Methods for regenerating amorphous iron oxide hydroxide after being used as desulfurizer by (1) grinding a waste mixture into waste powder, wherein the waste mixture results from use of the composition comprising amorphous iron oxide hydroxide as desulfurizer; (2) preparing the waste powder into a suspension and charging the suspension with a gas containing oxygen to obtain a slurry comprising amorphous iron oxide hydroxide and elemental sulfur; and (3) placing the slurry or a solid resulting from filtering the slurry into a container and charging the slurry or the solid with air so that the elemental sulfur floats and the amorphous iron oxide hydroxide precipitates.