As-containing nanoscale phases on iron sulfides (Devon Renock)

A challenge in identifying As-containing growth phases is their nanoscale dimensions.  High-angle annular dark-field STEM (HAADF-STEM) and elemental mapping using EDS-STEM were used in this study because of their improved spatial resolution compared to traditional TEM.  STEM shows variation in the distribution of As-rich nanoparticles depending on the pH of the solution.  The results complement our knowledge of As removal from solution derived from macroscopic sorption experiments in anoxic environments.  In order to study the dynamics of As sorption on iron sulfide minerals, we used scanning force microscopy (SFM) in an electrochemical cell.  Real-time observations of crystal growth were made over a wide range of pH, As concentration, and redox potential to show how solution conditions affect the molecular level processes.  A concise description of molecular level processes obtained from surface probe and STEM techniques can be used to improve macroscopic prediction models for environmental remediation of As. These results are presented at the ACS conference.