I think bagging it and throwing it in the trash would suffice. I wouldn't deem it to be toxic, it's mostly sodium usually.
drain any water. Tthe remaining ice melt is probably in a block- hit with a hammer to break it up. Dispose of by using on icy sidewalk next winter or givee to a neighbor.
Does anyone know what the protocol is for disposing of the stuff you use to deice your sidewalks? I have an old carton of it that has absorbed water. Can it just be tossed in the trash?