JPH01224091A - Treatment of waste containing cyanogen compound - Google Patents

Abstract

PURPOSE:To completely treat a cyanogen compd. in waste by adding a copper compd. and an iron compd. to the waste. CONSTITUTION:An iron compd. such as potassium ferricyanide and a copper compd. such as copper sulfate are added to waste contg. a cyanogen compd. such as waste water from a plating stage or a refining stage using a cyanide process and the waste is subjected to oxidative decomposition treatment with an oxidizing agent such as sodium hypochlorite. When matter having reducing power such as metallic iron powder is present in the waste, the waste is pretreated to magnetically separate magnetizable matter from nonmagnetizable matter. By the decomposition treatment, cyano-iron-complex in the waste is converted into separable salt and this salt is easily removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for treating waste containing cyanide.

[Prior art] Wastewater or solid waste containing cyanide (hereinafter referred to as "
(referred to as "waste") is discharged from the Metsuki Factory, Qinghua Seishin Factory, etc. The cyanide concentration in wastewater is regulated to be 1 ppm or less, and solid waste is regulated so that the cyanide concentration in the eluate is 1 ppm or less by elution test.

Generally, when cyanide compounds in a solution are treated, cyanide compounds such as free cyanide, silver, zinc, copper, etc. are relatively easily decomposed, so they are treated by an oxidative decomposition method. However, since iron cyano complex salts cannot be decomposed by oxidative decomposition methods, various methods have been proposed. For example, there are various methods such as chemical, electrical or photochemical decomposition methods, thermal decomposition methods, physical concentration methods, adsorption treatment methods, and precipitation treatment methods.

[Problems to be Solved by the Invention] However, the above-mentioned decomposition treatment method is not economical because iron cyano complex salts are chemically stable and must be carried out under harsh conditions using a large amount of energy. Therefore, it is not suitable as a waste treatment method. In addition, in the physical concentration method, the equipment used is expensive, and the concentrated liquid must be post-treated after treatment.In the adsorption treatment method, an adsorbent with a high adsorption power and low adsorption power has not yet appeared. There are problems such as impracticality. Although the precipitation treatment method is suitable as a method for treating large amounts of waste containing iron cyano complex salts, it has various problems. For example, in the navy blue method that uses iron salts as a precipitant or the treatment method that uses zinc compounds as a precipitant, the iron cyano complex in the precipitate may be redissolved by the oxidizing agent or oxygen in the air, so There is a problem that processing cannot be carried out conveniently. In the precipitation method in which a copper compound is added as a precipitant, the copper ferricyanide produced is very finely precipitated, making filtration difficult.

In addition, wastes may contain substances that are oxidized and decomposed in addition to cyanide compounds. For example, ossification smelting residues mainly contain metal iron powder, pyrite, etc. that are mixed in during the mining process. There are substances that have a reducing effect, such as sulfides. Since the oxidizing agent is consumed by this substance, the amount of oxidizing agent consumed increases in the oxidative decomposition treatment of cyanide compounds, and furthermore, the cyanide compounds may not be completely treated.

Therefore, the purpose of the present invention is to convert iron cyano complex salts, which cannot be treated by oxidative decomposition treatment, into hardly soluble salts and to easily remove them, and in addition, when the waste contains metallic iron powder, pyrite, etc. An object of the present invention is to provide a method for treating waste containing cyanide compounds, which can effectively perform oxidative decomposition treatment by pre-treating the waste.

(Means for Solving the Problems) To solve the above problems, the present invention provides a method for treating waste containing cyanide and removing cyanide, the waste containing copper compounds and The present invention provides a method for treating waste containing cyanide compounds, which includes a step of adding and treating iron compounds.

