JP4839653B2 - Method for treating waste containing chlorine and heavy metals - Google Patents

Description

  The present invention relates to a treatment method for removing chlorine by washing a waste containing chlorine and heavy metals with water.

  Conventionally, incineration ash and incineration fly ash generated by incineration of municipal waste and industrial waste have been mainly landfilled. Recently, however, the remaining years of existing landfill sites have decreased, and it is difficult to set up new landfill sites due to constraints such as environmental problems.

By the way, cement is mainly composed of CaO, SiO ₂ , Al ₂ O ₃ , Fe ₂ O _{3 and the} like, and wastes containing these can be used as raw materials. It is used as a raw material. Attempts have also been made to use incineration fly ash such as municipal waste and industrial waste and cement kiln dust as cement raw materials.

  However, in the dust produced in cement kilns, incineration ash and incineration fly ash from municipal waste and industrial waste (hereinafter, collectively referred to simply as “dust” unless otherwise required), a considerably high concentration of chlorine Therefore, when these dusts are used as a raw material for cement, the resulting cement also contains a large amount of chlorine.

  When a large amount of chlorine is contained in the cement, the reinforcing bars are easily corroded, so that the durability of the reinforced concrete is lowered. For this reason, the JIS standard (JIS R5210) stipulates that the chlorine content in ordinary cement is 350 ppm or less, and if the dust containing high concentration of chlorine is used as a raw material for ordinary cement, the amount that can be used is It will be quite limited.

  Therefore, after the dust is washed with water to remove chlorine, it is used as a cement raw material, and further, useful soluble salts eluted in the washing water are collected and reused. At the time of washing, after reducing the amount of washing water required, a device for obtaining a sufficient cleaning effect and a device for recovering salts with high purity have been made.

  That is, in the method of removing chlorine by washing the dust with water, if a large amount of washing water is used for the dust, the chlorine remaining in the dust after washing will certainly decrease, but at the same time a large amount of washing filtrate will be generated. However, the processing cost for processing this large amount of filtrate is high. On the other hand, when the amount of washing water is small, a high concentration of chlorine remains in the dust, the washing effect is not sufficient, and the soluble components remain in the dust, so the washing slurry is dehydrated. In the process, since this soluble component flows out from the dust, the dehydration rate is lowered, and the salt recovery rate is lowered.

  For this reason, there is a need for a technique for obtaining a high desalting effect with a small amount of washing water and increasing the recovery rate of salts.

Conventionally, as a method of washing dust with a small amount of water to sufficiently remove chlorine and efficiently recovering salts, Japanese Patent No. 3333310 discloses a process of washing and filtering dust in multiple stages. The filtrate obtained in the water washing / filtration process is evaporated to dryness to recover salts, and fresh water is used as washing water in the final washing / filtration process, and the washing filtrate is used as washing water in the previous washing / filtration process. A method of circulating use has been proposed. In this method, salts are efficiently recovered from the washing filtrate obtained in the first water washing / filtration process, and the washing filtrate having a relatively high detergency in the final stage of water washing / filtration process is circulated and used. Reduce the amount of washing water.
Japanese Patent No. 3333310

  The method of Japanese Patent No. 3333310 can enhance the desalting effect with a small amount of washing water, but it cannot be said to be sufficient, and further improvement is desired. In addition, this method has a drawback that a plurality of washing tanks and filters are required for water cleaning and filtration in a plurality of stages, resulting in high apparatus costs.

  The present invention contains the chlorine and heavy metals that solve the above-mentioned problems of the prior art, can efficiently and stably demineralize dust with a small amount of washing water, and can also reduce the cost of the apparatus. It aims at providing the processing method of the waste.

  It is another object of the present invention to provide a method for treating waste containing chlorine and heavy metals, which can efficiently recover salts eluted from dust by demineralization and washing in a quality that can be reused as industrial raw materials. And

The method for treating waste containing chlorine and heavy metals according to the present invention (Claim 1) is to treat chlorine and heavy metals which are dust generated from cement kilns, incineration ash of municipal waste and industrial waste, and incineration fly ash. In a method of eluting and removing chlorine contained in the waste by washing the waste contained with water, 10 to 100 times as much washing water as the waste is added to the waste to form a slurry. An elution step for eluting soluble components in the waste, a precipitation step for solid-liquid separation of the slurry from the elution step, and circulating 60% or more of the supernatant water obtained in the precipitation step as washing water for the elution step A dehydrating / washing step for dehydrating and washing the precipitate obtained in the precipitation step, wherein 0.1 to 4 of the waste is used as washing water for the dehydration / washing step. Add new water by weight 0 times and wash Characterized by circulating the washing water in the elution step.

