Oxidative absorption of H₂S and O₂ by iron chelate solutions

Abstract

Abstract Hydrogen sulfide is oxidized to elemental sulfur by ferric ion chelated with nitrilotriacetic acid (NTA) in aqueous solution at pH 3.5 to 4.5. The reaction appears to be fast relative to gas‐ and liquid‐phase diffusion, and the transfer of H 2 S from a gas stream is correlated well by the theory of absorption with instantaneous chemical reaction. The ferrous ion formed in this reaction may be reoxidized with oxygen absorbed from a stream of air. The presence of NTA catalyzes the reaction of O 2 and Fe 2+ in the same pH range, and diffusion is again controlling. Design calculations based on laboratory data for both absorption steps show that cocurrent gas‐liquid contactors are advantageous for achieving high reaction rates (e.g., ∼99.99% H 2 S removal), high gas velocities (10 to 20 m/s), low pressure drops [1 to 3 kPa (10 to 30 cm H 2 O)], and moderate column heights (10 to 15 m).