It was said that this method can raise the utilization ratio of pyrite cinder, nevertheless there was not only oxidizing reaction but also reducing reaction in the manufacturing process of PFS. So it will result in longer producing period and higher consumption, and its popularization and application will be very difficult, too. 

2.2 Manufacture of PFS with other slags containing iron

    Siderite, magnetite ore, iron mud, natural iron sand and open-hearth furnace dust^[25-28] are also the raw materials of PFS besides pyrite cinder. The contents of ferriferrous oxide and ferric oxide are high in them, too.

    Literature [26] had obtained better result in the manufacture of PFS using iron mud. Iron mud is the waste produced in the producing process of dye mediums. Its main component are ferriferrous oxide and a little ferric oxide, ferrous oxide, and iron besides. In China, the treatment method of iron mud is generally to store up or to bury. This causes easily environmental pollution again, and the useful resource in iron mud is also wasted. It is a good way of waste comprehensive utilization for iron mud to be used as the raw material of PFS.

    Natural iron sand is a kind of rich mineral resources of the Dabieshan Mountains area. Total iron content is 59.6% in it, and ferric content is 41.1%. It is a good raw material of preparing PFS. Literature [27] reported, using natural iron sand and sulfuric acid as the raw materials, high concentration PFS(220g/L) could be made through pickling, oxidizing, and polymerizing. Then , the liquid PFS was concentrated into solid by spray-drying process.

    Open-hearth furnace dust is another waste used also to manufacture PFS. It is the smoke and dirt in the open-hearth furnace steelmaking waste gas. The content of ferric oxide is more than 90% in it. Literature [28] reported that the dust could be used as the raw material of PFS: Firstly, the dust was dissolved in alkali solution for removing some impurity in it. The content of ferric oxide was more than 99.5% in the dust purified. Then PFS could be made through acid dissolving, hydrolysis and polymerization. When the PFS was used to treat washing waste water of blast furnace gas, the treated efficiency was very good. Moreover, because there is not other harmful ion in the PFS, it is very suitable for the PFS to treat drinking water.

    In other reports, waste residue containing ferric oxide was used to manufacturing PFS, too. Under certain temperature and pressure, PFS c

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