JP2009039664A - Acid treatment method for heavy metal contaminated soil - Google Patents
Acid treatment method for heavy metal contaminated soil Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 94
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000010306 acid treatment Methods 0.000 title 1
- 239000002253 acid Substances 0.000 claims abstract description 32
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910052500 inorganic mineral Inorganic materials 0.000 claims abstract description 25
- 239000011707 mineral Substances 0.000 claims abstract description 25
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 22
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 claims abstract description 21
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 claims description 14
- 235000019345 sodium thiosulphate Nutrition 0.000 claims description 14
- 238000002386 leaching Methods 0.000 abstract description 9
- 238000003756 stirring Methods 0.000 abstract description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 abstract description 4
- 229910017604 nitric acid Inorganic materials 0.000 abstract description 4
- 238000000926 separation method Methods 0.000 description 18
- 238000011109 contamination Methods 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 230000007613 environmental effect Effects 0.000 description 4
- -1 thiosulfuric acid compound Chemical class 0.000 description 4
- 229910052785 arsenic Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 229910052793 cadmium Inorganic materials 0.000 description 3
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- JPBGLQJDCUZXEF-UHFFFAOYSA-N chromenylium Chemical compound [O+]1=CC=CC2=CC=CC=C21 JPBGLQJDCUZXEF-UHFFFAOYSA-N 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 238000010828 elution Methods 0.000 description 2
- 238000012407 engineering method Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- PODWXQQNRWNDGD-UHFFFAOYSA-L sodium thiosulfate pentahydrate Chemical compound O.O.O.O.O.[Na+].[Na+].[O-]S([S-])(=O)=O PODWXQQNRWNDGD-UHFFFAOYSA-L 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- PIJPYDMVFNTHIP-UHFFFAOYSA-L lead sulfate Chemical compound [PbH4+2].[O-]S([O-])(=O)=O PIJPYDMVFNTHIP-UHFFFAOYSA-L 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000004056 waste incineration Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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- Processing Of Solid Wastes (AREA)
Abstract
【課題】
重金属で汚染された土壌を浄化するにあたって、重金属を安定した状態にする不溶化処理処理法がある。この方法でも重金属は安定した状態となり反応しないので、安全である。しかし、土壌中に重金属元素が含まれているため、さらに除去する事が望まれつつある。そこで、例えば、重金属汚染土壌に対しては、鉱酸を用いて土壌中の重金属類を溶解し、除去する方法がある。酸の種類としては、塩酸、硫酸、硝酸などが挙げられる。しかし、酸を取り扱うことから設備の構成を酸に強い高価な部材を用いる他、硫酸などには鉛が溶解しないなど課題があり、簡便でコストがかからない方法が望まれていた。
【解決手段】
重金属汚染土壌に対して鉱酸を添加し、撹拌し、該鉱酸により重金属を浸出した後、該重金属汚染土壌にチオ硫酸塩溶液を添加し、撹拌することにより重金属を浸出することを特徴とする重金属汚染土壌の処理方法。
【選択図】 なし
【Task】
When purifying soil contaminated with heavy metals, there is an insolubilization treatment method that stabilizes heavy metals. Even in this method, the heavy metal is stable and does not react, so it is safe. However, since heavy metal elements are contained in the soil, further removal is being desired. Thus, for example, for heavy metal contaminated soil, there is a method of dissolving and removing heavy metals in the soil using mineral acid. Examples of the acid include hydrochloric acid, sulfuric acid, and nitric acid. However, since an acid is used, an expensive member that is resistant to acid is used for the equipment configuration, and there is a problem that lead does not dissolve in sulfuric acid and the like, and a simple and inexpensive method has been desired.
[Solution]
Mineral acid is added to the heavy metal contaminated soil, stirred, and after leaching the heavy metal with the mineral acid, a thiosulfate solution is added to the heavy metal contaminated soil and the heavy metal is leached by stirring. To treat heavy metal contaminated soil.
[Selection figure] None
Description
本発明は、重金属汚染土壌から重金属を除去し、該重金属汚染土壌を浄化する処理技術に関する。 The present invention relates to a treatment technique for removing heavy metals from heavy metal contaminated soil and purifying the heavy metal contaminated soil.
