JP3245138B2 - Heavy metal removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for effectively removing heavy metals from heavy metal-containing materials, and more particularly, to a method for effectively utilizing heavy metal-containing materials and causing harmful problems when disposed of. The present invention relates to a method for removing heavy metals effectively and easily and economically.

[0002]

2. Description of the Related Art Objects and substances existing in our living environment are often contaminated with harmful heavy metals and contain heavy metals. For example, sewage sludge, organic sludge such as human waste sludge or food factory sludge, soil, livestock manure, bottom mud,
Although seafood, animals, plants and the like can be used as resources, it is not easy to remove heavy metals from these heavy metal-containing substances.

[0003] Also, since rivers, soils, punktons, and the like existing in our living environment contain harmful heavy metals, fish, shellfish, animals, plants, and the like that inhabit there are above the standard value. It is known that it is often contaminated with heavy metals. For example, scallop uro (soft body) and oysters contain high concentrations of heavy metals, especially cadmium, and human kidney and liver also contain high concentrations of cadmium. It is known that cereals such as these also contain heavy metals such as cadmium, which can be harmful to human health.

In recent years, it has become necessary to utilize unused resources from the viewpoints of preserving the global environment and effectively utilizing and circulating resources. Developing a method of removing and detoxifying methane is an urgent and important task.

[0005] Further, apart from the viewpoint of effective use and recycling of resources, even when simply disposing of the heavy metal-containing material as described above, high concentrations of harmful heavy metals accumulate in waste disposal sites and the like. There is a problem that the environment is adversely affected again.

In order to solve such problems and problems,
There is a strong demand for the development of a method for effectively removing heavy metals from heavy metal-containing substances. Until now, organic sludge such as sewage sludge, human waste sludge, and food factory sludge, soil and sediment, and livestock manure have been developed. Various studies have been conducted mainly on a method for removing contained heavy metals.

[0007] For example, zinc from sewage sludge using sulfuric acid,
A method for removing copper, cadmium and the like (Environ.
Sci. Technol. , 9 (9), 849-855
(1975)), a method of removing cadmium, chromium, copper, iron, lead, zinc, and nickel from sewage sludge using sulfuric acid or hydrochloric acid (Water Res., 10, 1077).
-1081 (1976)). Recently, as a method for removing cadmium from scallop uro, a method of treating with 2 vol% sulfuric acid (sulfuric acid of about 3.6% by weight), and furthermore, by using electrolysis and sulfuric acid together, scallop uro is used. A method for removing cadmium from water has also been proposed.

In addition, the present inventors have developed and proposed a method for removing heavy metals contained in organic sludge such as sewage sludge, human waste sludge, and food factory sludge using an aqueous phosphoric acid solution. (Japanese Patent No. 2975571).

[0009]

As described above, many methods for removing heavy metals have been studied so far. However, since there are a variety of substances and substances containing heavy metals, a method that can be put to practical use is obtained. Therefore, it is necessary to develop more methods.

[0010] By the way, heavy metals existing in the environment are:
In general, these heavy metals are easily dissolved and recovered because they are adsorbed on biopolymers constituting animals, plants and fish and shellfish, or exist as inorganic salts and sulfides. It was not something.

[0011]

Therefore, recently, as a method for removing cadmium from scallop uro, for example, a method of treating with about 3.6% by weight of sulfuric acid has been proposed.

Although this method has succeeded in removing a considerable amount of cadmium from scallop uro, there are problems such as an increase in the size of the processing apparatus and a long processing time. In addition, this method has problems that the acidity is strong, a large amount of water is required to wash out sulfuric acid after the treatment, and the burden on post-treatment of wastewater containing a large amount of heavy metals is increased.

As described above, the inventor of the present invention has shown that phosphoric acid solutions have been extremely effective as a method for removing heavy metals contained in organic sludges such as sewage sludge, human waste sludge, and food factory sludge. Has been developed and proposed (Japanese Patent No. 2975571).

