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RISS 인기검색어
- 검색키워드
- 저자 : ( Tokichiro Yamaguchi ) (검색결과 1 건)
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Leaching of Radio-cesium and Other Elements from Cement Solidified MSWI-APC Residues
( Masato Yamada ),( Kazuto Endo ),( Masahiro Sato ),( Satoshi Obokata ),( Tokichiro Yamaguchi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.1
The cement solidification is a method to dispose waste containing hazardous substances, such as heavy metals and radionuclides. Recently, cement solidified waste landfills for municipal solid waste incinerators (MSWIs) ash and their air pollution control (APC) residues have been operated in Japan. Also, the radio actively contaminated off-site waste caused by the accident of the Fukushima Dai-Ichi nuclear power plant at above a certain level should be disposed to landfill after solidified by cement. The land disposal of cement solidified waste can provide a containment structure to waste itself in the initial and control fluxes of pollutants to environment in the longer term. Test pieces of cement solidified MSWI-APC residues were made under actual landfill conditions and their leachability of pollutants and structural strength were investigated. Two kinds of MSWI-APC residues were tested. One (hot sample) is APC residues from a MSWI ash melting plant and contaminated by radio-cesium. Another (cold sample) is APC residues from a fluidized bed MSWI. Agents of 6 hazardous inorganics and stable cesium were spiked to the latter one. Both APC residues had been treated by chelate agents at plants before sampling. Same amount of APC residues and the Portland blast-furnace cement class B were mixed at 19 to 38% of the water cement ratio. A certain portions of mixtures were injected to mold of 110 mm diameter, pressed at 0.03 to 25 ton/m<sup>2</sup>. These processes were repeated until height of test pieces raising to 300 mm. Formed test pieces were held in molds and pressed heads for 7 to 19 days. Demolded test pieces were cured for 7 to 28 days in the air. The uniaxial compressive strengths of cement solidified test pieces molded under 25 ton/m<sup>2</sup> were 22 to 71 N/mm<sup>2</sup>. Permeability coefficients of test pieces molded at 25 ton/m<sup>2</sup> were less than 1.59 ×10<sup>-12</sup> cm/sec. These were satisfied conditions in the structural landfill standard in Japan. The tank leaching test with stirring for hot samples showed that around 90% of radio-cesium was leached in 6 hours. Less than 4% of radio-cesium was leached from cement solidified test pieces of hot samples. Leaching ratios for test pieces of hot samples obtained by the tank leaching test without stirring for 32 day were 9 to 17%. Leaching ratios for test pieces of spiked cold samples obtained by same test were 0.002% for total mercury form pieces loaded at 0.003 and 3 ton/m2, 0.4% for cesium from pieces loaded at 0.003 ton/m<sup>2</sup> and less than 0.04% from pieces loaded at 3 and 25 ton/m<sup>2</sup>. All other substances were not detected in leachate. These results suggested that higher compaction would be effective to suppress leaching of substances from the cement solidified waste. Avoidance of contacting the naked surface of cement solidified waste to water would also be important to keep containment of hazardous materials in the waste. This study was partly supported by the Environment Research and Technology Development Fund (3K113015) of Ministry of the Environment, Japan.
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