JP3932434B2 - Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method - Google Patents
Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method Download PDFInfo
- Publication number
- JP3932434B2 JP3932434B2 JP17792797A JP17792797A JP3932434B2 JP 3932434 B2 JP3932434 B2 JP 3932434B2 JP 17792797 A JP17792797 A JP 17792797A JP 17792797 A JP17792797 A JP 17792797A JP 3932434 B2 JP3932434 B2 JP 3932434B2
- Authority
- JP
- Japan
- Prior art keywords
- iron
- heavy metal
- salt solution
- weight
- ferrous
- 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 - Fee Related
Links
Landscapes
- Fire-Extinguishing Compositions (AREA)
- Processing Of Solid Wastes (AREA)
- Compounds Of Iron (AREA)
Description
【０００１】
【発明の属する技術分野】
この発明は、都市ゴミや各種廃棄物を焼却する焼却炉から排出される重金属を含有した焼却飛灰や、工場跡地のように重金属で汚染された土壌等の固形物を無害化処理する方法に関し、さらにその方法に使用する特殊な鉄塩溶液の製造方法に関する。
【０００２】
【従来の技術】
重金属の無害化処理方法として、重金属をフェライト化してその中に閉じ込め安定化させる方法が知られている。たとえば特開平６−２３８２５９号公報には、粉末飛灰等の重金属含有固形物に、水、第一鉄塩およびアルカリ成分を添加混練してｐＨを７〜１１．５に調整した後、空気を吹込みながら混合物を攪拌状態で加熱することにより固形物中の重金属を固定する方法が記載されている。
【０００３】
また、廃棄物中の重金属を吸着してその流出を防ぐ方法も知られている。たとえば、特開昭５２−８６９７４号公報には、水酸化第一鉄塩に亜硝酸塩などの酸化剤を添加するか、または、第一鉄塩と第二鉄塩の混合液をアルカリで処理することによって得られる活性フェライトを、重金属を含む廃棄物に予め混合しておき、重金属の流出を防ぐ、重金属含有廃棄物の処理方法が記載されている。
【０００４】
【発明が解決しようとする課題】
上述した重金属フェライト化を利用した従来技術は、重金属の将来的な溶出の可能性は少ないが、それぞれつぎのような問題を有する。
【０００５】
特開平６−２３８２５９号公報の方法では、固形物中に含まれる水銀化合物が第一鉄塩による還元条件により金属水銀となり、導入される空気によりこれが排ガス中に飛散するので、排ガス処理設備が必要である上に、長時間にわたり加熱するための設備とコストが必要である。
【０００６】
また、特開昭５２−８６９７４号公報の方法は、得られた活性フェライトを、濾過、乾燥を経て粉末化するという面倒な操作を必要とし、しかも処理物の形態は液状であって埋立てには適さない。
【０００７】
【課題を解決するための手段】
上記課題を解決するために、本発明では、特殊な鉄塩溶液を製造し、その溶液により廃棄物中あるいは汚染土壌中の重金属を簡単にフェライト化し、不溶化するという手段をとる。
【０００８】
すなわち、請求項１記載の発明は重金属をフェライト化させるのに用いられる鉄塩溶液の製造方法であって、第一鉄塩溶液に酸化剤を、溶液中に含まれる鉄総量の２０〜８０重量％の鉄が第一鉄から第二鉄へ変化するのに必要な量添加することを特徴とする方法である。
【０００９】
上記鉄塩溶液の製造方法において、第一鉄塩溶液としてはどの第一鉄塩でも使用可能であり、製鉄時の副産物である硫酸第一鉄や塩化第一鉄等が経済的であり好ましい。
【００１０】
酸化剤としては塩素酸ナトリウム、次亜塩素酸ナトリウム、過塩素酸ナトリウム、さらし粉などのハロゲン系酸化剤のどの酸化剤でも使用可能であり、第一鉄塩溶液中に含まれる鉄総量の２０〜８０重量％の鉄が第一鉄から第二鉄に酸化される量だけ酸化剤を添加すればよい。塩素酸ナトリウムの場合、これを鉄総量の好ましくは５〜２５重量％用いる。
【００１１】
上記鉄塩溶液を用いて重金属を簡単にフェライト化する方法を以下に詳しく説明する。
【００１２】
請求項３記載の発明は重金属含有固形物の処理方法であって、重金属を含有する固形物に、請求項１または２記載の方法で得られた鉄塩溶液を鉄として少なくとも１重量％、通常は１〜２０重量％、好ましくは１．５〜１０重量％となるように添加し、ｐＨをアルカリ性に調整し、全体を混練して、固形物中の重金属をフェライト化するものである。
【００１３】
