JPH01210096A - Removal of iron cyanide complex - Google Patents

Abstract

PURPOSE:To insolubilize an iron cyanide complex and remove it efficiently, by adding copper (II) ion in a specified amount to an aqueous soln. contg. an iron cyanide complex, adjusting the soln. at pH <=8, adding sulfite compounds, and separating produced precipitates. CONSTITUTION:Copper (II) ion is added to an aqueous soln. contg. an iron cyanide complex in an amount more than equivalent mole of iron cyanide. Then, after the soln. is adjusted at pH <=8, a sulfite compound is added to the soln. and produced precipitates are separated so as to remove the iron cyanide complex. In this case, it is preferable that active carbon is brought into contact in either processes before separation of said precipitates. Also in addition to the sulfite compound, while redox potential of the soln. is measured, the sulfite compound addition should preferably by finished by the time jumping of redox potential is at least finished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for separating and removing an iron cyanide complex from an aqueous solution containing the iron cyanide complex.

[Conventional technology]

Free cyanide or the cyanide compounds that easily generate it are generally easily decomposed by oxidation, and various treatment methods such as the alkali chlorine method, ozone oxidation method, and electrolytic oxidation method are available to detoxify wastewater containing such cyanide compounds. It has been developed and put into practical use. The most common treatment method at present is the alkali chlorine method. However, when heavy metal ions are contained, the heavy metal ions generally form a cyanide complex, making decomposition by the above method difficult. In particular, cyanide complexes of iron and nickel are known to be highly stable. Nickel cyanide complexes can be decomposed by the alkali chlorine method if sufficient treatment time is allowed, but iron cyanide complexes are difficult to decompose even by the alkali chlorine method, and the hexacyanoferrate (II) ion is converted into hexacyanoferrate (III). ) only oxidation to acid ions occurs. Iron cyanide complexes are relatively stable complex ions and are considered harmless to the human body.However, iron cyanide complexes gradually decompose under sunlight and liberate hydrogen cyanide, so even at low concentrations iron cyanide complexes are considered harmless to the human body. Discharging wastewater containing cyanide complexes into rivers should be avoided. Therefore, the iron cyanide complex must be thoroughly removed.

In the case of iron cyanide complexes, it is difficult to efficiently oxidize and decompose the cyano groups, so a method of forming an insoluble iron cyanide complex and removing it as a precipitate is being considered. A method is to add a copper(II) salt to a solution containing hexacyanoferrate(II[) acid ions, then add a sulfite salt, and separate and remove the generated precipitate from the solution.
This method is known to be effective as a method for rendering acid ions harmless.

Copper (
II) By adding sulfite in the presence of salt, hexacyanoferrate(III) acid ions are converted to hexacyanoferrate(II)
At the same time, the hexacyanoferrate (II) ion is reduced to an acid ion and forms a precipitate that is hardly soluble with the copper(II) salt that has been present in the solution, and by separating and removing this precipitate from the solution, the hexacyanoferrate (II) A solution containing (II[) acid ions can be rendered harmless. According to this method, by setting the pH of the solution at the time of separating and removing the precipitate from the solution to 8.5 or less, the total cyanide concentration, iron concentration, and copper concentration of the solution after precipitation separation are adjusted to the industrial wastewater discharge standard (cyanide). It is possible to reduce the total cyanide concentration to less than 0.1■71 under optimal conditions, making it highly harmless. It is said that it can be done.

However, this conventional method has the disadvantage that when the formed precipitate is separated and removed from the solution, the separation of the precipitate is incomplete. That is, when separating the precipitate by filtration using a furnace material with a retained particle size of about 5 μm or more (analytical grade 111 [L5A filter paper, furnace cloth, pre-coat filter made of cellulose powder as pre-coat material, etc.), the Although filtration is possible, it is difficult to obtain a sufficient filtration rate.On the other hand, if the pressure is too low, the precipitation cannot be retained, but the filtration will be incomplete, and the furnace liquid will not meet the discharge standards for industrial wastewater. The problem was that it couldn't be done. Also, relatively high p
When heavy metal ions, which cannot be removed as hydroxide precipitates without H, are present at the same time in a solution containing hexacyanoferrate(III) ions, this conventional method uses copper(II) salts as well as sulfite. In addition to separating and removing the precipitate formed by the addition at pH 8.5 or below, it is also necessary to separate and remove heavy metal ions, so the solutions containing hexacyanoferrate (III) ions and heavy metal ions are not the same. There were also problems, such as the difficulty of making it harmless through manipulation.

