JP3407039B2 - Arsenic-contaminated soil cleaner, arsenic-contaminated soil stabilizer, and method for remediating arsenic-contaminated soil using the same - Google Patents
Arsenic-contaminated soil cleaner, arsenic-contaminated soil stabilizer, and method for remediating arsenic-contaminated soil using the sameInfo
- Publication number
- JP3407039B2 JP3407039B2 JP2000208465A JP2000208465A JP3407039B2 JP 3407039 B2 JP3407039 B2 JP 3407039B2 JP 2000208465 A JP2000208465 A JP 2000208465A JP 2000208465 A JP2000208465 A JP 2000208465A JP 3407039 B2 JP3407039 B2 JP 3407039B2
- Authority
- JP
- Japan
- Prior art keywords
- arsenic
- soil
- contaminated soil
- acid
- aqueous solution
- 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.)
- Expired - Lifetime
Links
- 239000002689 soil Substances 0.000 title claims description 161
- 238000000034 method Methods 0.000 title claims description 27
- 239000003583 soil stabilizing agent Substances 0.000 title claims description 8
- 229910052785 arsenic Inorganic materials 0.000 claims description 95
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims description 95
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 58
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 52
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 48
- 239000007864 aqueous solution Substances 0.000 claims description 34
- 238000004140 cleaning Methods 0.000 claims description 29
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 26
- 238000005406 washing Methods 0.000 claims description 25
- 239000012459 cleaning agent Substances 0.000 claims description 19
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 18
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 18
- 239000003381 stabilizer Substances 0.000 claims description 17
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical class [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 claims description 9
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 9
- 150000002603 lanthanum Chemical class 0.000 claims description 8
- 239000012266 salt solution Substances 0.000 claims description 7
- XQTIWNLDFPPCIU-UHFFFAOYSA-N cerium(3+) Chemical class [Ce+3] XQTIWNLDFPPCIU-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- YXEUGTSPQFTXTR-UHFFFAOYSA-K lanthanum(3+);trihydroxide Chemical compound [OH-].[OH-].[OH-].[La+3] YXEUGTSPQFTXTR-UHFFFAOYSA-K 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 4
- CQGVSILDZJUINE-UHFFFAOYSA-N cerium;hydrate Chemical compound O.[Ce] CQGVSILDZJUINE-UHFFFAOYSA-N 0.000 claims description 4
- 238000011109 contamination Methods 0.000 claims description 3
- 238000005067 remediation Methods 0.000 claims 1
- 239000002253 acid Substances 0.000 description 32
- 238000011282 treatment Methods 0.000 description 32
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 26
- 230000007613 environmental effect Effects 0.000 description 23
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 20
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 18
- 238000010828 elution Methods 0.000 description 18
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 15
- 229910017604 nitric acid Inorganic materials 0.000 description 15
- 230000000694 effects Effects 0.000 description 14
- 150000007513 acids Chemical class 0.000 description 13
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 12
- 238000000605 extraction Methods 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- BMYNFMYTOJXKLE-UHFFFAOYSA-N 3-azaniumyl-2-hydroxypropanoate Chemical compound NCC(O)C(O)=O BMYNFMYTOJXKLE-UHFFFAOYSA-N 0.000 description 5
- 238000007922 dissolution test Methods 0.000 description 5
- 239000003673 groundwater Substances 0.000 description 5
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 description 4
- 239000000284 extract Substances 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 4
- 239000011777 magnesium Substances 0.000 description 4
- 229910052749 magnesium Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910004664 Cerium(III) chloride Inorganic materials 0.000 description 2
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000008346 aqueous phase Substances 0.000 description 2
- 238000009412 basement excavation Methods 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 238000004993 emission spectroscopy Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 150000004678 hydrides Chemical class 0.000 description 2
- -1 inorganic acid salts Chemical class 0.000 description 2
- ICAKDTKJOYSXGC-UHFFFAOYSA-K lanthanum(iii) chloride Chemical compound Cl[La](Cl)Cl ICAKDTKJOYSXGC-UHFFFAOYSA-K 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000003900 soil pollution Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- MHUWZNTUIIFHAS-XPWSMXQVSA-N 9-octadecenoic acid 1-[(phosphonoxy)methyl]-1,2-ethanediyl ester Chemical compound CCCCCCCC\C=C\CCCCCCCC(=O)OCC(COP(O)(O)=O)OC(=O)CCCCCCC\C=C\CCCCCCCC MHUWZNTUIIFHAS-XPWSMXQVSA-N 0.000 description 1
- 101100452374 Mus musculus Ikbke gene Proteins 0.000 description 1
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000003905 agrochemical Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 150000001785 cerium compounds Chemical class 0.000 description 1
- UNJPQTDTZAKTFK-UHFFFAOYSA-K cerium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Ce+3] UNJPQTDTZAKTFK-UHFFFAOYSA-K 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 239000000701 coagulant Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- MSNWSDPPULHLDL-UHFFFAOYSA-K ferric hydroxide Chemical compound [OH-].[OH-].[OH-].[Fe+3] MSNWSDPPULHLDL-UHFFFAOYSA-K 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 150000002506 iron compounds Chemical class 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 150000002604 lanthanum compounds Chemical class 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 229940047047 sodium arsenate Drugs 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Landscapes
- Fire-Extinguishing Compositions (AREA)
- Processing Of Solid Wastes (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、有害化学物質の不
適切な取扱い、不法投棄、鉱物資源の開発利用などの行
為の結果として発生しうるヒ素で汚染された土壌の修復
に関するものであり、更に詳しくは、ヒ素で汚染された
土壌からヒ素を高効率で除去することにより、ヒ素によ
る環境負荷を大幅に減らしてリスクを軽減すると共に、
微量に残留するヒ素を安定化してその溶出を抑制して土
壌環境基準を満足し、土壌の再利用を可能にするヒ素汚
染土壌洗浄剤、安定化剤及びこれらを用いたヒ素汚染土
壌の修復方法に関する。TECHNICAL FIELD The present invention relates to restoration of arsenic-contaminated soil which may be generated as a result of actions such as improper handling of hazardous chemical substances, illegal dumping, development and utilization of mineral resources, More specifically, by removing arsenic from soil contaminated with arsenic with high efficiency, the environmental load of arsenic can be significantly reduced and risk can be reduced.
Arsenic-contaminated soil cleaning agent, stabilizer that stabilizes trace amount of arsenic and suppresses its elution to satisfy soil environmental standards and enables reuse of soil, and method for repairing arsenic-contaminated soil using these Regarding
【０００２】[0002]
【従来の技術】ヒ素及びその化合物は生体に対する有害
性が顕著であるため、土壌環境基準の対象物質に指定さ
れている。環境庁の報告資料「平成１０年度土壌汚染事
例及び対応状況に関する調査結果の概要」（環境庁水質
保全局土壌農薬課 平成１２年３月２２日）によると昭
和５０年度〜平成１０年度に報告された土壌汚染事例の
総数は累積で２９２件であり、その数は工場跡地などで
年々増加している。土壌汚染の原因物質のうち、ヒ素
は、鉛、トリクロロエチレンに次いで多い。こうした汚
染土壌については、これまでは掘削除去、封じ込め、飛
散防止、セメントによる固形化・不溶化、最終処分場へ
の埋立処分といった対策がとられてきた。2. Description of the Related Art Arsenic and its compounds are markedly harmful to living organisms and are therefore designated as substances subject to soil environmental standards. According to the report material “Summary of Survey Results on Soil Contamination Cases and Countermeasures for the Fiscal Year 1998” (Environmental Agency Water Quality Conservation Bureau, Soil Agricultural Chemicals Division, March 22, 2000), it was reported from 1975 to 1998. The total number of soil pollution cases is 292, and the number is increasing year by year on the site of a factory. Of the causative substances of soil pollution, arsenic is the second most abundant substance after lead and trichlorethylene. For such contaminated soil, measures such as excavation removal, containment, scattering prevention, solidification / insolubilization with cement, and landfill disposal at the final disposal site have been taken so far.
