| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
To characterize the kinetics of speciation of heavy metals incorporated in soils, salts of copper, lead and zinc were added to six soi1s differed in major cation exchanger and the metals were fractionated into water soluble-, exchangeable-, oxide bound-, organically complexed- and residua1-fraction. In all soils more than 60% of the added heavy meta1s were in oxide bound fraction. The proportion of the fraction gradually increased in 30 days accompanied with the reduction in exchangeable heavy metals.
To obtain basic data required to improve the efficiency of electrokinetic heavy metal removal from soi1s, one of the soil examined in the first part of this study was packed in a plastic container and direct current of a voltage of 20 V was applied between the platinum electrode inserted into the soil. With the applied electric field, interstitial water moved toward the cathode and the dilute sodium chloride solution was supplied from the anode compartment to compensate the water flow.
As a result of electrolysis of water, the soil neighboring the cathode acidified and the acidic region expended towards the cathode. In the soil solution of the acidified region, aluminun ion appeared as a major cation accompanied with chloride ion as a counter ion and the both ions gradually moved towards the cathode as tine elapsed. The peak concentration of aluminun was higher when more concentrated sodium chloride was supplied. But the velocity of copper added to soils did not depend on the sodium chloride concentration. In the region neighboring the cathode, soil became strongly alkaline and the electrophoretically transported copper precipitated as hydroxides.
To prevent the hydrolysis of heavy metals, cation exchange resin saturated with hydrogen ion was placed around the cathode. With this device, the alkalinization of the soil was completelyprevented and the transported copper ion was quantitatively retained on the resin.
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