In addition, a major problem in the detoxification treatment of solutions containing hexacyanoferric (m> acid ions) using 1i4 (If) salts and sulfites is that
II) The amount of sulfite added to reduce acid ions to hexacyanoferrate (II) ions could not be accurately matched to the fluctuating concentration of hexacyanoferrate (III) ions in wastewater. It is. Ferric hexacyano(I[I) in solution prior to addition of sulfite
If the concentration of acid ions is not determined, or if the equivalence point of the reduction reaction between hexacyanoferrate (III) acid ions and sulfite is not detected in the process of adding sulfite, the hexacyanoferrate of hexacyanoferrate (II) ions must be determined. (II) This may lead to a situation where the amount of sulfite added is insufficient or excessive for the reduction reaction to acid ions, and as a result, iron hexacyano<I
II) Separation and removal of acid ions from the solution becomes incomplete,
There are problems such as not being able to satisfy the cyanide compound emission standard of 1/1, or sulfite added in large excess being detected as COD, and further treatment of this excess sulfite being required. Furthermore, since sulfite ions undergo autoxidation in water, it is difficult to accurately know the concentration of sulfite ions in water, and iron hexacyano (I
II) Depending on the pH of the solution during the acid ion reduction reaction and other oxidizing substances coexisting with hexacyanoferrate (III) ions, sulfite may be consumed in excess; (III) Even if the concentration of acid ions is determined in advance, there are problems such as it is difficult to add the necessary amount of sulfite to the hexacyanoferric (I [[) acid ions]. be.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the conventional problems and provide a method for removing hexacyanoferrate (III) ions by precipitation and separation using copper (II) ions and sulfite compounds. It is an object of the present invention to provide a method for adding a sufficient amount of sulfite compound in order to improve properties and insolubilize an iron cyanide complex.

[Means to solve the problem]

In order to solve the above problems, the method of the present invention firstly adds copper (II) ions to an aqueous solution containing an iron cyanide complex in an amount equivalent to or more than the mole of the iron cyanide complex, and then
The method is characterized in that H is set to 8 or less, a sulfite compound is added, and the resulting precipitate is separated. Second, copper (ff) ions are added to an aqueous solution containing an iron cyanide complex in an amount equal to or more than the same mole relative to the iron cyanide complex, and then the pH of the aqueous solution is adjusted to 8 or less, and a sulfite compound is added to form a precipitate. The method for separating the precipitate is characterized in that activated carbon is brought into contact with the precipitate in one of the steps before separating the precipitate. Thirdly, the method is characterized in that, while measuring the redox potential of the aqueous solution, the addition of the sulfite compound is terminated when at least the jump in the redox potential is completed.

[For production]

The iron cyanide complexes include hexacyanoferrate (I[[) acid ions, hexacyanoferrate(II) acid ions, or mixtures thereof, and the aqueous solutions containing the iron cyanide complexes include various industrial wastewaters, test wastewaters, etc. can be mentioned.

In the present invention, the addition of copper (II) ions is not particularly limited as long as it dissolves to give copper (II) ions, but examples of water-soluble copper (II) compounds include copper sulfate (■), nitric acid Copper (■), copper chloride (■), copper bromide (■),
Copper iodide (■), chlorine-coated copper (II), perchloric acid wi (I
Copper(II) salts such as copper(II) hypochlorite, copper(II) nitrite, copper(II) acetate, and the like may be mentioned. Also, metallic copper, copper hydroxide (■), copper oxide (■), basic copper carbonate (■), which gives copper (II) ions when dissolved in acid.
, copper fluoride (■), copper phosphorus (■), #il sulfide (I
Copper compounds such as F), or copper(I) chloride, copper(I) bromide, and iodine which produce copper(If) ions by oxidation reaction after dissolution or during precipitation with hexacyanoferrate ions. Copper oxide (■), copper oxide (I), copper sulfide (1
) and the like can also be used.

The amount of the copper (II) ion added must be equal to or more than the equivalent molar amount to the iron cyanide complex, and if the amount of the copper (II) ion added is less than the equivalent molar amount, precipitation of the iron dione complex will occur. This is not good because it is not done enough.

As the sulfite compound, salts such as sodium sulfite, sodium bisulfite, potassium sulfite, etc., sulfite water, sulfite gas, etc. are commonly used as long as they can form sulfite ions in an aqueous solution.
The above concentration is suitable.

