbonates.

An additional technical result is to increase the environmental friendliness of the method due to the possibility of using alkaline wastes of thermal power plants (TPPs) as chemical reagent sludge - chemical water treatment sludge (HVO).

The specified technical result is achieved due to the fact that the solutions and / or effluents are treated with a complex reagent-precipitator, including calcium carbonate, iron, silicon oxides and magnesium in the ratio of CaCO ₃ : Fe _total. : SiO ₂ : MgO = 100: 0.7-9.5: 1.3-4.8: 2.5-6.5, with vigorous stirring to obtain a pH of 5.0-5.5 in the pulp, after which the pulp is kept with active stirring for 0.5-2 hours, the precipitate is filtered off and washed;

The specified additional technical result is achieved due to the fact that the obtained precipitate is calcined at 720-770 ° C for 1-2 hours.

The specified additional technical result is achieved by ensuring the possibility of using alkaline waste from thermal power plants (TPPs) as chemical reagent sludge - chemical water treatment sludge (HVO), including calcium carbonate, iron, silicon and magnesium oxides, when bringing their composition in accordance with the above ratio.

The use of a complex reagent-precipitator, including calcium carbonate, iron, oxides of silicon and magnesium in the ratio of CaCO ₃ : Fe _total. : SiO _2: MgO = 100: 0,7-9.5: 1,3-4,8: 2.5-6.5 provides the interaction of calcium carbonate in industrial solutions and / or with the effluent being in their Cu ²⁺ metal ions, Zn ²⁺ , Fe ²⁺ and Fe ³⁺ , with the formation of a complex precipitate of these metals at a lower consumption than the prototype of the main active reagent CaO due to the possibility of the process at a lower pH of 5.0-5.5 that provides an increase in the efficiency of the process. The exposure of the obtained pulp with active stirring for 0.5-2 hours allows to obtain a high degree of metal deposition (98-99.0%), which is ensured by the presence of iron ions and silicon compounds (SiO ₃ ^{- -} ), which play the role of an additional factor for more complete deposition of heavy non-ferrous metals.

At the same time, magnesium compounds introduced into the composition of the precipitating reagent create conditions for coarsening and coagulation of finely dispersed colloidal precipitate of basic metal carbonates, which ensures a high rate of sedimentation of the complex precipitate (clarification of the pulp) and thickening of the pulp, which ensures an increase in the productivity of the process, and also provides from these solutions and / or effluents of a complex precipitate of heavy non-ferrous metals suitable for their subsequent extraction at existing non-ferrous meta enterprises Llurgy by known methods.

Annealing the precipitate at a temperature of 720-770 ° C for 1-2 hours allows you to remove hydrated moisture and carbon monoxide from the precipitated metal carbonates, which increases the concentration of these metals in the precipitate, and, therefore, reduce the cost of their further transportation and processing.

In addition to basic carbonates, carbonates and silicates of heavy non-ferrous metals and iron, the precipitate contains an excess of CaCO ₃ , which did not decompose at the precipitation stage. Derivatographic studies of this sample showed that the main mass loss associated with the completeness of decomposition of carbonates and the removal of hydrated moisture occurs in the range of 720-770 ° C.

The indicated additional technical result is also achieved due to the possibility of using alkaline waste from thermal power plants (TPPs) as chemical reagent sludge - chemical water treatment sludge (HVO) containing the necessary reagent-precipitant components, provided that their ratio matches the declared technical solution, which can be achieved by the introduction of the corresponding missing components in the specified waste.

When using these wastes as a precipitating reagent, material costs are reduced, and it is also possible to free up large land areas occupied by TPP sludge collectors, which will provide an additional economic and environmental effect.

The limits of pH and duration of the process during the deposition of heavy non-ferrous metals from industrial solutions and / or effluents when they are treated with a complex calcium-containing reagent, including calcium carbonate, iron, silicon and magnesium compounds, the ratio of these components, as well as temperature and precipitation calcination times, are selected by an experienced in the laboratory, as shown in the examples below.

In laboratory studies, the compositions of the complex reagent-precipitant are used, are shown in table 3.

The composition of the declared precipitating reagent can be controlled by additives to calcium carbonate (or materials or waste containing it), iron carbonate in terms of Fe total (or material or waste containing it, for example, natural siderite), magnesium carbonate in terms of magnesium oxide (or materials or waste containing it, for example, natural magnesite).

The silicon-containing reagent in terms of SiO ₂ can be added in the form of a soluble silicon compound or sand, crushed to a fraction (minus) of -0.05-0 mm, or pulverized silica (marshalite) - a natural pulverized silica material.

