To provide a method advantageous for non-polluting hazardous flying ash and to obtain a solidified material which contains the non-polluted flying ash and has excellent handing quality.
This method for treating the flying ash containing dioxins and heavy metals consists of (i) a non-polluting treatment stage for bringing the flying ash into contact with an aqueous acidic solution held at a temperature lower than 100°C and a pH in a range of 2 to 6 to extract heavy metal components in the flying ash into this aqueous solution and to crack the dioxins in the flying ash thereby making the dioxins non-polluting, (ii) a neutralizing treatment stage of adding an alkali to the non-polluting flying ash obtain by the non-polluting treatment stage and adjusting its pH to a range of 7.5 to 19 and (iii) a solidifying stage for adding a solidifying agent to the neutralized slurry liquid obtained in the neutralizing treatment stage to solidify the liquid. This solidified material has a structure to immobilize the non- polluting flying ash into the solidified material in the solidifying agent and the flying ash content in the solidified material is in a range of 7 to 40%, the metal-component content in the solidified material is in a range of 0.002 to 4% and the uniaxial compression strength of the solidified material is ≥3 kgf/cm2.
ONDA NOBUHIRO
ISHIKAWA AKIO
MOTOHASHI SATORU
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