The cyanide-containing waste that is treated by the method of the present invention includes cyanide compounds such as wood wastewater, wastewater from chemical refineries, ore processing wastewater from mines that use cyanide compounds, and wastewater from electronic material scrap processing factories. This refers to cyanide-containing wastewater, such as cyanide-containing wastewater, and solid waste containing cyanide compounds, such as slag from assimilation smelting. In the method of the present invention, solid waste containing cyanide compounds may be treated after adding water to form a slurry pulp.

In order to remove all cyanide from waste by the method of the present invention, copper compounds and iron compounds are usually added to the waste;
Preferably, the waste is subjected to oxidative decomposition treatment before treatment.

When performing oxidative decomposition treatment, if there are reducing substances such as metallic iron powder or sulfides such as pyrite in the waste containing cyanide, they may be disposed of as pretreatment for oxidative decomposition treatment. Magnetically separates objects into magnetic and non-magnetic objects. If the waste is solid, water is added, usually
Preferably the concentration is 20-60%, more preferably 30-60%
After adjusting the pulp to a 50% slurry, it is subjected to magnetic separation treatment.

If the pulp concentration is less than 20%, the processing volume will be large and the processing equipment will need to be large, which is uneconomical.
When it exceeds 60%, the viscosity of the pulp becomes high and processing becomes difficult.

Waste water or pulp whose concentration has been adjusted is magnetically separated using a magnetic separator and separated into magnetic materials and non-magnetic materials. The magnetic separator used in this magnetic separation step is not particularly limited, and may be a wet type magnetic separator used for normal magnetic separation, and the magnetic field strength is usually preferably 5.
00 to 1500 oersted, more preferably 500
~800 oersted. If the magnetic field strength of the magnetic separator used is too high, the amount of magnetic material will increase and excessive equipment will be required to wash and filter the magnetic material; if it is too low, the magnetic material will need to be separated and recovered. becomes insufficient, making it impossible to perform the subsequent oxidative decomposition treatment sufficiently.

The magnetic substances separated and collected by magnetic separation are washed with water and processed separately. The washing water is mixed with non-magnetic pulp 1 and transferred to the next treatment step.

Next, an oxidizing agent is added to the waste that does not require magnetic separation treatment or to the non-magnetic pulp obtained after magnetic separation treatment of the waste in order to oxidize and decompose the cyanide compounds contained therein.

The oxidizing agent used in the oxidative decomposition treatment can be the oxidizing agent used in the usual oxidative decomposition treatment of cyanide, such as sodium hypochlorite, chlorine gas, hydrogen peroxide, ozone, etc. . These can be used alone or in combination of two or more.

The amount of oxidizer used is determined by measuring the redox potential of the waste to be treated, i.e. waste or non-magnetic material.
adjusted. For example, the redox potential is 30 in the first stage reaction.
0-350m V, 600-650m for second stage reaction
The amount of oxidizing agent added is adjusted so that V.

Although ordinary cyanide compounds are decomposed by the oxidative decomposition, iron cyano complexes are not decomposed and remain in the waste after the oxidative decomposition treatment.

In the method of the present invention, in order to treat this iron cyano complex salt, a copper compound and an iron compound are added to the waste after oxidative decomposition treatment to convert the iron cyano complex salt into a sparingly soluble salt, which is then precipitated and removed. do. Here, the iron cyano complex salts treated by the method of the present invention are ferricyanides such as potassium ferricyanide and sodium ferricyanide, and ferrocyanides such as potassium ferrocyanide and sodium ferrocyanide.

The copper compounds used in the method of the present invention are copper salts that produce copper ions when dissolved in water, such as copper sulfate, copper nitrate,
Examples include cupric chloride, cuprous chloride, and copper carbonate, with copper sulfate being preferred. These can be used alone or in combination of two or more.

The amount of the copper compound to be used is preferably equal to or more than the iron cyano complex contained in the waste, and more preferably 1.
It is more than 2 times the equivalent. If the amount of the copper compound used is less than the equivalent amount of the iron cyano complex contained in the waste, the formation of the insoluble complex will be insufficient, and cyanide will remain in the waste as a complex ion.

