Microscopic synchrotron X-ray analysis of mercury waste in simulated landfill experiments

Mercury enters into the environment or waste streams because it is present as an impurity in natural minerals. Mercury must be appropriately managed as an hazardous waste. In this study, a waste layer of artificial mercury sulfide mixed with incinerator ash and sewage sludge compost in a simulated landfill experiment for 5 years was analyzed using microscopic synchrotron X-ray to obtain basic knowledge of mercury behavior in a landfill. Mapping by synchrotron X-ray revealed the distribution of mercury-containing particles in the waste layer. In most cases, the movement of mercury sulfide was not considered significant even within a microscopic range; however, water flows could enhance the movement of mercury sulfide particles. When disposing of mercury sulfide, “concentrated placement” or solidification, rather than mixing with other wastes, was more effective at preventing mercury leaching in lysimeters. The chemical form of mercury sulfide in each lysimeter was confirmed by X-ray absorption fine structure (XAFS) analysis, which showed that most of the mercury was present as metacinnabar and had not undergone any changes, indicating that it was extremely stable. The microscopic synchrotron X-ray analysis proved very useful for studying the behavior of mercury waste in a simulated landfill experiment

Conference -ISSS-5 - The EXAFS Debye-Waller Factors of the Tellurium Nanoparticles *

The Debye-Waller factors obtained by EXAFS analysis of the trigonal Te (t-Te) and the Te nanoparticles are analyzed by a Debye model. In t-Te the Debye temperature (ΘD) of the intrachain interactions is about two times higher than that of the interchain atomic interactions. The ΘD for the intrachain interactions of the Te nanoparticles is higher than that of t-Te, but ΘD for the interchain interactions of the Te nanoparticles is lower than that of t-Te. The reduction of the interchain interactions for the Te nanoparticles would induce the change of the Debye temperatures

Evaluation of the Electronic and Local Structure of Mn in Proton-Conducting Oxide, Ca(Zr,Mn)O3-δ, To Elucidate a Direct Hydrogen-Dissolution Reaction

The protonation mechanism in Mn-doped CaZrO3 (CZM), which involves a direct hydrogen dissolution from the surrounding H2 gas, was investigated by thermogravimetry (TG) and X-ray absorption spectroscopy (XAS). The TG results implied the formation of oxygen vacancies in a H2 atmosphere. The Mn K-edge XAS spectra indicated a reduction of the Mn ions and local structure variations around the Mn ion, but the Zr K-edge spectra were independent of the surrounding atmosphere. The amount of oxygen vacancies was smaller with respect to the reduction of the Mn ions, suggesting direct dissolution of hydrogen. Unlike many typical perovskite-type proton conductors, protonation by direct dissolution of hydrogen and not hydration was the predominant reaction in Mn-doped CaZrO3. Our experimental results demonstrated that the hydration reaction was suppressed because the oxygen vacancy was stable in the distorted ZrO6 symmetry in the CaZrO3 crystal host, whereas protonation proceeded by the direct dissolution of hydrogen stabilizing near the Mn ions in the interstitial sites at the distorted MnO6 octahedron symmetry. The experimental results showed that the structural configurations around dopants play important roles in the stabilization of protons in perovskite-type CZM materials. We demonstrated a new group of proton conductors that can overcome issues with conventional proton conductors by utilizing the direct hydrogen dissolution reaction

Investigation of cathodic reaction in SOFCs and PCFCs by using patterned thin film model electrodes

In recent years, fuel cells operating at relatively high temperatures, such as solid oxide fuel cells (SOFCs) using an oxide ion conducting electrolyte and proton ceramics fuel cells (PCFCs) using an proton conducting electrolyte, attract attentions as high-efficient energy-conversion devices. For further enhancements of the performance and the durability of SCFCs and PCFCs, it is essential to understand the electrode reactions. In particular, the knowledge on the dominant reaction path in the electrodes would help us to optimize the material and the microstructure of the electrode. Please click Additional Files below to see the full abstract

Pressure-induced polyamorphic transition in the CaAl2O4 glass

In situ high-pressure ultrasonic velocity measurements of CaAl2O4 glass reveal abrupt irreversible discontinuities in the elastic wave velocities at ∼8–10 GPa. Total structure factor and pair distribution functions measured by synchrotron x-ray diffraction show a rapid change in the intermediate range structure attributed to a rearrangement of calcium ions over this narrow pressure region. Atomistic models obtained from molecular dynamics simulations reveal that this intermediate range structure is explained by a transition of Ca–O void radius distribution from a bimodal distribution with peaks at ∼2.1 and ∼2.4 Å to a single distribution centered at ∼2.1 Å. These abrupt structural changes involving the rapid increase in elastic wave velocity are markedly different to the continuous transformations observed in conventional network-forming glasses, such as SiO