  The method for treating waste containing chlorine and heavy metals according to claim 2 is characterized in that, in the elution step, a pH adjuster is added to the slurry to maintain the pH at 7.0 to 11.0. To do.

  The method for treating waste containing chlorine and heavy metals according to claim 3 is the method according to claim 2, wherein the pH adjuster comprises carbon dioxide gas, exhaust gas from a firing furnace, exhaust gas from a cement kiln, inorganic acid, and organic acid. It is 1 type, or 2 or more types chosen from these.

  The method for treating waste containing chlorine and heavy metals according to claim 4 is the method according to any one of claims 1 to 3, wherein a flocculant and / or a heavy metal scavenger is added to the slurry from the elution step. And solid-liquid separation.

  The method for treating waste containing chlorine and heavy metals according to claim 5 is characterized in that, in claim 4, the flocculant is a polymer flocculant and / or an inorganic flocculant.

  The method for treating waste containing chlorine and heavy metals according to claim 6 is characterized in that, in claim 4 or 5, the heavy metal scavenger is a sulfide and / or a chelating agent.

  The method for treating a waste containing chlorine and heavy metals according to claim 7 is the crystallization treatment according to any one of claims 1 to 6, wherein 40% or less of the supernatant water obtained in the precipitation step is concentrated. And recovering the salt.

  The method for treating waste containing chlorine and heavy metals according to claim 8 is the method according to claim 7, wherein a carbonate is added to 40% or less of the supernatant water to remove calcium ions in the supernatant water as calcium carbonate. Then, it is subjected to the concentration and crystallization treatment.

  According to the present invention, the amount of washing water is low for waste containing chlorine and heavy metals, such as incineration ash and fly ash discharged from municipal waste incinerators and industrial waste incinerators, or dust generated in cement kilns. Therefore, desalting and cleaning can be performed efficiently and stably, and the cost of the apparatus can be reduced.

  That is, in the elution process, soluble components in dust (waste containing chlorine and heavy metals) are efficiently eluted with a sufficient amount of washing water, 10 to 100 times the weight of the dust, and precipitated. By performing solid-liquid separation in the process, a precipitate from which soluble components such as chlorine are sufficiently removed is obtained. Since 60% or more of the supernatant water in the precipitation process is circulated to the elution process, the amount of fresh water used can be reduced.

  By dehydrating and washing the precipitate obtained in the precipitation step, the water in which the soluble components contained in the precipitate are dissolved is sufficiently removed. In this dehydration / washing step, since fresh water is used as the washing water, the chlorine content remaining in the dewatered cake can be sufficiently washed away to obtain a high desalting washing effect. The amount of fresh water used here may be a relatively small amount of 0.1 to 4.0 times the amount of dust, and therefore the amount of fresh water used can be reduced.

  In the present invention, the dehydration process may be performed once, and therefore the apparatus cost can be reduced.

  According to the method of claim 2, heavy metals (lead, zinc, copper, etc.) in dust are added in the elution step by adding a pH adjuster to the slurry and adjusting the pH to 7.0-11.0. Elution into the slurry can be suppressed. As the pH adjuster, one or more selected from the group consisting of carbon dioxide gas, exhaust gas from a firing furnace, exhaust gas from a cement kiln, inorganic acid and organic acid can be used (Claim 3).

  Moreover, the solid-liquid separation efficiency and the heavy metal separation efficiency can be improved by adding a flocculant and / or a heavy metal scavenger to the slurry from the elution step and performing solid-liquid separation (claim 4). Here, a polymer flocculant and / or an inorganic flocculant can be used as the flocculant (Claim 5), and a sulfide and / or a chelating agent can be used as the heavy metal scavenger (Claim). Item 6).

  Of the supernatant water obtained in the slurry precipitation step, 40% or less that does not circulate to the elution step is concentrated and crystallized to efficiently recycle the contained salts as industrial raw materials. It can be recovered (claim 7). If the supernatant water is concentrated as it is in the concentration and crystallization treatment, a calcium scale problem occurs due to calcium ions contained in a large amount in the supernatant water. Therefore, prior to concentration and crystallization treatment, it is preferable to add carbonate to the supernatant water to remove calcium ions in the supernatant water as calcium carbonate (Claim 8).

  Embodiments of a method for treating waste containing chlorine and heavy metals according to the present invention will be described below in detail with reference to the drawings.

