JPH07108280A - Treating agent for water containing hexavalent chromium and method for treating it - Google Patents

Abstract

PURPOSE: To enhance removal efficiency by using a treating agent formed by mixing prescribed amts. of a specified alumina - silica stock containing prescribed amts. of silicon dioxide, aluminum oxide, sodium oxide and potassium oxide, metal iron powder and an inorg. acid.

CONSTITUTION: A mixture is formed by stirring and mixing 1-8 wt.% alumina - silica stock contg. ≥46% silicon dioxide, ≥13% aluminum oxide, ≥2% sodium oxide and ≥1% potassium oxide, 5-45 wt.% metal iron powder and about 30-50 wt.% inorg. acid such as concd. sulfuric acid. The mixture is added to water contg. hexavalent Cr, a flocculant is added and they are mixed to reduce the hexavalent Cr to trivalent Cr, which is precipitated and removed. The alumina - silica stock is prepd., e.g. by crushing quartz porphyry to ≤200 mesh and carrying out sieving.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment agent and treatment method for hexavalent chromium (Cr ^{6 +} )-containing water contained in, for example, industrial wastewater.

[0002]

2. Description of the Related Art Conventionally, as a method for treating hexavalent chromium (Cr ⁶⁺ ) contained in factory wastewater such as a plating factory, a metallurgical factory, a chemical / pharmaceutical factory or a mine wastewater, hydrogen sulfide is contained in the wastewater. Aeration or adding a sulfite aqueous solution,
Hexavalent chromium compound is converted to chromium hydroxide (Cr ₂ O ₃ · nH
A method is known in which a trivalent chromium compound such as ₂ O) is reduced to remove the precipitate.

[0003]

However, according to the above conventional method, 70% of hexavalent chromium (Cr ⁶⁺ ) in the waste water is ^removed.
In order to reduce the amount of hexavalent chromium (Cr ⁶⁺ ) contained in the wastewater to less than 0.5 mg / l, which is the water discharge standard, the treatment must be repeated several times. There is a problem that it is complicated and complicated, and the device becomes large. Furthermore, hydrogen sulfide is toxic and complicated to handle.

The present invention has been made in view of the above problems, and hexavalent chromium-containing water for easily and efficiently reducing hexavalent chromium (Cr ⁶⁺ ) to trivalent chromium (Cr ³⁺ ) and removing it. It is an object of the present invention to provide a treating agent and a treating method.

[0005]

A treatment agent for hexavalent chromium-containing water according to claim 1 is 46% or more of silicon oxide, 13% or more of aluminum oxide, 2% or more of sodium oxide and 1% or more of oxidation. 1% by weight or more and 8% by weight or less of an alumina-silica-based raw material containing potassium, 2.5% by weight or more and 45% by weight or less of metallic iron powder, and an inorganic acid are mixed.

According to a second aspect of the present invention, there is provided a method for treating hexavalent chromium-containing water, wherein the hexavalent chromium-containing water is mixed with a treatment agent for the hexavalent chromium-containing water and an inorganic base to neutralize and coagulate. The agent is mixed to precipitate and remove hexavalent chromium contained in the hexavalent chromium-containing water as trivalent chromium.

[0007]

The treatment agent for water containing hexavalent chromium according to claim 1 is
The divalent iron produced by the reaction between the inorganic acid and the metallic iron powder is oxidized to trivalent iron by the reaction with hexavalent chromium in the waste water to form ferric hydroxide colloidal particles, and the hexavalent chromium is removed. It is reduced to trivalent chromium to produce chromium hydroxide colloidal particles, and these chromium hydroxide colloidal particles are produced by an inorganic acid and an alumina-silica-based raw material, and colloidal particles of silicate and ferric hydroxide. With the colloidal particles, they are aggregated and separated and removed.

The method for treating hexavalent chromium-containing water according to claim 2 is a hydroxylation produced by neutralizing an inorganic base by reducing hexavalent chromium in waste water to trivalent chromium by the treating agent according to claim 1. The chromium colloidal particles are coagulated by a coagulant together with the ferric hydroxide colloidal particles and the silicate colloidal particles to be removed by precipitation.

