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Title: From Adsorption to Precipitation of U(VI): What is the Role of pH and Natural Organic Matter?

Authors: Velasco, Carmen A; Brearley, Adrian J; Gonzalez-Estrella, Jorge; Ali, Abdul-Mehdi S; Meza, María Isabel; Cabaniss, Stephen E; Thomson, Bruce M; Forbes, Tori Z; Lezama Pacheco, Juan S; Cerrato, José M

Published In Environ Sci Technol, (2021 12 07)

Abstract: We investigated interfacial reactions of U(VI) in the presence of Suwannee River natural organic matter (NOM) at acidic and neutral pH. Laboratory batch experiments show that the adsorption and precipitation of U(VI) in the presence of NOM occur at pH 2 and pH 4, while the aqueous complexation of U by dissolved organic matter is favored at pH 7, preventing its precipitation. Spectroscopic analyses indicate that U(VI) is mainly adsorbed to the particulate organic matter at pH 4. However, U(VI)-bearing ultrafine to nanocrystalline solids were identified at pH 4 by electron microscopy. This study shows the promotion of U(VI) precipitation by NOM at low pH which may be relevant to the formation of mineralized deposits, radioactive waste repositories, wetlands, and other U- and organic-rich environmental systems.

PubMed ID: 34797046 Exiting the NIEHS site

MeSH Terms: Adsorption; Dissolved Organic Matter; Hydrogen-Ion Concentration; Radioactive Waste*; Uranium*/analysis

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