【０００３】しかしこれらの方法では、ヒ素は土壌中に
残留したままであるため、長期間その対策効果が持続す
るものではない。風雨や地下水の浸透などによってヒ素
が溶出して、二次的環境汚染を引き起こすことが心配さ
れる。特に、地中のヒ素は溶出しやすく、環境庁の報告
資料「平成１０年度地下水質測定結果について」（環境
庁水質保全局企画課地下水・地盤環境室 平成１１年１
２月７日）によると、調査の対象となった 3,424 本の
井戸のうち 1.3 % の井戸でヒ素濃度が地下水質基準
（0.01 mg/L）を超過しており、その超過率は他の汚染
物質よりも飛び抜けて高い。However, in these methods, since arsenic remains in the soil, its countermeasure effect does not last for a long time. It is feared that arsenic will elute due to wind and rain or infiltration of groundwater, causing secondary environmental pollution. In particular, arsenic in the ground is liable to elute, and the “Annual report on the results of groundwater quality measurement in 1998” by the Environment Agency (Environmental Agency Water Quality Conservation Bureau Planning Division Groundwater and Ground Environment Office, 1999 1
According to (February 7), 1.3% of the 3,424 wells surveyed had an arsenic concentration exceeding the groundwater quality standard (0.01 mg / L), and the excess rate was other pollutants. By far higher than the substance.
【０００４】[0004]
【発明が解決しようとする課題】本発明は、上記このよ
うな技術的背景の下でなされたものであって、第一の目
的は、ヒ素汚染土壌からヒ素を効率的に洗浄できるヒ素
汚染土壌洗浄剤を提供することにあり、第二の目的は、
ヒ素汚染土壌からヒ素を効率的に安定・不溶化し得るヒ
素汚染土壌安定化剤を提供することにあり、第三の目的
は、洗浄処理によってヒ素を汚染土壌から効率よく抽出
除去することにより、ヒ素による環境負荷を大幅に減ら
してそのリスクを軽減し得るヒ素汚染土壌の洗浄方法を
提供することにあり、第四の目的は、該洗浄処理後にお
いても残留する微量ヒ素を不溶化しその溶出を最低限に
抑制して土壌の再利用を可能ならしめるヒ素汚染土壌の
修復方法を提供することにある。The present invention has been made under the above-mentioned technical background, and the first object is to provide an arsenic-contaminated soil capable of efficiently cleaning arsenic from arsenic-contaminated soil. The second purpose is to provide a cleaning agent.
The third objective is to provide an arsenic-contaminated soil stabilizer capable of efficiently stabilizing and insolubilizing arsenic from arsenic-contaminated soil. A third object is to efficiently extract and remove arsenic from contaminated soil by a washing treatment. The purpose of the present invention is to provide a method for cleaning arsenic-contaminated soil, which can significantly reduce the environmental load caused by arsenic, and a fourth object is to insolubilize the trace amount of arsenic remaining even after the cleaning treatment and minimize its elution. An object of the present invention is to provide a method for repairing arsenic-contaminated soil, which suppresses the soil as much as possible and enables reuse of the soil.
【０００５】[0005]
【課題を解決するための手段】本発明者は、上記課題を
達成するために、数多くの酸によるヒ素汚染土壌の洗浄
処理の有効性について、試行錯誤により鋭意検討した結
果、意外にもリン酸、硫酸、塩酸のみが特異的な作用・
効果を発現すること、及びランタン化合物、セリウム化
合物、及び鉄化合物が土壌中のヒ素の安定化（不溶化）
効果に極めて有効であることを見出し、本発明を完成す
るに至った。すなわち、本発明によれば、第一に、リン
酸水溶液、硫酸水溶液、及び塩酸水溶液から選ばれる少
なくとも一種の水溶液からなるヒ素汚染土壌洗浄剤が提
供される。第二に、ランタン塩水溶液、セリウム（II
I）塩水溶液、及び鉄（III）塩水溶液から選ばれる少な
くとも一種の水溶液からなるヒ素汚染土壌安定化剤が提
供される。第三に、酸化ランタン、水酸化ランタン、酸
化セリウム（IV）、及び水酸化セリウム（IV）から選ば
れる少なくとも一種の酸化物からなるヒ素汚染土壌安定
化剤が提供される。第四に、ヒ素汚染土壌を第一発明の
ヒ素汚染土壌洗浄剤で処理して、ヒ素を抽出除去するこ
とを特徴とするヒ素汚染土壌洗浄方法が提供される。第
五に、第四発明のヒ素汚染土壌洗浄方法で処理された土
壌に第二発明の安定化剤を添加混合し、更にアルカリで
中和処理して土壌中のヒ素を不溶化することを特徴とす
るヒ素汚染土壌修復方法が提供される。第六に、第四発
明のヒ素汚染土壌洗浄方法で処理された土壌に第三発明
の安定化剤を添加混合し、土壌中のヒ素を不溶化するこ
とを特徴とするヒ素汚染土壌修復方法が提供される。Means for Solving the Problems In order to achieve the above-mentioned object, the present inventor has surprisingly studied through trial and error the effectiveness of washing treatment of arsenic-contaminated soil with many acids, and as a result, surprisingly, phosphoric acid , Sulfuric acid, hydrochloric acid only
The effect is exhibited, and lanthanum compounds, cerium compounds, and iron compounds stabilize (insolubilize) arsenic in soil.
It was found that the effect was extremely effective, and the present invention was completed. That is, according to the present invention, firstly, there is provided an arsenic-contaminated soil cleaning agent comprising at least one aqueous solution selected from an aqueous phosphoric acid solution, an aqueous sulfuric acid solution, and an aqueous hydrochloric acid solution. Second, lanthanum salt solution, cerium (II
There is provided an arsenic-contaminated soil stabilizer comprising at least one kind of aqueous solution selected from I) salt aqueous solution and iron (III) salt aqueous solution. Thirdly, there is provided an arsenic-contaminated soil stabilizer comprising at least one oxide selected from lanthanum oxide, lanthanum hydroxide, cerium (IV) oxide, and cerium (IV) hydroxide. Fourthly, there is provided an arsenic-contaminated soil cleaning method, which comprises treating arsenic-contaminated soil with the arsenic-contaminated soil cleaning agent of the first invention to extract and remove arsenic. Fifth, by adding and mixing the stabilizer of the second invention to the soil treated by the arsenic-contaminated soil cleaning method of the fourth invention, further neutralizing with an alkali to insolubilize the arsenic in the soil, An arsenic-contaminated soil restoration method is provided. Sixth, there is provided a method for repairing arsenic-contaminated soil, which comprises adding and mixing the stabilizer of the third invention to soil treated by the method for cleaning arsenic-contaminated soil according to the fourth invention to insolubilize arsenic in the soil. To be done.