[0009]

EXAMPLES An example of the production of the treating agent for hexavalent chromium-containing water of the present invention will be described below.

First, in consideration of reactivity, various raw materials are adjusted to have a predetermined particle size or less. That is, activated carbon powder (C) is prepared as a coagulant by sieving activated carbon into 100 mesh or less using a Tyler standard sieve. In addition, an alumina-silica system (Al ₂ O ₃ -Si
As the O ₂ ) raw material, silicon oxide (SiO ₂ ) is 46% or more, aluminum oxide (Al ₂ O ₃ ) is 13% or more, sodium oxide (Na ₂ O) is 2% or more, and potassium oxide (K ₂ O) is used. Containing 1% or more of, for example, quartz porphyry (quar
tz porphyry) is crushed to, for example, 200 mesh or less, and sieved to prepare. Furthermore, metallic zinc powder (Zn)
The metal iron powder (Fe) is adjusted by, for example, sieving to 20 mesh or less.

Then, each of the adjusted raw materials was placed in a reaction tower having a heat resistance and an acid resistance, which was equipped with a stirring means, and was placed in Table 1.
It is added based on the formulation table shown in. At this time, the activated carbon powder (C) is 0.8% by weight or more and 1.2% by weight or less, preferably 1% by weight, and the powdered quartz porphyry is 1% by weight or more and 8% by weight or less, preferably 5% by weight, metal. Iron powder (Fe) is added in an amount of 2.5% by weight or more and 45% by weight or less, preferably 33.5% by weight.

The metal zinc powder (Zn) is not necessary when the wastewater to be treated does not contain an organic mercury compound. When an organic mercury compound is contained, zinc metal powder (Z
n) is 0.8% by weight or less, for example, 0.5% by weight is added when the mercury content in the wastewater of an electric plant contains 3 to 5 mg / l.

Thereafter, 20% by weight or more of water (H ₂ O) is added,
Preferably, it is added to a 26.5% by weight reaction tower, and while stirring with a stirring means, 30% of concentrated sulfuric acid (H ₂ SO ₄ ) which is an inorganic acid is added.
% To 50% by weight, preferably 33.5% by weight, gradually added and mixed. In order to accelerate the dissolution of quartz porphyry, for example, fluorite powder (CaF ₂ ) may be added in an amount of ₂ % by weight.

Since hydrogen gas (H ₂ ) is generated by the reaction due to the mixing of the concentrated sulfuric acid (H ₂ SO ₄ ), the hydrogen gas (H ₂ ) is removed.

[0015]

[Table 1] Then, after stirring for a predetermined time and after completion of the reaction, that is, after hydrogen gas (H ₂ ) is no longer generated, stirring is stopped and a treating agent is prepared.

Next, the reaction in the manufacturing process of the above treatment agent will be described.

When concentrated sulfuric acid (H ₂ SO ₄ ) is mixed, first, as shown in the reaction formulas 1 and 2, H ₂ SO ₄ dissociated by hydration is zinc (Zn) and iron (F).
By reacting with e) to generate hydrogen gas (H ₂ ), zinc sulfate (ZnSO ₄ ) and ferrous sulfate (FeSO ₄ ) are generated.

[0018]

[Chemical 1]

[Chemical 2] Furthermore, these zinc sulfate (ZnSO ₄ ) and ferrous sulfate (FeSO ₄ ) can be converted into Z by the hydration in water (H ₂ O).
It is dissociated into n ²⁺ , Fe ²⁺ and SO ⁴⁻ ions.

The remaining dissociated H ₂ SO ₄ reacts with quartz porphyry. In this reaction, H ₂ SO ₄ is a component such as sodium (Na), potassium (K) and other impurities such as iron (Fe), magnesium (Mg), calcium (Ca) and titanium (Ti) in quartz porphyry. Reacts with sodium sulfate (Na ₂ SO ₄ ) and potassium sulfate (K ₂ SO ₄ ) to produce various sulfates,
Reacting with aluminum (Al) and silicon (Si),
Aluminum sulfate such as Al ₂ (SO ₄ ) ₃ and S
It produces silicon sulfate salts such as i (SO ₄ ) ₂ .

Next, the compounding amount of the above treating agent will be described.