鉛(Pb)、砒素(As)、カドミニウム(Cd)、クロムニウム(Cr)などの重金属元素により汚染された重金属汚染土壌については、環境基準を満たす清浄土とする浄化処理が環境保全の見知からも当然として要望が発生している。さらには、より低コストかつ高効率の方法が市場で求められている。 For the preservation of heavy metal contaminated soil contaminated with heavy metal elements such as lead (Pb), arsenic (As), cadmium (Cd), and chromenium (Cr), a clean process that meets environmental standards is known for environmental conservation. As a matter of course, there is a demand. Furthermore, there is a need in the market for lower cost and higher efficiency methods.
重金属汚染土壌の浄化処理には、土壌中の重金属を不溶化する技術がある。例えば、特許文献1には、カドミウム、亜鉛、銅、水銀、鉛、砒素、セレン、ニッケルなどの有害重金属を含有する各種廃棄物、土壌・底質および排水中の重金属元素を固定化し、長期間にわたり再溶出しないように安定化することが可能で、かつ作業環境を悪化させない安全な廃棄物の重金属不溶化処理方法を関してあり、 重金属を含有する産業廃棄物、都市ゴミ焼却灰、土壌・底質、あるいは排水など汚染物質に、チオ硫酸化合物またはその溶液あるいはチオ硫酸化合物を含む廃液を、汚染物質中の重金属含有量に対してチオ硫酸化合物の量がモル比で5倍以上になるよう添加するとともに、必要に応じて更に水を添加した後、常温で撹拌混合処理する、または、95〜120℃で5〜36時間加熱処理することを特徴とする、汚染物質中の重金属元素の不溶化処理方法を開示している。 In the purification treatment of heavy metal contaminated soil, there is a technique for insolubilizing heavy metals in the soil. For example, in Patent Document 1, various wastes containing toxic heavy metals such as cadmium, zinc, copper, mercury, lead, arsenic, selenium, nickel, and heavy metal elements in soil / sediment and wastewater are fixed for a long time. Can be stabilized so that it does not re-elution over a long period of time, and it is related to a safe heavy metal insolubilization method that does not deteriorate the work environment. Industrial waste containing heavy metals, municipal waste incineration ash, soil and bottom Add thiosulfuric acid compound or its solution or waste liquid containing thiosulfuric acid to pollutants such as quality or waste water so that the amount of thiosulfuric acid compound is more than 5 times molar ratio to the heavy metal content in pollutants In addition, after adding water as needed, the mixture is stirred and mixed at room temperature, or is heat-treated at 95 to 120 ° C. for 5 to 36 hours. A method for insolubilizing heavy metal elements therein is disclosed.
不溶化処理によって汚染土壌からの重金属の溶出は抑制され、安全なものとなる。しかし、土壌中の重金属は残存するため、重金属汚染土壌中の重金属を該土壌から除去する方法が要望されている。 Due to the insolubilization treatment, the elution of heavy metals from the contaminated soil is suppressed, and it becomes safe. However, since heavy metals in soil remain, a method for removing heavy metals in heavy metal-contaminated soil from the soil is desired.
重金属を土壌から除去する方法として、例えば、重金属汚染土壌に対して、鉱酸を用いて土壌中の重金属類を溶解し、除去する方法がある。酸の種類としては、塩酸、硫酸、硝酸などが挙げられる。このうち、塩酸は重金属を溶解する効果が大きいが、同時に金属腐食性も強いため、設備の材質としてFRPなどが必要となり、設備に係るコストが高くなる。また、塩化水素ガスが発生するため、処理の際は拡散防止の対策が必要である。硝酸も塩酸と同様、腐食に対する問題があり、さらに排水において硝酸性窒素の問題があるため、処理装置を更に要し、コスト高となり採用できない。このため、これらの中で最もコストが小さく、かつ設備への影響が少ない硫酸が望ましい。
しかし、鉛汚染土壌の場合、鉛は硫酸と難溶性塩である硫酸鉛を形成するため、硫酸では除去できないという問題があった。
As a method of removing heavy metals from soil, for example, there is a method of dissolving and removing heavy metals in soil using mineral acid in heavy metal contaminated soil. Examples of the acid include hydrochloric acid, sulfuric acid, and nitric acid. Of these, hydrochloric acid has a great effect of dissolving heavy metals, but at the same time, it is also highly corrosive to metals, so that FRP or the like is required as a material for the equipment, which increases the cost of the equipment. Moreover, since hydrogen chloride gas is generated, it is necessary to take measures to prevent diffusion during the treatment. Nitric acid, like hydrochloric acid, has a problem with corrosion, and also has a problem with nitrate nitrogen in the waste water. For this reason, sulfuric acid with the lowest cost and the least influence on equipment is desirable among these.