When adding the sulfite ion to the aqueous solution, it is necessary to adjust the pH of the aqueous solution to 8 or less. When pit exceeds 8, the reaction in which hexacyanoferrate (III) ions in the aqueous solution are reduced to hexacyanoferrate (II) ions becomes difficult to proceed. According to the inventors' confirmation, the iron cyano iron (I[ It is a fine powder, and when the pH of the aqueous solution is adjusted to 8 or less and sulfite ions are added, the iron (III) constituting the steel cyanide complex is reduced to iron (II), and as soon as this happens, the steel cyanide complex becomes highly compatible. The particles coagulate together to form large precipitated particles.

The activated carbon that can be used in the method of the present invention may have any properties such as shape, starting material, activation method, surface area, composition, and impurity concentration, and the particle size of the activated carbon particles can be separated from the solution. The particle size may be as small as the activated carbon particles are uniformly dispersed in the solution, and the particle size is preferably about 1100 mesh.

To bring the aqueous solution into contact with the activated carbon, there are methods such as adding the activated carbon to the aqueous solution and passing the aqueous solution through a layer packed with the activated carbon, but in order to increase the effect of the method of the present invention, The above method of addition is more desirable. In the above method of adding, the activated carbon is added at 0.0% with respect to the total amount of the aqueous solution.
If an amount of 5% or less is used, retention of the precipitated particles and filtration rate can be improved, but in order to reduce the amount of the sulfite compound used during the reduction reaction by the sulfite compound, It is preferable to add a larger amount. Furthermore, if residual chlorine, gold, or silver is contained in the solution containing the hexacyanoferrate (III) ion by adding the activated carbon, there is a side effect that the residual chlorine, gold, or silver will be decomposed or adsorbed. You can also get some benefits. In addition, the timing of adding the activated carbon is before adding copper (II) ions to the solution containing hexacyanoferrate (III) ions, and before adding copper (II) ions to the solution containing hexacyanoferrate (III) ions. w4(II) before adding the sulfite compound and in the solution containing hexacyanoferrate (m) ions.
This can be done at any time, including before separating the precipitate from the solution after adding ions and sulfite compounds, or before adding copper(II) ions to a solution containing hexacyanoferric acid ions. It is more preferable to add copper (II) ions to the solution containing xacyanoferrate (III) ions and before adding the sulfite compound;
The coexistence of ions and activated carbon is due to the activation of hexacyanoiron (
III) The reduction reaction of acid ions is significantly promoted, and the amount of the sulfite compound used can be reduced. Furthermore, according to the above procedure, even if the pH of the solution is raised to 9.5 when the precipitate and the activated carbon used are simultaneously separated and removed, the total cyanide concentration in the treated solution remains below 0.1/1. It can also be highly rendered harmless.

A working electrode, a reference electrode, and a potentiometer are used to measure the redox potential of the reduction reaction in the present invention. As the working electrode, a non-reactive electrode that is not affected by the aqueous solution, such as a platinum electrode, a silver electrode, or a total electrode, is used, and as a reference electrode, a silver-silver chloride electrode, a sweet tooth electrode, a hydrogen electrode, etc. are used. .

Copper (If) per mole of hexacyanoferrate (DI) ions in a solution containing hexacyanoferrate (III) ions.
When a sulfite compound is added to the aqueous solution after 2 moles or more of ions are present, the observed redox potential decreases. When 0.5 mol or more is added, a jump is observed in the redox potential, and thereafter, even if the sulfite compound is added, the redox potential decreases slowly or does not occur at all. This jump in oxidation-reduction potential does not necessarily show a constant jump depending on the pH of the solution, but as a potential difference, it is
After this jump, the reduction in redox potential due to the addition of sulfite compounds is about 10 mV to 20 mV.
Only mV or less.

At the time when the jump in the redox potential is completed, the reaction in which iron (III) in the steel cyanide complex is reduced to iron (■)' has been sufficiently completed. The jump in redox potential is similarly observed when the activated carbon is involved.

In the measurement of the redox potential of the present invention, before adding the sulfite compound to the solution, hexacyanoferrate ion,
It is preferable to remove redox substances other than copper (II) ions and activated carbon as much as possible, and in particular, sulfite compounds are consumed by oxidizing substances present in the solution, so such oxidizing substances should be removed. It is preferable.