First, when the content of the metallic iron powder (Fe) is more than 45% by weight and the content of the concentrated sulfuric acid (H ₂ SO ₄ ) is less than 30% by weight, the content of the quartz porphyry is high. The amount of H ₂ SO ₄ dissociated by hydration involved in the reaction becomes insufficient, and aluminum sulfate and silicon sulfate can hardly be produced.

Therefore, when the treating agent is put into the waste water, colloids such as aluminum hydroxide (Al (OH) ₃ ) and metasilicic acid (H ₂ SiO ₃ ) which will be described later cannot be formed. Further, even when the content of quartz porphyry is less than 1% by weight, almost no aluminum sulfate and silicon sulfate can be produced, and aluminum hydroxide (Al
Almost no colloid such as (OH) ₃ ) and metasilicic acid (H ₂ SiO ₃ ) can be formed.

Therefore, the divalent iron ion (F
e ²⁺ ) and chromate ion (Cr ₂ O ₇ ) which is hexavalent chromium (Cr ⁶⁺ ) due to dissociation of chromic acid (H ₂ CrO ₄ ) and chromate (K ₂ CrO ₄ ) in wastewater. ^2- , Cr
The colloid of chromium hydroxide (Cr ₂ O ₃ · nH ₂ O) generated by the redox reaction with O ₄ ²⁻ ) cannot be aggregated. Therefore, the content of the metallic iron powder (Fe) is 45% by weight or less, The content of sulfuric acid (H ₂ SO ₄ ) is 30% by weight or more,
Quartz porphyry is blended at 1% by weight or more.

In general, the reaction between dissociated H ₂ SO ₄ and the metals zinc (Zn) and iron (Fe) proceeds rapidly, but by mixing quartz porphyry in advance, the reaction rate decreases, The manufacturing safety is improved, the processing agent can be easily manufactured, and the structure of the manufacturing apparatus can be simplified.

When the amount of metallic iron powder (Fe) is less than 2.5% by weight, the amount of ferrous sulfate (FeSO ₄ ) produced is reduced, and more than 8% by weight of quartz porphyry is added. Then, iron powder (Fe) and concentrated sulfuric acid (H ₂
As the amount of SO ₄ decreases, ferrous sulfate (Fe
The amount of SO ₄ ) produced is reduced.

For this reason, chromate ions (Cr ₂ O ₇ ²⁻ , Cr ² ) which are hexavalent chromium (Cr ⁶⁺ ) in the waste water described later are used.
Divalent iron ion (Fe) that reduces O ₄ ²⁻ ) to chromite ion (CrO ₂ ⁻ ) which is trivalent chromium (Cr ³⁺ ).
²⁺ ) decreases, so hexavalent chromium (C
2.5% by weight of metallic iron powder (Fe) to reduce r ⁶⁺ )
As described above, quartz porphyry is blended in an amount of 8% by weight or less.

When the amount of water (H ₂ O) is less than 20% by weight, or when the concentration of concentrated sulfuric acid (H ₂ SO ₄ ) is more than 50% by weight, H ₂ SO ₄ is converted to 2H ⁺ and SO ₄ by hydration. ^The amount of dissociation into ions with ^2- decreases, and sulfuric acid compounds cannot be produced well by the reaction with metallic iron powder (Fe) and quartz porphyry. Therefore, water (H ₂ O) of 20% by weight or more Sulfuric acid (H ₂ SO ₄ ) is added to 50% by weight or less.

Next, hexavalent chromium (C
The process of treating r ^{6 +} )-containing wastewater will be described.

First, the waste water containing hexavalent chromium (Cr ⁶⁺ ) is ^introduced into a pool-shaped treatment tank which is equipped with a stirring means and has an open top.

Next, the above-prepared treating agent is added with stirring in an amount of about 1/100 of the total amount of hexavalent chromium (Cr ⁶⁺ ) contained in the waste water in the treating tank. .

The total amount of hexavalent chromium (Cr ⁶⁺ ) in the waste water is determined by the diphenylcarbazide method, that is, hexavalent chromium (Cr ⁶⁺ ) is added to diphenylcarbazide ((C ₆ H ₅ NHN
H) ₂ CO) to form a purple-red complex compound,
Based on the absorbance measured by absorptiometry, the concentration of hexavalent chromium (Cr ⁶⁺ ) is converted into the amount of milligram in 1 liter of wastewater, and the total amount of hexavalent chromium (Cr ⁶⁺ ) in the entire wastewater is obtained.