上記処理方法において、ｐＨ調整後の固形物中の含水率は好ましくは２０〜９０重量％である。フェライト化は水溶液中で進行することから固形物中の含水率がフェライト生成に影響を及ぼす。フェライト化が十分に行われるためには、含水率は２０重量％以上とすることが望ましい。固形物中の水分含有率が９０重量％を超えると、重金属含有物が泥状物となり取り扱いが困難になることがある。固形物中の含水率は上記鉄塩溶液の添加量およびアルカリ溶液の添加量によって決まるが、固形物中の重金属含有量が多く、鉄塩溶液添加量も多くなる場合は、鉄塩溶液濃度を高くして、固形物中の含水率を７０重量％以下にすることが、処理操作上さらに好ましい。
【００１４】
ｐＨ調整剤としては水酸化ナトリウムなどの水酸化物が経済的である。好ましいｐＨ値は７から１１の範囲である。
【００１５】
この処理方法では、上記鉄塩溶液を添加するだけでフェライト化が進行し、重金属はフェライト中に閉じ込められ安定化させられる。
【００１６】
したがって、第一鉄塩のように高温で酸素等により酸化する必要はなく、反応も数分で終了する。
【００１７】
上記鉄塩溶液の添加量は固形物の性状により変わるため前もって予備試験により決定しておくことが好ましい。
【００１８】
特開平６−２３８２５９号公報記載の方法、および排水中の重金属をフェライト化する一般的な排水処理技術では温度を６０℃以上に維持し、１時間以上反応させることが必要であるが、本発明方法では常温、たとえば１５℃付近でも数分あれば反応が終了する。
【００１９】
請求項３記載の発明はつぎのような作用を有する。
重金属を含む固形物に上記鉄塩溶液とアルカリ溶液を添加し、全体をよく混練することによりｐＨをアルカリ性、たとえば７から１１に調整し、室温で数分の反応でフェライトを生成する。このように、請求項３記載の方法によれば、特殊な鉄塩溶液の使用によりフェライトが生成する。従来の方法では第一鉄が空気により徐々に酸化され、生成する第二鉄と第一鉄が徐々に反応してフェライトが生成しており、第二鉄の濃度が低く、反応が遅いため高温かつ長時間の反応条件が必要である。請求項３記載の発明では上記鉄塩溶液中の鉄は２価と３価の間にあり、空気による酸化がなくてもフェライト化が進行し、同時に２価の鉄と３価の鉄を高濃度で存在させるため、室温で数分の反応でフェライトが生成する。
【００４２】
【発明の実施の形態】
実施例１
鉄塩溶液の調製
ＦｅＳＯ4 ・ ７Ｈ2 Ｏ：１ｋｇと、９８％Ｈ2 ＳＯ4 ：１２０ｇを水に溶解させ、２．５リットルの混合溶液を得た。この混合溶液にＮａＣｌＯ3 （塩素酸ソーダ）３１．９ｇの結晶を徐々に加えて攪拌した。反応後、放冷するとＦｅとして８％（ｗｔ／ｖｏｌ）の鉄塩溶液が得られた。この溶液の第一鉄と第二鉄の比率は１：１であった。
【００４３】
飛灰の処理
清掃工場から排出される飛灰を用いて、フェライト化を検討した。用いた飛灰の環境庁告示１３号による溶出試験の結果を表１に示す。
【００４４】
【表１】
上記飛灰２０ｇに上記鉄塩溶液と水酸化ナトリウム水溶液を、鉄の添加量が３重量％、混合後のｐＨが１０、飛灰中の含水率が５０重量％となるようにそれぞれ添加し、全体を室温で窒素気流中で１０分間よく攪拌した。この混合物をただちに塩酸溶液中に懸濁させ、酸性化してフェライト化反応を停止させた。その後、この混合物の懸濁液を１μｍのガラス濾紙で濾過し、濾液中の重金属を定量したその結果を表２に示す。
【００４６】
【表２】
濾液中の各重金属が検出限界以下となり、重金属は非常に厳しい条件でも全く溶出しないことが確認できた。また、濾別した混合固形物は、乾燥後Ｘ線回折を実施したところ、フェライトが生成していることが確認できた。
【００４８】
実施例２
表１に示す溶出試験結果を有する飛灰２０ｇに実施例１で得られた鉄塩溶液を鉄添加量が０．３重量％、０．５重量％、１重量％、２重量％となるよう添加し、その他の条件は実施例１と同様にしてフェライト化を実施した。１０分後ただちに混合物の溶出試験を実施した。重金属の溶出試験は環境庁告示１３号により行った。測定結果を表３に示す。１重量％以上では廃棄物の埋立基準値を達成しているが、０．５重量％では達成していないことがわかる。
【００４９】
【表３】
実施例３
表１に示す溶出試験結果を有する飛灰２０ｇに実施例１で得られた鉄塩溶液を鉄として３重量％となるように添加し、アルカリ溶液または塩酸溶液によりｐＨを変化させ、その他の条件は実施例１と同様にしてフェライト化を実施した。混合物の溶出試験を実施例２と同様に実施した結果を表４に示す。分析は最も多く含まれているＰｂについて行った。従来のフェライト化条件と同様にｐＨ７〜１１の範囲でフェライト化が達成されていることがわかる。
【００５１】
【表４】
実施例４
表１に示す溶出試験結果を有する飛灰２０ｇに実施例１で得られた鉄塩溶液を鉄として２重量％となるように添加し、含水率を変化させ、その他の条件は実施例１と同様にしてフェライト化を実施した。混合物の溶出試験を実施例２と同様にＰｂについて実施した結果を表５に示す。含水率２０重量％以上においてフェライト化が達成されていることがわかる。
【００５３】
【表５】
実施例５
