JP2004122007A - Cleaning method for cadmium-containing soil - Google Patents
Cleaning method for cadmium-containing soil Download PDFInfo
- Publication number
- JP2004122007A JP2004122007A JP2002290721A JP2002290721A JP2004122007A JP 2004122007 A JP2004122007 A JP 2004122007A JP 2002290721 A JP2002290721 A JP 2002290721A JP 2002290721 A JP2002290721 A JP 2002290721A JP 2004122007 A JP2004122007 A JP 2004122007A
- Authority
- JP
- Japan
- Prior art keywords
- soil
- cadmium
- water
- concentration
- containing soil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002689 soil Substances 0.000 title claims abstract description 99
- 229910052793 cadmium Inorganic materials 0.000 title claims abstract description 70
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000004140 cleaning Methods 0.000 title abstract description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000011575 calcium Substances 0.000 claims abstract description 14
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 14
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000000460 chlorine Substances 0.000 claims abstract description 9
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 9
- 238000005406 washing Methods 0.000 claims description 29
- 239000001110 calcium chloride Substances 0.000 claims description 24
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 24
- 239000007864 aqueous solution Substances 0.000 claims description 23
- 230000003247 decreasing effect Effects 0.000 abstract 2
- 239000000523 sample Substances 0.000 description 8
- 239000007788 liquid Substances 0.000 description 7
- 150000001875 compounds Chemical class 0.000 description 4
- 230000035784 germination Effects 0.000 description 4
- 238000002386 leaching Methods 0.000 description 4
- 239000012488 sample solution Substances 0.000 description 4
- 239000012153 distilled water Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000007605 air drying Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 235000013311 vegetables Nutrition 0.000 description 2
- DCCWEYXHEXDZQW-BYPYZUCNSA-N (2s)-2-[bis(carboxymethyl)amino]butanedioic acid Chemical compound OC(=O)C[C@@H](C(O)=O)N(CC(O)=O)CC(O)=O DCCWEYXHEXDZQW-BYPYZUCNSA-N 0.000 description 1
- CIOXZGOUEYHNBF-UHFFFAOYSA-N (carboxymethoxy)succinic acid Chemical compound OC(=O)COC(C(O)=O)CC(O)=O CIOXZGOUEYHNBF-UHFFFAOYSA-N 0.000 description 1
- XYBHHDIIOKAINY-UHFFFAOYSA-N 2-(1,2-dicarboxyethylamino)-3-hydroxybutanedioic acid Chemical compound OC(=O)C(O)C(C(O)=O)NC(C(O)=O)CC(O)=O XYBHHDIIOKAINY-UHFFFAOYSA-N 0.000 description 1
- PUKLDDOGISCFCP-JSQCKWNTSA-N 21-Deoxycortisone Chemical compound C1CC2=CC(=O)CC[C@]2(C)[C@@H]2[C@@H]1[C@@H]1CC[C@@](C(=O)C)(O)[C@@]1(C)CC2=O PUKLDDOGISCFCP-JSQCKWNTSA-N 0.000 description 1
- 244000105624 Arachis hypogaea Species 0.000 description 1
