Speciation of U(VI) sorbed onto ZrP2O7 in the presence of citric and oxalic acid

Metal-Organic Framework-Based Materials for Adsorption and Detection of Uranium(VI) from Aqueous Solution

The steady supply of uranium resources and the reduction or elimination of the ecological and human health hazards of wastewater containing uranium make the recovery and detection of uranium in water greatly important. Thus, the development of effective adsorbents and sensors has received growing attention. Metal-organic frameworks (MOFs) possessing fascinating characteristics such as high surface area, high porosity, adjustable pore size, and luminescence have been widely used for either uranium adsorption or sensing. Now pertinent research has transited slowly into simultaneous uranium adsorption and detection. In this review, the progress on the research of MOF-based materials used for both adsorption and detection of uranium in water is first summarized. The adsorption mechanisms between uranium species in aqueous solution and MOF-based materials are elaborated by macroscopic batch experiments combined with microscopic spectral technology. Moreover, the application of MOF-based materials as uranium sensors is focused on their typical structures, sensing mechanisms, and the representative examples. Furthermore, the bifunctional MOF-based materials used for simultaneous detection and adsorption of U(VI) from aqueous solution are introduced. Finally, we also discuss the challenges and perspectives of MOF-based materials for uranium adsorption and detection to provide a useful inspiration and significant reference for further developing better adsorbents and sensors for uranium containment and detection.

Sorption of U(VI) onto ZrSiO4 gamma irradiated and functionalized with phytic acid

In the suitability assessment of candidate materials as engineering barriers for a Deep Geological Repository (DGR), new studies concerned with zirconium silicate have been carried out. The zirconium silicate extracted from beach sand, was submitted to gamma irradiation in order to evaluate its structural stability and then functionalized with phytic acid (IP6) and measured its sorption capacity vis-a-vis uranium. The purified, irradiated and functionalized material was then characterized by several analytical techniques. The surface parameters including the surface area and density of surface sites were also determined. The results obtained from physic-chemical characterization showed that there were no significant changes in the structure of zirconium silicate after its gamma-irradiation. These results are consistent with those of sorption experiments. Uranium (VI) sorption capacity of zirconium silicate is increased in the presence of phytic acid and remained constant after its exposition to high doses of gamma-radiation (10 and 30 MGy). These results show that the IP6-functionalized zirconium silicate can be used as engineering barriers for a DGR.

Interaction of salicylic acid with zirconium diphosphate and its reactivity toward uranium (VI)

The interaction of salicylic acid with zirconium diphosphate surface and its reactivity toward uranium (VI) was investigated. The interaction of salicylic acid with zirconium diphosphate was firstly studied using several analytical techniques including atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The sorption of uranium (VI) onto surface-modified zirconium diphosphate was evaluated by the classical batch method at room temperature. This study showed that the uranium (VI) sorption onto zirconium diphosphate is influenced by the presence of salicylic acid. A fluorescence spectroscopy study revealed the presence of a uranyl specie onto the modified solid surface. The spectroscopy results were then used to restrain the modeling of experimental sorption data, which are interpreted in terms of a constant capacitance model using the FITEQL code. The results indicated that interaction between the uranium (VI) and the surface of zirconium diphosphate modified with salicylic acid leads to the formation of a ternary surface complex.

Microwave-induced synthesis of pyrophosphate Zr1-xTixP2O7 and TiP2O7 with enhanced sorption capacity for uranium (VI)

A series of nanostructured pyrophosphates Zr1-xTixP2O7 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0), have been prepared via a facile microwave induced route in which zirconium hydroxide, titanium hydroxide and phosphoric acid were used as Zr, Ti and P sources, respectively. It is demonstrated the isomorphous substitution of Zr(4+) by Ti(4+) results in a decrease of the size and an enhancement of the adsorption capacity of the obtained particles for U(VI) in aqueous solution. The maximum amount of TiP2O7 for U(VI) reached up to 309.8 mgg(-1) under the experimental conditions (pH=5, t=60min and T=303K). The as-obtained specific metal pyrophosphates exhibit a considerably higher adsorption capability for U(VI) in aqueous solution compared with Zr1-xTixP2O7 prepared by calcined method, showing a high potential for U(VI) sequestration applications. The adsorption kinetics and thermodynamic analysis of Zr1-xTixP2O7 on adsorption of U (VI) were performed, and a possible adsoprtion mechanism was also proposed.