【０００６】[0006]
【発明の実施の形態】本発明者は、上記課題を達成する
ために、フッ化水素酸、リン酸、硫酸、塩酸、硝酸、過
塩素酸、臭化水素酸、酢酸、過酸化水素などの数多くの
広く工業的に使用されている酸のヒ素汚染土壌の洗浄処
理の有効性を、高いヒ素抽出除去効果、洗浄処理後
の土壌自体の損傷の有無、耐久性、後処理の容易
さ、処理剤コストの節減、などを指標にして、鋭意研
究を重ねた結果、これらの中でもリン酸、硫酸、塩酸の
みが他の酸と大きく異なり、汚染土壌中のヒ素の洗浄剤
として極めて有効であることを知見した。DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to achieve the above-mentioned object, the present inventor has selected hydrofluoric acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobromic acid, acetic acid, hydrogen peroxide and the like. The effectiveness of cleaning treatment of arsenic-contaminated soil with many widely used acids, high arsenic extraction and removal effect, presence or absence of damage of soil itself after cleaning treatment, durability, ease of post-treatment, treatment As a result of earnest researches using the reduction of agent cost as an index, among them, only phosphoric acid, sulfuric acid and hydrochloric acid are significantly different from other acids, and it is extremely effective as a cleaning agent for arsenic in contaminated soil. I found out.
【０００７】すなわち、本発明者は、フッ化水素酸、リ
ン酸、硫酸、塩酸、硝酸、過塩素酸、臭化水素酸、酢
酸、過酸化水素、混酸（塩酸＋硝酸）、混酸（硝酸＋過
塩素酸）の濃度を段階的に調節した水溶液に、ヒ素汚染
土壌を加え、その土壌洗浄効果についての考察実験を行
った（実施例１；図１）。That is, the present inventor has found that hydrofluoric acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobromic acid, acetic acid, hydrogen peroxide, mixed acid (hydrochloric acid + nitric acid), mixed acid (nitric acid + nitric acid + Arsenic-contaminated soil was added to an aqueous solution in which the concentration of perchloric acid) was adjusted stepwise, and a consideration experiment was conducted on the soil cleaning effect (Example 1; FIG. 1).
【０００８】その結果、酸濃度約１０(w/v)%における各
種の酸によるヒ素の抽出除去効果は、リン酸、硫酸、塩
酸は７０％以上の高いヒ素除去率を示し、他の酸化性の
硝酸、過塩素酸、過酸化水素及び有機酸である酢酸のヒ
素除去効果は低いことが判明した。なお、フッ化水素酸
はリン酸と並んで最も高いヒ素抽出除去効果を有するも
のであるが、フッ化水素酸の成分であるフッ素は土壌環
境基準の対象とされている有害元素のひとつであり、ま
た、フッ化水素酸による洗浄処理に伴って、シリカ及び
アルミナなどの土壌成分の大部分が溶出し、土壌を著し
く損傷するため、フッ化水素酸は汚染土壌の洗浄剤とし
ては好ましくないものである。こうした観点から、本発
明者は、ヒ素汚染土壌洗浄剤としては、リン酸、硫酸、
及び塩酸が最も適しているものと判断した。従って、こ
れらの酸でヒ素汚染土壌を洗浄すると、土壌に損傷を与
えることなく、低廉な価格で、大部分のヒ素を高い抽出
効率で除去することができ、ヒ素による環境負荷を大幅
に減らしてリスクを軽減することができる。As a result, as for the arsenic extraction and removal effect by various acids at an acid concentration of about 10 (w / v)%, phosphoric acid, sulfuric acid and hydrochloric acid show a high arsenic removal rate of 70% or more, and other oxidizing agents. It was found that nitric acid, perchloric acid, hydrogen peroxide and acetic acid, which is an organic acid, had a low arsenic removal effect. Although hydrofluoric acid has the highest arsenic extraction and removal effect along with phosphoric acid, fluorine, which is a component of hydrofluoric acid, is one of the harmful elements that are subject to the soil environmental standards. In addition, hydrofluoric acid is not preferable as a cleaning agent for contaminated soil because most of soil components such as silica and alumina are eluted with the cleaning treatment with hydrofluoric acid and the soil is significantly damaged. Is. From this point of view, the present inventor, as the arsenic-contaminated soil cleaning agent, phosphoric acid, sulfuric acid,
And hydrochloric acid was judged to be the most suitable. Therefore, washing arsenic-contaminated soil with these acids can remove most of the arsenic with high extraction efficiency at a low price without damaging the soil, greatly reducing the environmental burden of arsenic. The risk can be reduced.
【０００９】本発明の土壌洗浄剤は通常水溶液の形態で
使用される。水溶液中のリン酸、硫酸、又は塩酸の濃度
は処理対象土壌のヒ素汚染濃度にもよるが、通常１０(w
/v)%濃度としておけば充分である。The soil cleaning agent of the present invention is usually used in the form of an aqueous solution. The concentration of phosphoric acid, sulfuric acid, or hydrochloric acid in the aqueous solution is usually 10 (w
/ v)% concentration is sufficient.
【００１０】また、本発明の土壌洗浄剤の使用量は、土
壌中のヒ素濃度と用いる洗浄剤の水溶液濃度とを適宜勘
案して決めればよいが、通常汚染土壌１ｋｇ当たり１０
Ｌとしておけば充分である。The amount of the soil cleaning agent of the present invention to be used may be determined by appropriately considering the concentration of arsenic in the soil and the concentration of the cleaning agent used in the aqueous solution.
It is sufficient to set it as L.
【００１１】また、本発明に係るリン酸、硫酸、又は塩
酸水溶液による汚染土壌からのヒ素の除去速度は反応初
期において非常に大きく、その後比較的緩やかな上昇を
描くので、洗浄処理時間は短時間で充分である。Further, the removal rate of arsenic from contaminated soil with the phosphoric acid, sulfuric acid or hydrochloric acid aqueous solution according to the present invention is very large in the initial stage of the reaction, and thereafter, it gradually rises relatively, so that the cleaning treatment time is short. Is enough.
【００１２】また、本発明に係る洗浄剤処理による土壌
成分のうちのシリカ及びカルシウムの溶出量は数％以下
であり、洗浄処理後の土壌は比較的安定である。なお、
アルミニウム、鉄、マグネシウムの溶出はかかる酸洗浄
処理により溶出するが、、これらの成分の溶出は、ヒ素
の除去速度と比較して緩慢であるため、酸による洗浄を
短時間で終了することにより土壌成分の溶出を低く抑え
ることが可能である。これらのことから、本発明による
汚染土壌の酸による洗浄処理は約１〜２時間にすること
が望ましい。Further, the amount of silica and calcium eluted from the soil components by the detergent treatment according to the present invention is several% or less, and the soil after the washing treatment is relatively stable. In addition,
Elution of aluminum, iron, and magnesium is eluted by such an acid cleaning treatment, but since the elution of these components is slow compared to the removal rate of arsenic, it is necessary to finish the acid cleaning in a short time. It is possible to keep the elution of components low. For these reasons, it is desirable that the acid cleaning of the contaminated soil according to the present invention is performed for about 1 to 2 hours.