The present inventor has further studied the method for removing heavy metals using such a phosphoric acid solution. As a result, this method is not limited to organic sludges, but also includes a wide range of heavy metal-containing substances. That harmful heavy metals can be removed from water.

In particular, it has been found that by using this method for removing heavy metals, it is possible to effectively remove heavy metals from fish, shellfish, animals and plants, for which it has been conventionally difficult to remove heavy metals. Was.

[0017]

The present invention has been completed based on these findings and removes heavy metals from heavy metal-containing substances by using a specific acid aqueous solution as a treatment liquid for treating heavy metal-containing substances. In particular, it is an object of the present invention to provide a method for removing heavy metals effectively, easily and economically from fish, shellfish, animals and plants, which has been conventionally determined to be difficult to remove. The purpose is to:

[0019]

Means for Solving the Problems Heavy metal elimination according to the present invention
In the removing method, in order to achieve the above-mentioned object , removing the heavy metals including the step of contacting the treatment liquid with the heavy metal-containing substance to elute the heavy metals contained in the heavy metal-containing substance into the treatment liquid In the method, the heavy metal-containing material is at least one selected from soil, sediment, livestock manure, fish and shellfish, animals or plants, and the treatment liquid,
(A) phosphoric acid aqueous solution, or (B) the following B1 and B2
It is a phosphoric acid aqueous solution containing at least one of them . (B1) Other acids other than phosphoric acid (B2) Oxidizing agent

Examples of the heavy metal-containing material to be subjected to the method of the present invention include known heavy metal-containing materials except organic sludge, and include soil, bottom mud, livestock manure, fish and shellfish. , Animals or plants.

Therefore, the heavy metal-containing material to be subjected to the method of the present invention includes a mixture of a plurality of types of heavy metal-containing materials.

The heavy metal-containing material to be treated by the method of the present invention may be treated in a usual form, but is preferably cut into small pieces to facilitate removal of the metal,
Alternatively, it is preferably used in a powdered state.

In particular, when the heavy metal-containing substance is a seafood, an animal or a plant, etc., the heavy metal-containing substance contains oil components such as fish oil, animal oil, and vegetable oil which hinder the elution of the heavy metal. It is effective to remove oily components before processing.

In the method of the present invention , heavy metals are removed from these heavy metal-containing substances. Examples of the heavy metals include those which have a bad influence on the human body and cause environmental pollution. Can be

Specifically, for example, metals such as aluminum, cadmium, chromium, copper, iron, mercury, manganese, molybdenum, nickel, lead, zinc and the like can be mentioned. In addition, arsenic, selenium Etc. can be similarly removed. In the method of the present invention , not only the heavy metals described above but also these compounds are referred to as heavy metals.

In the method of the present invention , the treatment liquid used in the method for removing heavy metals includes: (A) phosphoric acid
Aqueous solution or (B) less of the following B1 and B2
And a phosphoric acid aqueous solution containing at least one of them . (B1) Other acids other than phosphoric acid (B2) Oxidizing agent

Here, phosphoric acid means condensed phosphoric acid such as orthophosphoric acid, metaphosphoric acid or polyphosphoric acid, phosphorous acid,
The term includes hypophosphorous acid, diphosphorus pentoxide and the like.

The concentration of the aqueous phosphoric acid solution in the method of the present invention is not particularly limited and may be appropriately selected depending on the heavy metal content and the type of metal to be removed, but is generally 85% by weight or less. And a concentration in the range of 0.01 to 85% by weight is more preferable.

When the concentration of the phosphoric acid aqueous solution is 85% by weight or more, the effect of removing heavy metals is limited, the acidity is strong, post-treatment is difficult, and the cost is increased. When the concentration of the aqueous phosphoric acid solution is 0.01% by weight or less, the removal rate of heavy metals such as mercury, chromium, and lead becomes low, which is not preferable.

