Hydrothermal-treatment desorption of cesium from clay minerals: The roles of organic acids and implications for soil decontamination. (15th June 2020)

• Record Type: Journal Article
• Authors: Yin, Xiangbiao; Zhang, Lijuan; Harigai, Miki; Wang, Xinpeng; Ning, Shunyan; Nakase, Masahiko; Koma, Yoshikazu; Inaba, Yusuke; Takeshita, Kenji
• Is Part Of: Water research. Volume 177(2020)
• Publication Date: 2020-06-15
• Subjects: Soil decontamination -- Cesium -- Low-molecular-weight organic acids -- Clay mineral -- Interlayer collapse -- Hydrothermal treatment; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115804
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: The adsorption and desorption of cesium (Cs) on clays of contaminated soil in a rhizosphere zone can be greatly affected by various biogeochemical processes, the timespans of which are usually months to years. Herein, we present several representative scenarios of the binding of Cs on diverse sites of vermiculitized biotite by controlled Cs adsorption to particles of different sizes. We investigated whether and how the fixed Cs in the different scenarios is desorbed by ambient and hydrothermal treatments with several low-molecular-weight organic acids (LMWOAs). The results showed that the sorbed Cs was discriminatively retained in the un-collapsed, partially collapsed, and thoroughly collapsed structures of vermiculites. The desorption of the sorbed Cs by hydrothermal LMWOAs extractions was easily realized in the un-collapsed structure, but was limited or minimal in the partially collapsed and thoroughly collapsed structures. The Cs desorption varied in accord with the LMWOA species applied and increased with the acid concentration, temperature, and number of treating cycles. The analysis of Cs-desorbed specimens confirmed their partial destruction and interlayer expansion, suggesting that the underlying mechanism of Cs removal by LMWOAs involves not only acid dissolution and complexation but also the accelerated weathering of clays within a short time under hydrothermal conditions. Our findings contribute novel insights into the mobility, bioavailability, and fate of Cs in contaminated soils and its removal from these soils for environmental restorations. Graphical abstract: Image 1 Highlights: Adsorption and desorption of Cs on typical clay of contaminated soil were studied. Representative scenarios of Cs binding to diverse sites of clay were confirmed. Cs retained on different sites of clay was extracted distinctively by organic acid. Cs removal by organic acid proceeded via accelerated clay weathering mechanism.