[Example-1] JIS K8801 special grade potassium hexacyanoferrate (III) was dissolved in water to prepare a 644 μ/It solution of hexacyanoferrate (III) ions. Also, JISK8
Copper (If) by dissolving 983 special grade copper sulfate (■) pentahydrate
An 850 μ/I solution of the ion was prepared. 80 ml of hexacyanoferrate(m) acid ion solution was taken out and stirred with a magnetic stirrer while water 240++4! Copper (If)
Add 40mA of ionic solution to bring the total liquid volume to 360a+J!
After adjusting the pH of this solution to 4.0, while maintaining the pH at 4.0, 2 ml of the 476 μ/l sulfite ion solution was added at 1 minute intervals to make a total of 124 ml.
After reduction was performed by adding water, water was added again to bring the total volume of the solution to 400 mff1.

Subsequently, 400 nl of the solution containing the precipitate was divided into two equal parts, and one part was coated with activated carbon (Toyo Carbon GRC-11 100 nm).
The solution was filtered after adding 0.2g of 0 mesh pulverized product) and stirring for 10 minutes, and the other was filtered after adjusting the pH of the solution to 8.5 without adding activated carbon. . pH of solution! Sulfuric acid and sodium hydroxide solution were used for JI adjustment. For filtration, Arashi 5A filter paper (filtration area I
Using pre-coated paper with 1 g of filter paper powder (50-100 mesh) on 10-'of), 10-10% of filter paper powder (50-100 mesh) was used, with and without activated carbon.
0 ml was filtered under normal pressure and reduced pressure (450 mmHg).

The iron and copper in the obtained liquid were quantified by ICP emission spectrometry, and the total cyanide concentration was determined by distillation of total cyanide according to the JIS KO102 factory wastewater test method. Quantified by photometry.

The preparation and standardization of the sulfite ion solution used in this experiment were performed as follows. That is, after preparing a sulfite ion solution by dissolving commercially available reagent grade sodium sulfite heptahydrate in water, hexacyanoiron (II) in which copper (II) ions were present was prepared.
III) Immediately before adding the sulfite ion solution to the acid ion solution, the sulfite ion solution was standardized by redox titration using an iodine solution and a sodium thiosulfate solution.

After setting the total liquid volume to 400mf, the total concentration of hexacyanoferrate ions in the solution was 129■/j2, the total concentration of copper(II) ions was 85■/It, and the initial concentration of hexacyanoferrate (I [[]1i4 for the number of moles of acid ion
(II) Ratio of moles of ions ((Cu”)/((Fe
(CN)6)'-)t) is 2.20, and the ratio of the number of moles of sulfite ion to the number of moles of hexacyanoferrate(III) ion added initially ((soi"-)/
((Fe(CN)b)'-)+) is 0.58.

Table 1 shows the quantitative results of total cyanide, iron, and copper in each solution and the time required to filter 100 ml of solution.

When filtration is carried out at normal pressure, the precipitate is separated by filtration with or without the addition of activated carbon, and hexacyanoferric (III)
Although it is possible to detoxify a solution containing acid ions, it took 50 to 60 minutes to filter 100 mj2 of the solution. On the other hand, when filtration is performed under reduced pressure, when activated carbon is added, it is possible to obtain a liquid with the same quality as that obtained under normal pressure, and the filtration is completed in 7 minutes. Although it is possible to increase the speed, when activated carbon is not added, precipitated particles are observed in the furnace liquid, making it difficult to reduce the pressure.

[Example-2] 80 mm of hexacyanoferrate (III) acid ion 644rrg/Il solution prepared in Example-1! While stirring with a magnetic cooler, add 240 ml of water and 40 val of the 850 mg/It solution of copper (II) ions prepared in Example-1 to make the total liquid volume 360 ml.
After adjusting the pH of the solution to 7.5, 0.4 g of activated carbon (Toyo Carbon GRC-11 1100 mesh pulverized product) was added and stirred for 30 minutes while maintaining the pH of the solution at 7.5. went. Subsequently, after adjusting the pH of the solution to 4.0, while maintaining the pH at 4.0, 2 ml of the 486■/E sulfite ion solution was added at 1 minute intervals.
Total 116n+j! The pH of the solution after reduction by adding
was adjusted to 8.5 and further water was added to bring the total volume of the solution to 400mj! The mixture was stirred for 10 minutes and then filtered. Adjustment of pH of solution Preparation and standardization of sulfite ion solution, filtration operation, and determination of total cyanide, iron, and copper in the furnace solution were performed in the same manner as in Example-1.

