Insolubilization of heavy metals contained in MSWI fly ash by co-heating with alkaline feldspar and realization of final storage quality

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H04298
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 64020:Environmental load reduction and remediation-related
• Research Institution: Hokkaido University
• Principal Investigator: Tojo Yasumasa 北海道大学, 工学研究院, 准教授 (70250470)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 焼却飛灰 / 重金属 / 難溶性態化 / アルミノ珪酸塩

Outline of Final Research Achievements

Aiming to make the hazardous heavy metals contained in incineration fly ash insoluble, effect of co-heating with aluminosilicate (amorphous Indian feldspar or sol reagent) was investigated. As a result of co-heating with the sol reagent, the leaching concentration of lead decreased significantly. However, the pH after the leaching test was high, suggesting the possibility of hydroxide precipitation formation. From the pH-dependent test of the heated sample, it was confirmed that re-leaching occurred when the pH was lower than 6. And the peak of hydrocerrusite was detected in the XRD analysis on the washed sample after heating. It was found that the decrease of leaching concentration was due to the formation of these hydroxide precipitates.

Free Research Field

廃棄物処分工学

Academic Significance and Societal Importance of the Research Achievements

焼却飛灰は有害重金属を多く含み、溶出濃度も埋立判定基準を超えることから埋立処分前に溶出抑制処理がなされる。しかし、今日広く使用される薬剤処理は長期的な効果に疑問がある。そのため、別の溶出抑制手段としてアルミノ珪酸塩との共加熱を検討した。鉛の溶出濃度は大幅に低下することを確認したが、アルミノ珪酸塩による捕捉ではなく水酸化物沈殿の生成による溶出低下であった。そのため、埋立層内環境がpH＝6以上で維持されれば溶出を回避できる。