Effects of Surface Features on Sulfur Dioxide Adsorption on Calcined NiAl Hydrotalcite-like Compounds

The hydrotalcite-based NiAl mixed oxides were synthesized by coprecipitation and urea hydrolysis approaches and employed for SO(2) removal. The samples were well characterized by inductively coupled plasma (ICP) elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N(2) adsorption/desorption isotherm analyses. The acid-base properties were characterized by pyridine chemisorption and CO(2) temperature-programmed desorption (TPD). The calcined NiAlO from the urea method showed excellent SO(2) adsorption and its adsorption equilibrium showed a type I isotherm, which significantly improved the adsorption performance for low-concentration SO(2). Both the physical structure and the acidic-basic sites were found to play important roles in the SO(2) adsorption process. In situ Fourier transform infrared spectroscopy (FTIR) investigation revealed that adsorbed SO(2) molecules formed surface bisulfite, sulfite, and bidentate binuclear sulfate. The mechanisms for SO(2) adsorption and transformation are discussed in detail