Detoxification and Recycling of fly ash by mechanochemical treatment

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Prevention of heavy metals elution by a mechanochamical processFly ash was treated by a mechanochamical (MC) process that involved milling with calcium oxide by using a planetary ball mill, and then heavy metals elution potencies among fly ash, MC-treated fly ash, and cemented MC process-treated fly ash were compared. The results confirmed prevention of heavy metals elution by MC treatment and cementation. When a stainless ball mill was used in MC treatment of fly ash, elution of Cr^<+6> from MC-treated fly ash was significantly enhanced, thereby indicating necessity of a change in the material of ball mill.MC degradation of dioxinsModel dioxin compounds, octachlorodibenzo-p-dioxin (OCDD), and octachlorodibenzofuran (OCDF) were degraded by a MC process. Measurements of chloride ions after MC treatment of OCDD and OCDF showed about 100% dechlorination of both compounds ; tetra- to heptachlorinated dibenzo-p-dioxins/furans (T4-H7CDD/Fs) were detected only at trace levels, and no other chlorinated organic compounds were observed. The residue after MC treatment was gray in color, indicating the possibility of carbonization. The results allow us to expect that the degradation products of OCDD and OCDF have no dioxin-like endocrine disruption potency.