The total concentration of hexacyanoferrate ions in the solution after the complete crushing was 19,400 ml was 129 nv/1. The total concentration of copper(II) ions was 85/It, and the copper(II) ion concentration was 85/It.
II) Ratio of moles of ions ((Cu”)/((Fe(
CN)a) 3-) 5) is 2.20, and furthermore, the ratio of the number of moles of sulfite ion to the number of moles of hexacyanoferrate (III) ion added initially ((S(h2-)/
((Fe(CN)b)'-) = ) is 0.40.

Table 2 shows the quantitative results of total cyanide, iron, and copper in each solution, as well as the time required for 100 nl of the solution.

Even when copper (II) salt was added to a solution containing hexacyanoferrate (III) ions, activated carbon was added to the solution, and a sulfite compound was further added, normal pressure was obtained by vacuum filtration. It is possible to obtain a liquid with the same quality as water, and it is possible to improve the retention of precipitated particles and the filtration rate. In addition, by adding activated carbon after adding a copper (II) salt to a solution containing hexacyanoferrate (III) ions, activated carbon can be obtained after adding a copper (II) salt to a solution containing hexacyanoferrate (III) ions. The amount of the sulfite compound used could be reduced compared to the case of Example 1, in which the sulfite compound was added immediately without adding the sulfite compound.

[Example-3] 80 ml of the hexacyanoferrate (III) ion 644 /It solution prepared in Example-1 was taken out and while stirring with a magnetic cooler, the copper (1
Add 40tall of 1M Oni/850q/1 solution, further add water to make the total liquid volume 400mn, and adjust the DH of the solution.
After adjusting to 4.0, 40 ml of the solution containing the precipitate was taken, and a mixed solution of disodium ethylenediaminetetraacetate and aqueous ammonia was added to the solution to dissolve the precipitate, and before adding activated carbon. iron hexacyano in a solution of (
m) The amount of M ions was quantified using absorption at 424 nm. Next, the remaining 360mj! Activated carbon (Toyo Calboy GRC-11)-100) 7 s pulverized product) in a solution of
0.36 g was added and stirred for 60 minutes while maintaining the pH of the solution at 4.0, during which precipitation and activated carbon were added at 5 minutes, 10 minutes, 20 minutes, 30 minutes, and 60 minutes after the addition of activated carbon. 40mj2 of the solution containing ethylenediamine4
A mixed solution of disodium acetate and aqueous ammonia was added to dissolve the precipitate, and the activated carbon and the solution were quickly separated by applying vacuum using an 11kL 5cF filter. The amount of xacyanoferrate(III) ions was quantified using absorption at 424 nm. Furthermore, when the PL of the solution is 4.0 to 1000 when adding activated carbon and stirring after adding activated carbon, the same operation is performed to add copper to the solution containing hexacyanoferrate (II) ions. The reduction of hexacyanoferrate (III) ions by activated carbon when (II) ions were added was investigated. A comparative example was prepared in the same manner as described above except that copper (II) ions were not added.

The horizontal axis represents the stirring time after the addition of activated carbon, and the amount of hexacyanoferrate ([[) acid ion (((
The amount of hexacyanoferrate(III) acid ions (((Fe
(CN)i) ”-) ) percentage (((Fe(CN)
a) '-)/ ((Fe(CN)b) '-) t
Figure 1 shows the influence of contact time on the reduction of hexacyanoferrate (m) ions by activated carbon when no copper (If) ions are added, with X 100 ) taken as the vertical axis.
Further, FIG. 2 shows the case where copper (II) ions are added.

In addition, the amount of hexacyanoferrate(III) acid ions (((Fe(ON
)i) ”-)Ei) of hexacyanoferrate(II) ion when stirred for 1 hour after addition of activated carbon! (((
Fe(CN)i ) '-) ) (7) Percentage (((
re(CN)a ) '-) / ((Fe(CN)h
) 3-) Taking tX100) as the vertical axis, the effect of p on the reduction of hexacyanoferrate (III) ion by activated carbon
The influence of H is shown in Figure 3.

It was confirmed that when copper (II) salt was added, the reduction of hexacyanoferrate (II) ion by activated carbon was accelerated compared to when no copper (RL) salt was added at any pH. . Particularly at pH around 7 to 8, the reduction reaction of hexacyanoferrate (III) ions by activated carbon was significantly promoted. It was also confirmed that when a copper (If) salt was added, the reduction reaction of hexacyanoferric (I[[) acid ions by activated carbon] progressed as the contact time became longer.

