Synchronous Catalysis of Sulfite Oxidation and Abatement of Hg2+ in Wet Desulfurization Using One-Pot Synthesized Co-TUD-1/S

Abstract Cobalt-based catalysts can promote sulfite oxidation to recover the valuable byproducts formed during wet magnesia desulfurization. However, Hg(II) in the desulfurization slurry degrades the quality of reclaimed products and poses considerable environmental risk. Here, a bifunctional sulfur-doped catalyst/adsorbent, Co-TUD-1/S, is prepared through one-pot synthesis, in which the sulfur site is designed for trapping aqueous Hg2+. The catalytic rate of Co-TUD-1/S for MgSO3 is 0.083 mmol/L/S, which is 10.4 times of that under non-catalytic condition, the removal efficiency of Hg2+ is higher than 90%. The isothermal models and kinetic models for the adsorption of Hg2+ are well-fitted to the Langmuir model and pseudo-second-order model, respectively, and the maximum adsorption capacity of experimental data is 96 mg/g. The characterization results confirm that Co3O4 is functioned as the active catalysis site, and the formation of S–Hg bonds plays a crucial role in Hg2+ capture. Density functional theory calculations reveal that the Co site is more likely to combine with sulfite rather than Hg2+, which reduces the interference of absorbed Hg2+ on the catalytic activity of Co. Specialization and cooperation between the catalysis site of –Co and adsorption site of –S are realized. The results reveal that the use of Co-TUD-1/S is a feasible strategy for improving wet desulfurization efficiency.