An efficient SO2-adsorbent from calcination of natural magnesite

MgO-based adsorbents were prepared by controlling the temperature of magnesite calcination, and the adsorption mechanism of SO2 and these adsorbents were investigated. The obtained adsorbents were characterized by a combination of characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption/desorption analysis and Hammett indicator method. XRD patterns and TEM images revealed that a complete decarbonation of MgCO3 occurred at ca. 650 degrees C, and the crystallinity and crystal size of MgO increased with the increase of calcination temperature. The maximum specific surface area (S-BET = 69.6 m(2)/g) was obtained for the sample calcined at 650 degrees C (M-650), which also had the maximum value of base site density as revealed by the Hammett indicator tests. The adsorption capacity of adsorbents towards SO2 increased with the increase of the base site density and M-650 with the highest base site density displayed the maximum adsorption capacity. The adsorption of SO2 onto MgO was mainly chemisorption, resulting in the formation of magnesium sulfite and magnesium sulfate on the surface of MgO-based adsorbents, as indicated by X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared (FTIR) spectra. The chemically bound SO2 could be desorbed at ca. 435 degrees C as revealed by thermal analysis under N-2. This study suggests that calcination of naturally occurring magnesite is highly amenable to obtain efficient SO2 adsorbents