Specifically, for example, when removing metals contained in soil and the like, a phosphoric acid concentration of 10% by weight or more is preferable. When removing metals contained in fish and shellfish, etc. Is preferably a phosphoric acid concentration of 20% by weight or less.

In the method of the present invention , examples of the oxidizing agent contained in the treatment liquid include hydrogen peroxide, hypochlorous acid, potassium hypochlorite, sodium hypochlorite, sodium perborate and the like. . In this case, by blowing air or introducing ozone by aeration, the oxidation effect can be improved, and the elution effect of heavy metals can be improved.

Further, the oxidizing agent is added to the processing solution in an amount of 0.0.
It is preferable that the oxidizing agent is blended in the treatment liquid at a ratio of from 0.01 to 20% by weight, preferably from 0.01 to 5% by weight.
It is not meaningful to mix the components. On the other hand, if the content exceeds 20% by weight, the effect is limited, the post-treatment becomes difficult, and the cost is increased.

Furthermore, by subjecting the treatment liquid to stirring, aeration treatment, ultrasonic treatment, homogenizer treatment, etc., the reaction promoting effect and the oxidation effect can be improved.

Acids other than phosphoric acid contained in the treatment liquid include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and boric acid, formic acid, acetic acid, oxalic acid, citric acid, maleic acid, fumaric acid, pyruvic acid, and succinic acid. And organic acids such as tartaric acid, phthalic acid and the like, which can be contained in an optional ratio to the aqueous phosphoric acid solution.

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

As described above, in the method of the present invention , a kind of aqueous phosphoric acid solution is used as the treatment liquid .
Phosphoric acid aqueous solutions include hydrochloric acid, sulfuric acid, nitric acid, organic acids, etc.
Is more preferable than the acids of

The reason for this is that phosphoric acids have a higher biological affinity than other acids, and heavy metals accumulated in living organisms can be effectively eluted by biosorption (biological adsorption). Because it can be.

The aqueous phosphoric acid solution is generally a weak acid and has a low risk. In addition, when heavy metals eluted in the treatment liquid are removed by using an adsorbent described later, measures such as pH adjustment are taken. This is because handling is extremely simple because it is not necessary.

In the method of the present invention , the heavy metals contained in the heavy metals are eluted into the processing solution by contacting the processing solution with the heavy metal-containing material. The treatment temperature and the treatment time are not particularly limited, and are appropriately selected and used depending on the type of the heavy metal-containing material and the amount and type of the heavy metal contained.

In general, it is preferable to use about 1 to 10 times the processing liquid with respect to the mass 1 of the heavy metal-containing material .
In particular, the amount is preferably 1 to 5 times.

In the method of the present invention , the temperature during the treatment can be selected from any temperature range from room temperature to the boiling point of the extract, but generally, room temperature to about 95 ° C. is preferable.

Further, the processing time is about 10 minutes to 1 day, and heavy metals can be easily removed.

In the method of the present invention , in order to achieve the above object, as described above, the treatment solution eluted with heavy metals in the heavy metal-containing material is brought into contact with the adsorbent,
It is preferable to further include a step of adsorbing and removing heavy metals in the treatment liquid by an adsorbent, and to use them together.

With this configuration, heavy metals can be easily adsorbed and removed from the processing solution by the adsorbent. Therefore, heavy metals are removed from the processing solution containing heavy metals, and the processing solution is recycled and reused (reused). ), And it is possible to obtain a heavy metal-containing material in which the concentration of heavy metals is significantly reduced, and reuse the heavy metal-containing material after treatment without performing post-treatment such as washing. This is because it becomes possible.

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

In the method of the present invention , as the heavy metal adsorbent, any of the known adsorbents capable of adsorbing heavy metals can be used. Specifically, for example, a strongly acidic cation exchange resin, An acidic cation exchange resin, a cation exchange membrane and the like can be mentioned.

[0057]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In addition,
In the following examples, all percentages are by weight unless otherwise specified.

