Effect of calcite on desulfurization and denitration performance of activated coke and its mechanism

Different contents of calcite (CaCO₃) were loaded on a deminerized Ningxia anthracite during the activated coke (AC) preparation, the influence of which on the preparation, desulfurization and/or denitrification of AC was investigated. The results show that calcite can regulate the pore structure and surface chemistry of AC. The total specific surface area and the micropore specific surface area decrease from 746 m²/g and 645 m²/g to 408 m²/g and 244 m²/g, respectively, when the calcite addition is up to 8%. The total volume and the micropore volume also decrease with the increase in the content of calcite, while the volume of mesopores and macropores increases. As the calcite addition rises, the oxygen-containing functional group and π−π* are increased linearly, and the sulfur capacity of AC first increases and then decreases during single desulfurization, the NX-2%CaCO₃-AC having the best desulfurization capacity (84.0 mg/g). The increase in the content of π−π* by the addition of calcite promotes the SO₂ oxidation process, and also promotes the denitrification process, the NO conversion (16.9%) with the addition of 2%CaCO₃ is 1.14 times higher than that of AC (7.9%), mainly owing to the increase in the number of basic groups. However, during simultaneous desulfurization and denitrification, the presence of CaO in the AC promotes the sulfur capacity but decreases the NO removal efficiency due to the competitive adsorption and ammonium salt generation.