The role of anatase in the behavior of heavy metals in the soil environemnt

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01571
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 22060:Environmental systems for civil engineering-related
• Research Institution: Yamaguchi University
• Principal Investigator: SUZUKI TASUMA 山口大学, 大学院創成科学研究科, 准教授 (00577489)
• Co-Investigator(Kenkyū-buntansha): 隅本 倫徳 山口大学, 大学院創成科学研究科, 准教授 (40414007)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 土壌汚染 / 地下水汚染 / 重金属類 / 微量金属酸化物 / 二酸化チタン

Outline of Final Research Achievements

This study was performed to enhance the understanding of the leaching mechanism of heavy metals from contaminated kaolinite with a focus on the role of anatase impurities. Anatase showed significantly higher Cd(II) adsorption capability than those of kaolinite and goethite (α-FeOOH), with inner-sphere complex formation as the dominant adsorption mechanism. Under acidic and near-neutral conditions, kaolinite absorbs Cd(II) mainly via outer-sphere complex formation, while both outer-sphere and inner-sphere complex formation are important at higher pH. Binding constants obtained from modeling analyses were then used to predict the leaching extent of Cd(II) from contaminated kaolinite with different contents of anatase impurity at pH 4.0 - 7.0. The experimental data and model predictions consistently showed that the leaching of Cd(II) decreased with increasing anatase content and this trend was more significant under acidic conditions.

Free Research Field

環境工学

Academic Significance and Societal Importance of the Research Achievements

土壌・地下水汚染は我が国における重要な環境問題である。土壌・地下水を汚染する物質の中で、重金属類（例：鉛、カドミウム、ヒ素、フッ素）による汚染は報告件数が多いが、土壌環境中における重金属類の挙動については、挙動に影響を与える土壌因子を含めて未解明である。そこで本研究では、これまでの研究では着目されてこなかった二酸化チタンに着目し、二酸化チタンと重金属類の親和性を定量的評価するとともに、その重要性を明らかにするための実験を行った。その結果、二酸化チタンは鉛やカドミウムなどの重金属と親和性が高く、二酸化チタンの含有量が高い土壌からはこれらの重金属が溶出しにくいことが明らかになった。