However, in the case of lead-contaminated soil, since lead forms lead sulfate which is a hardly soluble salt with sulfuric acid, there is a problem that it cannot be removed with sulfuric acid.
このように重金属汚染土壌の浄化において、重金属汚染土壌中の汚染源となっている重金属を該土壌から分離し、除去することが望まれ、且つ、産業上の実施ゆえにコストがかからない、簡便な方法が望まれていた。 Thus, in the purification of heavy metal-contaminated soil, it is desired to separate and remove the heavy metal that is the source of contamination in the heavy metal-contaminated soil from the soil, and there is a simple method that is not costly due to industrial implementation. It was desired.
発明者は、上記課題を解決すべく、本発明を見出した。すなわち、第1の発明は、重金属汚染土壌に対して鉱酸を添加し、撹拌し、該鉱酸と重金属とを反応せしめた後、該重金属汚染土壌にチオ硫酸塩溶液を添加し、撹拌し、重金属を浸出し、該重金属汚染土壌から該重金属を含む溶液を分離することを有することを特徴とする重金属汚染土壌の処理方法である。 The inventor has found the present invention to solve the above problems. That is, in the first invention, a mineral acid is added to the heavy metal-contaminated soil and stirred, and the mineral acid and the heavy metal are reacted. Then, a thiosulfate solution is added to the heavy metal-contaminated soil and stirred. A method for treating heavy metal contaminated soil, comprising leaching heavy metal and separating a solution containing the heavy metal from the heavy metal contaminated soil.
該重金属が鉛で第1の発明に記載の重金属汚染土壌の処理方法。従来の硫酸溶解による分離では、特に鉛の汚染土壌からの分離は難しいが、本発明では簡便に安価に可能とした。 The method for treating heavy metal-contaminated soil according to the first invention, wherein the heavy metal is lead. In the conventional separation by sulfuric acid dissolution, separation of lead from contaminated soil is difficult, but in the present invention, it can be easily and inexpensively.
第3の発明は、該鉱酸が、塩酸または硫酸である第1または第2の発明に記載の重金属汚染土壌の処理方法。さらに酸等においても産業上利用しやすい物を利用可能としている。 A third invention is a method for treating heavy metal-contaminated soil according to the first or second invention, wherein the mineral acid is hydrochloric acid or sulfuric acid. In addition, it is possible to use industrially easy-to-use products such as acids.
第4の発明は、該鉱酸を添加する際に、重金属汚染土壌をpH3以下とする、第1乃至第3の発明に記載の重金属汚染土壌の処理方法。酸によりpH を調整することで、重金属の分離を促進可能とした。 4th invention is a processing method of heavy metal contamination soil as described in 1st thru | or 3rd invention which makes heavy metal contamination soil pH3 or less when adding this mineral acid. By adjusting the pH with an acid, separation of heavy metals can be promoted.
第5の発明は、該チオ硫酸塩溶液がチオ硫酸ナトリム溶液であり、且つチオ硫酸ナトリウムを重金属に対してモル比で15倍以上の量で添加する第1乃至第4の発明に記載の重金属汚染土壌の処理方法。処理における副次的な発生物を抑制し、さらに分離後に重金属含まれる溶液は非鉄製錬の原料となりうる。
According to a fifth invention, the heavy metal according to the first to fourth inventions, wherein the thiosulfate solution is a sodium thiosulfate solution and sodium thiosulfate is added in a molar ratio of 15 times or more with respect to the heavy metal. How to treat contaminated soil. A secondary product in the treatment is suppressed, and a solution containing a heavy metal after separation can be a raw material for non-ferrous smelting.