- 240000002791 Brassica napus Species 0.000 description 1
- 235000004977 Brassica sinapistrum Nutrition 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- FCYKAQOGGFGCMD-UHFFFAOYSA-N Fulvic acid Natural products O1C2=CC(O)=C(O)C(C(O)=O)=C2C(=O)C2=C1CC(C)(O)OC2 FCYKAQOGGFGCMD-UHFFFAOYSA-N 0.000 description 1
- WHUUTDBJXJRKMK-UHFFFAOYSA-N Glutamic acid Natural products OC(=O)C(N)CCC(O)=O WHUUTDBJXJRKMK-UHFFFAOYSA-N 0.000 description 1
- 244000068988 Glycine max Species 0.000 description 1
- 235000010469 Glycine max Nutrition 0.000 description 1
- WHUUTDBJXJRKMK-VKHMYHEASA-N L-glutamic acid Chemical compound OC(=O)[C@@H](N)CCC(O)=O WHUUTDBJXJRKMK-VKHMYHEASA-N 0.000 description 1
- JYXGIOKAKDAARW-UHFFFAOYSA-N N-(2-hydroxyethyl)iminodiacetic acid Chemical compound OCCN(CC(O)=O)CC(O)=O JYXGIOKAKDAARW-UHFFFAOYSA-N 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 229920002230 Pectic acid Polymers 0.000 description 1
- 231100000674 Phytotoxicity Toxicity 0.000 description 1
- 229920000805 Polyaspartic acid Polymers 0.000 description 1
- 241000209140 Triticum Species 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- WDJHALXBUFZDSR-UHFFFAOYSA-N acetoacetic acid Chemical compound CC(=O)CC(O)=O WDJHALXBUFZDSR-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000009412 basement excavation Methods 0.000 description 1
- WLZRMCYVCSSEQC-UHFFFAOYSA-N cadmium(2+) Chemical group [Cd+2] WLZRMCYVCSSEQC-UHFFFAOYSA-N 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000012459 cleaning agent Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000002509 fulvic acid Substances 0.000 description 1
- 229940095100 fulvic acid Drugs 0.000 description 1
- 235000013922 glutamic acid Nutrition 0.000 description 1
- 239000004220 glutamic acid Substances 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000020232 peanut Nutrition 0.000 description 1
- LCLHHZYHLXDRQG-ZNKJPWOQSA-N pectic acid Chemical compound O[C@@H]1[C@@H](O)[C@@H](O)O[C@H](C(O)=O)[C@@H]1OC1[C@H](O)[C@@H](O)[C@@H](OC2[C@@H]([C@@H](O)[C@@H](O)[C@H](O2)C(O)=O)O)[C@@H](C(O)=O)O1 LCLHHZYHLXDRQG-ZNKJPWOQSA-N 0.000 description 1
- 108010064470 polyaspartate Proteins 0.000 description 1
- 239000010318 polygalacturonic acid Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- -1 put into a mixer Substances 0.000 description 1
- 239000001397 quillaja saponaria molina bark Substances 0.000 description 1
- 238000005067 remediation Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 229930182490 saponin Natural products 0.000 description 1
- 150000007949 saponins Chemical class 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Landscapes
- Processing Of Solid Wastes (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、カドミウム含有土壌の浄化方法に関する。
【０００２】
【従来の技術】