実施例１の鉄塩溶液の調製と同様にして、塩素酸ナトリウムの添加により第一鉄溶液に含まれる鉄総量の１４重量％、２１重量％、４０重量％、６０重量％、８０重量％、８８重量％が第一鉄から第二鉄に酸化された鉄塩溶液をそれぞれ調製した。これらの溶液を用いて表１に示す溶出試験結果を有する飛灰２０ｇを実施例１と同様にフェライト化処理した。１０分後ただちに混合物の溶出試験を環境庁告示１３号により行った。測定結果を表６に示す。第二鉄の量が鉄総量の２０〜８０重量％の範囲で廃棄物の埋立基準値を達成していることがわかる。
【００５５】
【表６】
参考例１
表１に示す溶出試験結果を有する飛灰２０ｇに第一鉄溶液と第二鉄溶液を鉄のモル比で１：１となるように、また鉄としての総重量が飛灰の３重量％となるように添加し、さらに混合後のｐＨが１０、含水率が５０重量％となるようにアルカリ溶液を添加して室温で１０分間よく攪拌をした。この混合物をただちに塩酸溶液中に懸濁させ、酸性として反応を停止させた。その後、この混合物の懸濁液を１μｍのガラス濾紙で濾過し、濾液中の重金属を定量したその結果を表７に示す。
【００５７】
【表７】
濾液中の各重金属が検出限界以下となり、重金属は非常に厳しい条件でも全く溶出しないことが確認できた。また、濾液中の各重金属が検出限界以下となり、重金属は非常に厳しい条件でも全く溶出しないことが確認できた。また、濾呂別した混合固形物は乾燥後Ｘ線回折を実施したところ、フェライトが生成していることが確認できた。
【００５９】
参考例２
表１に示す溶出試験結果を有する飛灰２０ｇに第一鉄塩溶液と第二鉄塩溶液をそれぞれの鉄のモル比が０．１、０．２、０．４、０．８、１．２、１．５、２．０で、かつ鉄としての総重量が３重量％となるように添加し、その他は実施例１と同様にしてフェライト化を実施した。１０分後ただちに重金属の溶出試験を環境庁告示１３号により行った。測定結果を表８に示す。モル比が０．２〜１．５の範囲で廃棄物の埋め立て基準値を達成していることがわかる。
【００６０】
【表８】
参考例３
表１に示す溶出試験結果を有する飛灰２０ｇに第一鉄塩溶液と第二鉄塩溶液を鉄のモル比が１．０で、鉄としての総重量％が０．３、０．５、１．０、２．０重量％となるように添加し、その他の条件は実施例１と同様にしてフェライト化を実施した。１０分後ただちに重金属の溶出試験を環境庁告示１３号により行った。測定結果を表９に示す。鉄添加量１重量％以上で埋立基準値を達成していることがわかる。
【００６２】
【表９】
参考例４
表１に示す溶出試験結果を有する飛灰２０ｇに第一鉄塩溶液と第二鉄塩溶液を鉄のモル比が１．０で鉄としての総重量が２．０重量％となるように添加し、混合後のｐＨが７〜１１となるようにアルカリ溶液を添加した後、混合物の含水率が変化させ室温で１０分間よく攪拌し、フェライト化を実施した。１０分後ただちに重金属の溶出試験を環境庁告示１３号により行った。測定結果を表１０に示す。含水率が２０重量％以上で埋立基準値を達成していることがわかる。
【００６４】
【表１０】
実施例６
反応時間を１分、５分、１０分、２０分、と変化させ、その他の条件は実施例１と同様にしてフェライト化を実施した。時間経過後ただちに重金属の溶出試験を環境庁告示１３号により行った。測定結果を表１１に示す。反応時間としては５分あれば十分に埋め立て基準値を達成していることがわかる。
【００６６】
【表１１】
参考例５
清掃工場から排出される飛灰（実施例１のものとは別の飛灰）を用いて、フェライト化を検討した。用いた飛灰の環境庁告示１３号による溶出試験の結果を表１２に示す。
【００６８】
【表１２】
上記飛灰２０ｇに硫酸第一鉄塩溶液と塩素酸ナトリウムと水酸化ナトリウム水溶液を、鉄の添加量が３重量％、混合後のｐＨが１０、飛灰中の含水率が５０重量％となるようにそれぞれに添加し、全体を室温で窒素気流中で１０分間よく攪拌した。この混合物をただちに塩酸溶液中に懸濁させ、酸性化してフェライト化反応を停止させた。その後、この混合物の懸濁液を１μｍのガラス濾紙で濾過し、濾液中の重金属を定量したその結果を表１３に示す。
【００７０】
【表１３】
濾液中の各重金属が検出限界以下となり、重金属は非常に厳しい条件でも全く溶出しないことが確認できた。また、炉別した混合固形物は、乾燥後Ｘ線回析を実施したところ、フェライトが生成していることが確認できた。
【００７２】
参考例６
表１２に示す溶出試験結果を有する飛灰２０ｇに、硫酸第一鉄塩溶液を鉄添加量が０．３重量％、０．５重量％、１重量％、２重量％となるように添加し、その他の条件は参考例５と同様にしてフェライト化を実施した。１０分後ただちに混合物の溶出試験を実施した。重金属の溶出試験は環境庁告示１３号により行った。測定結果を表１４に示す。１重量％以上では廃棄物の埋立基準値を達成しているが、０．５重量％では達成していないことがわかる。
【００７３】
【表１４】
参考例７
表１２に示す溶出試験結果を有する飛灰２０ｇに第一鉄塩溶液を鉄として３重量％となるように添加し、アルカリ溶液または塩酸溶液によりｐＨを変化させ、その他の条件は参考例５と同様にしてフェライト化を実施した。混合物の溶出試験を参考例５と同様に実施した結果を表１５に示す。分析は最も含まれているＰｂについて行った。従来のフェライト化条件と同様にｐＨ７〜１１の範囲でフェライト化が達成されていることがわかる。
【００７５】
【表１５】
参考例８
