Preparation and Characterization of Activated Semi-Coke used in SO2 Removal

Sulfur dioxide emitted from flue gas is one of the key precursors to acid rain and is a major environmental pollutant. Activated carbon-based materials are efficient for low temperature removal of SO₂ from flue gas. The physical and chemical characteristics of activated carbon- based material play an important role in SO₂ removal. In this paper, the activated semi-cokes used in SO₂ removal were prepared from lignite semi-coke by high-pressure hydrothermal treatment. The SO₂ removal performances for raw semi-coke and the activated semi-cokes were test in a fixed bed reactor. The compositions, surface acid-base properties, surface functional groups and pore structure for raw semi-coke and the activated semi-cokes were characterized by means of proximate analysis, elemental analysis, acid-base titration, FTIR and N₂ isothermal adsorption methods. The modification of high-pressure hydrothermal treatment can open up the closed pores in raw semi-coke, which lead to heighten micro-pore volume content, special area, total pore volume of the activated semi-cokes. The modification of high-pressure hydrothermal treatment results in the vaporization of oxygen-containing acidic functional groups, which raises the content of basic functional groups on the activated semi-cokes. The hydrothermal treatment can increase the SO₂ removal efficiency and capacity for the activated semi- cokes.