(215r) An ATR-FTIR Spectroscopic Approach for Measuring Active Functional Groups in Arsenic and Selenium Stabilization in Sulfur Environment

Arsenic and selenium are widely distributed in the environment and are found in wastewater discharge from oil and gas industries. These sources must be controlled to reduce adverse effects of these contaminants on human health and the environment. Arsenic and selenium are present in water in several different forms depending on the pH and oxidation potential of the water. Reductive stabilization would immobilize arsenic or selenium by reducing it to lower oxidation state and precipitate it as low-solubility solids. This study is to investigate the reduction of arsenic and selenium and subsequent precipitation of elemental arsenic and selenium in sulfidic solutions. Se(0) is relatively immobile and has low toxicity, while Se(IV) and Se(VI) are toxic. The residuals containing Se(0) will be stable and highly resistant to releasing Se when disposed. Arsenic sulfide precipitates in sulfate-reducing conditions at low pH has been reported. The overall goal of this project is to develop fundamental information on the behavior of reductive stabilization of arsenic and selenium to stable elemental (solid) forms in sulfidic environments. In this study, the rapid-scan attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy was utilized to investigate the oxidation states of arsenic and selenium in sulfur solutions. The experimental data of ATR-FTIR indicated that rapid-scan FTIR is an effective method for quantifying the change of significant functional groups regarding As and Se in liquid phase and solid phase. The effect of pH or different reducing agents on the significant functional groups were studied using ATR-FTIR with the observation of As or Se amount that involved in the solid formation and macroscopic examination (Scanning electron microscopy with energy-dispersive X-ray spectroscopy).