| This paper tends to prepare polymers of ferric-polysilicate (PFS), study their flocculation characteristics and their depression effect on coal-pyrite, and find some action mechanisms between PFS and minerals employing zeta potential and XRD measurement.Polymers of ferric-polysilicate (PFS) with different Fe/Si mole ratio were prepared in laboratory with a HC1 consumption predetermined according to the titration curve of silicate glass. The stability of these PFS is proved to be perfect and can be stored over ten months. During the preparation of PFS, the activation of silicate glass seems to be critical. Hydrochloric acid should be added quickly at one time with its consumption strictly controlled as to ensure that pH of the solution does not exceed 3.During the research of flocculation characteristics for PFS using kaolin as an object to be flocculated, PFS showed perfect effect on the flocculation of kaolin suspending liquid. The regular effect of Fe/Si mole ratio, curing time and PFS consumption on the supernate transmittance and the ultimate floccules volume was studied systematically. It was found that each PFS has an effective consumption range, and a most effective consumption within thisrange. Two new concepts are introduced for the first time, i.e. iron consumption and silicon consumption. Iron consumption is proved to be the ultimate decisive factor that controls the flocculation effect of PFS on kaolin. Effective flocculation happens when the iron consumption is between 9 to 32kg/t and most effective flocculation at 24 to 27kg/t. The highest transmittance can even exceed 95%. The silicon consumption is a less important factor that determines the ultimate floccules volume when iron consumption is most proper. Moreover, larger floccules volume is reached when the transmittance of the supernate is higher.PFS were applied in the flotation of coal-pyrite as a depressant. They showed extremely significant depression effect on the coal-pyrite flotation. It is almost certain that iron consumption and curing time are the most critical factors determining PFS's depression characteristics. The most proper curing time is between 6 to 10 days since the depression effect is not stable in the previous 3 days and decreases when curing time is longer than 13 days. The most effective iron consumption is about 3kg/t. The depression ratio can reach 80% or more when iron consumption and curing time are both proper. The silicon consumption is innegligible in the flotation since greater silicon consumption showed slightly better depression effect on coal-pyrite.To confirm the depression effect of iron in PFS, other inorganic reagents as FeCl3, FeCl2, FeSO4, Fe(SO4)3 and reducing iron powder were also used in the flotation of coal-pyrite. The results proved that they did not have stable or remarkable depression effect on coal-pyrite at any experimented pH ranges. Thus it is verified that only iron in PFS has remarkable depressioneffect on coal-pyrite.In order to find further information on the possibility of PFS used in desulfuring of coal, PFS was added in the flotation of coal. In contrast, PFS showed neither obvious nor stable depression on coal flotation in concerning productivity, ash content and sulfur content respectively. In fact, the depression effect is very sensitive to consumption fluctuation. It can be concluded that PFS might be used in the coal flotation as a desulfuring reagent.Zeta potential measurements and XRD were carried out on such minerals as kaolin, coal-pyrite, and coal. The mechanism between PFS and these minerals are analyzed initially. The zeta potential measurements showed that the addition of PFS can not only reduce the pH of solution but also increase the zeta potential of kaolin, coal-pyrite and coal significantly. The XRD for PFS proved that PFS takes some form beyond those crystals after it is dried.
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