重金属汚染土壌から重金属を分離し、清浄土壌を得られる。また、簡便な方法で浄化可能となるため、さらにはコストも抑制でき安価に達成できる。 Separation of heavy metals from heavy metal contaminated soil provides clean soil. Moreover, since it becomes possible to purify by a simple method, the cost can be further suppressed and the cost can be reduced.
重金属汚染土壌とは、汚染源である重金属が分子または酸化化合物等を汚染程度に含む土壌である。該土壌は、自然土地ににある地下、地表であるもの、人工的に形成された区画内にあるものであってもよい。 Heavy metal-contaminated soil is soil in which the heavy metal that is the source of contamination contains molecules or oxide compounds to the extent of contamination. The soil may be an underground, a ground surface, or an artificially formed section in natural land.
該重金属汚染土壌の汚染源である重金属は、鉛、砒素、カドミニウム、クロムニウム当などである。特に汚染源の重金属が鉛である場合は、本発明による分離は高度に達成できる。なお、上記の重金属が複数に混合存在する場合であっても、本発明に適用可能である。鉛が1000mg/Kgと高濃度に汚染された土壌であっても適用可能であり、特に500mg/Kg以上の高濃度の汚染土壌に適している。高濃度の場合であれば、土壌中の重金属が多様な形態になり他の方法では分離できない場合であっても処理可能となる。 The heavy metal that is a pollution source of the heavy metal-contaminated soil is lead, arsenic, cadmium, chromenium, and the like. The separation according to the invention can be achieved to a high degree, especially when the heavy metal of the source is lead. In addition, even if it is a case where said heavy metal is mixed in multiple, it is applicable to this invention. It can be applied even to soil contaminated with lead at a high concentration of 1000 mg / Kg, and is particularly suitable for contaminated soil having a high concentration of 500 mg / Kg or more. In the case of a high concentration, it is possible to treat heavy metals in the soil in various forms and cannot be separated by other methods.
鉱酸は、塩酸、硫酸、硝酸等が挙げられる。特には塩酸が好ましい。塩酸は、より多くの種類の重金属の溶解をするためである。また、鉱酸添加後のチオ硫酸塩溶液と組み合わせると、さらに重金属の分離を高度に達成するためである。なお、鉱酸、チオ硫酸塩溶液は、市販のものを使用してよい。チオ硫酸塩溶液は、チオ硫酸ナトリウム5水和溶液を用いることができる。 Examples of the mineral acid include hydrochloric acid, sulfuric acid, nitric acid and the like. In particular, hydrochloric acid is preferred. This is because hydrochloric acid dissolves more kinds of heavy metals. In addition, when combined with a thiosulfate solution after the addition of mineral acid, the separation of heavy metals is further achieved. In addition, a commercially available thing may be used for a mineral acid and a thiosulfate solution. As the thiosulfate solution, a sodium thiosulfate pentahydrate solution can be used.
本発明に係る重金属汚染土壌の処理は、原位置および場外処理であっても可能である。場外処理にあっては、原料処理として重金属汚染土壌を、分級、または水等により水洗処理をしてもよい。分級または水洗のみよっても多少の重金属が分離が可能であり、後工程での処理負荷の軽減となる。 The heavy metal-contaminated soil according to the present invention can be processed in-situ and off-site. In the off-site treatment, the heavy metal-contaminated soil may be subjected to water washing treatment with classification or water as a raw material treatment. Some heavy metals can be separated only by classification or water washing, and the processing load in the subsequent process is reduced.
本発明に係る重金属汚染土壌の処理は、該重金属汚染土壌に鉱酸を添加し、鉱酸を撹拌して混合する前処理工程と、撹拌後にチオ硫酸塩溶液を添加し、撹拌する浸出工程と、ろ過等により重金属を土壌から分離する分離工程とを有する。 The treatment of heavy metal contaminated soil according to the present invention includes a pretreatment step of adding mineral acid to the heavy metal contaminated soil and stirring and mixing the mineral acid, and a leaching step of adding and stirring the thiosulfate solution after stirring. Separating the heavy metal from the soil by filtration or the like.