表１２に示す溶出試験結果を有する飛灰２０ｇに硫酸第一鉄塩溶液を鉄として２重量％となるように添加し、含水率を変化させ、その他の条件は参考例５と同様にしてフェライト化を実施した。混合物の溶出試験を参考例５と同様にＰｂについて実施した結果を表１６に示す。含水率３０重量％以上においてフェライト化が達成されていることがわかる。
【００７７】
【表１６】
参考例９
反応時間を１分、５分、１０分、２０分、と変化させ、その他の条件は参考例５と同様にしてフェライト化を実施した。時間経過後ただちに重金属の溶出試験を環境庁告示１３号により行った。測定結果を表１７に示す。反応時間としては５分あれば十分に埋め立て基準値を達成されていることがわかる。
【００７９】
【表１７】
【発明の効果】
本発明によれば、上述した従来技術の問題を克服することができる上に、さらに下記の効果が発揮される。
【００８１】
ａ） 従来のフェライト法のように高温で長時間の反応を行う必要がないため、処理コストが安く、装置がコンパクトのものでよい。
【００８２】
還元状態で酸素を吹き込む必要がないため、水銀等の揮発性重金属が揮散する恐れがなく、ガス処理設備が不必要である。
【００８３】
ｂ） 重金属をフェライト化することにより重金属の長期安定化が可能となり、将来的な重金属の溶出の可能性が無くなる。
【００８４】
製鉄時の副産物である硫酸第一鉄等が利用できるため、処理コストが安くつく。
【００８５】
ｃ） 処理物はぱさぱさの状態であり、その後の埋立て等の取り扱いが容易である。
【００８６】
ｄ） 請求項３記載の発明では、請求項１記載の特殊な鉄塩溶液を用いることによって粉体状の飛灰が粒状の混合物となり容積の減少が達成できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detoxifying incineration fly ash containing heavy metals discharged from an incinerator that incinerates municipal waste and various wastes, and solids such as soil contaminated with heavy metals such as factory sites. Furthermore, the present invention relates to a method for producing a special iron salt solution used in the method.
[0002]
[Prior art]
As a detoxification method for heavy metals, a method is known in which heavy metals are ferritized and confined and stabilized therein. For example, in JP-A-6-238259, water, a ferrous salt and an alkali component are added and kneaded to a heavy metal-containing solid material such as fly ash, and the pH is adjusted to 7 to 11.5, and then air is added. A method for fixing heavy metals in solids by heating the mixture in a stirred state while blowing is described.
[0003]
Also known is a method for adsorbing heavy metals in waste to prevent the outflow. For example, in JP-A-52-86974, an oxidizing agent such as nitrite is added to ferrous hydroxide salt, or a mixed liquid of ferrous salt and ferric salt is treated with an alkali. There is described a method for treating heavy metal-containing waste, in which active ferrite obtained in this manner is mixed in advance with waste containing heavy metal to prevent heavy metal from flowing out.
[0004]
[Problems to be solved by the invention]
Although the above-described prior art using heavy metal ferritization has little possibility of elution of heavy metal in the future, it has the following problems.
[0005]
In the method of Japanese Patent Laid-Open No. 6-238259, the mercury compound contained in the solid is converted into metallic mercury under the reducing conditions with the ferrous salt, and this is scattered in the exhaust gas by the introduced air, so an exhaust gas treatment facility is required. In addition, equipment and cost for heating for a long time are required.
[0006]
In addition, the method of Japanese Patent Application Laid-Open No. 52-86974 requires a troublesome operation of pulverizing the obtained active ferrite through filtration and drying, and the form of the treated product is liquid and is used for landfilling. Is not suitable.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention takes a means of producing a special iron salt solution and easily ferritizing and insolubilizing heavy metals in waste or contaminated soil with the solution.
[0008]
That is, the invention according to claim 1 is a method for producing an iron salt solution used for ferritizing heavy metals, wherein an oxidizing agent is added to the ferrous salt solution, and the total amount of iron contained in the solution is 20 to 80 wt. % Iron is added in an amount necessary to change ferrous iron to ferric iron.
[0009]
In the method for producing an iron salt solution, any ferrous salt can be used as the ferrous salt solution, and ferrous sulfate, ferrous chloride and the like, which are by-products during iron making, are economical and preferable.
[0010]
As the oxidizing agent, any oxidizing agent of halogen-based oxidizing agents such as sodium chlorate, sodium hypochlorite, sodium perchlorate, and bleaching powder can be used, and the total amount of iron contained in the ferrous salt solution is 20 to 20%. It is only necessary to add an oxidizing agent in such an amount that 80% by weight of iron is oxidized from ferrous iron to ferric iron. In the case of sodium chlorate, this is preferably used in an amount of 5 to 25% by weight of the total iron.
[0011]
A method for easily ferritizing a heavy metal using the iron salt solution will be described in detail below.
[0012]
The invention according to claim 3 is a method for treating a heavy metal-containing solid, wherein the iron salt solution obtained by the method according to claim 1 or 2 is added to the solid containing a heavy metal as iron, usually at least 1% by weight. Is added in an amount of 1 to 20% by weight, preferably 1.5 to 10% by weight, the pH is adjusted to be alkaline, and the whole is kneaded to ferritize the heavy metal in the solid.
[0013]
In the said processing method, the moisture content in the solid substance after pH adjustment becomes like this. Preferably it is 20 to 90 weight%. Since ferritization proceeds in an aqueous solution, the moisture content in the solid matter affects the ferrite formation. In order to achieve sufficient ferritization, the water content is desirably 20% by weight or more. When the moisture content in the solid material exceeds 90% by weight, the heavy metal-containing material becomes a muddy material, which may be difficult to handle. The moisture content in the solid matter is determined by the amount of iron salt solution added and the amount of alkali solution added. If the content of heavy metal in the solid matter is large and the amount of iron salt solution added is large, the concentration of the iron salt solution should be adjusted. It is more preferable in terms of processing operation to increase the water content in the solid matter to 70% by weight or less.
[0014]
A hydroxide such as sodium hydroxide is economical as the pH adjuster. A preferred pH value is in the range of 7 to 11.
[0015]
In this treatment method, ferritization proceeds only by adding the iron salt solution, and the heavy metal is confined in the ferrite and stabilized.
[0016]
Therefore, it is not necessary to oxidize with oxygen or the like at a high temperature unlike ferrous salts, and the reaction is completed in a few minutes.
[0017]
Since the addition amount of the iron salt solution varies depending on the properties of the solid material, it is preferably determined in advance by a preliminary test.
[0018]
In the method described in JP-A-6-238259 and a general wastewater treatment technique for ferritizing heavy metals in wastewater, it is necessary to maintain the temperature at 60 ° C. or higher and react for 1 hour or longer. In the method, the reaction is completed within a few minutes even at room temperature, for example, around 15 ° C.
[0019]
The invention according to claim 3 has the following operation.
The iron salt solution and the alkali solution are added to a solid containing a heavy metal, and the whole is kneaded well to adjust the pH to alkalinity, for example, 7 to 11, and ferrite is generated by a reaction for several minutes at room temperature. Thus, according to the method of claim 3, ferrite is generated by using a special iron salt solution. In the conventional method, ferrous iron is gradually oxidized by air, and the produced ferric iron and ferrous iron react gradually to produce ferrite. The concentration of ferric iron is low and the reaction is slow, so the temperature is high. In addition, long reaction conditions are required. In the invention of claim 3, the iron in the iron salt solution is between divalent and trivalent, and ferritization proceeds even without oxidation by air, and at the same time, the divalent iron and the trivalent iron are increased. Since it is present at a concentration, ferrite is formed in a reaction for several minutes at room temperature.
[0042]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
Preparation of Iron Salt Solution FeSO 4 .7H 2 O: 1 kg and 98% H 2 SO 4 : 120 g were dissolved in water to obtain a mixed solution of 2.5 liters. To this mixed solution, 31.9 g of NaClO 3 (sodium chlorate) was gradually added and stirred. After the reaction, it was allowed to cool to obtain an iron salt solution of 8% (wt / vol) as Fe. The ratio of ferrous to ferric iron in this solution was 1: 1.
[0043]
Processing of fly ash Ferrite was examined using fly ash discharged from a cleaning plant. Table 1 shows the results of the dissolution test of the used fly ash according to Notification No. 13 of the Environment Agency.
[0044]
[Table 1]
The iron salt solution and the aqueous sodium hydroxide solution were added to 20 g of the fly ash so that the added amount of iron was 3 wt%, the pH after mixing was 10, and the water content in the fly ash was 50 wt%, The whole was well stirred for 10 minutes in a nitrogen stream at room temperature. This mixture was immediately suspended in a hydrochloric acid solution and acidified to stop the ferritization reaction. Then, the suspension of this mixture was filtered through a 1 μm glass filter paper, and the results of quantifying heavy metals in the filtrate are shown in Table 2.
[0046]
[Table 2]
Each heavy metal in the filtrate was below the detection limit, and it was confirmed that the heavy metal was not eluted at all even under very severe conditions. Moreover, when the mixed solid separated by filtration was subjected to X-ray diffraction after drying, it was confirmed that ferrite was generated.
[0048]
Example 2
The iron salt solution obtained in Example 1 was added to 0.3 g, 0.5 wt%, 1 wt% and 2 wt% of the iron salt solution obtained in Example 1 on 20 g of fly ash having the dissolution test results shown in Table 1. Addition and other conditions were carried out in the same manner as in Example 1 to perform ferritization. Immediately after 10 minutes, the mixture was tested for dissolution. The heavy metal dissolution test was conducted according to Notification 13 of the Environment Agency. Table 3 shows the measurement results. It can be seen that the waste landfill standard value is achieved at 1% by weight or more, but not at 0.5% by weight.
[0049]
[Table 3]
Example 3
The iron salt solution obtained in Example 1 was added to 20 g of fly ash having the dissolution test results shown in Table 1 so as to be 3% by weight as iron, the pH was changed with an alkaline solution or a hydrochloric acid solution, and other conditions. Was ferritized in the same manner as in Example 1. Table 4 shows the results of conducting the dissolution test of the mixture in the same manner as in Example 2. The analysis was performed on the most abundant Pb. It can be seen that ferritization is achieved in the pH range of 7 to 11 as in the conventional ferritization conditions.
[0051]
[Table 4]
Example 4
The iron salt solution obtained in Example 1 was added to 20 g of fly ash having the dissolution test results shown in Table 1 so as to be 2% by weight as iron, the water content was changed, and other conditions were as in Example 1. Ferritization was performed in the same manner. Table 5 shows the results of the elution test of the mixture performed on Pb in the same manner as in Example 2. It can be seen that ferritization is achieved at a moisture content of 20% by weight or more.
[0053]
[Table 5]
Example 5
In the same manner as in the preparation of the iron salt solution of Example 1, 14 wt%, 21 wt%, 40 wt%, 60 wt%, 80 wt% of the total iron contained in the ferrous solution by adding sodium chlorate, An iron salt solution in which 88% by weight was oxidized from ferrous iron to ferric iron was prepared. Using these solutions, 20 g of fly ash having the dissolution test results shown in Table 1 was ferritized in the same manner as in Example 1. Immediately after 10 minutes, the mixture was tested for dissolution according to Notification No. 13 of the Environment Agency. Table 6 shows the measurement results. It can be seen that the waste landfill reference value is achieved when the amount of ferric iron is in the range of 20 to 80% by weight of the total amount of iron.
[0055]
[Table 6]
Reference example 1
To the fly ash 20g having the dissolution test results shown in Table 1, the ferrous solution and the ferric solution were mixed at a molar ratio of iron of 1: 1, and the total weight as iron was 3% by weight of the fly ash. Further, an alkaline solution was added so that the pH after mixing was 10 and the water content was 50% by weight, and the mixture was stirred well at room temperature for 10 minutes. The mixture was immediately suspended in a hydrochloric acid solution and acidified to stop the reaction. Thereafter, the suspension of this mixture was filtered through a 1 μm glass filter paper, and the result of quantifying heavy metals in the filtrate is shown in Table 7.
[0057]
[Table 7]
Each heavy metal in the filtrate was below the detection limit, and it was confirmed that the heavy metal was not eluted at all even under very severe conditions. In addition, each heavy metal in the filtrate was below the detection limit, and it was confirmed that the heavy metal was not eluted at all even under very severe conditions. Moreover, when the mixed solid separated by filtration was subjected to X-ray diffraction after drying, it was confirmed that ferrite was generated.
[0059]
Reference example 2
20 g of fly ash having the dissolution test results shown in Table 1 are mixed with a ferrous salt solution and a ferric salt solution in a molar ratio of 0.1, 0.2, 0.4, 0.8, 1. Ferrite was carried out in the same manner as in Example 1 except that the total weight was 2, 1.5, 2.0 and the total weight as iron was 3% by weight. Immediately after 10 minutes, a heavy metal dissolution test was conducted according to Notification No. 13 of the Environment Agency. Table 8 shows the measurement results. It can be seen that the waste landfill reference value is achieved in the molar ratio range of 0.2 to 1.5.
[0060]
[Table 8]
Reference example 3
The molar ratio of iron of ferrous salt solution and ferric salt solution to 20 g of fly ash having the dissolution test results shown in Table 1 is 1.0, and the total weight% as iron is 0.3, 0.5, Ferrite was carried out in the same manner as in Example 1 except for adding 1.0 and 2.0% by weight. Immediately after 10 minutes, a heavy metal dissolution test was conducted according to Notification No. 13 of the Environment Agency. Table 9 shows the measurement results. It can be seen that the landfill standard value is achieved when the iron addition amount is 1% by weight or more.
[0062]
[Table 9]
Reference example 4
Add ferrous salt solution and ferric salt solution to 20 g of fly ash having the dissolution test results shown in Table 1 so that the molar ratio of iron is 1.0 and the total weight as iron is 2.0% by weight. Then, after adding an alkaline solution so that the pH after mixing was 7 to 11, the water content of the mixture was changed and stirred well at room temperature for 10 minutes to conduct ferrite. Immediately after 10 minutes, a heavy metal dissolution test was conducted according to Notification No. 13 of the Environment Agency. Table 10 shows the measurement results. It can be seen that the landfill standard value is achieved at a moisture content of 20% by weight or more.
[0064]
[Table 10]
Example 6
Ferritization was carried out in the same manner as in Example 1 except that the reaction time was changed to 1 minute, 5 minutes, 10 minutes, and 20 minutes. Immediately after the elapse of time, a heavy metal dissolution test was conducted according to Notification No. 13 of the Environment Agency. Table 11 shows the measurement results. It can be seen that if the reaction time is 5 minutes, the landfill reference value is sufficiently achieved.
[0066]
[Table 11]
Reference Example 5
Ferritization was studied using fly ash discharged from a cleaning plant (fly ash different from that of Example 1). Table 12 shows the results of the dissolution test of the used fly ash according to Environment Agency Notification No.13.
[0068]
[Table 12]
The ferrous sulfate salt solution, sodium chlorate, and aqueous sodium hydroxide solution are added to 20 g of the above fly ash, the amount of iron added is 3 wt%, the pH after mixing is 10, and the water content in the fly ash is 50 wt%. The whole was well stirred for 10 minutes in a nitrogen stream at room temperature. This mixture was immediately suspended in a hydrochloric acid solution and acidified to stop the ferritization reaction. Thereafter, the suspension of this mixture was filtered through a 1 μm glass filter paper, and the results of quantifying heavy metals in the filtrate are shown in Table 13.
[0070]
[Table 13]
Each heavy metal in the filtrate was below the detection limit, and it was confirmed that the heavy metal was not eluted at all even under very severe conditions. Moreover, when the mixed solid separated by furnace was subjected to X-ray diffraction after drying, it was confirmed that ferrite was generated.
[0072]
Reference Example 6
To 20 g of fly ash having the dissolution test results shown in Table 12, the ferrous sulfate salt solution was added so that the amount of iron added was 0.3 wt%, 0.5 wt%, 1 wt% and 2 wt%. The other conditions were the same as in Reference Example 5 , in which ferrite was formed. Immediately after 10 minutes, the mixture was tested for dissolution. The heavy metal dissolution test was conducted according to Notification 13 of the Environment Agency. Table 14 shows the measurement results. It can be seen that the waste landfill standard value is achieved at 1% by weight or more, but not at 0.5% by weight.
[0073]
[Table 14]
Reference Example 7
Ferrous salt solution fly ash 20g having a dissolution test results shown in Table 12 was added in an amount of 3% by weight of iron, by changing the pH with an alkaline solution or hydrochloric acid solution, and other conditions as in Reference Example 5 Ferritization was performed in the same manner. Table 15 shows the results of conducting the dissolution test of the mixture in the same manner as in Reference Example 5 . Analysis was performed on the most contained Pb. It can be seen that ferritization is achieved in the pH range of 7 to 11 as in the conventional ferritization conditions.
[0075]
[Table 15]
Reference Example 8
Ferrite sulfate solution was added to 20 g of fly ash having the dissolution test results shown in Table 12 so as to be 2% by weight as iron, the water content was changed, and the other conditions were the same as in Reference Example 5. Was implemented. Table 16 shows the results of the mixture dissolution test conducted on Pb in the same manner as in Reference Example 5 . It can be seen that ferritization is achieved at a moisture content of 30% by weight or more.
[0077]
[Table 16]
Reference Example 9
Ferritization was carried out in the same manner as in Reference Example 5 except that the reaction time was changed to 1 minute, 5 minutes, 10 minutes, and 20 minutes. Immediately after the elapse of time, a heavy metal dissolution test was conducted according to Notification No. 13 of the Environment Agency. Table 17 shows the measurement results. It can be seen that if the reaction time is 5 minutes, the landfill reference value is sufficiently achieved.
[0079]
[Table 17]
【The invention's effect】
According to the present invention, it is possible to overcome the above-mentioned problems of the prior art and further exert the following effects.
[0081]
a) Since it is not necessary to carry out the reaction at a high temperature for a long time unlike the conventional ferrite method, the processing cost is low and the apparatus may be compact.
[0082]
Since it is not necessary to blow oxygen in a reduced state, there is no fear that volatile heavy metals such as mercury are volatilized, and gas processing equipment is unnecessary.
[0083]
b) By ferritizing heavy metal, it is possible to stabilize heavy metal for a long period of time, and eliminate the possibility of elution of heavy metal in the future.
[0084]
Since ferrous sulfate, which is a by-product during iron making, can be used, processing costs are low.
[0085]
c) The treated product is in a crispy state and is easy to handle afterwards such as landfill.
[0086]
d) In the invention of claim 3 Symbol mounting, reduction of powdery fly ash by using a special iron salt solution of claim 1, wherein is a mixture of particulate volume can be achieved.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17792797A JP3932434B2 (en) | 1996-07-30 | 1997-07-03 | Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20014796 | 1996-07-30 | ||
| JP8-200147 | 1996-07-30 | ||
| JP17792797A JP3932434B2 (en) | 1996-07-30 | 1997-07-03 | Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1099821A JPH1099821A (en) | 1998-04-21 |
| JP3932434B2 true JP3932434B2 (en) | 2007-06-20 |
Family
ID=26498278
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17792797A Expired - Fee Related JP3932434B2 (en) | 1996-07-30 | 1997-07-03 | Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3932434B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10113637A (en) * | 1996-10-15 | 1998-05-06 | Sumitomo Osaka Cement Co Ltd | Method for lessening elution of heavy metals from dust collection ashes of waste incineration furnace |
| JP2012066158A (en) * | 2010-09-21 | 2012-04-05 | Swing Corp | Method for stabilizing collected dust ash |
-
1997
- 1997-07-03 JP JP17792797A patent/JP3932434B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1099821A (en) | 1998-04-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5252003A (en) | Attenuation of arsenic leaching from particulate material | |
| JPH0394881A (en) | Method for disposal of waste containing heavy metal compound | |
| JPH05309354A (en) | Treatment material for industrial waste | |
| CA2264181C (en) | A method for the treatment, in particular stabilization, of materials containing environmentally noxious constituents, especially from the incineration of waste, as well as a plant for carrying out the said method | |
| JP3932434B2 (en) | Method for treating heavy metal-containing solid and method for producing iron salt solution used in the method | |
| JPH10137716A (en) | Waste treating material and treatment of waste | |
| JP2004526555A (en) | Method for inactivating ash, artificial pozzolan obtained by the method | |
| JP2001121132A (en) | Insolubilizing method of soil and industrial waste containing cyan compound and soluble heavy metals | |
| JP3271534B2 (en) | Method for treating ash containing lead, hexavalent chromium, arsenic and selenium | |
| JPS63278589A (en) | Method for making fly ash harmless | |
| JP3300081B2 (en) | Method for treating fly ash from incinerators and melting furnaces | |
| JPH08309314A (en) | Treatment method for fly ash containing heavy metal | |
| JP2741645B2 (en) | Treatment method for heavy metal-containing ash | |
| JP4119534B2 (en) | Metal and dioxin and / or organochlorine compound simultaneous treating agent and processing method | |
| JP4820504B2 (en) | Fly ash treatment method | |
| JP3850205B2 (en) | Method for preventing heavy metal elution from molten fly ash and / or burned fly ash | |
| JP3850046B2 (en) | Treatment method for waste containing heavy metals | |
| JPS62183896A (en) | Method for stabilizing coal ash | |
| JP2961358B2 (en) | Prevention of elution of waste containing heavy metals | |
| JP4557666B2 (en) | Method for reducing elution of heavy metals | |
| JPH11302644A (en) | Additive for cemental soil solidifier | |
| JP2003320365A (en) | Method for treating object to be treated containing contaminant and treating agent for contaminated object to be treated | |
| JPH10113637A (en) | Method for lessening elution of heavy metals from dust collection ashes of waste incineration furnace | |
| JPH08224558A (en) | Treatment of industrial waste containing heavy metal | |
| JP2005270746A (en) | Treatment method of soil including heavy metal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20050523 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20050531 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20050706 |
|
| 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: 20070206 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20070305 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100330 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150330 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150330 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20170330 Year of fee payment: 10 |
|
| LAPS | Cancellation because of no payment of annual fees |