カドミウム含有土壌の浄化には、覆土法や排土客土法が一般的に用いられている。しかし、覆土法はカドミウム含有土の表土の拡散を防止するだけ、排土客土法は該土壌を移動させるだけの方法であり、根本的な解決策ではなかった。
【０００３】
また、カドミウム含有土壌中のカドミウムを、塩化カルシウム水溶液を用いて不溶化する方法（特許文献１）が提案されている。しかし、カドミウムを単に不溶化しただけでは根本的な浄化とは言い難く、その土壌の２次利用も困難である。
【０００４】
さらに、種々の薬剤を用いて、カドミウム含有土壌からカドミウムを溶出させて除去することにより、汚染土壌を浄化する方法が検討されており、洗浄剤として、サポニン（特許文献２）、ペクチン酸の単量体又はオリゴ体（特許文献３）、ＥＤＴＡ（特許文献４）、Ｌ−アスパラギン酸−Ｎ，Ｎ−二酢酸、グルタミン酸二酢酸、ヒドロキシエチルイミノ二酢酸、カルボキシメチルオキシコハク酸、３−ヒドロキシ−２，２’−イミノジコハク酸、ポリアスパラギン酸（特許文献５）等が用いられている。これらの化合物は、キレート効果によってカドミウムの浸出を促進するものであるが、これらの化合物を用いても、土壌中のカドミウムを効率良く除去することは困難であった。また、これらの化合物は、高価なものであり、実使用に適するものではなかった。
【０００５】
また、土壌中のカドミウムを除去するために、塩化カルシウムを用いるのが有効であることも知られている（非特許文献１）。しかしながら、非特許文献１には、カドミウム含有土壌をカラムに詰め、これに塩化カルシウム水溶液を流し続けたときのカドミウム除去率が記載されているのみであり、実際のカドミウム含有土壌において、どの程度の濃度の塩化カルシウムで、どのように洗浄すれば効率良く、しかもカルシウムの残存濃度を少なく浄化できるかについては、示されていない。
【０００６】
【特許文献１】
特開平６−３９０５５号公報
【特許文献２】
特開平１０−１３０６２３号公報
【特許文献３】
特開２００２−４５８３９号公報
【特許文献４】
特開平４−２６３８７４号公報
【特許文献５】
特開２００２−５２３７５号公報
【非特許文献１】
Ｗａｎｇ Ｗ．， Ａｒｔｉｏｌａ Ｊ．Ｆ．， Ｂｒｕｓｓｅａｕ Ｍ．Ｌ．， Ｍｉｌｌｅｒ Ｒ．Ｍ．，「土壌中のカドミウムの除去を促進するためのカルシウム及びフルボ酸の使用（Ｕｓｅ ｏｆ ｃａｌｃｉｕｍ ａｎｄ ｆｕｌｖｉｃ ａｃｉｄ ｔｏ ｆａｃｉｌｉｔａｔｅ ｔｒａｎｓｐｏｒｔ ｏｆ ｃａｄｍｉｕｍ ｉｎ ｓｏｉｌ）」，Ａｍ．Ｃｈｅｍ．Ｓｏｃ．Ｎａｔｌ．Ｍｅｅｔ．Ｄｉｖ．Ｅｎｖｉｒｏｎ．Ｃｈｅｍ．，１９９４年，第３４巻，第１号，ｐ２０８−２１０
【０００７】
【発明が解決しようとする課題】
従って、本発明の目的は、カドミウム含有土壌を効率良く浄化する方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明者らは、斯かる実情に鑑み、種々検討した結果、カドミウム含有土壌を、特定濃度の塩化カルシウム溶液、次いで水で洗浄すれば、カドミウムを効率よく除去し、しかも残存するカルシウムを少なくして、土壌を浄化できることを見出し、本発明を完成した。
【０００９】
すなわち、本発明は、カドミウム含有土壌を、０．０１〜０．５Ｍの塩化カルシウム水溶液で少なくとも１回洗浄し、可給態カドミウム濃度を０．３ｍｇ／ｋｇ以下とした後、水溶性カルシウム濃度が２ｇ／ｋｇ以下になるまで、水で洗浄することを特徴とするカドミウム含有土壌の浄化方法を提供するものである。
また、本発明は、カドミウム含有土壌を、０．０１〜０．５Ｍの塩化カルシウム水溶液で少なくとも１回洗浄し、可給態カドミウム濃度を０．３ｍｇ／ｋｇ以下とした後、水溶性塩素濃度が３．５ｇ／ｋｇ以下になるまで、水で洗浄することを特徴とするカドミウム含有土壌の浄化方法を提供するものである。
また、本発明は、カドミウム含有土壌を、０．０１〜０．５Ｍの塩化カルシウム水溶液で少なくとも１回洗浄し、可給態カドミウム濃度を０．３ｍｇ／ｋｇ以下とした後、土壌ＥＣ値が２ｍＳ／ｃｍ以下になるまで、水で洗浄することを特徴とするカドミウム含有土壌の浄化方法を提供するものである。
【００１０】
【発明の実施の形態】
本発明の浄化対象となるカドミウム含有土壌としては、市街地、山林、工場跡地、農用地、沼地、更には排土等でカドミウムの元素単位、化合物又はイオンを含有する土壌が挙げられ、例えば平成３年環境庁告示第４６号に定める方法によって測定されるカドミウムの溶出量が土壌環境基準を超える土壌や、土壌１ｋｇ当たりカドミウム重量で２ｍｇ以上のカドミウムを含有する土壌が好適に挙げられる。
【００１１】
また、農用地においては、農林省令第４７号に定める方法或いはこれと同等の測定法によって測定されるカドミウム含有量がコメ、小麦、ダイズ、落花生、葉菜類で１ｋｇ当たり０．２ｍｇ以上、その他の野菜類で０．０５ｍｇ以上となる土壌にも好適に適用することができる。
【００１２】
本発明で用いる水溶液は、塩化カルシウムの濃度が０．０１〜０．５Ｍ、好ましくは０．０４〜０．３Ｍである。０．０１Ｍ未満では、カドミウムの除去効果が小さく、洗浄液量及び洗浄回数が多くなり、効率が悪くなる。また、０．５Ｍを超えると、土壌に残留する塩化カルシウムが多くなり、後に述べる２次洗浄の回数が多くなり、効率が悪くなる。
【００１３】
このような水溶液を用いてカドミウム含有土壌を洗浄する方法としては、特に制限されず、現場にて洗浄する方法、土壌を掘削して洗浄した後、浄化土壌を埋め戻す方法等のいずれでも良い。
より具体的には、一例として以下の方法が挙げられる。
汚染土壌を掘削してミキサーに投入し、塩化カルシウム水溶液を加えて混練した後、フィルタープレスにより土壌と洗浄液とを分離する。続いて、土壌をサイドミキサーに投入し、水による２次洗浄を行い、再びフィルタープレスにより土壌と液体とを分離する。所定回数の２次洗浄が終了後、土壌を現場に埋め戻す。
【００１４】
また、本発明において、塩化カルシウム水溶液で洗浄するとは、土壌と塩化カルシウム水溶液を直接混合する以外に、土壌に塩化カルシウムと水を別々に加えて混合して洗浄する方法、水を含む土壌に塩化カルシウムを混合して洗浄する方法も含まれる。
水を含む土壌を洗浄する方法の一例としては、河川や湖沼の底土を水とともに浚渫し、ミキサーに投入して、塩化カルシウム粉末を所定濃度になるよう添加して混合する方法が挙げられる。
【００１５】