前処理工程では、該重金属汚染土壌に鉱酸を添加し、鉱酸を撹拌して混合する。該重金属汚染土壌と、鉱酸とのが量比にてほぼ均一に混合される状態とするのが望ましい。なお、均一に混合される状態は、重金属汚染土壌において全体であることが望ましいが、汚染の濃度分布に合わせ、鉱酸の添加濃度等を設計、設定してもよい。ここでの撹拌し、混合は、重機のバックフォーや、オーガによってもよい。従来の土木工事用の重機で簡便に利用可能で、従来の土木工法が利用可能ある。前処理工程によって、該重金属汚染土壌中の汚染源たる重金属が、浸出しやすい単一な化合物や、分子状態となり、次の浸出工程での該重金属の浸出を促進する。鉱酸は、該重金属汚染土壌を撹拌しながら添加しても良い。鉱酸工程は簡便に達成可能であり、薬剤も市販の容易に入手可能である。 In the pretreatment step, a mineral acid is added to the heavy metal contaminated soil, and the mineral acid is stirred and mixed. It is desirable that the heavy metal-contaminated soil and the mineral acid are mixed almost uniformly in a quantitative ratio. In addition, it is desirable that the uniformly mixed state is the whole in the heavy metal-contaminated soil, but the addition concentration of the mineral acid and the like may be designed and set according to the concentration distribution of the contamination. Stirring and mixing here may be performed by a heavy equipment back-for or auger. It can be easily used with conventional heavy machinery for civil engineering work, and conventional civil engineering methods can be used. By the pretreatment process, the heavy metal as a contamination source in the heavy metal-contaminated soil becomes a single compound or a molecular state that is easily leached, and promotes the leaching of the heavy metal in the next leaching process. Mineral acid may be added while stirring the heavy metal contaminated soil. The mineral acid process can be easily achieved, and drugs are also readily available on the market.
鉱酸の添加量は、重金属汚染土壌中の重金属の含有量等と、処理前の重金属汚染土壌のpH(水素イオン指数)により設計、設定される。なお、含有量とあるが、所望処理量としても同様である。鉱酸の添加の際には、重金属汚染土壌のpH値が3以下になる程度まで添加するのがよい。後工程で、重金属の分離を促すためである。また、前処理工程後の土壌は、乾燥等を施しても良い。余分な水分を除去することで土壌の取り扱いが容易になるからである。なお、コストを抑制する観点からもpHは、2以下に下げない方が望ましい。pHを過度に下げると薬剤の使用量が増加し、コスト増となり、さらに設備の部材等も高価になるからである。 The amount of mineral acid added is designed and set based on the heavy metal content in the heavy metal-contaminated soil and the pH (hydrogen ion index) of the heavy metal-contaminated soil before treatment. In addition, although it is with content, it is the same also as desired processing amount. When adding the mineral acid, it is preferable to add it until the pH value of the heavy metal-contaminated soil becomes 3 or less. This is to promote separation of heavy metals in a subsequent process. Moreover, the soil after the pretreatment step may be subjected to drying or the like. This is because the soil can be easily handled by removing excess water. From the viewpoint of cost reduction, it is desirable not to lower the pH to 2 or less. This is because if the pH is lowered excessively, the amount of the drug used increases, the cost increases, and the equipment members and the like become more expensive.