【００１３】本発明に係るリン酸、硫酸、又は塩酸から
なる洗浄剤が、このように優れたヒ素抽出除去機能を有
する理由は現時点では定かではないが、これらの酸が土
壌中のヒ素吸着能を有する遊離酸化アルミニウム或いは
遊離酸化鉄に作用してそれらを溶解させることにより、
吸着されていたヒ素も溶出することによるものと推定さ
れる。The reason why the cleaning agent comprising phosphoric acid, sulfuric acid or hydrochloric acid according to the present invention has such an excellent arsenic extraction / removal function is not clear at present, but these acids are capable of adsorbing arsenic in soil. By acting on free aluminum oxide or free iron oxide having
It is presumed that the adsorbed arsenic is also eluted.
【００１４】本発明に係る土壌洗浄剤を用いて、ヒ素汚
染土壌を処理するには、該ヒ素汚染土壌を掘削などの手
段で地中から取り出し、所定の洗浄装置に搬入した後、
洗浄剤であるリン酸、硫酸、又は塩酸水溶液を適量添加
し、混合攪拌し、ヒ素を抽出し、ついで抽出されたヒ素
を含む洗浄液を回収する方法をとればよい。回収した洗
浄剤は、ヒ素濃度及び溶解成分濃度が所定値に達するま
で循環使用できる。In order to treat arsenic-contaminated soil with the soil cleaning agent of the present invention, the arsenic-contaminated soil is taken out from the ground by means such as excavation and carried into a predetermined cleaning device.
A suitable method is to add an appropriate amount of a cleaning solution of phosphoric acid, sulfuric acid, or hydrochloric acid, mix and stir, extract arsenic, and then collect the extracted cleaning solution containing arsenic. The collected cleaning agent can be circulated and used until the arsenic concentration and the dissolved component concentration reach predetermined values.
【００１５】本発明においては、前記した土壌洗浄剤を
用いることにより、ヒ素汚染土壌に損傷を与えることな
く、低廉な価格で、大部分のヒ素を高い抽出効率で除去
することができるが、更に、洗浄後の土壌に、ランタン
塩水溶液、セリウム（III）塩水溶液及び鉄（III）塩水
溶液から選ばれる少なくとも一種の水溶液、あるいは酸
化ランタン、水酸化ランタン、酸化セリウム（IV）及び
水酸化セリウム（IV）から選ばれる少なくとも一種の酸
化物からなるヒ素汚染土壌安定化剤を混合することによ
り、ヒ素による環境負荷を更に大幅に低減することでき
る。In the present invention, by using the above-mentioned soil cleaning agent, most arsenic can be removed with high extraction efficiency at a low price without damaging arsenic-contaminated soil. , At least one aqueous solution selected from a lanthanum salt aqueous solution, a cerium (III) salt aqueous solution and an iron (III) salt aqueous solution, or lanthanum oxide, lanthanum hydroxide, cerium (IV) oxide and cerium hydroxide ( By mixing an arsenic-contaminated soil stabilizer consisting of at least one oxide selected from IV), the environmental load due to arsenic can be further reduced significantly.
【００１６】すなわち、かかる安定化剤を利用すること
により、ヒ素汚染土壌を修復しその土地、土壌の再利用
を可能にするために環境庁が定めた、「溶出ヒ素濃度が
土壌環境基準（０．０１ｍｇ／Ｌ）以下にならなければ
ならない」とする土壌環境基準（環境庁水質保全局編
「土壌・地下水汚染に係る調査・対策指針運用基準」、
１３３頁、平成１１年３月８日大蔵省印刷局発行）を満
たすことが可能となる。例えば、後記実施例３の結果の
表３に示すように、リン酸、硫酸、又は塩酸で参考例１
の汚染土壌を後記参考例２に従って２時間洗浄処理した
ときのヒ素除去率は、それぞれ９７．９％、８７．７
％、８２．３％であり、洗浄処理後もある程度のヒ素が
土壌中に残留している。そして、これらの酸で洗浄処理
した後の土壌について溶出試験を行うと、それぞれ０．
１７７、０．３７５、０．２３２ｍｇ／Ｌのヒ素が溶出
する。しかし、該酸洗浄処理後の土壌を、ランタン塩水
溶液、セリウム（III）塩水溶液、鉄（III）塩水溶液で
処理しついでアルカリで中和し、土壌中のヒ素を不溶化
させた土壌、あるいは該酸洗浄処理後の土壌を酸化ラン
タン、水酸化ランタン、酸化セリウム（IV）又は水酸化
セリウム（IV）で処理し土壌中のヒ素を不溶化させた土
壌は、その後の溶出試験を行っても、ヒ素の溶出量は後
記実施例３にみられるように、極めて少なくなり前記土
壌環境基準を満足したものとなる。That is, by using such a stabilizer, the "Environmental concentration of dissolved arsenic is a soil environmental standard (0 Soil environmental standards (“Environmental Agency Water Quality Conservation Bureau,“ Soil / Groundwater Contamination Survey / Countermeasure Guideline Operation Standards ”,
Page 133, published by the Ministry of Finance, Printing Bureau on March 8, 1999). For example, as shown in Table 3 of the results of Example 3 below, phosphoric acid, sulfuric acid, or hydrochloric acid was used for Reference Example 1.
The arsenic removal rates when the contaminated soil of No. 2 was washed for 2 hours according to Reference Example 2 described later were 97.9% and 87.7, respectively.
%, 82.3%, and some arsenic remains in the soil even after the washing treatment. Then, when a dissolution test was performed on the soil after the washing treatment with these acids, the results were 0.
177, 0.375 and 0.232 mg / L of arsenic elute. However, the soil after the acid washing treatment is treated with an aqueous lanthanum salt solution, an aqueous cerium (III) salt solution, an aqueous iron (III) salt solution and then neutralized with an alkali to insolubilize arsenic in the soil, or Soil after acid washing is treated with lanthanum oxide, lanthanum hydroxide, cerium (IV) oxide or cerium (IV) hydroxide to insolubilize the arsenic in the soil, but the soil will be arsenic As will be seen in Example 3 below, the amount of elution was extremely small and the soil environmental standard was satisfied.
【００１７】本発明に係る安定化剤のうち、ランタン
塩、セリウム（III）塩、又は鉄（III）塩を用いて、土
壌中のヒ素を安定化（不溶化）するには、汚染土壌を上
記の洗浄処理を行った後、該安定化剤水溶液を適量添加
し、混合攪拌し、アルカリで中和し、しばらく放置した
後、余分の水を脱水する方法をとればよい。To stabilize (insolubilize) arsenic in the soil by using lanthanum salt, cerium (III) salt or iron (III) salt among the stabilizers according to the present invention, the contaminated soil is treated as described above. After the washing treatment described in (1), an appropriate amount of the stabilizer aqueous solution is added, mixed and stirred, neutralized with an alkali, left for a while, and then excess water is dehydrated.