処理する際に用いる水溶液の量は、重量比で、土壌：水溶液＝１：１〜１０、特に１：２〜５であるのが好ましい。
また、このような塩化カルシウムによる洗浄は、少なくとも１回、好ましくは１〜３回行われる。
【００１６】
このように処理することにより、土壌中のカドミウムは水溶液中に溶出する。洗浄後の土壌中の可給態カドミウム濃度が、０．３ｍｇ／ｋｇ以下になるまで、洗浄を繰り返すのが好ましい。なお、可給態カドミウム濃度は、実施例に記載の方法により、測定される。
排出されたカドミウム含有水は、イオン交換、電気分解、不溶化凝集沈殿等により、カドミウムの除去処理を行えば良い。
【００１７】
一方、処理された土壌には、用いた水溶液中のカルシウムや塩素の一部が残存する場合があるため、更に土壌を水で洗浄することにより、カルシウムや塩素を除去する。
水による洗浄は、水溶液による洗浄と同様に行えば良く、土壌中の水溶性カルシウム濃度が２ｇ／ｋｇ以下、若しくは水溶性塩素濃度が３．５ｇ／ｋｇ以下、又は土壌ＥＣ値が２ｍＳ／ｃｍ以下になるまで、少なくとも１回、好ましくは１〜３回、水で洗浄する。
なお、土壌ＥＣ値とは、土壌の電気伝導度であり、風乾した土壌試料に５倍重量の蒸留水を加えて攪拌し、静置した後、電気伝導度計により、液層の電気伝導度を測定することにより、求めることができる。
土壌中の水溶性カルシウム濃度、水溶性塩素濃度、及び土壌ＥＣ値のいずれかがこれら以下になることにより、浄化土壌を、例えば農用地として利用する際に、植物に対する薬害を低減することができる。
【００１８】
【実施例】
次に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらに何ら制限されるものではない。
【００１９】
実施例１
（１）カドミウム溶脱率：
風乾したカドミウム含有土壌１（可給態カドミウム濃度０．５ｍｇ／ｋｇ）を、５００ｍＬの蓋付きビンに５０ｇ計量し、各種濃度の塩化カルシウム水溶液を２５０ｍＬ添加し、軽く攪拌した後、１６時間静置した。
液層をシリンジにて取り出し、０．４５μｍメンブランフィルターにて濾過し、試料溶液とした。
得られた試料溶液は、ＩＣＰによりカドミウム濃度を測定し、次式に従ってカドミウムの溶脱率を算出した。結果を図１に示す。
【００２０】
【数１】
洗浄後の土壌を濾紙により濾過し、風乾した後、可給態カドミウム濃度の測定を行った。結果を図２に示す。
なお、０．０１Ｍの試料を濾過した後、２回目の塩化カルシウム水溶液洗浄（前記と同様に洗浄）に供した。０．０１Ｍ塩化カルシウム水溶液２回洗浄の結果を図１及び図２に併せて示す。
【００２２】
（可給態カドミウム濃度の測定）
風乾した土壌試料４０ｇを５００ｍＬの蓋付きビンに計量し、０．１Ｎ塩酸を２００ｍＬ添加し、３０℃で１時間振盪攪拌した後、静置した。液層をシリンジにて取り出し、０．４５μｍメンブランフィルターにて濾過し、試料溶液とした。
得られた試料溶液は、ＩＣＰによりカドミウム濃度を測定し、測定値を５倍して土壌あたりの可給態カドミウム濃度に換算した。
【００２３】
（２）２次洗浄：
（１）の方法に従い、風乾したカドミウム含有土壌１（可給態カドミウム濃度０．５ｍｇ／ｋｇ）５０ｇを０．５Ｍ又は０．１Ｍの塩化カルシウム水溶液２５０ｍＬで洗浄した後、濾紙で濾過し、濾紙上の土壌試料を１００ｍＬ又は２５０ｍＬの蒸留水にて洗浄した。洗浄方法は、（１）と同様に蓋付きビン内で軽く攪拌した後、１６時間静置し、濾紙で濾過して行った。２次洗浄は１〜３回行い、各試料を風乾後、土壌試料に残留した水溶性カルシウム、水溶性塩素の濃度、及び土壌ＥＣ値を測定した。結果を表１に示す。
【００２４】
（水溶性カルシウム及び水溶性塩素濃度の測定）
環境庁告示第４６号法に準じて、風乾した土壌試料に１０倍重量の蒸留水を加え、６時間振盪した後静置し、液層を０．４５μｍのメンブランフィルターで濾過して検液とした。検液は、ＩＰＣにてカルシウムイオン濃度を、イオンクロマトグラフィーにて塩素イオン濃度を測定した。
【００２５】
また、２次洗浄後の土壌を風乾した土壌試料にアブラナの種子を２０粒播種し、散水して、２５℃暗黒下で１週間養生し、発芽率の測定を行った。発芽率は、播種した種子のうち、双葉が展開したものを発芽とし、園芸土壌で養生したコントロールの発芽率を１００とし、下記式により求めた。結果を表１に併せて示す。
【００２６】
【数２】
なお、比較例として、０．５Ｍ又は０．１Ｍの塩化カルシウム水溶液による洗浄の後、２次洗浄を行うことなく、風乾した土壌試料についても、同様に、残留した水溶性カルシウム、水溶性塩素の濃度、及び土壌ＥＣの測定と、発芽試験を行った。結果を表１に併せて示す。
【００２８】
【表１】
【発明の効果】
本発明によれば、土壌中のカドミウムを効率良く除去し、土壌を浄化することができる。
【図面の簡単な説明】
【図１】カドミウム含有土壌を各種濃度の塩化カルシウム水溶液で洗浄したときのカドミウム溶脱率を示す図である。
【図２】カドミウム含有土壌を各種濃度の塩化カルシウム水溶液で洗浄したときの土壌に残留した可給態カドミウム濃度を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying cadmium-containing soil.
[0002]
[Prior art]
For remediation of cadmium-containing soil, the soil covering method and the soil removal method are generally used. However, the soil covering method only prevents the spread of the top soil of the cadmium-containing soil, and the soil excavation customer soil method only moves the soil, and is not a fundamental solution.
[0003]
Moreover, the method (patent document 1) which insolubilizes cadmium in a cadmium containing soil using calcium chloride aqueous solution is proposed. However, simply insolubilizing cadmium is not a fundamental purification, and secondary use of the soil is also difficult.
