Pacific Northwest National Laboratory

About: Pacific Northwest National Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Catalysis & Aerosol. The organization has 11581 authors who have published 27934 publications receiving 1120489 citations. The organization is also known as: PNL & PNNL.

Effects of pH on Heavy Metal Sorption on Mineral Apatite

Abstract: The sorption of aqueous Pb, Cd, and Zn onto a mineral apatite from North Carolina was investigated in relation to a wide range of pH. The effects of pH on solid-phase precipitation were particularly emphasized. The heavy metals were applied as single or multiple species. Solution pH greatly affected metal sorption mechanism by apatite and metal−apatite reaction products. The sorption of aqueous Pb was primarily through a process of the dissolution of apatite followed by the precipitation of variable pyromorphite-type minerals under acidic condition or of hydrocerussite [Pb3(CO3)2(OH)2] and lead oxide fluoride (Pb2OF2) under alkaline condition. Otavite (CdCO3), cadmium hydroxide [Cd(OH)2], and zincite (ZnO) were formed in the Cd or Zn system, especially under alkaline condition; while hopeite [Zn3(PO4)2·4H2O] might precipitate only under very acidic condition. Alternative sorption mechanisms other than precipitation of the crystalline phases were important in reducing Cd and Zn concentrations by the apatit...

What is microbial community ecology

Abstract: The activities of complex communities of microbes affect biogeochemical transformations in natural, managed and engineered ecosystems. Meaningfully defining what constitutes a community of interacting microbial populations is not trivial, but is important for rigorous progress in the field. Important elements of research in microbial community ecology include the analysis of functional pathways for nutrient resource and energy flows, mechanistic understanding of interactions between microbial populations and their environment, and the emergent properties of the complex community. Some emergent properties mirror those analyzed by community ecologists who study plants and animals: biological diversity, functional redundancy and system stability. However, because microbes possess mechanisms for the horizontal transfer of genetic information, the metagenome may also be considered as a community property.

Electron transport via polaron hopping in bulk Ti O 2 : A density functional theory characterization

Abstract: In this work we describe our use of Marcus theory to model the electron transfer process in TiO2. Electron transport is described by a polaron model, whereby a photo-excited electron is localized at a Ti4+ site and hops to an adjacent Ti4+ site. We obtained the relevant parameters in Marcus theory (namely the activation energy ΔG*, the reorganization energy λ, and the electronic coupling matrix elements Vab) for selected crystallographic directions in rutile and anatase, using periodic DFT+U and Hartree-Fock cluster calculations. The DFT+U method was necessary to correct for the ubiquitous electron self-interaction problem? in DFT. Our results give non-adiabatic activation energies of similar magnitude in rutile and anatase, all near 0.3 eV. The electronic coupling matrix element, Vab, was determined to be largest for electron transfer parallel to the c direction in rutile, with a value of 0.20 eV, while the other directions investigated in both rutile and anatase gave Vab values near 0 eV. The results are indicative of adiabatic transfer (thermal hopping mechanism) in rutile and of diabatic transfer (tunneling mechanism) in anatase. This work was supported by the Office of Basic Energy Sciences of the Department of Energy, in part by the Chemical Sciences programmore » and in part by the Engineering and Geosciences Division. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less