Removal of heavy metals from contaminated soils using cooling and heating cycles to induce soil water freezing and evaporation

• Project/Area Number: 18K13826
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Gifu University
• Principal Investigator: KOJIMA YUKI 岐阜大学, 工学部, 准教授 (70767475)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000); Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2019: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2018: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
• Keywords: 土壌汚染 / 土壌凍結 / 土中水蒸発現象 / 重金属移動 / 土中蒸発 / 地盤凍結・加熱 / 土中重金属移動 / 数値解析 / 吸着現象 / 水・熱・溶質同時移動現象 / 土壌加熱 / 重金属汚染 / 土壌中の熱・物質移動

Outline of Final Research Achievements

We proposed a new method to remove heavy metals from contaminated soils using artificial soil cooling and heating cycles which induce dynamic soil freezing/thawing and soil water evaporation. In this study, we aimed 1) to develop a sensor for estimating soil ice contents and 2) to understand the effects of the soil type, moisture content, cooling/heating temperature, and cooling/heating duration on heavy metal migration in soils.
We developed a method to estimate soil ice contents by partially thawing the frozen soil using a soil moisture sensor with a built-in heater. Numerical studies revealed the soil type, moisture content, soil cooling/heating temperature, and cycle duration to obtain the heavy metal's most efficient removal rate. Laboratory tests using lead-contaminated soil showed practical applicability of the proposed method.

Academic Significance and Societal Importance of the Research Achievements

近年顕在化している重金属類による土壌汚染に対して，従来法の原位置浄化法よりも効率的な手法として地盤を人工的に冷却・加熱した際に生じる水と重金属の移動現象を利用した重金属除去手法を提案した．この手法の実現に向けて，シミュレーションや室内実験を通して，土壌の種類や水分量，冷却．加熱時温度，そしてその継続時間が土壌中の重金属除去効率に与える影響を明らかにした．本研究成果から，適切な冷却・加熱方法や適用対象地盤の選定方法など，本手法の実用化に向けて重要な知見が得られた．

Research Products

• [Journal Article] A new thermo-time domain reflectometry approach to quantify soil ice content at temperatures near the freezing point (2020)
  • Author(s): Kojima, Y., Y. Nakano, C. Kato, K. Noborio, K. Kamiya, and R. Horton.
  • Journal Title: Cold Region Science and Technology Volume: 174 Pages: 103060-103060
  • DOI: 10.1016/j.coldregions.2020.103060
  • Peer Reviewed / Int'l Joint Research
• [Presentation] 冷却・加熱サイクルを利用した土壌中重金属除去法の室内試験による検討 (2020)
  • Author(s): 寺田隼大，小島悠揮，小谷映輔，神谷浩二
  • Organizer: 2020年度土壌物理学会大会
• [Presentation] 射撃場跡地の鉛汚染土壌における粒径別性質の評価 (2020)
  • Author(s): 社本凜太郎，小島悠揮，神谷浩二
  • Organizer: 2020年度土壌物理学会大会
• [Presentation] A numerical study of contaminant accumulation using soil cooling and heating to induce soil water freezing and evaporation (2019)
  • Author(s): Kojima, Y., Nakano, Y., Flerchinger, G.N., Kamiya, K., Horton, R.
  • Organizer: Soil Science Society of America annual meeting
  • Int'l Joint Research
• [Presentation] A new thermo-time domain reflectometry approach to quantify soil ice content at temperatures near the freezing point (2019)
  • Author(s): Kojima, Y., Nakano, Y., Kato, C., Noborio, K., Kamiya, K., Horton, R.
  • Organizer: Symposium on Freezing and Cold Region Phenomena
• [Presentation] 土壌の冷却・加熱サイクルを用いた汚染物質除去法の数値解析的検討 (2019)
  • Author(s): 小島悠揮，中野雄太，Gerald N. Flerchinger，神谷浩二，Robert Horton
  • Organizer: 土壌物理学会大会
• [Presentation] Evaluating improvement techniques for phytosuction separation method to remove heavy metals from contaminated soils (2019)
  • Author(s): Kojima, Y., Terada, H., Katoh, M., Kamiya, K.
  • Organizer: Japan Geoscience Union annual meeting
• [Presentation] 数値解析による人工地盤凍結・加熱サイクル下での土壌中の熱・物質移動現象の解明 (2019)
  • Author(s): 小島悠揮，中野雄太，神谷浩二
  • Organizer: 地盤工学会
• [Presentation] サーモTDR を用いた凝固点近傍の温度域における凍土氷含有量の新たな測定法 (2019)
  • Author(s): 小島悠揮，中野雄太，加藤千尋，登尾浩介，神谷浩二，Robert Horton
  • Organizer: 農業農村工学会