Study on the complexation mechanism of humic substance by nano-calorimetry

2014 Fiscal Year Final Research Report

• Project/Area Number: 24760713
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Nuclear engineering
• Research Institution: Tohoku University
• Principal Investigator: KIRISHIMA Akira 東北大学, 多元物質科学研究所, 准教授 (00400424)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: フミン物質 / 核種移行 / 錯生成 / カロリメトリー / エンタルピー

Outline of Final Research Achievements

Humic substances (HSs) are heterogeneous mixture of high-molecular-weight organic materials formed by humification of animals, plants and microbes. HSs plays an important role in the transportation of cations in environment, and are confirmed to be present even in the deep underground where radioactive wastes are planned to be disposed. The purpose of this study is accurate determination of delta_G, _H,_S in protonation and complexation of natural humic acid with Cu(II) by calorimetric titration. Furthermore, the reaction mechanism is discussed from the obtained thermodynamic quantities. It is revealed that the absolute value of complexation enthalpy is negative and decreases with pH increase. In addition, the complexation reaction of Elliot Soil humic acid is driven by enthalpy term, while the protonation reaction in this pH range is driven by entropy term. This difference is considered to be caused by the difference of the bonding mode between proton and Cu(II) to humic acid.

Free Research Field

溶液化学・原子力化学