Non-uraninite products of microbial U(VI) reduction

A promising remediation approach to mitigate subsurface uranium contamination is the stimulation of indigenous bacteria to reduce mobile U(VI) to sparingly soluble U(IV). The product of microbial uranium reduction is often reported as the mineral uraninite. Here, we show that the end products of uranium reduction by several environmentally relevant bacteria (Gram-positive and Gram-negative) and their spores include a variety of U(IV) species other than uraninite. U(IV) products were prepared in chemically variable media and characterized using transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) to elucidate the factors favoring/inhibiting uraninite formation and to constrain molecular structure/composition of the non-uraninite reduction products. Molecular complexes of U(IV) were found to be bound to biomass, most likely through P-containing ligands. Minor U(IV)-orthophosphates such as ningyoite [CaU(PO(4))(2)], U(2)O(PO(4))(2), and U(2)(PO(4))(P(3)O(10)) were observed in addition to uraninite. Although factors controlling the predominance of these species are complex, the presence of various solutes was found to generally inhibit uraninite formation. These results suggest a new paradigm for U(IV) in the subsurface, i.e., that non-uraninite U(IV) products may be found more commonly than anticipated. These findings are relevant for bioremediation strategies and underscore the need for characterizing the stability of non-uraninite U(IV) species in natural settings.     

On the Influence of the Functionalization of Graphene Nanoplatelets and Glass Fiber on the Mechanical Properties of GFRP Composites

Applied Composite Materials - This work presents the influence of functionalised graphene nanoplatelets (f-GnPs) and functionalised glass fibers (f-fiber) on the tensile strength and the fracture...     

Hydrothermal Synthesis and Photocatalytic Activity of Mn3O4 Nanoparticles

Topics in Catalysis - In this work, Mn3O4 nanoparticles (NPs) were synthesized by hydrothermal method using the precursor manganese acetate and polyvinyl alcohol (PVA) as...     

Microbial technologies for heavy metal remediation: effect of process conditions and current practices

Clean Technologies and Environmental Policy - Heavy metal (HM) contamination is a persisting environmental problem in many countries. The major sources of soil contamination due to heavy metals...     

The influence of thermal barrier coating on an LHR engine fueled by soybean biodiesel blended with various additive spectrums: Performance,combustion, and emission analysis

The novelty of this research work deals with green synthesized nanoadditives (5% of graphene, carbon nanotubes, and carbon black), oxygenated additives (5% of n-butanol, n-heptane, and n-pentanol), and then the test fuels are prepared by blending of 20% of soybean biodiesel and 70%, 80%, and 100% of premium diesel. The experimental outcomes revealed that the Nickel Chromium Aluminum (NiCrAl-120 micron), partially stabilized zirconia, and titanium dioxide ceramic composites at about 400 microns achieve the thermal barrier coat of low heat rejection (LHR) engine parts by the air-plasma spray method. Compared with Blend B, green synthesized carbon black (5%), premium diesel (70%), and n-pentanol (5%) mixed soybean biodiesel (20%) fuel (Blend E) tested on the LHR engine achieved 4.90% higher brake thermal efficiency and 25.31% lower brake-specific fuel consumption at peak load owing to the presence of an oxygenated agent (n-pentanol) in the fuel blend, which minimizes carbon deposition. The carbon monoxide, hydrocarbon, NO_x, and smoke emissions were reduced by 25.58%, 29.41%, 5.06%, and 7.75% when compared to Blend B at peak load. Then, the in-cylinder pressure and heat release rate were found to be 4.52% and 8.87% higher for Blend E at peak load compared to Blend B. This was because the mix of oxygenated additive and carbon black bio-based nanofuels made the combustion process go faster. These fuel blends were tested on LHR diesel engines at various load conditions.     

A secure and robust color image watermarking using nature-inspired intelligence

Neural Computing and Applications - The security of multimedia information is a prime concern in the present digital world. As a remedy, a robust color image watermarking in the transform domain...