[0004]
Furthermore, a method for purifying contaminated soil by eluting and removing cadmium from cadmium-containing soil using various chemicals has been studied. As a cleaning agent, saponin (Patent Document 2), simple substance of pectic acid is studied. Mer or oligo form (Patent Document 3), EDTA (Patent Document 4), L-aspartic acid-N, N-diacetic acid, glutamic acid diacetic acid, hydroxyethyliminodiacetic acid, carboxymethyloxysuccinic acid, 3-hydroxy- 2,2′-iminodisuccinic acid, polyaspartic acid (Patent Document 5) and the like are used. Although these compounds promote leaching of cadmium by a chelating effect, it has been difficult to efficiently remove cadmium in soil even if these compounds are used. In addition, these compounds are expensive and are not suitable for actual use.
[0005]
It is also known that calcium chloride is effective for removing cadmium in the soil (Non-patent Document 1). However, Non-Patent Document 1 only describes the cadmium removal rate when the cadmium-containing soil is packed in a column and the calcium chloride aqueous solution is kept flowing in this column. In actual cadmium-containing soil, There is no indication as to how it can be cleaned with a high concentration of calcium chloride and can be purified with low residual calcium concentration.
[0006]
[Patent Document 1]
JP-A-6-39055 [Patent Document 2]
Japanese Patent Laid-Open No. 10-130623 [Patent Document 3]
JP 2002-45839 A [Patent Document 4]
JP-A-4-263874 [Patent Document 5]
JP 2002-52375 A [Non-Patent Document 1]
Wang W. , Artiola J. et al. F. Brusseau M. L. , Miller R. M.M. , "Use of calcium and fulvic acid to transport of cadmium in soil", Am. Chem. Soc. Natl. Meet. Div. Environ. Chem. 1994, 34, No. 1, p208-210
[0007]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for efficiently purifying cadmium-containing soil.
[0008]
[Means for Solving the Problems]
As a result of various studies in view of such circumstances, the present inventors have efficiently removed cadmium and reduced the residual calcium by washing the cadmium-containing soil with a specific concentration of calcium chloride solution and then with water. Thus, the present inventors have found that the soil can be purified and completed the present invention.
[0009]
That is, in the present invention, after the cadmium-containing soil is washed at least once with a 0.01 to 0.5 M calcium chloride aqueous solution and the available cadmium concentration is 0.3 mg / kg or less, the water-soluble calcium concentration is The present invention provides a method for purifying cadmium-containing soil, wherein the soil is washed with water until it becomes 2 g / kg or less.