Further, an aggregating agent, which is an aggregating agent, is appropriately added to the waste water in the treatment tank under agitation, and after stirring for a certain period of time, for example, about 3 minutes, the stirring is stopped and allowed to stand for about 10 minutes, Allow the precipitate to separate. The aggregation promoter is about 0.5% by weight of polyacrylamide, about 2% by weight of barium hydroxide (Ba (OH) ₂ .7H ₂ O), and sodium hydroxide (NaOH) which is an inorganic base. 4) and about 50% by weight of water (H ₂ O).

Then, hexavalent chromium (C
After confirming that r ⁶⁺ ) is not contained, the supernatant liquid is discharged.

Hexavalent chromium (Cr ⁶⁺ ) in the supernatant liquid
For confirmation, 0.1 g of diphenylcarbazide was dissolved in 50 ml of ethanol (C ₂ H ₅ OH), and sulfuric acid (1 + 9) 20
2.5 ml of the reagent prepared by mixing 0 ml with the supernatant liquid 50
Mix in ml and let stand for about 5 minutes to make sure it does not turn purple.

The separated agglomerates are mixed and fired with coal powder to obtain a stable spinel structure fired product, which is used as a raw material for landfills and other inorganic materials such as refractories. Even if it is landfilled, for example, meta-silicic acid (H ₂ SiO ₃ ) which is a silicate may be converted into silicic acid (H ₄ Si).
Converted to O ₄ ) and converted to aluminum hydroxide (Al (O
H) ₃ ) is combined with various trivalent colloidal particles to take in heavy metal particles and colloidal particles to form sludge-like hardly soluble silicate minerals. Do not convert to chrome. In addition to the separation by precipitation, it can be separated and removed by filtration separation, centrifugation, or the like. Further, when the trivalent chromium content is high, the trivalent chromium can be purified.

Next, the reaction in the above processing method will be described.

By adding the treating agent to the wastewater, divalent iron ions (Fe ²⁺ ) due to dissociation of ferrous sulfate in the treating agent are discharged as shown in the reaction formulas shown in Chemical formulas 3 and 4. Chromate ion (Cr ₂ O ₇ ²⁻ , CrO ₄ ²⁻ ) which is hexavalent chromium (Cr ⁶⁺ ) due to dissociation of chromic acid (H ₂ CrO ₄ ) and chromate (K ₂ CrO ₄ ) in ) And an oxidation-reduction reaction with trivalent iron (Fe ³⁺ ) and trivalent chromium (Cr ³⁺ )
And chromite ion (CrO ₂ ⁻ ) which is

[0038]

[Chemical 3]

[Chemical 4] Then, the trivalent iron (Fe ³⁺ ) and the trivalent chromium (Cr ³⁺ ) CrO ₂ ⁻ are adjusted to pH 7 by NaOH.
By neutralizing to ~ 8, the water (H
At ₂ O), respectively ferric hydroxide (Fe ₂ O ₃ · nH
₂ O, FeO (OH)) and chromium hydroxide (Cr ₂ O
₃ · nH ₂ O) is produced. In addition, ferric hydroxide (F
e ₂ O ₃ .nH ₂ O, FeO (OH)) and chromium hydroxide (Cr ₂ O ₃ .nH ₂ O) form colloids.

When the treating agent is added to the wastewater, the aluminum sulfate and the silicon sulfate in the treating agent are converted into aluminum hydroxide (Al (OH) ₃ ) in the wastewater (H ₂ O).
And forming colloids such as metasilicic acid (H ₂ SiO ₃ ).

Then, various colloids are aggregated on the activated carbon powder (C) mixed in the treating agent due to the adsorptivity of the activated carbon. Furthermore, by adding the aggregation promoter, the particles aggregated with the activated carbon powder (C) as the aggregate are rapidly precipitated.