  1 (a) and 1 (b) are system diagrams showing an embodiment of a method for treating waste containing chlorine and heavy metals according to the present invention.

[Elution step 1]
As shown in the figure, in the present invention, first, dust to be desalted and cleaned, that is, incinerated ash and fly ash discharged from a municipal waste incinerator or industrial waste incinerator, or dust generated in a cement kiln, etc. To the waste containing chlorine and heavy metals, 10 to 100 times as much washing water as dust is added to form a slurry. When the amount of washing water used here is less than 10 times the weight of the dust, the soluble components in the dust are not sufficiently eluted in the washing water, and the soluble components remain in the dehydrated cake obtained in the subsequent dehydration / washing step 4. Therefore, when the dewatered cake is washed with fresh water, the remaining soluble components are eluted into the fresh water, resulting in a problem that the dewatering efficiency is lowered. On the other hand, even if the washing water exceeds 100 times the weight of dust, the elution effect of soluble components corresponding to the amount of washing water is not obtained, but rather the increase in the load of equipment cost due to the large amount of washing water becomes a problem. . Therefore, the amount of washing water is 10 to 100 times by weight, preferably 10 to 40 times by weight, that is, L (water) / S (dust) ratio = 10 to 100, preferably 10 to 40.

  In the present invention, as the washing water, 60% or more of the supernatant water in the subsequent precipitation step 3 and the washing waste water in the dehydration / washing step 4 are used. Accordingly, when the amount of the washing water is insufficient with the supernatant water of the subsequent precipitation step 3 and the washing waste water of the dehydration / washing step 4, fresh water is appropriately added from outside the system.

  In addition, normal water, such as industrial water and city water, can be used as the new water used in the present invention.

[Adjustment step 2]
In the elution step 1, chlorine in the dust is eluted by adding washing water to the dust to form a slurry, but the dust contains heavy metals (lead, zinc, copper, etc.) in addition to chlorine. Therefore, these are eluted in the slurry. For this reason, the adjustment step 2 is provided after the elution step 1, and the pH is adjusted to 7.0 to 11.0 by adding a pH adjuster to an alkaline slurry usually prepared by adding washing water to dust and having a pH of 12 or more. It is preferable to suppress elution of these heavy metals into the slurry, preferably by adjusting to 8.0 to 10.5. Here, as the pH adjusting agent, carbon dioxide, incinerator containing carbon dioxide, exhaust gas from cement kiln, inorganic acid such as nitric acid and sulfuric acid, or one or more organic acids such as acetic acid and citric acid are used. Can do. Among these, since carbon dioxide has a feature that pH is not extremely lowered even when used excessively, carbon dioxide can be suitably used.

  The adjustment step 2 is not necessarily provided separately from the elution step 1, and the pH may be adjusted in the elution step 1. Further, the pH may be adjusted in the subsequent precipitation step 3.

[Precipitation step 3]
The slurry prepared in the elution step 1 and further adjusted in pH in the adjustment step 2 is then subjected to solid-liquid separation in the precipitation step 3.

  In this solid-liquid separation, an aggregating floc can be formed by adding a flocculant to the slurry, and efficient solid-liquid separation can be performed. Moreover, precipitation of heavy metals can also be promoted by adding a heavy metal scavenger.

  As the flocculant, inorganic flocculants such as sulfate band (aluminum sulfate), PAC (polyaluminum chloride), ferric chloride, polyferric sulfate, polyacrylamide copolymer, polyacrylic acid, acrylamide and acrylic acid A polymer flocculant such as a copolymer with sodium can be used, and these may be used in combination. In addition, as the heavy metal scavenger, one or more of a chelating agent and a sulfide can be used. As the chelating agent, a commercially available dithiocarbamic acid chelating agent can be suitably used.

  Here, the addition amount of the flocculant and the heavy metal scavenger varies depending on the kind of the agent used, the concentration and properties of the slurry, but usually the inorganic flocculant is 10 to 300 mg / L, and the polymer flocculant is 0.5. ˜10.0 mg / L and the heavy metal scavenger is preferably about 10 to 200 mg / L.

  These flocculants and heavy metal scavengers can also be added in the adjustment step 2 in the previous stage.

  In this precipitation step 3, it is preferable to perform solid-liquid separation so as to obtain 0.01 to 1.0% of the supernatant water and 3.0 to 10.0% of the precipitate.

[Circulation process]
60% or more of the supernatant water obtained in the precipitation step 3 is circulated and used as the wash water in the previous elution step 1.