Example 1 Paddy soil was collected, and the content of heavy metals contained in the soil was measured by the aqua regia boiling method. [Unit: ppm (dry weight): As, 125; Cd,
4.51, Cr, 24.7; Cu, 64.3; Fe, 9
600; Hg, 35.8; Ni, 7.18; Pb, 9
0.4; Zn, 332]

To 10.0 g of this soil, an aqueous phosphoric acid solution of various concentrations (20%, 8%) containing 2% hydrogen peroxide was added.
After stirring for 1 hour at room temperature, the soil was filtered, and the concentration of heavy metals contained in the aqueous phosphoric acid solution was determined by ICP.
(Inductively Coupled Plas
(Ma Spectrometry) method, and the removal rate was calculated. Table 1 shows the results.

[0060]

[Table 1]

When the soil was treated with a 20% aqueous solution of phosphoric acid containing no hydrogen peroxide under the same conditions, the removal rate of copper was 7%. Furthermore, when the soil was treated at 90 ° C. using a 20% aqueous phosphoric acid solution containing 2% hydrogen peroxide, the removal rate of copper was 55%.

Example 2 The soil of a field was collected, and the content of heavy metals contained in the soil was measured by the aqua regia boiling method. [Unit: ppm (dry weight): As, 168; Cd,
5.36; Cr, 27.6; Cu, 115; Fe, 11
600; Hg, 44.4; Ni, 6.42; Pb, 12
0; Zn, 378]

To 10.0 g of this soil, an aqueous solution of phosphoric acid of various concentrations (40%, 20%) containing 2% hydrogen peroxide was added.
After adding 0 ml and stirring at room temperature for 1 hour, the soil was filtered, the concentration of heavy metals contained in the aqueous phosphoric acid solution was measured by the ICP method, and the removal rate was calculated. Table 2 shows the results.

[0064]

[Table 2] A Cr removal rate of 123% indicates that a measured value 1.23 times the actual measured value (standard value) of the Cr by the aqua regia boiling method was obtained.

When the treatment was performed at 60 ° C. using a 20% phosphoric acid aqueous solution containing 2% hydrogen peroxide, the removal rate of copper was 58%. Furthermore, the removal rate of copper was 32% when ultrasonic treatment was performed using an 8% phosphoric acid aqueous solution while aeration at room temperature.

Example 3 30 ml of a 20% phosphoric acid aqueous solution containing 2% hydrogen peroxide was added to 10.0 g of commercially available fermented beef dung (dried product), and the mixture was added at room temperature.
After stirring for an hour, the cow dung was collected by filtration, and the content of heavy metals in the aqueous phosphoric acid solution was measured using the ICP method.

In this case, the content of heavy metals in the aqueous phosphoric acid solution was as follows. [(Unit: ppm): As, 22.9; Cd, 1.0;
Cr, 7.6; Cu, 0.67; Fe, 365; Ni,
1.41; Pb, 12.6; Zn, 65.2]

Example 4 2% in 10.0 g of bottom mud (dried product) at the mouth of the Katsuura River in Tokushima City
100 ml of a 40% phosphoric acid aqueous solution containing hydrogen peroxide was added, and the mixture was stirred at 50 ° C. for 3 hours. Next, the bottom mud was filtered, and the content of heavy metals in the aqueous phosphoric acid solution was measured by the ICP method. The measured values were as follows. [(Unit: ppm): Cr, 1.83; Cu, 3.8
5; Zn, 17.9]

Reference Example The content of cadmium contained in scallop uro was determined by decomposing a sample using the aqua regia boiling method and using the ICP method. That is, 10 g of scallop uro (midgut gland, washed with water to remove oil, solid content 34%) is placed in a 200 ml beaker, 60 ml of aqua regia is added, and the mixture is boiled down to be contained in the decomposition solution. The content of heavy metals was measured using the ICP method. The average content of heavy metals contained in the scallop uro was as follows. [(Unit: ppm dry weight): Cd, 98.4 ppm;
Zn, 121.1 ppm; Cu, 36.9 ppm]