浸出工程では、前処理工程後の該重金属汚染土壌に、チオ硫酸塩溶液等を添加し、チオ硫酸塩溶液を撹拌して混合する。チオ硫酸塩溶液によって前処理工程後の土壌から重金属を液中に溶解する、このように浸出をすることで、土壌からの重金属の分離を可能な状態とした。チオ硫酸塩溶液とのが量比にてほぼ均一に混合される状態とするのが望ましい。なお、均一に混合される状態は、重金属汚染土壌において全体であることが望ましいが、汚染の濃度分布に合わせ、チオ硫酸塩溶液の添加濃度等を設計、設定してもよい。ここでの撹拌し、混合は、重機のバックフォーや、オーガによってもよい。土木工事用の重機であれば、簡便に利用可能である。前処理工程後にチオ硫酸を添加することにより簡便に重金属を浸出可能とした。用いる重機は、前処理工程と同様であってもよい。従来の土木工法も簡便に利用可能である。なお、処理量が少なく、重機が過大設備となる場合は、振とう器を用いても良い。このように浸出工程においても簡便に実施可能であり、チオ硫酸塩も市場から容易に水和物として入手可能である。 In the leaching step, a thiosulfate solution or the like is added to the heavy metal contaminated soil after the pretreatment step, and the thiosulfate solution is stirred and mixed. The heavy metal was dissolved in the liquid from the soil after the pretreatment step with the thiosulfate solution, and the leaching was performed in this manner, so that the heavy metal could be separated from the soil. It is desirable that the thiosulfate solution is mixed almost uniformly in a quantitative ratio. It is desirable that the uniformly mixed state is the whole in heavy metal contaminated soil, but the addition concentration of the thiosulfate solution may be designed and set in accordance with the concentration distribution of the contamination. Stirring and mixing here may be performed by a heavy equipment back-for or auger. If it is a heavy machine for civil engineering work, it can be used easily. By adding thiosulfuric acid after the pretreatment step, it was possible to easily leach heavy metals. The heavy machine to be used may be the same as the pretreatment process. Conventional civil engineering methods can also be used easily. Note that a shaker may be used when the amount of processing is small and the heavy machinery is excessively installed. Thus, the leaching process can be easily carried out, and thiosulfate can be easily obtained as a hydrate from the market.
チオ硫酸塩溶液の添加する量は、土壌に含有する重金属のモル量に対してモル比ですくなとも15倍当量程度以上(例、チオ硫酸ナトリウム:鉛=15:1)、望ましくは、150倍当量以上が望ましい。チオ硫酸塩溶液は、チオ硫酸ナトリウムが好ましい。不要な分解物、化合物を生成しないから、重金属の分離制御が容易となり、さらなる処理が発生せず、安価にできる。 The amount of the thiosulfate solution added is at least 15 times equivalent to the molar amount of heavy metals contained in the soil (eg, sodium thiosulfate: lead = 15: 1), preferably 150 A double equivalent or more is desirable. The thiosulfate solution is preferably sodium thiosulfate. Since unnecessary decomposition products and compounds are not generated, separation control of heavy metals is facilitated, no further treatment occurs, and the cost can be reduced.
分離工程では、浸出工程後の含液土壌をチオ硫酸塩溶液による重金属が溶解された液と、土壌と、をろ過等により固液分離することで土壌から重金属を分離する。このようにして、重金属を含まない清浄土壌が得られる。ろ過は、吸引によるフィルターろ過、加圧フィルターろ過、遠心分離等の方法または装置によって可能である。市販の装置を用いれば十分に固液分離が可能であり、簡便に安価に実施可能である。 In the separation step, the heavy metal is separated from the soil by solid-liquid separation of the liquid-containing soil after the leaching step from the solution in which the heavy metal is dissolved by the thiosulfate solution and the soil. In this way, a clean soil free from heavy metals is obtained. Filtration can be performed by a method or an apparatus such as filter filtration by suction, pressure filter filtration, or centrifugal separation. If a commercially available apparatus is used, sufficient solid-liquid separation is possible, and it can be carried out simply and inexpensively.
分離工程後に得られた清浄土壌は、原位置に覆土する他、清浄土壌としてさらに産業上において有効活用可能である。一方、分離工程により得られた液の液中には、重金属がイオンとして含まれ、重金属の回収が容易な状態となっている。このため非鉄製錬の原料として利用可能である。 The clean soil obtained after the separation step can be effectively used industrially as clean soil in addition to covering in situ. On the other hand, heavy metals are contained as ions in the liquid obtained by the separation step, and it is easy to recover heavy metals. For this reason, it can be used as a raw material for non-ferrous smelting.
