Tailoring of transition metal Mn-Ni doped acid-modified activated carbon for efficient SO2 removal

The desulfurization performance for Mn-Ni supported on activated carbons (Mn-Ni/NAC) calcined at different temperatures varies considerably. The physicochemical properties of Mn-Ni/NAC have been investigated by a series of characterization studies. The moderate calcination temperature contributed to a larger surface area and abundant oxygen-containing functional groups (C = O), thus provided more anchoring sites for the dispersion of Mn 2+ and Ni 0 species. The optimal Mn-Ni/NAC-700 exhibited superior desulfurization performance, achieving breakthrough sulfur capacity and breakthrough time of 287 mg/g and 531 min, respectively. The nucleophilic C = O groups served as active sites for chemically absorbing SO 2 . Ni 0 could serve as an oxygen activator, and promote the transfer of oxygen molecules to oxidize SO 2 . During the desulfurization, SO 2 adsorbed on the C = O groups gradually mainly converted into sulfate (SO 4 2− ). This conversion process was closely linked to the decrease of surface C = O groups and the formation of C–O groups. As the reaction proceeds, reaction products (SO 4 2+ ) begin to accumulate, blocking the pore channels of the catalyst and generating MnSO 4 , resulting in catalyst deactivation. This work will guide the design of high-performance activated carbon-based adsorbents suitable for practical applications.