In the present invention, the cadmium-containing soil is washed at least once with a 0.01 to 0.5 M calcium chloride aqueous solution, and the available cadmium concentration is 0.3 mg / kg or less. The present invention provides a method for purifying cadmium-containing soil, wherein the soil is washed with water until 3.5 g / kg or less.
Moreover, this invention wash | cleans a cadmium containing soil at least once with 0.01-0.5M calcium chloride aqueous solution, and after making an available cadmium density | concentration 0.3 mg / kg or less, soil EC value is 2 mS. The present invention provides a method for purifying cadmium-containing soil, characterized by washing with water until it becomes less than / cm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the cadmium-containing soil to be purified according to the present invention include urban areas, mountain forests, factory sites, agricultural land, swamps, and soil containing cadmium elemental units, compounds, or ions such as waste soil. Preferable examples include soil in which the cadmium elution amount measured by the method specified in Environment Agency Notification No. 46 exceeds the soil environment standard, and soil containing cadmium in an amount of 2 mg or more per kg of soil.
[0011]
In agricultural land, the cadmium content is 0.2 mg or more per kg for rice, wheat, soybeans, peanuts, leafy vegetables, as measured by the method specified in Ordinance No. 47 of the Ministry of Agriculture and Forestry or equivalent, and other vegetables. Can be suitably applied to soil having a concentration of 0.05 mg or more.
[0012]
The aqueous solution used in the present invention has a calcium chloride concentration of 0.01 to 0.5M, preferably 0.04 to 0.3M. If it is less than 0.01M, the removal effect of cadmium is small, the amount of washing liquid and the number of washings are increased, and the efficiency is lowered. Moreover, when it exceeds 0.5M, the calcium chloride which remains in soil will increase, the frequency | count of the secondary washing described later will increase, and efficiency will worsen.
[0013]
The method for washing the cadmium-containing soil using such an aqueous solution is not particularly limited and may be any method such as a method of washing on site, a method of excavating and washing the soil, and then refilling the purified soil.
More specifically, the following method is mentioned as an example.
The contaminated soil is excavated and put into a mixer, and after adding a calcium chloride aqueous solution and kneading, the soil and the cleaning liquid are separated by a filter press. Subsequently, the soil is put into a side mixer, secondary washing with water is performed, and the soil and liquid are separated again by a filter press. After completion of the predetermined number of secondary washings, the soil is backfilled on the site.
[0014]
In the present invention, washing with an aqueous solution of calcium chloride means not only mixing the soil and the aqueous solution of calcium chloride directly, but also a method of washing the soil by adding calcium chloride and water separately, and washing the soil containing water. A method of mixing and washing calcium is also included.
As an example of a method for washing soil containing water, there is a method in which bottom soil of rivers and lakes is dredged with water, put into a mixer, and calcium chloride powder is added to a predetermined concentration and mixed.
[0015]
The amount of the aqueous solution used in the treatment is, by weight, soil: aqueous solution = 1: 1 to 10, particularly 1: 2 to 5.
Such washing with calcium chloride is performed at least once, preferably 1 to 3 times.
[0016]
By treating in this way, cadmium in the soil is eluted in the aqueous solution. Washing is preferably repeated until the available cadmium concentration in the soil after washing is 0.3 mg / kg or less. The available cadmium concentration is measured by the method described in the examples.
The discharged cadmium-containing water may be subjected to cadmium removal treatment by ion exchange, electrolysis, insolubilized aggregation precipitation, or the like.
[0017]
On the other hand, since some of the calcium and chlorine in the used aqueous solution may remain in the treated soil, the calcium and chlorine are removed by further washing the soil with water.
Washing with water may be performed in the same manner as washing with an aqueous solution. The water-soluble calcium concentration in the soil is 2 g / kg or less, or the water-soluble chlorine concentration is 3.5 g / kg or less, or the soil EC value is 2 mS / cm or less. Until at least once, preferably 1-3 times with water.
The soil EC value is the electrical conductivity of the soil, and after adding 5 times weight of distilled water to an air-dried soil sample, stirring and allowing to stand, the electrical conductivity of the liquid layer was measured by an electrical conductivity meter. Can be determined by measuring.
When any one of the water-soluble calcium concentration, the water-soluble chlorine concentration, and the soil EC value in the soil is lower than these, when using the purified soil as, for example, agricultural land, phytotoxicity to plants can be reduced.
[0018]
【Example】
EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited to these at all.
[0019]
Example 1
(1) Cadmium leaching rate:
50 g of air-dried cadmium-containing soil 1 (available cadmium concentration 0.5 mg / kg) was weighed into a 500 mL lidded bottle, added with 250 mL of various concentrations of calcium chloride aqueous solution, stirred gently, and allowed to stand for 16 hours did.
