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This research focuses on the spatial and temporal patterns of heavy metals from the Yangtze River estuary and the tidal flat of north Jiangsu. Most heavy metals in the surficial sediments after normalization to Ti decreased seaward at the Yangtze River estuary. The core records showed that the heavy metal variations in the last 50 years were primarily linked to natural weathering input of trace elements. However, significant heavy metal pollution (mainly Ni, Pb, Cd, Cu and As) were in the two study areas, with anthropogenic inventories accounting for 23–40% percent of the total pollution. Sequential extraction showed that Pb, Cu and Ni were present largely in the non-residual fraction, which indicated the potential bioavailability in the study areas. The SEM/EDS together with sequential extraction facilitated the easy tracing of the origin/sources of heavy metals in a simple way in the estuary and the tidal flat. [ABSTRACT FROM AUTHOR]

Abstract In the present study, the macroscopic sorption behaviors and microscopic immobilization mechanisms of Ni(II) at cryptomelane/water interfaces were explored using the combination of batch sorption technique, desorption procedure, theoretical simulation, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) analyses. The good simulation of the pseudo-second-order model on the sorption kinetics data suggests a driving force of chemical sorption rather than mass transport or physical interaction. The sorption trends and uptake mechanisms are obviously related to the solution pH, with cation exchange or outer-sphere surface complexation at an acidic pH of 4.0, inner-sphere surface complexation in both the edge-shared (ES) and double corner-shared (DCS) modes at a neutral pH of 7.0, and precipitation of α-Ni(OH) 2 (s) phase at a highly alkaline pH of 10.0. The gradual increase of Ni(II) sorption amount with solution temperature rising from 293 K to 333 K is consistent with the increased ratio of the weak DCS configuration. The research findings herein can help us better understand the migration and transformation trends of Ni(II) in the manganese mineral-riched aquatic environment. Graphical abstract Image 1 Highlights • Interaction mechanisms of Ni(II) with cryptomelane were explored by combining multiple techniques. • Relative contributions of different uptake processes were verified from ligand extraction data. • Ni(II) binding modes were clearly identified with theoretical simulation and spectroscopic analyses. • Temperature rising enhanced the sorption amount of Ni(II) in double corner-shared binding mode. • Research findings facilitated the assessment of Ni(II) migration and fate in Mn-riched environment. [ABSTRACT FROM AUTHOR]

In this study, the inorganic-organic hybrid of PA/TNTs was synthesized and characterized by using multiple analysis techniques. Batch experiments were conducted to investigate the removal performance of PA/TNTs towards U(VI). The sorption kinetics procedure achieved equilibrium within 6 h. The maximum sorption capacity at 293 K and pH 5.0 was calculated to be 1.16 × 10 −3 mol/g. In addition, the PA/TNTs composite showed a higher sorption selectivity towards U(VI) over many other metal ions. The ionic strength experiments, desorption results, X-ray diffraction (XRD), solid fluorescence, extended X-ray adsorption fine structure (EXAFS) and Fourier transform infrared spectroscopy (FTIR) analysis suggested the predominant sorption mechanism was inner-sphere complexation rather than ion exchange or precipitation. Overall, the synthesized PA/TNTs composite could be utilized as a cost-effective material for the removal of U(VI) from wastewater. [ABSTRACT FROM AUTHOR]

