A novel copolymer PADA which has two functions of flocculation and surface activity was synthesized in aqueous solution. The copolymer was applied to filtration aiding on wet-process phosphoric acid (WPA). The results show that PADA can increase the filtration rate of the phosphoric acid slurry and decrease the moisture of the filter cake. The mechanism of filtration aiding was studied. PADA neutralizes the surface potential of the phosphogypsum and makes the microcrystal particles flocculate to conglobation, which indicate that electrostatic neutralization and flocculation might be the action modes in the process of filtration aiding. The shortest flocculation time and largest average diameter of floccules can be obtained with the addition of 10 ppm PADA. The average pore size and porosity of the filter cake are enlarged by 0.22 μm and 15.38% respectively with the addition of PADA. The surface contact angle of the phosphogypsum is increased by 3.4° with PADA presence.

A non-ionic copolymer PAMA which has two functions of flocculation and surface activity was synthesized in aqueous solution. The copolymer was also characterized by means of infrared spectroscopic and unclear magnetic. The application performance of PAMA were studied, and the results show that the filtration rate of the phosphoric acid can be increased by about 3.8 times,the water content of the filter cake can be reduced by about 9.8%. Meanwhile, PAMA may increase the cake porosity by 25.82%,increase the mean void area about 7 times ,increase the surface contact angle of phophogypsum by 9.8°and decrease the surface tension by 7.4 mN·m-1 according to the SEM photos and hydrophobic experiment. All this confirms that PAMA is useful for vacuum filter system of wet process phosphoric acid.