Example 5 Various concentrations (W / W%) were added to 20 g of scallop uro (midgut gland).
Of phosphoric acid aqueous solution was added and immersed for 24 hours.
Next, the cadmium concentration in the phosphoric acid aqueous solution after 24 hours was measured by using the ICP method, and the amount of cadmium removed from the urine [unit: mg / kg (ppm) · uro dry weight] was measured. [Eluted (removed) amount in phosphoric acid aqueous solution]: 5% phosphoric acid, 83.0 ppm; 10% phosphoric acid, 105 ppm;
20% phosphoric acid, 82.1 ppm; 40% phosphoric acid, 49.
5 ppm.

Example 6 Scallop uro (middle gut, washed with water to remove oil)
To 20 g, 100 ml of an aqueous acid solution of various concentrations (W / W%) was added and immersed for 24 hours. Next, the concentration of heavy metals in the aqueous acid solution after 24 hours was measured by ICP method, and the amount of heavy metals eluted (removed) from uro [mg / kg (pp
m) · Uro dry weight] was measured. [Eluted (removed) amount in aqueous acid solution]: 5% phosphoric acid, Cd
(107 ppm), Zn (137 ppm); 10% phosphoric acid, Cd (100 ppm), Zn (127 ppm); 2
0% phosphoric acid, Cd (64.4 ppm), Zn (100 p
pm); 40% phosphoric acid, Cd (48.0 ppm), Zn
(65.5 ppm); 2% sulfuric acid, Cd (93.6 pp)
m), Zn (130 ppm).

Example 7 200 g of scallop uro (midgut gland, cut to a width of 0.3 to 0.5 mm, solid content 32%) was centrifugally dehydrated to obtain 137 g of uro. 100 ml of phosphoric acid aqueous solutions of various concentrations were added to 13.7 g of the urethane and immersed for 24 hours. Next, after separating the phosphoric acid aqueous solution by decantation, the uro was centrifugally dehydrated, and 100 ml of water was added to the uro and left for 3 hours. Thereafter, the aqueous layer was separated by decantation, and the uro was centrifugally dehydrated, followed by boiling in aqua regia. And
The cadmium content and the cadmium removal rate in the phosphoric acid aqueous solution, the washing solution, and the urethane after the treatment were measured using the ICP method. Table 3 shows the measurement results.

[0073]

[Table 3]

The contents of copper and zinc when a 0.3% phosphoric acid aqueous solution was used were as follows. Copper: [Aqueous solution of phosphoric acid (6.0 ppm), washing solution (2.4
ppm), Uro after treatment (26.5 ppm, removal rate of copper 2)
4%)] Zinc: [Aqueous solution of phosphoric acid (112 ppm), washing solution (1
0.2 ppm), Uro after treatment (5.4 ppm, removal rate of zinc 96%)]

Example 8 20 g of scallop uro (midgut gland, cut to a width of 0.3-0.5 mm) was centrifugally dehydrated to obtain 14.4 g of uro. 100 ml of a 2.5% phosphoric acid aqueous solution was added to
Stirred at 0 rpm. 10 ml of the phosphoric acid aqueous solution was collected over time, and the cadmium concentration was measured by the ICP method. The results were as follows. 1 hour (5.465 ppm), 2 hours (6.329 pp)
m), 4 hours (6.944 ppm), 6 hours (7.05 ppm)
7 ppm), 24 hours (7.269 ppm).

The urine after the reaction is centrifugally dehydrated, and 100 ml of water
Was added and left for 3 hours. The aqueous layer was separated, and the uro was centrifugally dehydrated and then decomposed by the aqua regia boiling method. The cadmium content of the aqueous layer and the treated uro was 10 ppm and 1.
It was 5 ppm (cadmium removal rate 99%).