When various salts such as copper (Cu), cadmium (Cd), and nickel (Ni) are present in the waste water, these various salts also contain chromate ions (Cr ₂ O ₇ ²⁻ , C ²
Similar to rO ₄ ²⁻ ), it is reduced by divalent iron ions (Fe ²⁺ ), forms a colloid as hydroxide by adjusting pH with NaOH, and aggregates with activated carbon powder (C) as aggregate. . Further, a part of lead (Pb) and mercury (Hg) is precipitated as lead sulfate (PbSO ₄ ) and mercury sulfate (Hg ₂ SO ₄ ). In addition, mercury (H
Part of g) is precipitated as amalgam by zinc sulphate (ZnSO ₄ ) which dissociates by hydration in the waste water.

As shown in Chemical formula 5, arsenic (As) is used as ferric hydroxide (Fe ₂ O ₃ .nH ₂ O, FeO (O)
It is separated by precipitation by reaction with H)).

[0043]

[Chemical 5] Next, Table 2 shows the experimental results obtained by dissolving various salts in water to synthesize wastewater, treating the wastewater synthesized using the above treating agent, and performing various quantitative analyzes.

First, as an experiment 1, chromate ion (C
r ₂ O ₇ ²⁻ , CrO ₄ ²⁻ ) having different concentrations are synthesized, and 1/10 of the total amount of hexavalent chromium (Cr ⁶⁺ ) in each wastewater is synthesized.
The above treatment agent was mixed at a ratio of 0, and a coagulation accelerator was added as appropriate to precipitate and separate the resulting colloid. Then, diphenylcarbazide method was used to precipitate hexavalent chromium (C
The concentration of r ⁶⁺ ) was measured.

In Experiment 2, chromate ion (C
In addition to r ₂ O ₇ ²⁻ , CrO ₄ ²⁻ ), wastewater containing salts of lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) was synthesized, and in this synthesized wastewater After mixing the above treatment agents in a ratio of 1/100 of the total amount of hexavalent chromium (Cr ⁶⁺ ) in the waste water, and further adding a coagulation promoter as appropriate to precipitate and separate the produced colloids, various quantitative analyzes are conducted. The chromium (Cr ⁶⁺ ) concentration, copper (Cu) concentration, lead (Pb) concentration, arsenic (As) concentration, and mercury (Hg) concentration of the supernatant were measured.

[0046]

[Table 2] From the results of Experiment 1 shown in Table 2, for example,
The concentration of chromium (Cr ⁶⁺ ) contained in the wastewater of mines and effluents of metallurgical factories, chemical and pharmaceutical factories, etc. is about 10ppm, but the concentration of chromium (C ⁶ ) is 50 times higher than that of these wastewaters.
Even synthetic wastewater containing r ⁶⁺ ) contains chromium (C
r ⁶⁺ ) cannot be detected, and even with 1000 ppm of wastewater, 0.01 pp, which is much less than the discharge standard of 0.5 ppm.
Only m can be detected, and it can be seen that hexavalent chromium (Cr ⁶⁺ ) can be reliably removed by precipitation.

From Experiment 2 shown in Table 2, chromium (C
r ⁶⁺ ), lead (Pb), cadmium (Cd) were not detected, and it was found that most of arsenic (As) and mercury (Hg) were also removed by precipitation.

Therefore, a treating agent which can simultaneously precipitate and separate hexavalent chromium (Cr ⁶⁺ ) and other heavy metals can be easily produced from inexpensive raw materials. Furthermore, with this treatment agent, hexavalent chromium (Cr ⁶⁺ ) can be securely and easily used without toxicity 3.
It can be reduced to valent chromium (Cr ³⁺ ) and precipitated and separated, and other heavy metals can be simultaneously precipitated and separated, facilitating purification of wastewater.

In the above example, the activated carbon powder (C) was mixed in the treatment agent and the wastewater was purified by this treatment agent. However, the activated carbon powder was not mixed in the treatment agent. It can also be purified by adding activated carbon powder to the waste water together with a treating agent. In addition, a colloid produced by performing precipitation or separation without using activated carbon powder and only with a coagulation promoter, or by gradually separating without using a coagulation promoter, or by using both without using both. Can be separated by any method such as separation.