Uranium (U(VI)) pollution comes from the development and utilization of natural minerals. Based on a new concept of ecological restoration of uranium pollution into natural minerals, a new artificial mineralized process was proposed to immobilize uranium (U(VI)) for wastewater decontamination. In this work, three systems of Mg 3 (PO 4) 2 + UO 2 2+, Mg2+ + PO 4 3− + UO 2 2+ and Mg2+ + PO 4 3− + Mg 3 (PO 4) 2 + UO 2 2+ were designed. Batch experiments and theoretical calculation were conducted to study the U(VI) immobilization effectiveness and artificial mineralization mechanisms. U(VI) removal efficiencies reached up to 96% in the pH value of 5.0 in the three systems. Both precipitation and surface adsorption contributed to favorable U(VI) removal in Mg 3 (PO 4) 2 + UO 2 2+, but resulting in U desorption. Precipitation of Mg2+, PO 4 3− and UO 2 2+ into saleeite (Mg(UO 2) 2 (PO 4) 2 ·10H 2 O) crystal contributed to UO 2 2+ immobilization in the Mg2+ + PO 4 3− + UO 2 2+ and Mg2+ + PO 4 3− + Mg 3 (PO 4) 2 + UO 2 2+ systems, resulting in the negligible U desorption. It is due to the crystallization of the Mg(UO 2) 2 (PO 4) 2 ·10H 2 O through precipitation of Mg2+ and PO 4 3− with UO 2 2+ in acidic medium. PHREEQC and Visual MINTEQ fitting confirmed the favorable precipitation of Mg2+ and PO 4 3− with UO 2 2+ into saleeite in acidic medium. Thus, the U(VI) immobilization effectiveness and artificial mineralization mechanism were understood, providing a promising strategy of artificial induced mineralization of Mg(UO 2) 2 (PO 4) 2 ·10H 2 O for U(VI) decontamination in wastewater. [Display omitted] • Artificially mineralization is proposed for immobilizing uranium. • Formation of Saleéite and chernikovite is the fate of uranium immobilization. • Theorical fitting confirmed the mineralization of dissolved Mg2+ and PO 4 3− with UO 2 2+. • The leaching rate of saleéite and chernikovites is negligible. • P/U and Mg/U molar ratios determined the artificially mineralization process. [ABSTRACT FROM AUTHOR]

Barium cerate doped with tetravalent Th is successfully synthesized by a traditional Pechni method. The BaCe 0.7 Th 0.1 Y 0.2 O 3−δ (BCT71) composites were applied to an anode supported coin single cell consisting of Ni-BCT71 anode/BCT71 electrolyte/ BCT71-La 0.7 Sr 0.3 FeO 3−δ cathode. The assembled cell is tested from 600 °C to 700 °C with humidified hydrogen (∼3% H 2 O) as the fuel and the static air as the oxidant. An open-circuit potential of 0.93 V and a maximum power density of 104 mW cm −2 are obtained for the single cell with an interface resistance of 0.98 Ω cm 2 at 700 °C. [ABSTRACT FROM AUTHOR]

Under hydrothermal condition, the decomposition of methanesulfonic acid to sulfate anion is observed, resulting in the formation of a novel thorium sulfate fluoride compound ThF 2 (SO 4 )(H 2 O) ( 1 ). This complex is structurally characterized by single crystal X-ray diffraction, revealing a three-dimensional structure crystallized in the monoclinic space-group P 2 1 / n , where thorium cation is nine coordinated by four SO 4 2− oxygen atoms, four bridging F − , and one H 2 O molecule. The crystal lattice parameters are a = 6.9065(7) Å, b = 6.9256(7) Å, c = 10.5892(11) Å, β = 96.755(2)°, V = 502.98(9) Å 3 , Z = 4. The temperature dependent UV–Vis–NIR absorption spectra and fluorescence spectra were collected from 77 K to 300 K, where the intensities of the peaks varied as a function of temperature. The Raman vibrational spectrum of the samples collected from 100 to 2000 cm −1 shows identical SO 4 2− vibration modes. [ABSTRACT FROM AUTHOR]

Recently, an increasing number of publications concerned on the catalytic oxidation of refractory organic pollutants in wastewater dependent on the iron-based catalysts. Until now, the iron-based catalysts are diversity including Fe2+/Fe3+, ZVI, iron oxides (FeOOH, Fe 2 O 3 , Fe 3 O 4 , FeO), iron sulfides (Fe x S y) and Fe-bimetallic due to various valences and phases. A comprehensive understanding on the synthesis and applications of them as catalysts were little concerned. In this work, the methods for synthesis and control of the size, morphology, crystal phase and chemical valent properties of the iron-based catalysts were reviewed by classifying as Fe2+/Fe3+, ZVI, iron oxides, pyrite, Fe-MOF and Fe-bimetallic. Their applications in Fenton/Fenton-like oxidation, ozonation, wet air oxidation, PMS/PS activation, photocatalytic oxidation etc., for refractory organic pollutants oxidation were summarized. Generation of free radicals for oxidation of refractory organic pollutants in different systems was regarded as the main catalytic mechanisms. Refining controlled growth of size, morphology, crystal phase and chemical valence of iron-based catalysts will be prospective and challenge in synthesis of iron-based catalysts. Co-catalytic reaction will be promising for accelerating the electron transfer for generation of radicals. Quantitative analysis of the free radical is remained the challenge to understand the catalytic oxidation mechanism. We look forward to the fact that this review could inspire the readers to refine the synthesis of iron-based catalysts with special catalytic property for constructing the catalytic oxidation process and to understand the mechanism of degradation of refractory organic pollutants in wastewater. [Display omitted] • Synthesis of iron-based catalysts in various valent were reviewed. • Diversity of iron species resulted in various catalytic oxidation processes. • Electron transfer contributed to the iron induced catalytic oxidation. • Coupling catalytic oxidation with biological is promising for refractory organic pollutants degradation. [ABSTRACT FROM AUTHOR]