  Here, when the amount of circulating water is less than 60% of the supernatant water that has been subjected to solid-liquid separation, the amount of fresh water used is undesirably increased. Thus, in the present invention, the amount of fresh water used can be reduced by circulating 60% or more of the supernatant water.

  In addition, when the amount of circulating water is the total amount of supernatant water obtained by solid-liquid separation, the soluble component concentration of washing water in the elution step increases, so that the elution efficiency of soluble components deteriorates.

  Therefore, in the present invention, it is preferable to circulate 60 to 95%, particularly 80 to 95% of the supernatant water obtained by solid-liquid separation in the precipitation step to the elution step.

  The remaining portion of the supernatant that does not circulate in the elution step is discharged as shown in FIG. 1 (a), or the salt is recovered by concentration and crystallization as described later.

[Dehydration and washing process 4]
The precipitate separated in the solid-liquid separation in the precipitation step 3 is dehydrated by a filter press dehydrator, a belt press dehydrator, a centrifugal dehydrator or the like in the dehydration step. At this time, moisture in which the soluble component is dissolved remains in the dehydrated cake obtained in the dehydration step. In order to remove moisture in the dehydrated cake in which the soluble components are dissolved, the dehydrated cake is 0.1 to 4.0 times by weight, preferably 0.5 to 2.0 times the dust subjected to desalting washing. Wash with twice the weight of fresh water. By washing with this new water, the chlorine content in the dehydrated cake can be sufficiently reduced. When the amount of fresh water is less than 0.1 times the weight of dust, the cleaning effect is not sufficient, and when it exceeds 4.0 times the amount of dust, the amount of fresh water used becomes too large, which is not economical.

  The washing waste water with the fresh water is circulated as the washing water of the elution process 1 in the previous stage.

  The method of dewatering / washing the precipitate in the dehydration / washing step 4 may be either a method of dewatering the precipitate and then washing the dehydrated cake with fresh water, or a method of washing with fresh water during dehydration of the precipitate. However, a method of dewatering the precipitate and washing the obtained dehydrated cake, particularly a method of penetrating and washing the dehydrated cake is preferred. The through-cleaning is an operation for washing the dewatered cake in the dehydrator without opening the dehydrator after dehydrating with a filter press or the like.

  In this case, it is preferable that the dehydrated filtrate is discharged or concentrated and crystallized to recover salts, and the through-washed filtrate is circulated to the elution step.

  This washing wastewater can be partly circulated without circulating the entire amount to the elution process, but this washing wastewater has a relatively low chlorine concentration detergency obtained by washing with fresh water. Since it is high water, it is preferable to circulate 90% or more of this washing waste water, particularly the entire amount, to the elution step.

[Salt recovery process]
The supernatant water obtained in the precipitation step contains useful elution salts. Therefore, it is effective to recover and reuse these salts in terms of effective use of resources and waste disposal. However, since this supernatant water contains a large amount of calcium, if this supernatant water is directly subjected to concentration and crystallization treatment for salt recovery, adhesion of calcium scale becomes a problem. ), It is preferable to perform concentration and crystallization after decalcification.

<Decalcification step 5>
Although there is no restriction | limiting in particular as a decalcification process of supernatant water, The method of adding carbonate to supernatant water, precipitating calcium ion in supernatant water as calcium carbonate, and solid-liquid-separating this is preferable.

  Although there is no restriction | limiting in particular as carbonate used here, When potassium carbonate is used, the potassium chloride density | concentration in the crystal | crystallization collect | recovered by a concentration / crystallization process of a latter stage can be made high, and it is preferable.

  The amount of carbonate added to the supernatant is appropriately determined according to the calcium concentration in the supernatant, and is usually about 1000 to 10,000 mg / L with respect to the supernatant. In addition, in the decalcification treatment, a solid-liquid separation efficiency may be increased by adding a flocculant to form a floc floc. As a method for separating the precipitated calcium carbonate, a membrane separation method can be adopted in addition to the precipitation separation.

  By this decalcification treatment, it is preferable for the calcium concentration in the supernatant water to be 50 mg / L or less in order to prevent the subsequent calcium scale.

<Concentration / crystallization process 6>
In the concentration and crystallization step, the decalcified supernatant water is concentrated by heating with a commercially available evaporative concentration apparatus or the like to precipitate crystals.