【００１８】ランタン塩、セリウム（III）塩、及び鉄
（III）塩としては、それら無機酸塩、有機酸塩が挙げ
られ、具体的には塩化物、硝酸塩、硫酸塩などを例示す
ることができる。これらの安定化剤は通常水溶液の形態
で使用される。水溶液中のランタン塩、セリウム（II
I）塩、又は鉄（III）塩の濃度は処理対象土壌中の残留
ヒ素濃度にもよるが、通常１当量濃度としておけば充分
である。また、これらの安定化剤の使用量は、土壌中の
残留ヒ素濃度を適宜勘案して決めればよいが、通常土壌
１ｋｇ当たり１Ｌとしておけば充分である。Examples of the lanthanum salt, cerium (III) salt, and iron (III) salt include inorganic acid salts and organic acid salts thereof, and specific examples thereof include chlorides, nitrates, and sulfates. it can. These stabilizers are usually used in the form of an aqueous solution. Lanthanum salt, cerium (II
The concentration of I) salt or iron (III) salt depends on the concentration of residual arsenic in the soil to be treated, but it is usually sufficient to set the concentration to 1 equivalent. The amount of these stabilizers to be used may be determined in consideration of the residual arsenic concentration in the soil, but usually 1 L per 1 kg of soil is sufficient.
【００１９】また、本発明に係る安定化剤のうち、酸化
ランタン又は酸化セリウム（IV）を用いて、土壌中のヒ
素を安定化するには、汚染土壌を上記の洗浄処理を行っ
た後、安定化剤の適量を粉体のままもしくは少量の水に
懸濁させて添加し、混合攪拌し、しばらく放置した後、
余分の水を脱水する方法をとればよい。また、酸化ラン
タン又は酸化セリウム（IV）の代わりに、水酸化ランタ
ン又は水酸化セリウム（IV）を用いてもよい。In order to stabilize arsenic in the soil by using lanthanum oxide or cerium (IV) oxide among the stabilizers according to the present invention, after contaminated soil is subjected to the above-mentioned washing treatment, Add an appropriate amount of stabilizer as a powder or suspend it in a small amount of water, mix and stir, and leave it for a while,
The method of dehydrating excess water may be used. Further, lanthanum hydroxide or cerium (IV) hydroxide may be used instead of lanthanum oxide or cerium (IV) oxide.
【００２０】これらの安定化剤の使用量は、土壌中の残
留ヒ素濃度と用いる安定化剤の水溶液濃度とを適宜勘案
して決めればよいが、通常土壌１ｋｇ当たり１０〜２０
ｇとしておけば充分である。The amount of these stabilizers used may be determined in consideration of the concentration of residual arsenic in the soil and the concentration of the aqueous solution of the stabilizer to be used, but usually 10 to 20 per 1 kg of soil.
It is sufficient to use g.
【００２１】本発明に係るヒ素汚染土壌修復方法は要約
すれば、図５に示す通りである。即ち、ヒ素で汚染され
た土壌を掘削して、所定の洗浄装置に搬入する。リン
酸、硫酸、又は塩酸水溶液の適量を加え、例えば１〜２
時間混合かくはんする。次に、重力沈降法、遠心分離な
どにより固液分離し、洗浄液は回収して循環使用する。
但し、洗浄液中のヒ素或いは溶解成分の濃度が所定値以
上になれば、次の工程からの廃液と合わせる。洗浄処理
した土壌は、残留する酸を除去するために、適宜水洗す
る。洗液及び前記の使用ずみ洗浄液は既存の水処理法に
より処理する。こうした酸洗浄により、汚染土壌中の大
部分のヒ素を抽出除去して、リスクを軽減する。洗浄処
理した土壌は、微量のヒ素を含有しているため、次のい
ずれかの安定化法でヒ素を不溶化する。ひとつは、洗浄
処理した土壌にランタン塩、セリウム（III）塩、又は
鉄（III）塩水溶液を加えた後、中和する方法である。
もうひとつは、酸化ランタン又は酸化セリウム（IV）の
粉末もしくは懸濁液を添加混合する方法である。こうし
て安定化処理を施した土壌は、環境庁が定める土壌環境
基準を満足し、該土壌の再利用が可能となる。The arsenic-contaminated soil restoration method according to the present invention is summarized as shown in FIG. That is, the soil contaminated with arsenic is excavated and carried into a predetermined cleaning device. Add an appropriate amount of phosphoric acid, sulfuric acid, or hydrochloric acid aqueous solution, for example, 1-2
Stir for hours. Next, solid-liquid separation is performed by a gravity sedimentation method, centrifugal separation, etc., and the washing liquid is recovered and reused.
However, if the concentration of arsenic or dissolved components in the cleaning liquid exceeds a predetermined value, it is combined with the waste liquid from the next step. The washed soil is appropriately washed with water to remove residual acid. The washing liquid and the used washing liquid are treated by the existing water treatment method. Such acid washing extracts and removes most of the arsenic in the contaminated soil, reducing risk. Since the washed soil contains a small amount of arsenic, arsenic is insolubilized by one of the following stabilization methods. One is a method of neutralizing after adding lanthanum salt, cerium (III) salt or iron (III) salt aqueous solution to the washed soil.
The other is a method of adding and mixing a powder or suspension of lanthanum oxide or cerium (IV) oxide. The thus stabilized soil satisfies the soil environmental standards set by the Environmental Agency and can be reused.
【００２２】[0022]
【実施例】以下、本発明を実施例によりさらに詳細に説
明する。なお、モデルヒ素汚染土壌の調製は参考例１に
より、また土壌洗浄実験は参考例２によった。EXAMPLES The present invention will now be described in more detail with reference to examples. The model arsenic-contaminated soil was prepared according to Reference Example 1, and the soil washing experiment was performed according to Reference Example 2.
【００２３】参考例１（モデルヒ素汚染土壌の調製）
茨城県つくば市において採集した黒ボク土を１週間風乾
したのち、標準ふるいで粒径２ｍｍ以下の土壌をふるい
分けた。その１．５ｋｇを５Ｌ容塩化ビニル製容器にと
り、２５ｍＭのヒ酸ナトリウム水溶液４．０Ｌを加え、
ｐＨを約４に調節し、ときどきしんとうしながら３カ月
間処理して汚染させた。水相をろ別し、得られたろ過残
渣を数回水洗した後風乾して、モデルヒ素汚染土壌を調
製した。汚染土壌の特性及び化学組成はそれぞれ表１及
び表２に示すとおりである。該汚染土壌のヒ素含有量は
３７．８ｍｍｏｌ／ｋｇ ＝ ２，８３０ｍｇ／ｋｇ
（Ａｓとして）であった。該土壌は日本の代表的な土壌
のひとつであり、有機質に富み弱酸性を示す。また、遊
離酸化アルミニウム及び遊離酸化鉄に富んでいるため、
比較的高いヒ素吸着容量を有するものである。Reference Example 1 (Preparation of model arsenic-contaminated soil) After the black soil Ikki collected in Tsukuba City, Ibaraki Prefecture was air-dried for 1 week, the soil having a particle size of 2 mm or less was sieved with a standard sieve. 1.5 kg of the solution was placed in a 5 L vinyl chloride container, and 4.0 L of a 25 mM sodium arsenate aqueous solution was added.
