High adsorption activated calcium silicate enabling high-capacity adsorption for sulfur dioxide

Abstract

Porous materials with developed pore structures are vital to obtaining high adsorption properties. Fly ash is rich in silicon with high porosity and a large specific surface area, and it is an excellent precursor for porous silica-based sorbents. Here, we report activated calcium silicate (ACS), which was prepared by fly ash and a two-step hydrothermal method to greatly enhance the activity of the pozzolanic reaction. Of importance, the adsorption capacity of ACS for sulfur dioxide (SO₂) is up to 38.2 mg g⁻¹. The results show that ACS has a honeycomb-like structure with high porosity and a large specific surface area. The adsorption process of SO₂ on ACS involves the coexistence of physical and chemical adsorption. In particular, SO₂ is first attached to the surface of ACS, and then diffused into the interior of ACS. At the same time, oxygen and water vapor are adhered to the surface of ACS, and SO₂ is further oxidized to sulfuric acid and sulfate. In addition, the cycling performance of ACS can remain 71.2% through the adsorption–regeneration cycle for 20 cycles, forecasting the excellent cycle stability of ACS. The ACS material can be considered a new type of adsorbent with great development potential in the removal of fly ash and sulfur dioxide from coal-fired power plants.