The liquid layer was taken out with a syringe and filtered through a 0.45 μm membrane filter to obtain a sample solution.
The obtained sample solution was measured for cadmium concentration by ICP, and the leaching rate of cadmium was calculated according to the following formula. The results are shown in FIG.
[0020]
[Expression 1]
The washed soil was filtered with filter paper and air-dried, and then the concentration of available cadmium was measured. The results are shown in FIG.
A 0.01 M sample was filtered and then subjected to a second calcium chloride aqueous solution cleaning (cleaning in the same manner as described above). The results of washing twice with 0.01M calcium chloride aqueous solution are shown in FIGS.
[0022]
(Measurement of available cadmium concentration)
40 g of an air-dried soil sample was weighed into a 500 mL bottle with a lid, 200 mL of 0.1N hydrochloric acid was added, and the mixture was shaken and stirred at 30 ° C. for 1 hour, and allowed to stand. The liquid layer was taken out with a syringe and filtered through a 0.45 μm membrane filter to obtain a sample solution.
The obtained sample solution was measured for cadmium concentration by ICP, and the measured value was multiplied by 5 to convert it into available cadmium concentration per soil.
[0023]
(2) Secondary cleaning:
According to the method of (1), 50 g of air-dried cadmium-containing soil 1 (available cadmium concentration of 0.5 mg / kg) was washed with 250 mL of 0.5 M or 0.1 M calcium chloride aqueous solution, filtered through filter paper, and filter paper The above soil sample was washed with 100 mL or 250 mL of distilled water. The washing method was performed by agitating lightly in a bottle with a lid in the same manner as in (1), then allowing to stand for 16 hours, and filtering with a filter paper. Secondary washing was performed 1 to 3 times, and after air-drying each sample, the concentration of water-soluble calcium and water-soluble chlorine remaining in the soil sample and the soil EC value were measured. The results are shown in Table 1.
[0024]
(Measurement of water-soluble calcium and water-soluble chlorine concentration)
In accordance with the Environmental Agency Notification No. 46, add 10-fold weight of distilled water to an air-dried soil sample, shake for 6 hours, and let stand, and filter the liquid layer with a 0.45 μm membrane filter. did. For the test solution, the calcium ion concentration was measured by IPC, and the chloride ion concentration was measured by ion chromatography.
[0025]
In addition, 20 seeds of rapeseed were sown on a soil sample obtained by air-drying the soil after secondary washing, sprinkled, and cured for one week in the dark at 25 ° C., and the germination rate was measured. The germination rate was determined by the following formula, with the germinated seeds of the sowed seeds being germinated and the germination rate of the control cured in horticultural soil as 100. The results are also shown in Table 1.
[0026]
[Expression 2]
In addition, as a comparative example, the remaining water-soluble calcium and water-soluble chlorine were similarly applied to soil samples that had been air-dried without performing secondary washing after washing with 0.5 M or 0.1 M calcium chloride aqueous solution. Concentration and soil EC measurements and germination tests were performed. The results are also shown in Table 1.
[0028]
[Table 1]
【The invention's effect】
According to the present invention, cadmium in soil can be efficiently removed and the soil can be purified.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing cadmium leaching rates when cadmium-containing soil is washed with aqueous calcium chloride solutions having various concentrations.