In addition to activated carbon powder, any carbon source such as charcoal can be used. In addition to quartz porphyry,
Silicon oxide (SiO ₂ ) is 46% or more, aluminum oxide (Al ₂ O ₃ ) is 13% or more, sodium oxide (Na ₂
Any alumina-silica (Al ₂ O ₃ —SiO ₂ ) raw material such as ore, clay, or synthetic raw material containing 2% or more of O) and 1% or more of potassium oxide (K ₂ O) can be used.

Next, another embodiment of the production of the treating agent for hexavalent chromium-containing water of the present invention will be described.

Instead of the quartz porphyry of the above-mentioned embodiment, as an alumina-silica (Al ₂ O ₃ —SiO ₂ ) raw material,
It uses coal husks (Cinders).

That is, using a Tyler standard sieve, the coal shell is sieved to, for example, 200 mesh or less and adjusted. Also, the metallic iron powder (Fe) is adjusted in the same manner as in the above-mentioned embodiment.

Then, based on the formulation table shown in Table 3, various raw materials are charged into the reaction tower in the same manner as in the above-mentioned Examples. At this time, the powdered coal shell is 1% by weight or more and 8% by weight or less, preferably 1.13% by weight, and the metallic iron powder (Fe) is 2.5% by weight.
The above amount is 45% by weight or less, preferably 11.3% by weight.

The metal zinc powder (Zn) does not need to be used if the wastewater to be treated does not contain an organic mercury compound. When an organic mercury compound is contained, zinc metal powder (Z
n) is 0.8% by weight or less, for example, 0.11% by weight when the mercury content in electric factory wastewater contains 3 to 5 mg / l.
throw into.

Thereafter, 1% by weight or more and 96.5% by weight or less of an (1: 1) sulfuric acid aqueous solution as an inorganic acid having a mixing ratio of water and concentrated sulfuric acid of 1: 1 is stirred with a stirring means. , Preferably 87.46% by weight.

[0057]

[Table 3] After stirring for a predetermined time, the hydrogen gas (H
_{After 2} ) is no longer generated, stirring is stopped and the treatment agent is prepared.

Next, in the same manner as in the above-mentioned embodiment, the prepared treating agent was ^added to the treatment tank into which the waste water containing hexavalent chromium (Cr ⁶⁺ ) was ^{introduced, and} was contained in the waste water in the treatment tank. An amount of about 1/10 of the total amount of valent chromium (Cr ⁶⁺ ) was added with stirring, and divalent iron ions (Fe at ^2+), hexavalent chromium in waste water (Cr ⁶⁺⁾ chromate ions (Cr ₂
O ₇ ²⁻ , CrO ₄ ²⁻ ) is produced by redox reaction to generate trivalent iron (Fe ³⁺ ) and trivalent chromium (Cr ³⁺ ) chromite ion (CrO ₂ ⁻ ). . In addition, the total amount of hexavalent chromium (Cr ⁶⁺ ) in the waste water is similarly determined by the diphenylcarbazide method.

Further, an aggregating accelerator is appropriately added to the waste water under stirring in the treatment tank. Then, as in the above embodiment, N
The pH is adjusted with aOH to precipitate and separate trivalent iron (Fe ³⁺ ) and chromite (trivalent chromium (Cr ³⁺ )) as colloidal particles, and other heavy metals also as colloidal particles. Allow the precipitate to separate. Furthermore, confirming that the supernatant does not contain hexavalent chromium (Cr ⁶⁺ ),
Discharge the supernatant.

Therefore, as in the case of the above-mentioned one embodiment, a treating agent capable of simultaneously separating and separating hexavalent chromium (Cr ⁶⁺ ) and other heavy metals can be easily produced using particularly inexpensive lime shells and raw materials. Furthermore, with this treatment agent, 6
Trivalent chromium (Cr ⁶⁺ ) is non-toxic trivalent chromium (Cr
^It can be reduced to ³⁺ ) and precipitated and separated, and other heavy metals can be simultaneously precipitated and separated, facilitating purification of wastewater.

Since the coal shell is almost amorphous, it is more easily dissolved in a (1: 1) sulfuric acid aqueous solution than quartz porphyry. Therefore, it is not necessary to add a dissolution accelerator such as fluorite powder, and it can be easily dissolved in a short time, and a silicate or the like that forms colloidal particles can be easily formed.

