Excited-state properties of lamellar solids derived from metal complexes and hydrogen uranyl phosphate
TL;DR: In this article, the authors summarized the results of intercalative ion exchange reactions with guest cationic species spanning the periodic table and showed that the host lattice exhibits highly efficient green photoluminescence (PL) characteristic of the uranyl (UO 2 2+ moiety).
Abstract: Hydrogen uranyl phosphate (HUP), HUO 2 PO 4 ·4H 2 O, is a layered solid that undergoes intercalative ion-exchange reactions with guest cationic species spanning the periodic table. The host lattice exhibits highly efficient green photoluminescence (PL) characteristic of the uranyl (UO 2 2+ moiety. Structural and optical perturbations of the host and guest generally accompany intercalation reactions. Guest metal complexes have afforded an opportunity to study host-to-guest energy transfer, interlamellar acid-base/precipitation chemistry, interlamellar redox chemistry, and host lattice substitution chemistry. These reactions are summarized in this article.
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01 Jan 2000
TL;DR: To implement biotechnology to treat large areas contaminated with historic waste, the challenges are to gain a better understanding of microbial communities at site and devise effective methods of stimulating or augmenting microbial activities required in situ.
Abstract: This chapter highlights the key steps in the nuclear fuel cycle where biological treatment strategies may replace or augment existing chemical processes. Radionuclide-containing wastes are produced at all steps in the nuclear fuel cycle. The mechanisms of microbial interactions with key radionuclides in the wastes are discussed alongside the possible antagonistic effects of other organic and inorganic species copresented in solution. Although emphasis is placed on the development of "end-of-pipe" treatments, the application of biological agents in the detoxification of already polluted ecosystems via in situ bioremediation is also highlighted. Microorganisms can interact with radionuclides via several mechanisms, some of which may be used as the basis of potential bioremediation strategies. The major types of interaction are summarized in this chapter. Technical challenges associated with large-scale clean-up of highly complex wastes must be overcome prior to the full commercial realization of the technologies currently under consideration. The chapter summarizes the major technical challenges. Since biosorption of uranium has been covered extensively in the literature and since biosorbents relate in general to structural, not metabolic, aspects of the biomass, this chapter notes only a few recent developments. To implement biotechnology to treat large areas contaminated with historic waste, the challenges are to gain a better understanding of microbial communities at site and devise effective methods of stimulating or augmenting microbial activities required in situ.
107 citations
TL;DR: In this paper, a general approach for the encapsulation of a variety of saturated polymers between the layers of MoS2 giving electrically conductive lamellar compounds is reported.
Abstract: A general approach for the encapsulation of a variety of saturated polymers between the layers of MoS2 giving electrically conductive lamellar compounds is reported.
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78 citations
01 Jan 2005
TL;DR: An overview of metal-microbe interactions and how they could be harnessed to clean up metal-contaminated water, soil, and land are described and supported by genomics-enabled studies ongoing in many laboratories worldwide are described.
Abstract: This chapter provides an overview of metal-microbe interactions and describes how they could be harnessed to clean up metal-contaminated water, soil, and land. Biosorption of metals has been reviewed extensively, and this chapter notes only some salient points and recent developments of interest. Biosensors may prove very useful in identifying the need for metal remediation, which will be dictated in many cases by the concentration of bioavailable toxic metals in a given soil or water matrix, and also in defining the end point for bioremediation efforts. The biodegradation of toxic organotin compounds used as biocides and antifouling agents has also received recent attention. Laboratory tests have indicated that the immobilization of metals and radionuclides by bioremediation could be very effective, with removal of contaminants from the mobile aqueous phase to below critical values. Nevertheless, contaminant immobilization caused by bioremediation must be regarded as the retardation of contaminant migration rather than as a permanent solution to the problem. However, driven by the realization that large areas of land contaminated with metal and radionuclides cannot be economically remediated by conventional chemical approaches, significant resources have become available for this research area. Supported by genomics-enabled studies ongoing in many laboratories worldwide, one can expect this research area to develop further in the near future, delivering more robust technologies for the bioremediation of metal-contaminated waters and land.
60 citations
TL;DR: ‘Microbially Enhanced Chemisorption of Heavy Metals’ (MECHM) is proposed to describe this hybrid mechanism of metal bioaccu-mulation via intercalation into preformed, biogenic crystals, and it is noted that MECHM can promote the removal of the transuranic radionuclide neptunium, which is difficult to achieve by conventional methods.
Abstract: A Citrobacter sp. accumulates uranyl ion (UO{sub 2}{sup 2+}) as crystalline HUO{sub 2}PO{sub 4}{center_dot}4H{sub 2}O (HUP), using enzymatically generated inorganic phosphate. Ni was not removed by this mechanism, but cells already loaded with HUP removed Ni{sup 2+} by intercalative ion-exchange, forming Ni(UO{sub 2}PO{sub 4}){sub 2}{center_dot}7H{sub 2}O, as concluded by x-ray diffraction (XRD) and proton induced x-ray emission (PIXE) analyses. The loaded biomass became saturated with Ni rapidly, with a molar ratio of Ni:U in the cellbound deposit of approx. 1:6; Ni penetration was probably surface-localized. Cochallenge of the cells with Ni{sup 2+} and UO{sub 2}{sup 2+}, and glycerol 2-phosphate (phosphate donor for phosphate release and metal bioprecipitation) gave sustained removal of both metals in a flow through bioreactor, with more extensively accumulated Ni. We propose `Microbially Enhanced Chemisorption of Heavy Metals` (MECHM) to describe this hybrid mechanism of metal bioaccumulation via intercalation into preformed, biogenic crystals, and note also that MECHM can promote the removal of the transuranic radionuclide neptunium, which is difficult to achieve by conventional methods. 42 refs., 1 fig., 1 tab.
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