[Example 4] JIS K8801 special grade potassium hexacyanoferrate (III) was dissolved in water to prepare a 3220 µ/l solution of hexacyanoferrate (II) ions. Also, JIS 89
Dissolve 83 special grade sulfuric acid steel (■) pentahydrate in water to make copper (If
). A 2900 μ/Il solution of ion was prepared. Hexacyanoferrate (m) acid ion solution 40II11 was taken out, and while stirring with a magnetic cooler, 860 m2 of water was added to make the total liquid volume 900 mj+, and the pl+ of the solution was 8
．． After adding activated carbon (the same as that used in Example-1) Ig while maintaining the temperature at 5 and stirring for 10 minutes,
While maintaining the pH of the solution at 7.5, add 24 ml of the copper (I[) ion solution by rail at 1 minute intervals! Then, 12 mff1 of copper (II) ion solution was added. continue,
While maintaining the pH of the solution at 6.5, add 1 tag of 2490 μ/L sulfite ion solution at 1 minute intervals, and after adding a total amount of 9IIN to perform reduction, water was further added. The total liquid volume was adjusted to 1000 ml, stirred for 10 minutes, and then filtered. In addition, a comparative example was prepared in the same manner as described above except that activated carbon was not added. In this comparative example, 15II11 of a 2570 μ/1 sulfite ion solution was required to complete the reduction reaction by the sulfite compound. Adjustment of pi of the solution, preparation and standardization of sulfite ion solution, filtration operation, and quantitative determination of total cyanide, iron, and copper in the furnace solution were performed in the same manner as in Example 1.

The total concentration of hexacyanoferrate ions in the solution after adjusting the total volume to 1000 nl was 129/1, the total concentration of copper(II) ions was 104.4trg/l, and the initial concentration of hexacyanoferrate ( Ill) Ratio of the number of moles of copper(II) ions to the number of moles of acid ions ((Cu”)/((
Fe(CN)i ) ”-) = ) is 2.70, and furthermore, the ratio of the number of moles of sulfite ion to the number of moles of hexacyanoferrate (III) ion added initially ((SOs”
-)/((Fe(CN)a)'-)E) is 0.46 when activated carbon is added and 0.79 when activated carbon is not added.

Table 3 shows the quantitative results of total cyanide, iron, and copper in the furnace fluid.

When filtration is performed at normal pressure, it is possible to detoxify the solution containing hexacyanoferrate (I) ions by separating the precipitate by filtration regardless of whether activated carbon is added or not. On the other hand, when performing filtration under reduced pressure, when activated carbon is added, it is possible to obtain a liquid with the same quality as that obtained under normal pressure, improving the retention of precipitated particles and increasing the filtration rate. However, when activated carbon was not added, precipitated particles were observed in the furnace liquid, making it difficult to reduce the pressure.

Furthermore, when activated carbon was added, the amount of sulfite used could be reduced.

Table 3 ・ [Example 5] The residual liquid obtained when the susceptibility of the ll&lsA furnace material pre-coated with filter paper powder in Example 4 was investigated was used as a sample, and a sodium hydroxide solution was used. pH of the solution
After maintaining the pore size between 6.5 and 10, vacuum filtration was performed using a membrane filter with a pore size of 1 μm, and the total cyanide, iron, and copper in the resulting solution were quantified. The results are shown in Table 4.

When activated carbon is present, even if the pH of the solution is raised to 9.5 when separating and removing the precipitate, the cyanide concentration in the solution can be highly rendered harmless to 0.1/1 or less. has become possible, and the pH range for separating and removing the precipitate has been expanded.

[Example-6] In Example-1, Example-2, and Example-4, copper(II) was added to the solution containing hexacyanoferrate(III) ions.
After adding the ion solution, the oxidation-reduction potential of the solution was measured while adding the sulfite ion solution into the solution.

A platinum electrode and a silver-silver chloride electrode using a saturated potassium chloride solution as the internal solution were used to measure the redox potential.

The ratio of the number of moles of sulfite ion added to the number of moles of hexacyanoferrate (I[r) acid ion added initially ((S
O3''-) / ((Fe(CN)6:l''-) i
) is plotted on the horizontal axis and the redox potential is plotted on the vertical axis. Changes in reduction potential are shown in FIG. 4 for Example 1, FIG. 5 for Example 2, and FIG. 6 for Example 4.