上述したように本発明により、重金属汚染土壌から重金属を分離し、清浄土壌を得られる。簡便な方法で浄化可能となるため、さらにはコストも抑制でき安価に達成できる。また、得られた清浄土壌、ならびに分離した重金属もさらに産業上利用となり、極めて環境負荷が少なく、循環型環境社会へ適合している。 As described above, according to the present invention, it is possible to separate heavy metals from heavy metal contaminated soil and obtain clean soil. Since it can be purified by a simple method, the cost can be further reduced and it can be achieved at a low cost. In addition, the obtained clean soil and separated heavy metals are further industrially utilized, and have very little environmental impact and are suitable for a recycling-oriented environmental society.
(実施例1)
重金属汚染土壌として、擬似的に製造した鉛含有量が906mg/Kgの鉛汚染土壌を用意した。表1に未処理土として示す。5Lのガラス製ビーカーに該鉛汚染土壌1kg、およびイオン交換水2Lをいれ、撹拌機で撹拌した。
そこに前処理として、5%塩酸を添加して、pH 2に調整し、1時間撹拌した。
撹拌後、No.5Cのろ紙を使用して、鉛汚染土壌から液分を吸引ろ過した。
ろ過後は、鉛汚染土壌を40℃で乾燥した。1Lのポリエチレン製瓶に乾燥後の鉛汚染土壌を50g、0.5mol/Lに調整したチオ硫酸ナトリウム5水和物溶液を500mL添加し、振とう器で1時間振とうした。これにより鉛を浸出した。振とう後は、先ほどと同様に吸引ろ過し、40℃で乾燥した。これにより、固液分離を実施した。
乾燥後、環境省告示第19号に記載された方法で土壌中の鉛含有量を測定した。鉛の分析は、ICP分析装置を用い分析値を得た。
Example 1
As the heavy metal-contaminated soil, a lead-contaminated soil having a lead content of 906 mg / Kg produced in a pseudo manner was prepared. Table 1 shows the untreated soil. Into a 5 L glass beaker, 1 kg of the lead-contaminated soil and 2 L of ion-exchanged water were added and stirred with a stirrer.
As a pretreatment, 5% hydrochloric acid was added to adjust the pH to 2, followed by stirring for 1 hour.
After stirring, no. Using 5C filter paper, the liquid was suction filtered from the lead-contaminated soil.
After filtration, the lead-contaminated soil was dried at 40 ° C. To a 1 L polyethylene bottle, 50 g of dried lead-contaminated soil and 500 mL of sodium thiosulfate pentahydrate solution adjusted to 0.5 mol / L were added, and shaken for 1 hour with a shaker. This leached lead. After shaking, suction filtration was performed in the same manner as before, and drying was performed at 40 ° C. Thereby, solid-liquid separation was implemented.
After drying, the lead content in the soil was measured by the method described in Ministry of the Environment Notification No. 19. For analysis of lead, an analysis value was obtained using an ICP analyzer.
この結果を表1に示す。結果として、塩酸による前処理によって、鉛含有量は906mg/Kgから690mg/Kgまで低減し、さらにチオ硫酸塩溶液で抽出することにより、最終的に67mg/Kgとなった。これより、本方法によって土壌から鉛を除去、分離できることがわかった。
なお、チオ硫酸ナトリウム溶液で振とうした際、pHは7.1であり、中性で処理できるため、設備への負荷はほとんどなく、安価な設備で可能である。簡便でコストが安価で重金属の分離が可能となった。なお、表1には、実施例1〜10、比較例1〜3を掲載してある。
The results are shown in Table 1. As a result, the lead content was reduced from 906 mg / Kg to 690 mg / Kg by pretreatment with hydrochloric acid, and further extracted with a thiosulfate solution to 67 mg / Kg. From this, it was found that this method can remove and separate lead from soil.
In addition, when shaken with a sodium thiosulfate solution, the pH is 7.1 and the treatment can be carried out in a neutral state, so there is almost no load on the equipment, and an inexpensive equipment is possible. It is simple and inexpensive, and heavy metals can be separated. In Table 1, Examples 1 to 10 and Comparative Examples 1 to 3 are listed.
(実施例2)
実施例1において、5%塩酸の代わりに5%硫酸を使用した以外は同様の処理を行った。
その結果、鉛含有量は906mg/Kgから170mg/Kgに低減した。
(Example 2)
In Example 1, the same treatment was performed except that 5% sulfuric acid was used instead of 5% hydrochloric acid.