In the method of the present invention, copper ions generated in the waste form insoluble complex salts with both ferricyanide and ferrocyanide ions by adding the ferricyanide compound to the waste. Not only solutions, but also mixed solutions of ferricyanide and ferrocyanide, solutions containing oxidizing agents, etc. can be treated without the need for pretreatment such as reduction.

The iron compound added together with the copper compound functions to promote precipitation of the insoluble complex salt produced by the reaction between the iron cyano complex salt and the copper compound. Examples of the iron compound include ferrous sulfate, ferric sulfate, ferrous chloride, and ferric chloride, with ferrous sulfate being preferred. These can be used alone or in combination of two or more.

The amount of iron compound used is usually preferably 10 to 50%, more preferably 30 to 50% of the cyanide concentration in the waste.
It is. If the amount of iron compound used is too large, the amount of precipitate will increase and excessive filtration equipment will be required. If the amount of iron compound is too small, the effect of the iron compound as an auxiliary agent for precipitation will be reduced, and copper ferricyanide will be mixed into the filtrate. , waste treatment will be inadequate.

The method of adding the copper compound and iron compound is not particularly limited, but it is preferable to dissolve the copper compound and iron compound separately in water and add them separately as an aqueous solution.

The pH of the waste when treated by adding a copper compound and an iron compound is preferably 5 to 9, more preferably 6 to 8.
It is good that it is within the range of . If the pH is less than 5, the added copper compound and iron compound may remain in the treated material as copper ions or iron ions, and if the pH exceeds 9, the iron cyano complex will be redissolved. Therefore, if the pH of the waste is not within the above range, the pH is adjusted to the above range as necessary before and after adding the copper compound and iron compound.

In particular, if the pH is on the alkaline side, the pH should be adjusted to 9 before adding the copper compound or before adding the recompound.
It is preferable to keep it below.

The order of addition of the copper compound and iron compound is not particularly limited, but if the waste contains cyanide compounds other than iron cyano complex salts, the iron compound is added in advance to convert those cyanide compounds into iron cyano complex salts. It is necessary to keep it. When only the iron cyano complex salt is contained, the iron compound and the copper compound may be added at the same time, or either may be added first. If they are added at the same time, a mixed solution of both compounds may be prepared in advance and added.

In the method of the present invention, after adding the above-mentioned copper compound and iron compound, the pH is adjusted after stirring for about 10 minutes, further stirring for about 10 minutes, and then standing for 2 to 24 hours. The material settles and a cyanide-free supernatant is obtained. The precipitated water-insoluble material is filtered and roasted to thermally decompose the cyanide. The resulting roasted residue has a high copper grade, so it can be reused as a copper raw material.

As described above, in the method of the present invention, since there is no re-dissolution of iron cyano complex salt due to oxidation, the treatment can be carried out conveniently in the atmosphere. Moreover, since the sedimentation and concentration treatment of the precipitate is easy, the filtration process of the precipitate can be greatly simplified.
It has high practical value.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

In the following Examples and Comparative Examples, the total cyanide concentration was measured by the pyridine carboxylic acid method, and the analysis of copper and iron was performed by atomic absorption spectrometry.

In addition, dilute sulfuric acid or sodium hydroxide was used for p1131 adjustment. The increase in liquid volume due to the addition of reagents and p 11 adjustment was less than 5% of the total liquid volume.

Example 1 Red blood salt solution LOOM containing 139 ppm as cyanide was
While stirring, add ferric sulfate to 50 ppm as iron, stir for 10 minutes, then add copper sulfate to 150 ppm as copper, adjust the pl+ of the solution to 7, and then add 30 ppm as iron. Stir for a minute. Next, 5 ppm of anionic organic flocculant (Sumifloc FA40, manufactured by Sumitomo Chemical Co., Ltd.) was added and slowly stirred for 1 minute, and then
It was immediately filtered using a glass filter GC-50, and the total cyanide concentration, copper ion concentration, and iron ion concentration of the obtained filtrate were measured. As a result, the total cyan density is 0. O5ppm,
The copper ion concentration was 0.7 ppm and the iron ion concentration was 0.7 ppm.
It was 1 ppm or less.