In all cases of Example-1, Example-2, and Example-4, a jump in the redox potential of the solution was observed by the time the addition of the sulfite ion solution was finished, and furthermore, the addition of the sulfite ion solution was It was observed that the jump in redox potential was completed at the end of the test. Iron hexacyano(III)
In this way, the sulfite compound was added to the solution containing the acid ions after adding the copper(II) salt to the solution containing the acid ions, and Example-1
As shown in Example-2 and Example-4, by separating and removing the generated precipitate or the generated precipitate and activated carbon from the solution, the solution containing hexacyanoferrate (I [[) acid ion] can be rendered harmless. is formed, and iron hexacyano (I[[
) A sufficient amount of sulfite compound can be added to detoxify a solution containing acid ions.

[Example 7] A leachate was prepared by immersing ore containing heavy metals such as gold, iron, and iron in a sodium cyanide solution. This leachate has total cyanide of 960 μ/l, iron of 1101 rr/l, and copper of 8.8
2mg/j! , zinc 1.03 N/a, nickel 0.
Contains 99 ■/l, gold 23.8 ■/l, silver 16.2 ■/1, etc.

To 2000n+1 of this leachate, add 7170μ of sodium hypochlorite (hypochlorite ion concentration 38.5μ/mβ) solution as hypochlorite ion, and add 98 to 12
．． After stirring for 60 minutes while keeping the pH at 3 to 12.4 and stirring for 60 minutes while keeping the pH at 8.5 to oxidize and decompose free cyanide and cyanide compounds that tend to generate it by the alkali chlorine method, activated carbon (Toyo Carbon GRC) was used. -11-100
After adding 2 g/ll of mesh (pulverized product) and stirring at pH 8.5 for 5 minutes, and further stirring at pH 4.0 for 5 minutes,
The solution was divided into two equal parts.

Add sulfuric acid to one of the two halves of the solution while still containing activated carbon! Prepared by dissolving 1iiiI(II) pentahydrate LJ, w4(II) I, t7 (10mg/mj ?IJtEL'r1rn1 at 1 minute intervals for 17mj?
91111 and then sulfite ion (10n) prepared by dissolving sodium sulfite heptahydrate.
++r/nu) solution at 1 mf increments of 9 ml of sulfite ion at 1 minute intervals until the jump in redox potential ends.
After adding, the pH of the solution was adjusted to 8.5 and filtered.

The other solution, which was divided into two equal parts, was filtered under reduced pressure using 5 cp paper to remove activated carbon from the solution.
) ion (10 μ/ml) solution was added in 1 ml portions at 1 minute intervals, then 9 ml was added, and then sulfite ions (10 μ/ml) solution was added in 1 ml portions at 1 minute intervals with a jump in redox potential. After adding 11 nj! of sulfite ions until the end of the reaction, the pH of the solution was adjusted to 8.
Filtration was performed after adjusting the concentration to 0. For filtration, 1 g of filter paper powder (50-1
Using a furnace material pre-coated with 00 mesh), 250 ml of the solution with activated carbon coexisting and with the activated carbon removed were filtered at normal pressure, and then filtered under reduced pressure (450 ml).
mHg). Sulfuric acid and sodium hydroxide solution were used to adjust the pH of the solution. The steel making and standardization of the sulfite ion solution were performed in the same manner as in Example 1, and the measurement of the redox potential was performed in the same manner as in Example 6. In addition, the total cyanide in each furnace liquid was determined in the same manner as in Example 1.
Quantification of iron, copper, zinc, nickel, gold, and silver was performed by ICP emission spectrometry.

When treatment is performed with activated carbon coexisting, the ratio of the number of moles of added copper (If) ions to the number of moles of iron ((C
u”) / (Fe)) is 2.26, and the ratio of the number of moles of added sulfite ion to the number of moles of iron ((S03
” ) / (Fe) ) was 0.62.
When the treatment is performed after removing activated carbon, the ratio of the number of moles of added copper(II) ions to the number of moles of iron is 2.2.
6, and the ratio of the number of moles of added sulfite ion to the number of moles of iron was 0.76.

FIG. 7 shows the changes in the redox potential as the sulfite ion solution was added, with the horizontal axis representing the amount of sulfite ion added and the redox potential representing the vertical axis. Further, Table 5 shows the quantitative results of total cyanide, iron, copper, zinc, nickel, gold, and silver in each liquid, as well as the time used for filtration.

