Chelated iron processes Such as LO-CAT and SulFerox(SM) utilize ferric chelate solutions for the oxidation of hydrogen sulfide to form aqueous suspensions of sulfur. During the ferrous chelate reoxidation, dioxygen reduction intermediates are believed to initiate oxidative degradation reactions of the aminocarboxylate ligands used in the process. This Study shows that the same degree of Fe(II) oxidation (regeneration) can be achieved with reduced ligand degradation by decreasing the rate at which 0, is Supplied to a reactor. This apparent mass transfer limited degradation is explained in terms of dioxygen reduction intermediate formation and reactions. A model for bubble Column regeneration was used to predict local partial pressures of dioxygen for a number of reactor Configurations. Such analysis predicts several changes in regenerator design which could Substantially reduce the amount of chemical usage in such a process. Changes include reduction of the stoichiometric excess of air, use of multiple reactors, and recycling of spent air.