Next, another embodiment of the production of the treating agent for hexavalent chromium-containing water of the present invention will be described.

Instead of the (1: 1) sulfuric acid aqueous solution of the example using the above-mentioned coal shell, an inorganic acid (1: 1) hydrochloric acid aqueous solution in which the mixing ratio of water and concentrated hydrochloric acid was 1: 1 was used. It is a thing.

That is, based on the formulation table shown in Table 4,
In the reaction tower, the amount of coal shell powder, which is an alumina-silica-based raw material, is 1% by weight or more and 8% by weight or less, preferably 2.82.
%, And the metallic iron powder (Fe) is mixed in the range of 2.5% by weight or more and 45% by weight or less, preferably 28.2% by weight.

The metal zinc powder (Zn) is not necessary when the wastewater to be treated does not contain an organic mercury compound. When an organic mercury compound is contained, zinc metal powder (Z
n) is 0.8% by weight or less, for example, 0.28% by weight when the mercury content in the wastewater of an electric plant contains 3 to 5 mg / l.
Mix.

After that, 1% by weight or more and 96.5% by weight or less, preferably 68% by weight of a 1: 1 (1: 1) hydrochloric acid aqueous solution in which the mixing ratio of water and concentrated hydrochloric acid is 1 is stirred. .7
Mix by weight percent.

[0067]

[Table 4] After stirring for a predetermined time, the hydrogen gas (H
_{After 2} ) is no longer generated, stirring is stopped and the treatment agent is prepared.

Then, the treatment agent thus prepared is contained in the waste water in the treatment tank in the treatment tank into which the waste water containing hexavalent chromium (Cr ⁶⁺ ) is ^introduced , as in the above-mentioned embodiments. An amount of about one tenth of the total amount of hexavalent chromium (Cr ⁶⁺ ) is added with stirring. In addition, hexavalent chromium (Cr ⁶⁺ ) in the wastewater
Similarly, the total amount of is determined by the diphenylcarbazide method.

Further, similarly to each of the above-mentioned examples, the aggregating promoter is appropriately added to the waste water under stirring in the treatment tank, and the agitation is performed for a certain period of time.
For example, after stirring for about 3 minutes, the stirring is stopped, and the mixture is allowed to stand for, for example, about 10 minutes to precipitate and separate. Then, after confirming that the supernatant does not contain hexavalent chromium (Cr ⁶⁺ ), the supernatant is discharged.

Next, the reaction in the process of producing the above treatment agent will be described.

When a (1: 1) hydrochloric acid aqueous solution (HCl) is mixed, first, HCl, which is dissociated by hydration, is zinc (Zn) and iron (Fe), which are dissociated by hydration, as shown in reaction formulas 6 and 7. Reacting with and generating hydrogen gas (H ₂ ),
Zinc chloride (ZnCl ₂ ) and zinc chlorate (Zn (Cl
O ₃ ) ₂ ) and the like, and ferrous chloride (FeCl ₂ ) and iron chlorate are generated.

[0072]

[Chemical 6]

[Chemical 7] Further, these zinc chloride (ZnCl ₂ ) and ferrous chloride (FeCl ₂ ) are ionized such as Zn ²⁺ , Fe ²⁺ , Cl ⁻ , ClO ₃ ⁻ by hydration in water (H ₂ O). Has been dissociated into.

The remaining dissociated HCl reacts with the coal shell. In this reaction, HCl is aluminum (Al), silicon (Si), sodium (Na), potassium (K), iron (Fe), magnesium (Mg), calcium (Ca), titanium (Ti), etc. in the coal shell. Reacts with the components of to form salts such as various chlorides and chlorates.

Next, the reaction in the above processing step will be described.

By adding the treating agent to the waste water, the divalent iron ion (Fe) due to the dissociation of ferrous chloride in the treating agent can be obtained as shown in the reaction formulas shown in Chemical formulas 3 and 4 of the above-mentioned embodiment.
²⁺ ) undergoes a redox reaction with chromate ions (Cr ₂ O ₇ ²⁻ , CrO ₄ ²⁻ ), which are hexavalent chromium (Cr ⁶⁺ ) in the waste water, to generate trivalent iron (Fe ^{3 +} ) And trivalent chromium (C
r ³⁺ ) and chromite ion (CrO ₂ ⁻ ) are produced.