FIG. 2 is a diagram showing the concentration of available cadmium remaining in soil when cadmium-containing soil is washed with various concentrations of aqueous calcium chloride solution.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002290721A JP3884690B2 (en) | 2002-10-03 | 2002-10-03 | Purification method of soil containing cadmium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002290721A JP3884690B2 (en) | 2002-10-03 | 2002-10-03 | Purification method of soil containing cadmium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2004122007A true JP2004122007A (en) | 2004-04-22 |
| JP3884690B2 JP3884690B2 (en) | 2007-02-21 |
Family
ID=32282504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2002290721A Expired - Fee Related JP3884690B2 (en) | 2002-10-03 | 2002-10-03 | Purification method of soil containing cadmium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3884690B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006075721A (en) * | 2004-09-09 | 2006-03-23 | National Institute For Agro-Environmental Science | Purification method of heavy metal contaminated soil |
| JP2007160272A (en) * | 2005-12-16 | 2007-06-28 | Kowa Co | Cleaning method of cadmium-contaminated soil |
| JP2008264626A (en) * | 2007-04-17 | 2008-11-06 | Taiheiyo Cement Corp | Method for treating soil-washed waste water |
| US8017303B2 (en) * | 2009-02-23 | 2011-09-13 | International Business Machines Corporation | Ultra low post exposure bake photoresist materials |
| JP2013167567A (en) * | 2012-02-16 | 2013-08-29 | Taiheiyo Material Kk | Method for measuring soil salinity concentration |
-
2002
- 2002-10-03 JP JP2002290721A patent/JP3884690B2/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006075721A (en) * | 2004-09-09 | 2006-03-23 | National Institute For Agro-Environmental Science | Purification method of heavy metal contaminated soil |
| JP4509708B2 (en) * | 2004-09-09 | 2010-07-21 | 独立行政法人農業環境技術研究所 | Purification method for heavy metal contaminated soil |
| JP2007160272A (en) * | 2005-12-16 | 2007-06-28 | Kowa Co | Cleaning method of cadmium-contaminated soil |
| JP4550731B2 (en) * | 2005-12-16 | 2010-09-22 | 興和株式会社 | Purification method of cadmium contaminated soil |
| JP2008264626A (en) * | 2007-04-17 | 2008-11-06 | Taiheiyo Cement Corp | Method for treating soil-washed waste water |
| US8017303B2 (en) * | 2009-02-23 | 2011-09-13 | International Business Machines Corporation | Ultra low post exposure bake photoresist materials |
| JP2013167567A (en) * | 2012-02-16 | 2013-08-29 | Taiheiyo Material Kk | Method for measuring soil salinity concentration |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3884690B2 (en) | 2007-02-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Paz et al. | Fate of carbamazepine, its metabolites, and lamotrigine in soils irrigated with reclaimed wastewater: Sorption, leaching and plant uptake | |
| Makino et al. | Restoration of cadmium-contaminated paddy soils by washing with ferric chloride: Cd extraction mechanism and bench-scale verification | |
| Jez et al. | EDTA retention and emissions from remediated soil | |
| Kos et al. | Induced phytoextraction/soil washing of lead using biodegradable chelate and permeable barriers | |
| Luo et al. | DGT methodology is more sensitive than conventional extraction strategies in assessing amendment-induced soil cadmium availability to rice | |
| Andreu et al. | Evolution of heavy metals in marsh areas under rice farming | |
| Gluhar et al. | Demonstrational gardens with EDTA-washed soil. Part I: Remediation efficiency, effect on soil properties and toxicity hazards | |
| Chen et al. | Cadmium phytoavailability evaluation in rice-soil system using a field capacity-derived soil solution extraction: an entire growth period study in subtropical China | |
| JP3884690B2 (en) | Purification method of soil containing cadmium | |
| JP2005169381A (en) | Method for cleaning heavy metal-contaminated soil | |
| JP4550731B2 (en) | Purification method of cadmium contaminated soil | |
| JP2004136205A (en) | Method of purifying cadmium-containing soil | |
| JP4116975B2 (en) | Purification method for contaminated soil | |
| Zhang et al. | Extraction methods optimization of available heavy metals and the health risk assessment of the suburb soil in China | |
| JP2004148279A (en) | Purifying method of cadmium-containing soil | |
| Li et al. | New insights into sulfur input induced methylmercury production and accumulation in paddy soil and rice | |
| JP4509708B2 (en) | Purification method for heavy metal contaminated soil | |
| Krützmann et al. | Evaluation of the effects of fluoride and associated with lead in animal model and physical-chemical analysis of public supply water and of the Sinos river in the south of Brazil | |
| FOTO et al. | Assessment of Water Contamination by Metallic Trace Elements at Mining Sites: The Case of the Ouham River in the Central African Republic | |
| Dokuchayeva | The effects of long-term aging on the distribution and behavior of heavy metals in the soil: Solubility, mobility, bioavailability, and toxicity | |
| Spires et al. | Contribution of phosphorus from agricultural land to streams by surface runoff | |
| Bashir et al. | Heavy metals uptake by vegetables growing in sewage irrigated soil: relationship with heavy metal fractionation in soil | |
| Ahmed | Estimate of cd, pb and physico-chemical properties in soils of Kani-qrzhala Dumpsite in Erbil, Kurdistan Region of Iraq | |
| JP2010207675A (en) | Method of cleaning heavy metal-contaminated soil | |
| Mehrab et al. | Effectiveness of nitrilotriacetic acid (NTA) on cadmium removal in calcareous soil and acidic soil |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20050317 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20061108 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20061114 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20061117 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 Ref document number: 3884690 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091124 Year of fee payment: 3 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091124 Year of fee payment: 3 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20091124 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20101124 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111124 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121124 Year of fee payment: 6 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121124 Year of fee payment: 6 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131124 Year of fee payment: 7 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |