報告書番号

U96039

タイトル（和文）

電気化学的手法によるヘドロ中の重金属除去

タイトル（英文）

HEAVY-METAL REMOVAL FROM SLUDGE USING ELECTROCHEMICAL METHOD

概要 （図表や脚注は「報告書全文」に掲載しております）

ダム，貯水池，湖沼に堆積したヘドロの有効利用策として，コンポスト化による，農地還元がある。本報では，この場合に必要となる，含有重金属の除去を電気化学的手法により効率よく行う方法を検討した。試作した装置は，正極を入れたヘドロ槽と負極を入れた水槽からなる二槽式の形状を有する電解槽である。本装置によると，ヘドロ中の重金属類は正極の酸化反応でイオン化し負極方向へ電気泳動し，負極のアルカリ環境下で沈澱として回収できた。４００ｍＡの定電流電解を４日間行うことで，亜鉛の濃度をコンポスト化の規制値以下にすることが出来た。また，電解中，負極側を流水する事により，除去効率は向上した。なお本手法は，現状でもコスト的に十分に適用可能であることが試算された。

概要 （英文）

DISPOSAL OF SLUDGE ON LAKE BOTTOMS IS POSINGA SERIOUS PROBLEM AND APPLICATION OF SLUDGE ON AGRICULTURAL FIELD IS AN OPTIONS, BUT THE HIGH CONCENTRATION OF HEAVY METALS IN THE SLUDGE IS AN OBSTACLE.TO SOLVE THIS PROBLEM,WE DEVELOPED A METHOD OF REMOVING METALS USING AN ELECTROCHEMICAL BATH.THE BATH IS SEPARATED INTO TWO PARTS BY A FILTER.THE EXPERIMENTAL SYSTEM COMPRISES A SLUDGE PART WITH A C ANODE AND A WATER PART WITH A PT CATHODE; THE TOTAL VOLUME IS 500 ML.WHENELECTRIC ENERGY IS APPLIED FROM A POWER SUPPLY,HEAVY METAL IONS ABSORBED ON THE SURFACES OF SLUDGE PARTICLES ARE RELEASED BY PROTONS GENERATED FROM THE ANODE REACTION.THE HEAVY METAL IONS MOVE ELECTROPHORETICALLYTO THE WATER PART AND ARE PRECIPITATED BY THE ALKALI CONDITIONS CREATED BY THE CATHODE REACTION.THE CONCENTRATION OF MOST OF HEAVY METAL SPECIES WAS REDUCED IN SLUDGE BY 6 DAYS OF ELECTROLYSIS AT 200 MA AND THE METALS WERE SEPARATED AS PRECIPITATE.IT WAS POSSIBLE TO REDUCE THE ZN LEVELS TO 120 PPM,THE LEGAL CONCENTRATION IN SLUDGE FOR AGRICULTURAL LANDAPPLICATION,BY 4 DAYS ELECTROLYSIS OF 400MA. IN ADDITION,THE HEAVY-METAL REMOVAL RATE WAS DOUBLED BY ELECTROLYSIS WITH FLOWING WATER IN THE CATHODE PART.FURTHERMORE,THE CONSUMED ELECTRIC POWER WAS 25% LESS WITH FLOWING WATER THAN WITH STILL WATER.IT IS SUGGESTED THAT THE FLOWING WATER REMOVES PRECIPITATE AND MAINTAINS CONDUCTIVITY. THE THEORETICAL REMOVAL RATIO WAS CALCULATED FROM THE RELATIONSHIP BETWEEN ELECTRIC CURRENTAND ELECTROLYSIS TIME.PRELIMINARY COST ESTIMATION SUGGESTS THAT THIS METHOD IS PRACTICAL.

報告者

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