The trivalent iron (Fe ³⁺ ) and the trivalent chromium (Cr ³⁺ ) CrO ₂ ⁻ are neutralized to pH 7 to 8 by the inorganic base NaOH, and the wastewater is discharged. Ferric hydroxide (Fe ₂ O ₃ · nH ₂ O, FeO (OH)) and chromium hydroxide (Cr ₂ O ₃ · nH ₂ O) are produced in water (H ₂ O) in the medium, respectively. . In addition, ferric hydroxide (Fe ₂ O ₃ · nH ₂ O, FeO (O
H)) and chromium hydroxide (Cr ₂ O ₃ · nH ₂ O)
Form a colloid.

By adding the treatment agent to the wastewater, various salts of aluminum and silicon in the treatment agent are removed from the wastewater (H
Form colloids such as aluminum hydroxide (Al (OH) ₃ ) and metasilicic acid (H ₂ SiO ₃ ) in ₂ O).

Then, various colloids are aggregated on the activated carbon powder (C) blended in the treating agent due to the adsorptivity of the activated carbon. Furthermore, by adding the aggregation promoter, the particles aggregated with the activated carbon powder (C) as the aggregate are rapidly precipitated.

Also, when various salts such as copper (Cu), cadmium (Cd) and nickel (Ni) are present in the waste water, these various salts are also chromate ion (similar to the above-mentioned various examples). Similarly to Cr ₂ O ₇ ²⁻ , CrO ₄ ²⁻ ), it is reduced by divalent iron ions (Fe ²⁺ ) and precipitated by dissociating Cl ⁻ , ClO ₃ ^{− and the} like.

Therefore, as in the above-mentioned embodiment, a treating agent capable of simultaneously separating and separating hexavalent chromium (Cr ⁶⁺ ) and other heavy metals can be easily produced from inexpensive raw materials. Furthermore, this treatment agent can reliably and easily reduce hexavalent chromium (Cr ⁶⁺ ) to non-toxic trivalent chromium (Cr ³⁺ ) for precipitation and separation, and at the same time for precipitation and separation of other heavy metals. , Easy purification of waste water.

In each of the above examples, the inorganic acid is not limited to sulfuric acid or hydrochloric acid, and the inorganic base is not limited to sodium hydroxide.

[0082]

According to the treatment agent for hexavalent chromium-containing water according to claim 1, the produced divalent iron is oxidized to trivalent iron by the reaction with hexavalent chromium in the wastewater, and hydroxide is added. In addition to becoming ferric colloidal particles, hexavalent chromium is reduced to trivalent chromium to form colloidal particles. The chromium hydroxide colloidal particles are used as silicate colloidal particles and ferric hydroxide colloidal particles. As a result, the treating agent capable of reliably and easily separating hexavalent chromium can be easily produced from inexpensive raw materials because the coagulating agent is separated and removed.

According to the method for treating hexavalent chromium-containing water according to claim 2, the treatment agent according to claim 1 is used to remove 6
To agglomerate the colloidal particles of chromium hydroxide, which is generated by the reduction of trivalent chromium to trivalent chromium and the neutralization of the inorganic base, with the colloidal particles of ferric hydroxide and the colloidal particles of silicate, to remove the precipitates. The wastewater containing hexavalent chromium can be reliably and easily purified.

Claims (2)

[Claims] 1. 46% or more silicon oxide, 13% or more aluminum oxide, 2% or more sodium oxide and 1%
1% by weight or more and 8% by weight or less of an alumina-silica-based raw material containing the above potassium oxide, 2.5% by weight or more and 45% by weight or less of metallic iron powder, and an inorganic acid A treatment agent for water containing hexavalent chromium. 2. The method according to claim 1, wherein the water containing hexavalent chromium is used.
It is characterized in that a treatment agent for valent chromium-containing water and an inorganic base are mixed and neutralized, and a coagulant is mixed to precipitate and remove hexavalent chromium contained in the hexavalent chromium-containing water as trivalent chromium. A method for treating water containing hexavalent chromium.