Method for production of needle-like crystals from waste phosphogypsum using recrystallization in acid conditions

摘要

The aim of present work is study of possibility to convert waste phosphogypsum into effective mineral filler for polymer composites. The focus of this research is on obtaining of needle-like crystals using crystallization in acid conditions. Depending on the crystallization conditions (phosphogypsum concentration, temperature, presence of impurities, crystallization on glass plate or in volume of the reactive mass, etc) were obtained different morphlogical forms of gypsum crystals. The phosphogypsum recrystallization process gives possibility for obtaining of Franklin fibers (needle-like crystals) with different ratio I/d values 100-150 (mu)m. This process can be carried in HCl solution with different concentration (3, 5, 10, 12 and 15 percent) at constant concentration of CaSO_(4)(centre dot)2H_(2)O in presence of FeCl_(3)(centre dot)6H_(2)O - 1.4 g/l and Al_(2)(SO_(4))_(3)(centre dot)18H_(2)O, Al(NO_(3))_(3)(centre dot)9H_(2)O - 0.3 g/l. There was proved that optimal ratio between the main components is phosphogypsum 10 g in 350 ml 10percent-HCl.