Porous titania beads for remediation of arsenic contamination from acid mine drainage.

Hierarchically porous titania beads with and without amine functionalisation have been developed and tested as adsorbents for removal of highly toxic As(V) from environments affected by acid mine drainage (AMD). The unique acid stability of the titania framework enables these adsorbents to function in highly acidified environments and their granular form facilitates practical deployment under continuous flow conditions. Herein, both non-functionalised and amine-functionalised titania beads have been demonstrated to selectively remove As(V) from simulated and real AMD solutions at pH 2.6. Novel selectivity for As(V) over Na(I), Mg(II), Al(III), Si(VI), Ca(II), Co(II), Cu(II), Zn(II), Nd(III) and Ho(III) was achieved, with competing element concentrations similar to or up to an order of magnitude greater than that of As(V). Although Fe(III) and some Fe(II) were also adsorbed by the titania beads, Fe adsorption did not inhibit As(V) adsorption, indicating different adsorption mechanisms for these two elements. The As(V) adsorption capacity of the titania beads decreased from ∼20 mg/g from pure As(V) solution to ∼10 mg/g from real AMD solution, demonstrating the importance of adsorbent testing under applied conditions. Amine functionalisation increased the kinetics of adsorption, but the non-functionalised titania beads showed greater selectivity for As(V) over Fe(II) and Fe(III) and hence were considered preferable for As remediation applications. Nevertheless, the functionalisation ability of the porous titania beads makes them a promising, flexible technology for remediation of a wide range of AMD affected environments.

Hydrothermal Syntheses of Uranium Oxide Hydrate Materials with Sm(III) Ions: pH-Driven Diversities in Structures and Morphologies and Sm-Doped Porous Uranium Oxides Derived from Their Thermal Decompositions.

We report the hydrothermal syntheses of three uranyl oxide hydroxy-hydrate (UOH) materials containing Sm(III) ions (UOH-Sm) by controlling the solution pH and a new way to make Sm-doped porous uranium oxides with different U-to-Sm atomic ratios via their thermal decompositions. While layer-structured UOH-Sm phases with U-to-Sm atomic ratios of 1 (UOH-Sm1) and 4 (UOH-Sm2) were obtained from the reaction of schoepite and samarium nitrate with final solution pH values of over 4, similar reactions without pH adjustment with final solution pH values of less than 4 led to the formation of a uranyl oxide framework (UOF-Sm) with a U-to-Sm atomic ratio of 5.5. The crystal structure of compound UOF-Sm was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron microscopy. The two-dimensional uranyl oxide hydroxide layers, similar to that for ß-U3O8, are linked by double pentagonal uranyl polyhedra to form a three-dimensional framework with Sm(III) ions in the channels. Scanning electron microscopy characterization revealed nanoplate crystal morphologies for the two UOH-Sm phases, in contrast to the needle morphology for UOF-Sm. Subsequent thermal treatments led to the formation of Sm-doped uranium oxides, maintaining the original crystal shapes and U-to-Sm ratios but with nanopores. This work demonstrated that the hydrothermal synthesis conditions, especially fine-tuning of the solution pH, have a significant impact on the uranium hydrolysis, thus leading to well-defined products. This will facilitate the targeted syntheses of UOH phases with lanthanide (Ln) ions and explore the subsequent applications of these materials and Ln-doped porous uranium oxides as potential nuclear or functional materials.

Naturally occurring radioactive materials in offshore infrastructure: Understanding formation and characteristics of baryte scale during decommissioning planning.

Contaminants, including naturally occurring radioactive material (NORM) of the 238-uranium and 232-thorium decay series, have been recognized as a global research priority to inform offshore petroleum infrastructure decommissioning decisions. This study aimed to characterize pipeline scale retrieved from a decommissioned subsea well tubular pipe through high-resolution elemental mapping and isotopic analysis. This was achieved by utilizing transmission electron microscopy, Synchrotron x-ray fluorescence, photostimulated luminescence autoradiography and Isotope Ratio Mass Spectrometry. The scale was identified as baryte (BaSO4) forming a dense crystalline matrix, with heterogenous texture and elongated crystals. The changing chemical and physical microenvironment within the pipe influenced the gradual growth rate of baryte over the production life of this infrastructure. A distinct compositional banding of baryte and celestine (SrSO4) bands was observed. Radioactivity attributed by the presence of radionuclides (226Ra, 228Ra) throughout the scale was strongly correlated with baryte. From the detailed scale characterization, we can infer the baryte scale gradually formed within the internals of the tubular well pipe along the duration of production (i.e., 17 years). This new knowledge and insight into the characteristics and formation of petroleum waste products will assist with decommissioning planning to mitigate potential radiological risks to marine ecosystems.