In addition, the addition of MgO and SiO ₂ can be introduced in the form of substances containing pyroxenes, for example, acid-soluble enstatite - Mg ₂ [Si ₂ O ₆ ]. Orthosilicates of alkaline earth elements are acid-soluble and, when introduced into acidic solutions and / or effluents, decompose and hydrolyze, creating in the system a specific ratio of Mg ²⁺ and SiO ₃ ^2- ions calculated by technologists, necessary for the deposition of heavy non-ferrous metals and increasing the sedimentation rate in the pulp ( clarification).

The following are examples of specific implementation of the method, confirming the selection of the appropriate ratios of the components, as well as the modes of implementation of the claimed method.

Example 1

To 0.4 l of zinc sulfate solution containing 0.500 g / l of zinc, having a pH of 2.8 due to the addition of 0.1N H ₂ SO ₄ with active stirring, a complex reagent precipitant was gradually added in small portions (composition No. 3 is given in the table 3) and adjusted in the resulting pulp pH in experiments 1-5, respectively 4.8; 5.0; 5.2; 5.4 and 5.6. Then the pulp was actively stirred for 1 hour at room temperature, the precipitate was filtered off and washed with 0.025 L of water.

The experimental results shown in table 1 show that at pH = 5.2-5.5, complete precipitation of zinc is achieved. Lowering the pH to 4.8 does not allow to obtain complete deposition - the degree of deposition of 81.4%. An increase in pH above 5.5 is impractical because in this case, the consumption of the precipitating reagent increases, the yield of the precipitate increases, and the zinc content in the precipitate decreases, which affects its quality.

Example 2

To 0.4 l of a solution containing in g / l: 0.165 Cu; 0.413 Zn; 0.730 Fe ²⁺ introduced in the composition of the sulfate salts, with vigorous stirring, 0.198 g of ammonium sulfate was added based on the oxidation of 33% iron (II) to iron (III) and the pH of the initial solution was 2.80. This composition and pH indicator correspond to the characteristics of the waters of the Levikhinsky mine in a technogenic lake in the territory of the Sverdlovsk region. A precipitating reagent (composition No. 3, table 3) was added to each portion of the initial solution of the obtained composition according to the procedure described in example 1, and the pH was adjusted to 5.20. Then, with active stirring, a pulp of 0.25 was kept; 0.54; 1.0; 2.0 and 2.5 hours. After appropriate exposure, the precipitates were filtered off, washed, and dried.

The results of the experiments, are shown in table 2, show that the exposure for 0.25 hours is insufficient to complete the deposition of copper, zinc and iron. And over 2 hours is impractical, because the degree of their deposition remains virtually unchanged. Therefore, the best option for holding pulp with vigorous stirring is 0.5-2.0 hours.

Example 3

To determine the optimal composition of the complex reagent-precipitant, mixtures (fraction -0.2 + 0 mm) prepared from calcium, iron and magnesium carbonates and finely divided silicon oxide (fraction (minus) -0.05 + 0 mm) were used. Their composition is given in table 3.

For the experiments we used solutions prepared from sulfates of copper, zinc and iron (II), the preparation procedure of which is described in Example 2. The experiments were carried out with the gradual introduction of CaCO ₃ (experiment 1 table 3) of one of the compositions of the precipitating reagent with active stirring (experiments 2-6 table 3). After that, in each experiment, the rate of sedimentation of solutions was measured at a fixed time for its complete sedimentation, followed by a calculation of the rate of clarification (Table 3). Then the precipitate was filtered off, washed, dried, weighed, its composition and solution composition were analyzed. Based on the analysis results, the degree of metal deposition was determined.

The results shown in table 3 show that the introduction of iron and SiO ₂ into the pulp composition (passes in acidic solutions to SiO ₃ ^- ion) within the framework of the claimed method increases the degree of metal deposition: copper from 95.2 (op. 2) up to 98.9-99.8%; zinc in experiment 2 from 97.1% to 99.8 and, practically, up to 100% (experiments 3-5); from 96% iron (in experiment 2) to 97.4-99.6% in experiments 3-5. A further increase in the addition of iron and SiO _{2 is} impractical because the degree of metal deposition practically does not increase, and their content in the solid phase precipitate only decreases. In addition, iron (II), oxidizing to iron (III) with active stirring of the pulp due to autooxidation (atmospheric oxygen), becomes iron hydroxide and plays the role of an additional coagulant in the formation of a precipitate.

The addition of magnesium-containing compounds (in the pulp these are Mg ^{2+ ions} ) is necessary to create conditions in the system that lead to the formation of larger aggregates, the deposition of which occurs faster than the initial particles. The formation of larger particles in a complex colloidal system of hydroxides, basic carbonates, carbonates and silicates of heavy non-ferrous metals and iron, an increase in the rate of clarification (settling) and thickening of the pulp can reduce the amount of pulp entering the filtration and, consequently, reduce energy and labor costs.