The pH was adjusted to about 4 and treated for 3 months with occasional agitation to contaminate. The aqueous phase was filtered off, the obtained filtration residue was washed with water several times and then air-dried to prepare a model arsenic-contaminated soil. The characteristics and chemical composition of the contaminated soil are shown in Table 1 and Table 2, respectively. The arsenic content of the contaminated soil is 37.8 mmol / kg = 2,830 mg / kg
(As As). This soil is one of the representative soils in Japan and is rich in organic matter and shows weak acidity. Also, since it is rich in free aluminum oxide and free iron oxide,
It has a relatively high arsenic adsorption capacity.
【００２４】参考例２（土壌洗浄実験）
３５ｍＬ容ポリカーボネート製遠心沈殿管に参考例１で
調製したヒ素汚染土壌１ｇと洗浄剤水溶液２５ｍＬを入
れ、２０℃に保持した恒温槽中でしんとう器にて横方向
（振幅１０ｃｍ）に所定時間しんとうした。ついで、冷
凍機付き高速遠心機を用いて９，０００ｒｐｍで２０分
間遠心分離し、分離した上澄液を孔径０．４５μｍのメ
ンブレンフィルタでろ過した。得られたろ液について、
ヒ素濃度を水素化物発生原子吸光法により、またアルミ
ニウム、鉄、マグネシウム、カルシウム、シリカ濃度を
ＩＣＰ発光分析法により測定した。Reference Example 2 (Soil Washing Experiment) 1 g of the arsenic-contaminated soil prepared in Reference Example 1 and 25 mL of an aqueous detergent solution were placed in a 35-mL polycarbonate centrifuge settling tube and placed in a thermostat at 20 ° C. in a thermostat. Strained in the lateral direction (amplitude 10 cm) for a predetermined time. Then, it was centrifuged at 9,000 rpm for 20 minutes using a high-speed centrifuge with a refrigerator, and the separated supernatant was filtered with a membrane filter having a pore size of 0.45 μm. About the obtained filtrate,
The arsenic concentration was measured by a hydride generation atomic absorption method, and the concentrations of aluminum, iron, magnesium, calcium and silica were measured by an ICP emission spectrometry.
【００２５】[0025]
【表１】 [Table 1]
【００２６】[0026]
【表２】 [Table 2]
【００２７】実施例１
ヒ素汚染土壌の洗浄処理の目的は、土壌中からヒ素をで
きるだけ除去して、ヒ素によるリスクを軽減することで
ある。この実施例では、広く工業的に使用されている数
多くの酸について、ヒ素汚染土壌に対する洗浄効果を比
較検討した。初濃度を段階的に変化させたフッ化水素
酸、リン酸、硫酸、塩酸、硝酸、過塩素酸、臭化水素
酸、酢酸、過酸化水素、混酸（３：１塩酸＋硝酸）、混
酸（２：１硝酸＋過塩素酸）水溶液に参考例１のヒ素汚
染土壌１ｇを加え、参考例２に従って６時間洗浄処理を
行った。その結果を図１に示す。なお、グラフの縦軸の
ヒ素除去率は、水相のヒ素溶出量の未処理土壌中のヒ素
含有量に対する割合で示したものである。図１において
酸濃度約１０(w/v)%における各種の酸によるヒ素の抽出
除去効果を見てみると、フッ化水素酸＝リン酸＞硫酸＞
塩酸＞混酸（塩酸＋硝酸）＞臭化水素酸＝硝酸＝混酸
（硝酸＋過塩素酸）＞過塩素酸＞酢酸＞過酸化水素 の
順であった。即ち、リン酸、硫酸、塩酸は７０％以上の
高いヒ素除去率を示している。なお、フッ化水素酸はリ
ン酸と並んで最も高いヒ素抽出除去効果を示したが、フ
ッ化水素酸の成分であるフッ素は土壌環境基準の対象と
されている有害元素のひとつであること、及びフッ化水
素酸による洗浄処理に伴って、シリカ及びアルミナなど
の土壌成分の大部分が溶出し、土壌を著しく損傷するこ
とから、フッ化水素酸はヒ素汚染土壌の洗浄剤としては
好ましくないものである。従って、これらの酸のうち、
高いヒ素抽出除去効果、低い有害性及び価格の点から、
リン酸、硫酸、塩酸がヒ素汚染土壌の洗浄剤として最も
適したものであり、これらの酸でヒ素汚染土壌を洗浄し
て、ヒ素の大部分を抽出除去することにより、ヒ素によ
る環境負荷を大幅に減らしてリスクを軽減することがで
きる。Example 1 The purpose of cleaning treatment of arsenic-contaminated soil is to remove arsenic from the soil as much as possible to reduce the risk of arsenic. In this example, cleaning effects on arsenic-contaminated soil were comparatively examined with respect to a number of widely-used industrial acids. Hydrofluoric acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobromic acid, acetic acid, hydrogen peroxide, mixed acid (3: 1 hydrochloric acid + nitric acid), mixed acid ( 1 g of the arsenic-contaminated soil of Reference Example 1 was added to a 2: 1 nitric acid + perchloric acid) aqueous solution, and a washing treatment was performed for 6 hours according to Reference Example 2. The result is shown in FIG. The arsenic removal rate on the vertical axis of the graph is the ratio of the arsenic elution amount in the aqueous phase to the arsenic content in the untreated soil. Looking at the extraction and removal effect of arsenic by various acids at an acid concentration of about 10 (w / v)% in Fig. 1, hydrofluoric acid = phosphoric acid> sulfuric acid>
The order was hydrochloric acid> mixed acid (hydrochloric acid + nitric acid)> hydrobromic acid = nitric acid = mixed acid (nitric acid + perchloric acid)> perchloric acid> acetic acid> hydrogen peroxide. That is, phosphoric acid, sulfuric acid and hydrochloric acid show a high arsenic removal rate of 70% or more. In addition, hydrofluoric acid showed the highest arsenic extraction removal effect along with phosphoric acid, but fluorine, which is a component of hydrofluoric acid, is one of the harmful elements that are the targets of soil environmental standards, Also, with the cleaning treatment with hydrofluoric acid, most of the soil components such as silica and alumina are eluted, and the soil is significantly damaged. Therefore, hydrofluoric acid is not preferable as a cleaning agent for arsenic-contaminated soil. Is. Therefore, of these acids,
In terms of high arsenic extraction and removal effect, low toxicity and price,
Phosphoric acid, sulfuric acid, and hydrochloric acid are the most suitable cleaners for arsenic-contaminated soil, and by cleaning arsenic-contaminated soil with these acids and extracting and removing most of arsenic, the environmental load caused by arsenic can be significantly reduced. To reduce the risk.