Example 9 100 ml of a 10% phosphoric acid aqueous solution was added to 20 g of scallop uro (midgut gland, 0.3-0.5 mm width cut),
After heating at 90 ° C. for 30 minutes, it was allowed to cool. The amount of elution (removal) of heavy metals from uro [mg / kg (ppm) / dry weight] was as follows. [Cd, 91.2 ppm; Cu, 30.2 ppm]

Example 10 100 ml of a 10% phosphoric acid aqueous solution was added to 20 g of scallop uro (midgut gland, 0.3-0.5 mm width cut).
The mixture was stirred at 100 rpm for 4 hours. After the treated product was subjected to centrifugal filtration, the uro was washed with 600 ml of water, and the uro was centrifugally dehydrated. Removal amount of heavy metals from phosphoric acid aqueous solution [mg / kg
(Ppm) · Uro dry weight], and the content and elution (removal) rate% of heavy metals in the treated uro were as follows. Phosphoric acid aqueous solution: [Cd, 60.3 ppm; Cu, 29.
2 ppm] Uro after treatment: [Cd, 0.39 ppm (removal rate 99
%); Cu, 8.9 ppm (removal rate 70%)]

Example 11 Scallop uro (midgut gland, chopped) 10% in 20 g
100 ml of a phosphoric acid aqueous solution was added and shaken for 30 minutes. Next, the urine was collected by filtration and washed repeatedly with a small amount of water (water amount: 120 ml). Furthermore, after centrifugally dewatering the uro, aqua regia boiling treatment was performed. The amount of elution (removal) of heavy metals into the phosphoric acid aqueous solution [mg / kg (ppm) / uro dry weight] is 61.0 ppm, and the cadmium content in the treated ururo is 1.95 ppm (removal rate 97%). )Met.

Example 12 300 ml of a 10% aqueous solution of phosphoric acid was added to 100 g of the soft part of the scallops (uro), and the mixture was stirred at room temperature for 1 hour. The cadmium content in the uro decreased from 65 mg / kg (ppm) dry weight before the treatment to 0.85 mg / kg (ppm) dry weight after the treatment.

Example 13 200 ml of a 2.5% phosphoric acid aqueous solution was added to 13.7 g of scallop uro (midgut gland, cut to a width of 0.3 to 0.5 mm, solid content 47%) for 24 hours Dipped. Next, after separating the aqueous phosphoric acid solution by decantation, the uro was centrifugally dehydrated. The amount of elution (removal) of heavy metals into the phosphoric acid aqueous solution [mg / kg (ppm) · uro dry weight] and the cadmium content in the treated uro are 75%, respectively.
ppm and 3.4 ppm (96% removal rate).

Example 14 To 20 g of scallop uro (midgut gland, cut to a width of 0.3 to 0.5 mm), 99 ml of a 10% phosphoric acid aqueous solution and 1 ml of a 30% hydrogen peroxide solution were added, and the mixture was added at 100 rpm for 4 hours. Stirred. The amount of elution (removal) of heavy metals into this phosphoric acid aqueous solution [mg / kg (ppm) / uro dry weight] was as follows. [Cd, 95.5 ppm; Cu, 29.7 ppm]

[0083]

[0084]

[0085]

[0086]

[0087]

Example 17 To 50 g of scallop uro (midgut, cut to 0.3-0.5 mm width, solid content: 44%), 500 ml of a 1% phosphoric acid aqueous solution was added and immersed for 12 hours. Uro was centrifugally dehydrated. Next, 2.5 g of powdered activated carbon was added to the treated liquid, followed by filtration. The filtrate was passed through a cation exchange resin (Amberlite IR-120B) column to recover an aqueous phosphoric acid solution. The cadmium content in the recovered phosphoric acid aqueous solution is 0.
ppm.

The recovered phosphoric acid aqueous solution was added to the urine again and 12
After soaking for hours, the uro was centrifugally dehydrated. The cadmium content of the obtained uro was 0.38 ppm (as solid matter).