  Here, the crystal components to be precipitated depend on the components contained in the supernatant water. For example, when a large amount of potassium chloride is contained in the supernatant water, a salt mainly composed of potassium chloride is recovered. Of the recovered crystals, potassium chloride is used as a raw material for fertilizers and antifreeze agents, and sodium chloride is used as a soda raw material.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

  In the following, A dust discharged from the cement kiln was used as the dust to be desalted and cleaned. The dust components are as shown in Table 1.

  Moreover, demineralized water was used as new water.

Example 1
Desalination washing was performed according to the following procedure.
(1) 60.0 L of fresh water was added to 3.0 kg of A dust and stirred for about 6 hours to prepare a slurry of L / S = 20.
(2) Carbon dioxide gas was bubbled through the A dust water slurry (pH 12.5) prepared in (1) at a flow rate of 6.0 L / min for 90 minutes to lower the pH of the slurry to 10.0. . Then, piperazine dithiocarbamic acid chelating agent 50 mg / L, ferrous chloride aqueous solution (31 wt% concentration as FeCl2) 100 mg / L, and flocculant (copolymer of acrylamide and Na acrylate) 2 mg / L The mixture was added and stirred, and then solid-liquid separation was performed by decantation to obtain 54 L of supernatant water and a precipitate.
(3) The precipitate obtained in (2) (concentration and pH as shown in Table 2) was squeezed with a filter press under the dehydrating conditions shown in Table 2. The dehydrated filtrate (pressed liquid) at this time was discharged out of the system. The dewatered cake after pressing was subjected to through-cleaning using fresh water under the conditions shown in Table 2 (first dehydration cleaning). 1.0 L (L / S = 0.33) of fresh water was used.
(4) The dehydrated cake after washing with fresh water was collected, and the chlorine content and water content were measured. Further, the pH and chlorine content of the through-cleaning filtrate were measured. These measurement results are shown in Table 2 (first treatment).
(5) 50L of the supernatant water 54L obtained in (2) is added with 1.0L of the filtrate for dewatering cake through the filter press, and 51L is used as circulating water. A total of 60 L of 51.0 L of water and 9.0 L of fresh water was added and stirred for about 6 hours to prepare a slurry of L / S = 20.
(6) Similarly to (2), carbon dioxide gas is aerated at a flow rate of 6.0 L / min for 90 minutes to the slurry (pH 12.5) prepared in (5), and the pH of the slurry is increased to 10.0. Reduced. Then, piperazine dithiocarbamic acid chelating agent 50 mg / L, ferrous chloride aqueous solution (31 wt% concentration as FeCl2) 100 mg / L, and flocculant (copolymer of acrylamide and Na acrylate) 2 mg / L The mixture was added and treated, followed by solid-liquid separation by decantation to obtain 54 L of supernatant water and a precipitate.
(7) The precipitate obtained in (6) (concentration and pH as shown in Table 2) is squeezed with a filter press in the same manner as in (3) under the dehydration conditions shown in Table 2, and the dehydrated cake after squeezing is displayed. Through-cleaning was performed using fresh water under the conditions shown in 2 (second dehydration cleaning). 1.0 L (L / S = 0.33) of fresh water was used.
(8) The dehydrated cake after washing with fresh water was collected, and the chlorine content and water content were measured. Further, the pH and chlorine content of the through-cleaning filtrate were measured. These measurement results are shown in Table 2 (second treatment).

Comparative Example 1
Desalination washing was performed according to the following procedure.
(1) 60.0 L of fresh water was added to 3.0 kg of A dust, and the mixture was stirred for about 6 hours to prepare a slurry of L / S = 20.
(2) The slurry (concentration and pH as shown in Table 2) prepared in (1) was squeezed with a filter press under the dehydrating conditions shown in Table 2. The dehydrated filtrate (pressed liquid) at this time was discharged. The dewatered cake after pressing was subjected to through-cleaning using fresh water under the conditions shown in Table 2. 1.0 L (L / S = 0.33) of fresh water was used.
(3) The dehydrated cake after washing with fresh water was collected, and the chlorine content and water content were measured. Further, the pH and chlorine content of the through-cleaning filtrate were measured. The measurement results are shown in Table 2.

Comparative Example 2
Desalination washing was performed according to the following procedure.
(1) 9.0 L of fresh water was added to 3.0 kg of A dust, and the mixture was stirred for about 6 hours to prepare a slurry of L / S = 3.
(2) The slurry (concentration and pH as shown in Table 2) prepared in (1) was squeezed with a filter press under the dehydrating conditions shown in Table 2. The dehydrated filtrate (pressed liquid) at this time was discharged. The dewatered cake after pressing was subjected to through-cleaning using fresh water under the conditions shown in Table 2. 1.0 L (L / S = 0.33) of fresh water was used.
(3) The dehydrated cake after washing with fresh water was collected, and the chlorine content and water content were measured. Further, the pH and chlorine content of the through-cleaning filtrate were measured. The measurement results are shown in Table 2.

