Co0 anchored on Co/N co-doped porous carbon material induces H migration to accelerate sulfite oxidation and Hg(ii) adsorption in flue gas desulfurization

Abstract

The low oxidation rate of (NH₄)₂SO₃ and the coexistence of Hg(II) in desulfurization liquids restrict sulfur recovery for use as a high-value fertilizer. In this study, zero-valent cobalt anchored on Co/N co-doped porous carbon (Co⁰@Co–N-C) was developed, realizing efficient (NH₄)₂SO₃ oxidation and simultaneous Hg(II) removal by harnessing the synergistic effect of the super-dispersed Co–N and Co⁰ sites on the Co⁰@Co–N-C material. The production of reactive oxygen species (˙O₂⁻, ˙OH) was induced via the activation of dissolved oxygen and water molecules by the Co⁰ sites, thus promoting the (NH₄)₂SO₃ catalytic oxidation. Adsorption traps (Co–O–H and Co–O–O–H) were formed via H cracking and migration from water molecules to the Co⁰ sites, therefore achieving efficient Hg(II) removal. By this means, an (NH₄)₂SO₃ oxidation rate of 0.0944 mmol L⁻¹ s⁻¹ was achieved, 7.87 times that achieved under non-catalytic conditions, and an Hg(II) removal efficiency of 96.66% was reached. By regulating the catalytic and adsorption sites on the bifunctional Co⁰@Co–N-C material, the sulfur recovery from the desulfurization liquid was ensured, a finding that is of great significance for the control of multiple pollutants in coal-fired power plant flue gas.