In comparison with experiment 1, where only calcium carbonate was added to treat the initial solution, the pulp clarification rate increases by 1.3-1.8 times when magnesium and iron compounds were added to the precipitating agent within the claimed method (experiments 3-5) .

It should be noted that a high rate of clarification of solutions and thickening of pulp is very important for large (and then enormous) volumes of initial toxic solutions supplied to neutralization, neutralization and the separation of valuable metals in the form of commodity concentrates, for example, solutions of underground leaching or hydrometallurgical processing of poor polymetallic ores .

Example 4

To optimize calcination, a precipitate was used, obtained according to the conditions set forth in Example 3 (experiment 4, Table 3) using a precipitating reagent having the ratio CaCO ₃ : Fe _total : SiO ₂ : MgO = 100: 2.5: 1.8 : 4.4.

After drying it at 105 ° C to constant weight, the precipitate contained in wt%: 4.0 Cu; 10.18 Zn; 17.8 Fe and 1.3 S.

In addition to basic carbonates, carbonates and silicates of heavy non-ferrous metals and iron, the precipitate contains an excess of CaCO ₃ , which did not decompose at the precipitation stage. Derivatographic studies of this sample showed that the main mass loss occurs in the region of 700-800 ° C. Calculation optimization experiments were carried out with 3 g samples of concentrate placed in alundum boats in the temperature range of 700-800 ° C and the exposure time at a given temperature of 1.5 hours (table 4). The completeness of the decomposition of carbonates and the removal of hydrated moisture were monitored when determining losses during calcination (hereinafter referred to as SPP), i.e. weight reduction of the initial concentrate in% relative under certain conditions. The experimental results shown in table 4 show that the calcination of the complex precipitate - copper-zinc-iron-containing concentrate should be carried out at a temperature of 720-770 ° C.

At a temperature of 700 ° C, the decomposition of carbonates is not complete - SPP = 18.9% with an output of calcined concentrate 81.1%. Calcination at temperatures above 770 ° C is impractical because SPP, and hence the yield of calcined concentrate, are practically unchanged, which means that the process has passed quite fully.

The determination of the optimal duration of calcination was carried out at a temperature of 770 ° C, calcining the samples of the concentrate for 0.5; 1.0; 1.5; 2.0 and 2.5 hours (table 5).

Experiments have shown that the optimal calcination time is 1.0-2 hours. For 0.5 hours, the process of decomposition of hydroxides, basic carbonates and carbonates is not complete - PPP = 17.9%, and exposure over 2 hours is impractical, because it is completed and the RFP is practically unchanged.

As a result of calcination in experiment 3 (table. 5), a concentrate was obtained containing, in% wt .: 5.06 CuO; 12.6 ZnO and 25.5 Fe ₂ O ₃ , 1.2 S, the rest is CaO, SiO ₂ , MgO and other oxides, suitable for the further extraction of valuable heavy non-ferrous metals by known methods at existing non-ferrous metallurgy enterprises, and the involvement of the obtained complex heavy non-ferrous metal concentrates in recycling, which eliminates the discharge of toxic waste into the environment.

This composition of the concentrate is suitable for processing in existing non-ferrous metallurgy plants. In addition, reducing the mass of complex concentrate by 22-26% will reduce the cost of transportation and further processing.

The proposed method is simple, economical for the treatment of industrial solutions and / or effluents, with obtaining concentrates suitable for their processing at non-ferrous metallurgy enterprises. This is important not only from an economic point of view, but also from an environmental point of view - industrial effluents will become a raw material source of heavy non-ferrous metals. The use of CVD sludge for the treatment of toxic solutions and / or effluents will dramatically reduce the cost of initial reagents and get an additional environmental effect in the industrial zone of thermal power plants.

Claims (3)

1. The method of deposition of heavy non-ferrous metals from industrial solutions and / or effluents, comprising treating with a calcium-containing reagent, characterized in that the solutions and / or effluents are treated with a complex precipitating reagent, including calcium carbonate, iron, silicon and magnesium oxides in a mass ratio of CaCO ₃ : Fe _total : SiO ₂ : MgO = 100: 0.7-9.5: 1.3-4.8: 2.5-6.5, with vigorous stirring to obtain a pH of 5.0-5.5 in the pulp, then the pulp is kept at active stirring for 0.5-2 hours, the precipitate is filtered off and washed. 2. The method according to p. 1, characterized in that the obtained precipitate is calcined at a temperature of 720-770 ° C for 1-2 hours. 3. The method according to p. 1, characterized in that as a reagent-precipitator use sludge chemical treatment of thermal power plants, including calcium carbonate, iron, oxides of silicon and magnesium, bringing their composition in accordance with the mass ratio specified in paragraph 1.