The invention relates to a method for preparing
calcium sulfate crystal whiskers (CaSO4) by using
impurity-containing
gypsum as a
raw material. The method comprises the following steps of: removing main impurities in the
raw material which is the low-priced
impurity-containing
gypsum resource in a mode of
roasting, acid-complex leaching and alkaline leaching and simultaneously
thinning crystal grains to obtain a superfine
dihydrate calcium sulfate precursor which is high in purity and dispersibility; and preparing the
anhydrous calcium sulfate crystal whiskers with a length of 20 to 2,000mu m, a
diameter of 0.5 to 20 mu m, a length-
diameter ratio of 40 to 1,000 and a weight percent content of over 95 percent in a mode of hydrothermal conversion-
roasting of a fluxing agent. The method has the advantages of low-priced and easily bought raw materials, simple process, wide application range, and high added value. The
calcium sulfate crystal
whiskers prepared by the method have a big length-
diameter ratio and regular shape, and can be used as reinforcing, heat insulating or
flame retardant materials in industries of plastics, rubbers, coatings,
papermaking, building materials and the like.