【００２８】実施例２
９．４(w/v)%リン酸、１０．３(w/v)%硫酸、又は１２．
０(w/v)%塩酸水溶液５００ｍＬに参考例１のヒ素汚染土
壌２０ｇを加え、マグネチックスターラを用いて連続的
にかくはんした。所定時間ごとに該懸濁試料の約１０ｍ
Ｌをプラスチック製注射筒を用いてとり、ただちに孔径
０．４５μｍのメンブレンフィルタでろ過した。得られ
たろ液について、ヒ素濃度を水素化物発生原子吸光法に
より、またアルミニウム、鉄、マグネシウム、カルシウ
ム、シリカ濃度をＩＣＰ発光分析法により測定した。得
られた結果を図２、３、及び４に示す。この結果から、
いずれの酸による洗浄処理においても、ヒ素の抽出除去
は処理開始６０分後にはほぼ平衡に到達しており、汚染
土壌の洗浄処理に要する時間は短時間でよいことが分か
る。また、土壌成分のうちシリカ及びカルシウムの溶出
量は数％以下であり、本発明による洗浄処理においては
比較的安定であることが分かる。一方、アルミニウム、
鉄、マグネシウムの溶出は、処理開始６時間後にはそれ
らの溶出率はそれぞれ、３５〜４０％、３５〜４０％、
２５〜４０％に達している。しかし、これらの成分の溶
出は、ヒ素の除去速度と比較して緩慢であるため、酸に
よる洗浄処理を短時間で終了することにより土壌成分の
溶出を低く抑えることが可能である。Example 2 9.4 (w / v)% phosphoric acid, 10.3 (w / v)% sulfuric acid, or 12.
20 g of the arsenic-contaminated soil of Reference Example 1 was added to 500 mL of 0 (w / v)% hydrochloric acid aqueous solution, and continuously stirred using a magnetic stirrer. Approximately 10 m of the suspension sample every predetermined time
L was taken using a plastic injection cylinder and immediately filtered with a membrane filter having a pore size of 0.45 μm. With respect to the obtained filtrate, the arsenic concentration was measured by a hydride generation atomic absorption method, and the concentrations of aluminum, iron, magnesium, calcium and silica were measured by an ICP emission spectrometry. The obtained results are shown in FIGS. from this result,
In any of the acid washing treatments, the extraction and removal of arsenic reached almost equilibrium 60 minutes after the treatment was started, and it can be seen that the time required for the washing treatment of the contaminated soil is short. Further, the elution amount of silica and calcium among the soil components is several% or less, which shows that the washing treatment according to the present invention is relatively stable. On the other hand, aluminum,
The elution rate of iron and magnesium was 35-40%, 35-40%, respectively, 6 hours after the start of treatment.
It has reached 25-40%. However, since the elution of these components is slower than the arsenic removal rate, it is possible to suppress the elution of soil components to a low level by finishing the acid cleaning treatment in a short time.
【００２９】実施例３
９．４(w/v)%リン酸、１０．３(w/v)%硫酸、又は１２．
０(w/v)%塩酸水溶液２５ｍＬに参考例１に示すヒ素汚染
土壌１ｇを加え、実施例１に従って２時間洗浄処理し
た。処理後の土壌に少量の水を加え水洗した。得られた
洗浄土壌に１当量濃度の塩化ランタン、塩化セリウム
（III）、塩化鉄（III）、又は塩化カルシウム水溶液１
ｍＬ及び水２０ｍＬを加え、十分にかき混ぜた。１規定
水酸化ナトリウム水溶液を用いて、ｐＨ値が約７になる
ように中和した。一夜放置したのち遠心分離し、得られ
た残渣について溶出試験を行った。一方、上記の安定化
剤水溶液の代わりに、洗浄処理を行った土壌に酸化ラン
タン、酸化セリウム（IV）、水酸化鉄、水酸化カルシウ
ム懸濁液を加え十分にかき混ぜた。一夜放置したのち遠
心分離し、得られた残渣について溶出試験を行った。そ
の結果を表３に示す。リン酸、硫酸、又は塩酸によるヒ
素除去率は、それぞれ９７．９％、８７．７％、８２．
３％であり、洗浄処理後もある程度のヒ素が土壌中に残
留している。これらの酸で洗浄処理した後の土壌につい
て溶出試験を行うと、それぞれ０．１７７、０．３７
５、０．２３２ ｍｇ／Ｌのヒ素が溶出している。しか
し、酸洗浄処理後の土壌に塩化ランタン、塩化セリウム
（III）、又は塩化鉄（III）水溶液を添加混合し、更に
前記の金属塩を加水分解するために、水酸化ナトリウム
水溶液を用いてｐＨ値が約７になるように中和し、一夜
放置した土壌について、その溶出試験を行った結果、ヒ
素の溶出量は、塩酸洗浄処理後の鉄（III）塩添加の場
合を除いて、それぞれ、１．５ｐｐｂ以下、８．６ｐｐ
ｂ以下、６．８ｐｐｂ以下となり、該安定化処理した土
壌は前記土壌環境基準を満たすことが判った。一方、凝
集沈殿剤などとして広く使用されている塩化カルシウム
で処理したものは、いずれの場合も土壌環境基準を満足
せず、安定化効果は認められなかった。また、表３か
ら、リン酸、硫酸、塩酸で洗浄処理を行った土壌に適量
の酸化ランタン又は酸化セリウム（IV）を添加混合する
ことにより、ヒ素の溶出量はそれぞれ０．７ｐｐｂ以
下、３０３ｐｐｂ以下であり、ヒ素の溶出を大幅に抑制
できることが認められた。しかし、水酸化鉄（III）及
び水酸化カルシウムの添加は効果的ではなかった。Example 3 9.4 (w / v)% phosphoric acid, 10.3 (w / v)% sulfuric acid, or 12.
1 g of the arsenic-contaminated soil shown in Reference Example 1 was added to 25 mL of a 0 (w / v)% hydrochloric acid aqueous solution, and washed according to Example 1 for 2 hours. A small amount of water was added to the treated soil and washed. 1 equivalent concentration of lanthanum chloride, cerium (III) chloride, iron (III) chloride, or calcium chloride aqueous solution 1 in the obtained washed soil
mL and 20 mL of water were added and mixed well. The mixture was neutralized with a 1N aqueous sodium hydroxide solution so that the pH value was about 7. After leaving it overnight, it was centrifuged, and the obtained residue was subjected to a dissolution test. On the other hand, instead of the above stabilizer aqueous solution, lanthanum oxide, cerium (IV) oxide, iron hydroxide, and calcium hydroxide suspensions were added to the washed soil and stirred thoroughly. After leaving it overnight, it was centrifuged, and the obtained residue was subjected to a dissolution test. The results are shown in Table 3. The removal rates of arsenic with phosphoric acid, sulfuric acid, or hydrochloric acid were 97.9%, 87.7%, and 82.
3%, and some arsenic remains in the soil even after the washing treatment. Dissolution tests on the soil after washing with these acids gave 0.177 and 0.37, respectively.
