Extraction of uranium from water is an essential step in in situ leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO2)(O2)(H2O)2](H2O)2, by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma. Precipitation of studtite is observed within 5 min of the onset of plasma treatment as confirmed by X-ray diffraction and Raman spectral analysis. The faradaic efficiency of studtite formation is analyzed to estimate the values of hydrogen peroxide yield, 1.23 molecules per incident ion, and the rate constant of the studtite-forming reaction, 4.44 x 107 M-1 s-1. This work is a proof of concept and identifies significant parameters for the future development of a larger scale, higher throughput system.

The effects of water vapor and He ion irradiation on the alteration of particles of the uranyl hydroxide phase metaschoepite, [(UO2)8O2(OH)12](H2O)10, are determined. Raman spectra collected immediately postirradiation revealed the presence of a uranyl oxide phase structurally similar to γ-UO3 or U2O7. Short-term storage postirradiation at elevated relative humidity accelerated formation of the uranyl peroxide phase studtite, [(UO2)(O2)(H2O)2](H2O)2. Experiments examining the degradation of metaschoepite and the hydration of UO3 enabled spectral assignments and identification of reaction pathways. The results provide insights into thermal and radiolytic degradation products in both irradiated uranyl hydroxide phases and uranyl peroxide phases, which follow similar degradation pathways.

Metaschoepite, [(UO2)8O2(OH)12](H2O)10, main-tained in a high relative humidity (RH) environment with air initially transformed into an intermediate phase that subsequently was replaced by the peroxide phase studtite, [(UO2)(O2)(H2O)2]-(H2O)2, over the course of 42 days, as observed using Raman and infrared spectroscopy and powder X-ray diffraction. Addition of atmospheric ozone vastly increased the rate and extent of the transformation to studtite but only in a high-RH atmosphere. Owing to its strong affinity for peroxide, uranyl reacted with hydrogen peroxide as it formed and precipitated stable studtite. In this work, we provide a previously unidentified source of hydrogen peroxide and make a case for the re-examination of storage systems where the consequences of atmospheric ozone are not considered.

The analysis and characterization of uranium dioxide (UO2) under controlled storage conditions can provide insight into potential alteration products and overall stability, which has relevance for nuclear fuel cycle processes, environmental management, and the stability of used nuclear fuel in a repository. In this work, UO2 was monitored as a function of time (6–24 months) and temperature at constant relative humidity (81% RH) in the presence of ammonium sulfate. The morphology of the aged material was described using scanning electron microscopy and a previously published lexicon, while phase changes were confirmed using X-ray diffraction. Additional characterization was carried out using energy dispersive X-ray spectroscopy, transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy to further identify aging effects. Over time, UO2 transitioned to a mixed phase assemblage. Among the alteration was ammonium uranate, a common fuel cycle compound, which was identified from its morphological and spectral characteristics. This work highlights the affinity and persistence of ammonium uranate compounds and emphasizes the need to continue investigating these alteration systems.

Perovskite solar cells (PSCs) based on methylammonium lead iodide (CH3NH3PbI3) have shown unprecedentedly outstanding performance in the recent years. Nevertheless, due to the weak interaction between polar CH3NH3+ (MA+) and inorganic PbI3− sublattices, CH3NH3PbI3 dramatically suffers from poor moisture stability, thermal decomposition and device hysteresis. As such, strong electrostatic interactions between cations and anionic frameworks are desired for synergistic improvements of the abovementioned issues. While replacements of I− with Br− and/or Cl− evidently widen optical bandgaps of perovskite materials, compositional modifications can solely be applied on cation components in order to preserve the broad absorption of solar spectrum. Herein, we review the current successful practices in achieving efficient, stable and minimally hysteretic PSCs with lead iodide perovskite systems that employ photoactive cesium lead iodide (CsPbI3), formamidinium lead iodide (HC(NH2)2PbI3, or FAPbI3), MA1−x−y−zFAxCsyRbzPbI3 mixed-cation settings as well as two-dimensional butylammonium (C4H9NH3+, or BA+)/MA+, polymeric ammonium (PEI+)/MA+ co-cation layered structures. Fundamental aspects behind the stabilization of perovskite phases α-CsPbI3, α-FAPbI3, mixed-cation MA1−x−y−zFAxCsyRbzPbI3 and crystallographic alignment of (BA)2(MA)3Pb4I13 for effective light absorption and charge transport will be discussed. This review will contribute to the continuous development of photovoltaic technology based on PSCs.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTToward Improved Scalability of Cation Exchange Reactions of Metal Chalcogenide NanocrystalsAlexander L. Morris, Chen Lin, Savannah E. Benjamin, V. V. N. Manohar Devarasetty, W. Ryan Tilluck, Edgar I. Lozano, Helene Hamo, Xyan A. Aguilar, and P. Gregory Van Patten*View Author Information Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, United States*P. G. Van Patten. Email: [email protected]Cite this: Chem. Mater. 2017, 29, 16, 6596–6600Publication Date (Web):July 21, 2017Publication History Received15 March 2017Revised20 July 2017Published online7 August 2017Published inissue 22 August 2017https://pubs.acs.org/doi/10.1021/acs.chemmater.7b01065https://doi.org/10.1021/acs.chemmater.7b01065rapid-communicationACS PublicationsCopyright © 2017 American Chemical SocietyRequest reuse permissionsArticle Views1609Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Cadmium selenide,Cadmium sulfide,Cations,Mixtures,Reagents Get e-Alerts