With the wide application of nuclear energy and the rapid development of mining, a great quantity of uranium (U(VI)) containing wastewater is inevitably generated. In this work, a facile environmental-friendly coprecipitation method was proposed for the green synthesis of binary layered double hydroxides (Ni–Co LDH W -7), which could be used to efficiently adsorb U(VI) from wastewater. Pseudo-second-order kinetic model and Dubinin-Radushkevich model fitted well with the adsorption of U(VI) on Ni–Co LDH W -7, the maximum adsorption capacity of U(VI) on Ni–Co LDH W -7 was 201.09 mg/g calculated by the Langmuir model. Adsorption equilibrium reached after 30 min, which is a spontaneous and endothermic process. Fourier Transform Infrared Spectrometer (FTIR) and X-ray Photoelectron Spectroscopy (XPS) measurements manifested that the favorable U(VI) extraction on Ni–Co LDH W -7 is mainly ascribed to inner-layer surface electrostatic interaction and complexation, which is dominated by abundant oxygen-containing M-OH and interlayer OH− ions. Briefly, this work provides a facial and environmental-friendly Ni–Co LDH W -7 for removing U(VI) in actual uranium-containing wastewater. [Display omitted] • A facile environmental-friendly coprecipitation method was proposed for green synthesis of Ni–Co LDH W -7. • Adsorption capacity of uranium reached 201.09 mg/g calculated by Langmuir model at pH = 6 and 298 K. • Metal hydroxyl group configuration and the hydroxyl groups contributed to U(VI) binding on Ni–Co LDH W -7. • Ni–Co LDH W -7 showed good stability. [ABSTRACT FROM AUTHOR]

Radioactive iodine-129 (129I) and technetium-99 (99Tc) pose a risk to groundwater due to their long half-lives, toxicity, and high environmental mobility. Based on literature reviewed in Moore et al. (2019) and Pearce et al. (2019), natural and engineered materials, including iron oxides, low-solubility sulfides, tin-based materials, bismuth-based materials, organoclays, and metal organic frameworks, were tested for potential use as a deployed technology for the treatment of 129I and 99Tc to reduce environmental mobility. Materials were evaluated with metrics including capacity for IO 3 − and TcO 4 − uptake, selectivity and long-term immobilization potential. Batch testing was used to determine IO 3 − and TcO 4 − sorption under aerobic conditions for each material in synthetic groundwater at different solution to solid ratios. Material association with IO 3 − and TcO 4 − was spatially resolved using scanning electron microscopy and X-ray microprobe mapping. The potential for redox reactions was assessed using X-ray absorption near edge structure spectroscopy. Of the materials tested, bismuth oxy(hydroxide) and ferrihydrite performed the best for IO 3 −. The commercial Purolite A530E anion-exchange resin outperformed all materials in its sorption capacity for TcO 4 −. Tin-based materials had high capacity for TcO 4 −, but immobilized TcO 4 − via reductive precipitation. Bismuth-based materials had high capacity for TcO 4 −, though slightly lower than the tin-based materials, but did not immobilize TcO 4 − by a redox-drive process, mitigating potential negative re-oxidation effects over longer time periods under oxic conditions. Cationic metal organic frameworks and polymer networks had high Tc removal capacity, with TcO 4 − trapped within the framework of the sorbent material. Although organoclays did not have the highest capacity for IO 3 − and TcO 4 − removal in batch experiments, they are available commercially in large quantities, are relatively low cost and have low environmental impact, so were investigated in column experiments, demonstrating scale-up and removal of IO 3 − and TcO 4 − via sorption, and reductive immobilization with iron- and sulfur-based species. Unlabelled Image • 129I and 99Tc are a risk to groundwater due to toxicity, long half-life, and mobility. • Natural and engineered materials were tested for potential to reduce mobility. • Bismuth oxy(hydroxide) was the most promising material for iodate immobilization. • Anion-exchange resins outperformed all materials for pertechnetate sorption. • Immobilization capacity of material depends on uptake mechanism and reaction product. [ABSTRACT FROM AUTHOR]