As a result, the lead content was reduced from 906 mg / Kg to 170 mg / Kg.
(実施例3〜7)
実施例1において、チオ硫酸ナトリウム溶液の濃度を、0.001(実施例3)、0.005(実施例4)、0.01(実施例5)、0.05(実施例6)、0.1mol/L(実施例7)とした以外は、同様に行った。
その結果、処理後の鉛含有量はそれぞれ、680、630、450、105、69mg/Kgとなった。
これより、チオ硫酸ナトリウム溶液の濃度としては0.05mol/L以上(チオ硫酸ナトリウムと鉛のモル比で150倍当量以上)が望ましいことがわかる。
(Examples 3 to 7)
In Example 1, the concentration of the sodium thiosulfate solution was 0.001 (Example 3), 0.005 (Example 4), 0.01 (Example 5), 0.05 (Example 6), 0 .1 mol / L (Example 7)
As a result, the lead contents after the treatment were 680, 630, 450, 105, and 69 mg / Kg, respectively.
From this, it is understood that the concentration of the sodium thiosulfate solution is preferably 0.05 mol / L or more (150 molar equivalents or more in terms of the molar ratio of sodium thiosulfate to lead).
(実施例8〜10)
実施例1において、前処理のpHを3(実施例8)、4(実施例9)、5(実施例10)にした以外は同様の試験を行った。
その結果、処理後の鉛含有量はそれぞれ、86、410、470mg/Kgとなった。
これより、pHは3以下で顕著に鉛が分離可能であることがわかる。また、pHも3以下と大量の酸を要しないことから簡便で安価に達成可能である。
(Examples 8 to 10)
In Example 1, the same test was performed except that the pH of the pretreatment was 3 (Example 8), 4 (Example 9), and 5 (Example 10).
As a result, the lead content after processing was 86, 410, and 470 mg / Kg, respectively.
This shows that lead can be remarkably separated when the pH is 3 or less. Further, since the pH is 3 or less and does not require a large amount of acid, it can be achieved simply and inexpensively.
(比較例1)
実施例1において、5%塩酸を用いてpH 2に調整し、撹拌処理した土壌に対し、チオ硫酸ナトリウム溶液を加えて振とうする工程を省略した。このとき、鉛含有量は690mg/Kgとなり、鉛の十分な分離はできなかった。
よって、実施例1〜10において、塩酸で処理し、さらにチオ硫酸ナトリウム溶液で振とうすることで汚染土壌中の鉛を大幅に除去できることがわかる。
(Comparative Example 1)
In Example 1, the step of adjusting the pH to 2 with 5% hydrochloric acid and adding the sodium thiosulfate solution to the stirred soil was omitted. At this time, the lead content was 690 mg / Kg, and lead could not be sufficiently separated.
Therefore, in Examples 1-10, it turns out that the lead in contaminated soil can be removed significantly by treating with hydrochloric acid and shaking with a sodium thiosulfate solution.
(比較例2)
実施例2において、比較例1と同様に、チオ硫酸ナトリウム溶液を加えて振とうする工程を省略した。その結果、鉛含有量は890mg/Kgであった。鉛の十分な分離はできなかった。
(Comparative Example 2)
In Example 2, as in Comparative Example 1, the step of adding sodium thiosulfate solution and shaking was omitted. As a result, the lead content was 890 mg / Kg. Sufficient separation of lead was not possible.
(比較例3)
実施例1において、前処理工程を省略し、0.5mol/Lのチオ硫酸ナトリウム溶液で振とうのみを試験した。その結果、鉛含有量は870mg/Kgであった。鉛の十分な分離はできなかった。
(Comparative Example 3)
In Example 1, the pretreatment step was omitted and only shaking with a 0.5 mol / L sodium thiosulfate solution was tested. As a result, the lead content was 870 mg / Kg. Sufficient separation of lead was not possible.
Claims (5)
The method for treating heavy metal-contaminated soil according to claim 1, wherein the thiosulfate solution is a sodium thiosulfate solution, and sodium thiosulfate is added in a molar ratio of 15 times or more with respect to the heavy metal.
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