Bifunctional Redox Iron/Cerium (Hydr)oxide Process for H2S Removal from Pulp and Paper Emissions

Abstract

Hydrogen sulfide is the most abundant contaminant among the total reduced sulfur (TRS) quartet in the kraft mill atmospheric emissions. An advantage of the association of oxygen with TRS in the pulp and paper effluents is exploited in a new bifunctional redox scrubbing process based on iron chemistry for the removal of hydrogen sulfide. As synthesized iron/cerium (hydr)oxide composite materials were tested at ambient and alkaline conditions in an agitated batch reactor for oxidizing dissolved bisulfide (HS-) in both aerobic and anoxic environments. Polysulfides and thiosulfate were the main detected reaction products. The presence of dissolved oxygen contributed to the sustained active surface iron sites regeneration thereby improving significantly HS- removal. Testing the material in three-cycle bisulfide oxidation without reactivation and in the presence of oxygen demonstrated its long-term efficiency.