Mechanisms of Capturing Mercury with Novel Nano-Structured Sulfide Stabilizers

Professor Shih, Kaimin   (Principal Investigator (PI))

36

2017-01-01

844559

Mechanisms of Capturing Mercury with Novel Nano-Structured Sulfide Stabilizers

Hazardous Metal, Leaching Behavior, Mineral Surface, Nanostructure, Quantitative XRD

Environmental

Engineering (E)

17257616

General Research Fund (GRF)

2016

Completed

1) Nano-structured metal sulfides will be fabricated using different precursors and synthesis methods. The crystal growth of the sulfide products and the development of nano-structural features will be systematically observed through high-resolution scanning and transmission electron microscopies (SEM and TEM). Quantitative material characterizations, for instance, of the surface area, particle/pore size distributions and surface roughness using atomic force microscopy (AFM), will further assist in confirming the achievement of the material design goals; 2) Our unique QXRD analysis skill (using Rietveld refinement method with the fundamental parameter approach and an amorphous content quantification protocol) will then report the quantities and structural characteristics (lattice parameters, cation distribution, crystal size, etc.) of different sulfide phases in the stabilizers through high-resolution diffraction data. The amorphous content quantification will use commonly available calcium fluoride and silicon carbide as internal standards to assist the development of a reliable quantification method for the amorphous content in multiple-phase sulfide samples; 3) The mercury removal performances of the fabricated sulfide products will be assessed using self-regulating fixed-bed reactors, and the influences from different gas components and process operation parameters will be evaluated. By combining material structural features and their mercury adsorption characteristics, key factors related to the effective enhancement of mercury capture by sulfide surfaces will be revealed. Moreover, the uses of surface-sensitive characterization techniques such as X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to observe the reacted samples will further provide direct evidence to support the discussion of reaction behavior; 4) In addition to the observation of mercury capture behavior, the subsequent stabilization mechanisms occurring on the sulfide surfaces will be evaluated through leaching and chamber reemission experiments. Electron microscopies and surface-sensitive characterization tools will again provide direct comparisons for mechanistic analyses. Moreover, molecular interaction simulations based on the density functional theory and the material property parameters will be carried out to assist in the comparison and explanation of the observed mercury transport and reaction behavior on the sulfide surfaces; 5) Based on the mechanistic understanding of the mercury adsorption and stabilization behavior on the different sulfide surfaces, techniques will be elaborated for fabricating the desired nano- and micro-structural features necessary to create efficient stabilizer products, together with designs for their subsequent beneficial use strategies. The optimal operational parameters associated with different stabilizer designs will also be provided to extend the technological flexibility to different practical application requirements. Overall, the implementation of this project will facilitate the goals of enhancing mercury removal from combustion flue gas and reliably immobilizing mercury with the new sulfide stabilizers through a scientifically sound and economically feasible strategy.