The effects of pH, ionic strength and temperature on sorption of Eu(III) on attapulgite were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The results indicated that the sorption of Eu(III) on attapulgite was strongly dependent on pH and ionic strength, and independent of temperature. In the presence of FA/HA, Eu(III) sorption was enhanced at pH 7. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the sorption of Eu(III) might be expressed as ?X3Eu0 ?SwOHEu3+ and ?SOEu-OOC-/HA in the ternary Eu/HA/attapulgite system. The extended X-ray absorption fine structure (EXAFS) analysis of Eu-HA complexes indicated that the distances of d(Eu-O) decreased from 2.451 to 2.360 A with increasing pH from 1.76 to 9.50, whereas the coordination number (N) decreased from ~9.94 to ~8.56. Different complexation species were also found for the different addition sequences of HA and Eu(III) to attapulgite suspension. The results are important to understand the influence of humic substances on Eu(III) behavior in the natural environment.

Sorption of Eu(III) on Attapulgite Studied by Batch, XPS and EXAFS Techniques

Synthesis of magnetic biochar composites for enhanced uranium(VI) adsorption.

Graphene oxide (GO), one of the most important graphene derivatives, has many oxygen-containing functional groups on its basal plane and on the edges in the form of epoxy, hydroxyl and carboxyl groups. It has attracted increasing interest in multidisciplinary research because of its unique structure and exceptional physicochemical properties. In particular, GO-based materials have great potential in environmental remediation and energy applications. Herein, we review the recent advances in GO-based materials for the sorption of radionuclides, mainly from the last decade. This review summarizes the preparation of GO-based materials and their application in the sorption of radionuclides (such as U(VI), Eu(III), Sr(II), etc.) from aqueous systems. The main sorption mechanisms are investigated using kinetic analysis, thermodynamic analysis, surface complexation models, spectroscopic techniques and theoretical calculations. It is evident that GO-based materials have good potential for the removal of radionuclides from aqueous systems. However, it is necessary to carry out more research focusing on the development of lower cost, higher efficiency and more environmentally friendly GO-based materials, either for scientific interest or practical applications.

Sorption of radionuclides from aqueous systems onto graphene oxide-based materials: a review

Lanthanides/actinides sorption speciation on minerals and oxides by means of time resolved laser fluorescence spectroscopy (TRLFS), extended X-ray absorption fine structure spectroscopy (EXAFS) and density functional theory (DFT) is reviewed in the field of nuclear disposal safety research. The theoretical aspects of the methods are concisely presented. Examples of recent research results of lanthanide/actinide speciation and local atomic structures using TRLFS, EXAFS and DFT are discussed. The interaction of lanthanides/actinides with oxides and minerals as well as their uptake are also of common interest in radionuclide chemistry. Especially the sorption and inclusion of radionuclides into several minerals lead to an improvement in knowledge of minor components in solids. In the solid-liquid interface, the speciation and local atomic structures of Eu(III), Cm(III), U(VI), and Np(IV/VI) in several natural and synthetic minerals and oxides are also reviewed and discussed. The review is important to understand the physicochemical behavior of lanthanides/actinides at a molecular level in the natural environment.

https://www.mdpi.com/1420-3049/15/11/8431/pdf

Sorption speciation of lanthanides/actinides on minerals by TRLFS, EXAFS and DFT studies: a review

Impact of water quality parameters on the sorption of U(VI) onto hematite

Bentonite has been extensively studied because of its strong sorption ability and low permeability. In this work, the Na-bentonite from Gaomiaozi County (China) has been characterized by XRD, FTIR and acid-base titration. The sorption of Eu(III) on Na-bentonite in the absence/presence of humic acid (HA) was studied at T = 25 ± 2 °C and in 0.01 mol/L NaClO4 solution. The effects of pH, HA, contact time and initial Eu(III) concentrations were also investigated. The results indicate that the sorption of Eu(III) on Na-bentonite was dependent on pH values. The presence of HA had little effect on Eu(III) sorption at low pH values, but decreased Eu(III) sorption at high pH values. X-ray absorption fine structure spectroscopy (XAFS) was applied to characterize the local structural environment of the adsorbed Eu(III) on bare Na-bentonite and HA-bentonite hybrids. The results indicate that Eu(III) was bound to O atoms at a distance of about 2.39 A at pH 4.15. The results are crucial for the evaluation of the sorption and migration of other trivalent lanthanides and actinides in bentonite as backfill materials.

Zhi Xie

Papers

Sorption of Eu(III) on GMZ bentonite in the absence/presence of humic acid studied by batch and XAFS techniques