Example 2 The total cyanide concentration, copper ion concentration, and iron ion concentration were measured in the same manner as in Example 1, except that copper sheath acid was added in place of copper sulfate to give a copper content of 150 ppm. did. As a result, the total cyan concentration was 0.06 ppm.
, the ill ion concentration was 0.9 ppm and the iron ion concentration was below 0.1 ppm.

Example 3 150 ppm of cupric chloride as copper instead of copper sulfate
The total cyanide concentration, sinus ion concentration, and iron ion concentration of the obtained filtrate were measured in the same manner as in Example 1, except that the amount of cyanide was added so as to be as follows. As a result, the total cyan density is 0. O4p
pm, the copper ion concentration was 0.06 ppm, and the iron ion concentration was less than 0.1 ppm.

Example 4 The total cyanide concentration, copper ion concentration and The iron ion concentration was measured. As a result, the total cyan density is 0. O3 ppm, copper ion concentration was 1, OppHl and iron ion concentration were 0.1 ppm or less.

Example 5 Red blood salt solution containing 150 ppm as cyanide 60! While stirring, add ferric sulfate to 50 ppm as iron and copper sulfate to 150 ppm as copper, and adjust the pH of the solution.
After adjusting H to 6.8 and stirring for 120 minutes, the mixture was allowed to stand for 20 hours to allow water-insoluble substances to settle and clear supernatant water 26β was removed. After stirring for an additional 10 minutes, the solution was
The sample was placed in a cylindrical container with a height of 150 cm and a height of 150 cm, and left to stand for 24 hours. Supernatant water was collected from a depth of 5 cm below the water surface at intervals shown in Table 5, and the total cyanide concentration was measured. Also 2
After standing still for 4 hours, the copper ion concentration and iron ion concentration of the supernatant water were measured. The results are shown in Table 1.

Table 1 Example 6 All ores were leached with sodium cyanide and gold and silver were removed with activated carbon.
Sodium hypochlorite was added to 6(le, and oxidative decomposition was carried out according to the usual method to remove free cyanide. The cyanide concentration after oxidative decomposition was 36.3 ppm). After adjusting the concentration to 7 and further removing trace amounts of gold and silver contained in the waste liquid with activated carbon, ferrous sulfate was adjusted to 50 ppm as iron, and copper sulfate was adjusted to 15 ppm as copper.
After adding 0 ppm, the pH was adjusted to 7. After stirring for 30 minutes, the resulting supernatant water was collected after stirring for 30 minutes, and the total cyanide concentration, sinus ion concentration, and iron ion concentration were measured.
m and o, 3ppIrl.

Comparative Example 1 To 2000 mf of the same red blood salt solution used in Example 5, copper sulfate was added to 1 soppm as copper while stirring, and after adjusting the pH of the solution to 7,
Stir for a minute. Next, the mixture was allowed to stand for 6 hours, and the supernatant water was collected and the total cyanide concentration was measured. As a result, the total cyan density is 18
It was ppm.

Example 7 Leaching residue of whole ore with sodium cyanide solution 2k
After repulping the pulp to a pulp concentration of 33% using a leachate from which gold and silver have been removed using activated carbon, and oxidizing and decomposing free cyanide to remove iron cyano complex salts using sodium hypochlorite, p)l of the pulp is 6 and sop with ferrous sulfate as iron.
pm was added, and further 200 ppm of copper sulfate was added as copper. After addition, p)l was adjusted to 7 and stirred for 30 minutes. Next, filter the pulp (using Toyo Roshi Nα5C),
The total cyanide concentration and free cyanide concentration of the obtained filtrate were measured. Further, the residue was repulped to a pulp concentration of 10%, and an elution test was conducted to measure the total cyanide concentration of the eluate.