When filtration is performed at normal pressure, it is possible to filter and separate the precipitate regardless of whether activated carbon is added, and to highly detoxify a solution containing hexacyanoferric acid ions. However, it takes about 130 minutes to 16 minutes to heat 250 mf of solution.
It took 0 minutes. On the other hand, when filtration is performed under reduced pressure and activated carbon is present, it is possible to obtain water quality equivalent to that obtained under normal pressure, and the solution is 250 mJ! 7
Although it is possible to improve the retention of precipitated particles and the filtration speed by allowing filtration to take place within minutes, when activated carbon is removed, precipitated particles are observed in the furnace liquid and it is difficult to reduce the pressure. Furthermore, when activated carbon was present during the reduction operation using sodium sulfite, the amount of sodium sulfite used could be reduced.

〔Effect of the invention〕

According to the method of the present invention, in the method of separating and removing a precipitate produced by adding copper (If) ions and a sulfite compound to a solution containing hexacyanoferrate (III) ions from the solution, retention of the produced precipitate particles is achieved. , it is possible to significantly improve the filtration rate and efficiently separate the precipitate, and the total cyanide concentration in the solution after separating and removing the precipitate can be made extremely low, 0.1 mg/j! It is also possible to perform highly detoxifying treatment to the following levels. Furthermore, the method of the present invention reduces the amount of sulfite compounds used, and
An advantage is obtained that it becomes possible to expand the pH range of the solution when the generated precipitate is separated and removed from the solution.

Furthermore, the present invention provides an extremely simple method for controlling the amount of sulfite compounds added, making it an extremely significant contribution to industry.

[Brief explanation of the drawing]

Figures 1 and 2 show the effect of activated carbon contact time obtained in Example-3, Figure 3 show the effect of pH change obtained in Example-3, and Figures 4, 5, and 6. are Examples-1, 2, and
Changes in redox potential obtained in 4, Figure 7 shows Example-7
This figure shows the relationship between the amount of sulfite ion added and the change in redox potential obtained in . Patent Applicant: Sumitomo Metal Mining Co., Ltd. Figure 3 Figure 4 [50 knee] / [[Fe (cN) 6] 3-17 No. 55i [50'', -] / [[Fe (CN included]'-1 No. Figure 6 [5O=-]/[[Fe(cN)6I'l. Figure 7 SOS-(mg) Procedural Amendment (Voluntary) 19861 lθ month/Japanese Patent Office Commissioner Yoshi 1) Moon Takeshi 1 , Indication of the case Patent Application No. 33955 of 1988 2 Name of the invention Method for removing iron cyanide complexes 3 Person making the amendment Relationship to the case Patent applicant address 5-11-3 Shinbashi, Minato-ku, Tokyo (11 "Sulfite" on page 7, lines 1 to 2 of the specification is corrected to "sulfite." (2) "Iron cyanoferric (■)" on page 10, line 5 of the same specification is changed to "hexacyanoferrous (■)." (3) Correct “precipitation” in lines 7-8 of page 10 to “sedimentation”. (4) Correct “all electrodes” in line 16 of page 12 to “gold electrode”.
I am corrected. (5) Add 0.2 g of r on page 15, lines 3 to 4 and 10
2 g of rO was added for 20 minutes to further adjust the pH of the solution to 8.
5 for 10 minutes.'' (6) On page 19, line 17, "adjusted sulfite" is corrected to "adjusted sulfite." (7) On page 25, line 5, "Hexacyanoiron (■)" is corrected to "Hexacyanoiron (■)." (8) “Hexacyanoiron (■)” on page 25, line 12 [
Hexacyanoiron (■)” is corrected.

Claims (3)

[Claims] (1) After adding copper (II) ions to an aqueous solution containing an iron cyanide complex in an amount equal to or more than the equivalent mole of the iron cyanide complex, the pH of the aqueous solution is adjusted to 8 or less, and a sulfite compound is added, resulting in a precipitate. A method for removing an iron cyanide complex, characterized by separating the iron cyanide complex. (2) Copper (II) ions are added to an aqueous solution containing an iron cyanide complex in an amount equal to or more than the equivalent mole of the iron cyanide complex, and then the pH of the aqueous solution is adjusted to 8 or less, and a sulfite compound is added to form a precipitate. A method for removing an iron cyanide complex, which comprises contacting activated carbon in any step before separating the precipitate. (3) The iron cyanide complex according to item (1), wherein the addition of the sulfite compound is terminated at least when the jump in the redox potential is completed while measuring the redox potential of the aqueous solution. Removal method.