  A comparison between Example 1 (second treatment) and Comparative Examples 1 and 2 is shown in Table 3.

表３より、実施例１は排水量（新水使用量）は少なく、かつ脱水ケーキ中のＣｌ含有率も低いこと、比較例１は脱水ケーキ中のＣｌ含有率は低いが、排水量（新水使用量）が多いこと、比較例２は排水量（新水使用量）は少ないが、脱水ケーキ中のＣｌ含有率が高いことが分かる。

From Table 3, Example 1 has a small amount of wastewater (amount of fresh water used) and a low Cl content in the dehydrated cake, while Comparative Example 1 has a low Cl content in the dehydrated cake, but the amount of wastewater (the amount of fresh water used) It can be seen that Comparative Example 2 has a small amount of drainage (amount of fresh water used) but a high Cl content in the dehydrated cake.

  In Example 1, the operations of (5) to (9) were repeated 5 times in the same manner, but the water content in the dehydrated cake obtained by the seventh dehydration and washing was 38.2%, The chlorine content was 0.09%, and it was confirmed that a stable dehydration cleaning effect was obtained.

Example 2
In Example 1, when the calcium ion concentration was analyzed for the remaining 5L of the supernatant water 54L obtained by the solid-liquid separation in the second treatment, it was 477 mg / L.

  To the remainder of the supernatant water, 3500 mg / L of potassium carbonate was added and the precipitated calcium carbonate was filtered off. The obtained filtrate was evaporated and concentrated to about 20% slurry with an evaporator, and crystallization process was performed while washing the crystal with a separating tower to obtain 209 g of crystals containing 75% by weight of potassium chloride.

It is a systematic diagram which shows embodiment of the processing method of the waste containing chlorine and heavy metals of this invention.

Explanation of symbols

1 Elution process 2 Adjustment process 3 Precipitation process 4 Dehydration / washing process 5 Decalcification process 6 Concentration / crystallization process

Claims (8)

Dust generated from cement kiln, municipal waste and industrial waste incineration ash, incineration fly ash and waste containing chlorine and heavy metals are washed with water to elute and remove chlorine contained in the waste In the method
An elution step of adding 10 to 100 times the washing water of the waste to the waste to make a slurry to elute soluble components in the waste;
A precipitation step for solid-liquid separation of the slurry from the elution step;
A circulation step of circulating 60% or more of the supernatant water obtained in the precipitation step as washing water in the elution step;
A dehydration / washing step of dehydrating and washing the precipitate obtained in the precipitation step,
Chlorine and heavy metals characterized in that 0.1 to 4.0 times by weight of fresh water is added as washing water in the dehydration / washing process, and washing wastewater is circulated as washing water in the elution process For the treatment of waste containing sucrose.   The method for treating waste containing chlorine and heavy metals according to claim 1, wherein, in the elution step, a pH adjusting agent is added to the slurry to maintain the pH at 7.0 to 11.0.   3. The chlorine according to claim 2, wherein the pH adjuster is one or more selected from the group consisting of carbon dioxide gas, exhaust gas from a firing furnace, exhaust gas from a cement kiln, inorganic acid, and organic acid. A method for treating waste containing heavy metals.   The waste containing chlorine and heavy metals according to any one of claims 1 to 3, wherein a flocculant and / or a heavy metal scavenger is added to the slurry from the elution step for solid-liquid separation. How to handle things.   5. The method for treating waste containing chlorine and heavy metals according to claim 4, wherein the flocculant is a polymer flocculant and / or an inorganic flocculant.   6. The method for treating waste containing chlorine and heavy metals according to claim 4, wherein the heavy metal scavenger is a sulfide and / or a chelating agent.   The waste containing chlorine and heavy metals according to any one of claims 1 to 6, wherein 40% or less of the supernatant water obtained in the precipitation step is concentrated and then crystallized to recover salts. How to handle things.   The chlorine according to claim 7, wherein carbonate is added to 40% or less of the supernatant water, calcium ions in the supernatant water are removed as calcium carbonate, and then subjected to the concentration and crystallization treatment. A method for treating waste containing heavy metals.

Images