Oxidation of iron sulfide and surface-bound iron to regenerate granular ferric hydroxide for in-situ hydrogen sulfide control by persulfate, chlorine and peroxide

Hydrogen sulfide emission from sediments in storm drainage networks, estuaries and marine seafloor is a nuisance. The regeneration of the GFH for reuse is crucial to make dosing granular ferric hydroxide (GFH) an effective, long-lasting solution than doing liquid oxidants to the control of sedimentary hydrogen sulfide. This paper investigated the oxidation of iron sulfide and surface-bound iron compounds to regenerate GHF using persulfate, chlorine and peroxide for the in-situ control of hydrogen sulfide. The hydrogen sulfide removal capacities of virgin, persulfate, chlorine-and peroxide-regenerated GFH were 68.34, 77.49, 67.87 and 57.59 mg S/g, respectively. The recovery of the capacities was mainly attributed to the oxidation of iron sulfide, surface-bound Fe(II) and released Fe2+ to amorphous ferric hydroxides. Iron sulfide was mainly oxidized to sulfate (SO42-) (97.8%) by persulfate, and to elemental sulfur (S(0)) (5.8 and 25%), thiosulfate (S2O32-) (27.7 and 11.3%) and SO42-(66.5 and 63.7%) by chlorine and peroxide, respectively. In addition to the oxidation by persulfate, the reaction between persulfate and the surface Fe(II) compounds also generated sulfate radicals and hydroxyl radicals, which enhanced the oxidation of the iron sulfide and surface-bound iron compounds on the GFH surface and regenerated GFH more completely.