MgO, CaCO3 and zeolite composite coatings for the removal NO2, SO2 and CO

Air pollution control requires low-cost materials that can remove toxic gases under ambient conditions. In this study, two binary composite coatings, CaCO 3 /MgO and CaCO 3 /zeolite, were prepared from commercial powders by additive free aqueous drop-casting on glass and compared for the removal of NO 2 , CO, and SO 2 . The crystalline phases of the composite coatings were examined by X–ray diffraction (XRD), the morphology and vibrational properties of the starting powders by field–emission scanning electron microscopy (FE–SEM) and Raman spectroscopy, and the textural properties of the individual powders by N 2 physisorption (Brunauer–Emmett–Teller, BET), which showed porosity dominated by interparticle voids. Gas removal was evaluated in a static 10 L chamber at 25°C and 50% relative humidity, using the same coated area, dry mass, and geometry for both composites. Both coatings reduced the concentrations of all three gases within 50–80s. CaCO 3 /MgO showed higher removal efficiency than CaCO 3 /zeolite for NO 3 , CO, and SO 2 . The superior performance of CaCO 3 /MgO is attributed to the basic surface sites of MgO, which interact with acidic gases. These results indicate that low–cost CaCO 3 /MgO coatings are promising for air purification, while single component and multi–concentration studies are needed to clarify synergistic effects and maximum capacities.