5, 0.232 mg / L of arsenic is eluted. However, lanthanum chloride, cerium (III) chloride, or iron (III) chloride aqueous solution is added to and mixed with the acid-washed soil, and the pH is adjusted with sodium hydroxide aqueous solution to further hydrolyze the metal salts. The soil was neutralized to a value of about 7, and the soil was left overnight. As a result of the dissolution test, the amount of arsenic released was measured except for the case of adding iron (III) salt after hydrochloric acid washing treatment. , 1.5 ppb or less, 8.6 pp
b or less and 6.8 ppb or less, and it was found that the stabilized soil satisfies the soil environmental standards. On the other hand, those treated with calcium chloride, which is widely used as a coagulant / precipitant, did not satisfy the soil environmental standard in any case, and the stabilizing effect was not recognized. Further, from Table 3, by adding and mixing an appropriate amount of lanthanum oxide or cerium (IV) oxide to the soil washed with phosphoric acid, sulfuric acid, hydrochloric acid, the elution amount of arsenic is 0.7 ppb or less and 303 ppb or less, respectively. It was confirmed that the elution of arsenic can be suppressed significantly. However, the addition of iron (III) hydroxide and calcium hydroxide was not effective.
【００３０】[0030]
【表３】 [Table 3]
【００３１】[0031]
【発明の効果】本発明のヒ素汚染土壌洗浄剤は、ヒ素
抽出除去効果が高い、洗浄処理しても土壌自体を損傷
させない、耐久性に優れる、後処理が容易である、
コストが低廉である、などの多くの利点を有するもの
である。従って、これらの酸でヒ素汚染土壌を洗浄する
と、土壌に損傷を与えることなく、低廉な価格で、大部
分のヒ素を高い抽出効率で除去することができ、ヒ素に
よる環境負荷を大幅に減らしてリスクを軽減することが
できる。また、本発明のヒ素汚染土壌安定化剤は、土壌
中の微量のヒ素を強く不溶化して、溶出試験において土
壌環境基準を満足する程度までヒ素の溶出を低く抑える
機能をもつものであり、しかも安価なものである。従っ
て、本発明の土壌洗浄剤及び安定化剤を用いた汚染土壌
修復方法は、ヒ素汚染土壌からヒ素を簡単に抽出除去す
ることができ、ヒ素による環境負荷を大幅に軽減すると
ともに、土壌中に残留する微量のヒ素を安定化させて汚
染土壌を確実に修復して該土壌の再利用を可能ならしめ
るものである。The arsenic-contaminated soil cleaning agent of the present invention has a high arsenic extraction / removal effect, does not damage the soil itself even if washed, has excellent durability, and is easy to post-treat.
It has many advantages such as low cost. Therefore, washing arsenic-contaminated soil with these acids can remove most of the arsenic with high extraction efficiency at a low price without damaging the soil, greatly reducing the environmental burden of arsenic. The risk can be reduced. Further, the arsenic-contaminated soil stabilizer of the present invention strongly insolubilizes a trace amount of arsenic in the soil, and has a function of suppressing the elution of arsenic to the extent that the soil environmental standard is satisfied in the elution test, and It is cheap. Therefore, the contaminated soil restoration method using the soil cleaning agent and the stabilizer of the present invention can easily extract and remove arsenic from arsenic-contaminated soil, and significantly reduce the environmental load caused by arsenic, and It stabilizes a trace amount of arsenic that remains and reliably repairs contaminated soil so that the soil can be reused.
【図１】フッ化水素酸、リン酸、硫酸、塩酸、硝酸、過
塩素酸、臭化水素酸、酢酸、過酸化水素、混酸（塩酸＋
硝酸）、混酸（硝酸＋過塩素酸）によるヒ素汚染土壌か
らのヒ素除去効果の説明図。FIG. 1 Hydrofluoric acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobromic acid, acetic acid, hydrogen peroxide, mixed acid (hydrochloric acid +
Explanatory drawing of the arsenic removal effect from arsenic contaminated soil by nitric acid) and mixed acid (nitric acid + perchloric acid).
【図２】リン酸水溶液によるヒ素汚染土壌の洗浄処理に
おけるヒ素除去率及び土壌成分溶出率の時間変化を表す
図。FIG. 2 is a diagram showing a time change of an arsenic removal rate and a soil component elution rate in a cleaning treatment of an arsenic-contaminated soil with a phosphoric acid aqueous solution.
【図３】硫酸水溶液によるヒ素汚染土壌の洗浄処理にお
けるヒ素除去率及び土壌成分溶出率の時間変化を表す
図。FIG. 3 is a diagram showing a time change of an arsenic removal rate and a soil component elution rate in a cleaning treatment of an arsenic-contaminated soil with a sulfuric acid aqueous solution.
【図４】塩酸水溶液によるヒ素汚染土壌の洗浄処理にお
けるヒ素除去率及び土壌成分溶出率の時間変化を表す
図。FIG. 4 is a view showing a time change of an arsenic removal rate and a soil component elution rate in a cleaning treatment of an arsenic-contaminated soil with a hydrochloric acid aqueous solution.
【図５】本発明に係る土壌洗浄剤及び安定化剤を用いた
ヒ素汚染土壌修復方法の概要説明図。FIG. 5 is a schematic explanatory diagram of an arsenic-contaminated soil restoration method using a soil cleaning agent and a stabilizer according to the present invention.
Claims (6)
液から選ばれる少なくとも一種の水溶液からなるヒ素汚
染土壌洗浄剤。1. An arsenic-contaminated soil cleaner comprising at least one aqueous solution selected from a phosphoric acid aqueous solution, a sulfuric acid aqueous solution, and a hydrochloric acid aqueous solution.
溶液、及び鉄（III）塩水溶液から選ばれる少なくとも
一種の水溶液からなるヒ素汚染土壌安定化剤。2. An arsenic-contaminated soil stabilizer comprising at least one aqueous solution selected from an aqueous lanthanum salt solution, an aqueous cerium (III) salt solution, and an aqueous iron (III) salt solution.
ウム（IV）、及び水酸化セリウム（IV）から選ばれる少
なくとも一種の酸化物からなるヒ素汚染土壌安定化剤。3. An arsenic-contaminated soil stabilizer comprising at least one oxide selected from lanthanum oxide, lanthanum hydroxide, cerium (IV) oxide and cerium (IV) hydroxide.
土壌洗浄剤で処理して、ヒ素を抽出除去することを特徴
とするヒ素汚染土壌洗浄方法。4. A method for cleaning arsenic-contaminated soil, which comprises treating arsenic-contaminated soil with the cleaning agent for arsenic-contaminated soil according to claim 1 to extract and remove arsenic.
処理された土壌に請求項２に記載の安定化剤を添加混合
し、更にアルカリで中和処理して土壌中のヒ素を不溶化
することを特徴とするヒ素汚染土壌修復方法。5. The soil treated by the arsenic-contaminated soil washing method according to claim 4 is admixed with the stabilizer according to claim 2 and neutralized with an alkali to insolubilize arsenic in the soil. A method for repairing arsenic-contaminated soil, which comprises:
処理された土壌に請求項３に記載の安定化剤を添加混合
し、土壌中のヒ素を不溶化することを特徴とするヒ素汚
染土壌修復方法。6. Arsenic contamination characterized by insolubilizing arsenic in soil by adding and mixing the stabilizer according to claim 3 to the soil treated by the arsenic-contaminated soil cleaning method according to claim 4. Soil remediation method.
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