The results are shown in Table 2.

Comparative Example 2 All ores were leached with sodium cyanide at a pulp concentration of 40%, and then filtered, and the resulting residue was repulped with fresh water into three types of liquids at pulp concentrations of 20.30 and 40%. For these three types of pulp, the total cyanide concentration in the filtrate obtained when the operations of water washing and filtration were repeated was calculated.

The water content of the filtered cake was 25%, and the cyanide concentration of the water attached to the residue before treatment was 185 ppm, the same as in Example 7 above.
It was calculated as In addition, the number of times of water washing required to reduce the total cyanide concentration of the water adhering to the cake to 1 ppm or less, the amount of water required per ton of residue (e), and the average cyanide concentration of the filtrate at that time were calculated. The results are shown in Table 3.

Table 3 Note: Required amount of water per ton of residue to reduce the total cyanide concentration of the water attached to the cake to 1 ppm or less **: Filtrate when the total cyanide concentration of the water attached to the cake is reduced to 11m or less Average Cyan Concentration Example 8 In order to confirm the effectiveness of the magnetic separation process, the following experiment was conducted.

6 kg of total ore was wet-milled to a particle size of 25 μm through 80%, leached with sodium cyanide, and the residue obtained by filtration was repulped to a pulp concentration of 33%. Magnetic ore beneficiation was performed using a wet magnetic ore separator (manufactured by Eriez Magnetic Co., Ltd., model L-4) at a magnetic field strength of 1000 Oersted.

As a result, 190 g of magnetic material and 5800 g of non-magnetic material were obtained.

Analysis of the magnetic material revealed that it was mainly metallic iron powder, and also contained sulfides such as pyrite.

The obtained non-magnetic material was filtered, and the obtained residue was repulped to a pulp concentration of 33% using a solution obtained by removing gold and silver from the leachate using activated carbon.

4.74 f of this pulp was separated so that the residue was 2 kg, and while stirring with a stirrer, a sodium hypochlorite solution (available chlorine 12%) was added four times at a rate of 10 d/j2 every hour. . Samples were collected for 500 d every hour and filtered (
Toyo Roshi Nα5C) was used, and the total cyanide concentration in the filtrate and T! The dicyan concentration was measured. Further, the residue was repulped with pure water to a pulp concentration of 10%, an elution test was conducted, and the total cyanide concentration and free cyanide concentration were measured. The results are shown in Table 4.

Further, the treatment was carried out in the same manner as above except that magnetic separation was not performed. Table 5 shows the measurement results of total cyanide concentration and free cyanide concentration.

Table 4 It was found that the leachate contained iron cyano complex salts that could not be oxidized and decomposed by sodium hypochlorite, but other free cyanide was oxidatively decomposed by almost 100% within 2 hours.

Table 5 [Effects of the Invention] According to the method of the present invention, iron cyano complex salts in waste that cannot be treated by oxidative decomposition treatment can be easily removed by converting them into poorly soluble salts. By combining the oxidative decomposition process, other cyanide compounds can be removed, and even if the waste contains reducing substances such as metal iron powder and pyrite, by combining the magnetic separation process as a pretreatment, these can be removed. By removing , the oxidative decomposition treatment of cyanide compounds can be effectively performed.

Agent Patent Attorney Shushi Iwamiya

Claims (3)

[Claims] (1) A method for treating waste containing cyanide and removing cyanide, which includes a step of adding a copper compound and an iron compound to the waste and treating the waste. Method. (2) The method according to claim 1, in which the waste is oxidized and decomposed with an oxidizing agent before the step of adding and treating the copper compound and iron compound. (3) The method according to claim 2, in which the waste is magnetically separated before the step of oxidizing and decomposing the waste with an oxidizing agent.