Example 18 100 ml of a 2% phosphoric acid aqueous solution was added to 13.4 g of scallop uro (midgut, cut into 0.3 to 0.5 mm width, solid content: 44%), and the mixture was treated with a cation exchange resin. (Amberlite IR-120B) (5 ml) was added and left to stand for 40 hours. Next, the uro was fractionated and centrifugally dehydrated. The cadmium content of the obtained uro was 2.3 ppm (in terms of solids).

After the treatment mixture was stirred at 100 rpm for 24 hours, the uro was centrifugally dehydrated. The cadmium content of the obtained uro was 0.13 ppm.

Example 19 To 8.0 g of crested squid liver (solid content: 44%) was added 40 ml of a 1% phosphoric acid aqueous solution, mixed, left to stand for 2 hours, and then the phosphoric acid aqueous solution was filtered off. The content (removal rate%) of heavy metals in the phosphoric acid aqueous solution was as follows. [Cd, 3.90 ppm (99%); Zn, 75.5p
pm (95%); Cu, 196 ppm (58%)]

Example 20 50 ml of a 1% phosphoric acid aqueous solution was added to 10 g of oyster guts (solid content: 20%), and the mixture was immersed for 24 hours, and the phosphoric acid aqueous solution was collected by filtration. The content (removal rate%) of heavy metals in the phosphoric acid aqueous solution was as follows. [Cd, 1.60 ppm (99%); Zn, 972 pp
m (80%); Cu, 78 ppm (58%)]

Example 21 50 ml of a 5% phosphoric acid aqueous solution was added to 10 g of beef liver,
After immersion for 24 hours, the aqueous phosphoric acid solution was collected by filtration. The content of heavy metals in the aqueous phosphoric acid solution was as follows. [Cd, 0.0082 ppm; Zn, 12.1 pp
m; Cu, 7.2 ppm]

Example 22 To 10.0 g of Canadian peat moss, 30 ml of a 20% phosphoric acid aqueous solution containing 2% hydrogen peroxide was added and immersed for 3 hours.
The elution (removal) amounts of the heavy metals were as follows. [As, 84.4 ppm; Cd, 2.36 ppm; C
r, 30.2 ppm; Cu, 1.17 ppm; Fe, 3
33 ppm, Ni, 5.98 ppm; Pb, 45.9 p
pm; Zn, 9.71 ppm]

Example 23 To 10 g of brown rice was added 50 ml of a 5% aqueous solution of phosphoric acid, and the resultant was immersed for 24 hours. The content (removal) of heavy metals in this phosphoric acid aqueous solution was as follows. [Cd, 0.0023 ppm; Zn, 2.47 ppm;
Cu, 0.20 ppm]

[0097]

[0098]

[0099]

[0100]

[0101]

The method for removing heavy metals according to the present invention has the above-mentioned structure, that is, by contacting a specific processing solution with a specific heavy metal-containing substance, the harmful substance contained in the heavy metal-containing substance is removed. It has the effect that the heavy metals can be effectively eluted and removed from the processing solution.

According to the method for removing heavy metals of the present invention,
As described above, harmful heavy metals can be effectively and economically removed from specific heavy metal-containing materials, which has been difficult to remove. The effect can be achieved on a scale.

Further, since the heavy metal-containing material from which heavy metals have been removed by the heavy metal removal method of the present invention has no risk of environmental pollution, it is disposed of as it is, or is fermented and used as compost rich in organic matter. This has the effect that it can be reused as a new resource.

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Claims (1)

(57) [Claims] 1. A method for removing heavy metals, comprising: contacting a treatment liquid with a heavy metal-containing substance to elute heavy metals contained in the heavy metal-containing substance into the treatment liquid. And the treatment liquid is: (A) a phosphoric acid aqueous solution, or (B) the following:
Phosphoric acid containing at least one of B1 and B2
A method for removing heavy metals, which is an aqueous solution . (B1) Other acids other than phosphoric acid (B2) Oxidizing agent