Improving Gypsum Slurry Filtration in the Production of Phosphoric Acid by Adding Cationic Amphiphilic Copolymer

Abstract

A cationic amphiphilic copolymer was synthesized with acrylamide (AM), dimethyl diallyl ammonium chloride (DMDAAC), monomer B by solution copolymerization. Through the orthogonal test, the optimum synthesis condition was obtained as follow: the solid content of the polymerization system is 10%, the pH value is 4.0, the polymerization temperature is 60°C, the concentration of the initiator is 0.06%, and the monomer ratio of m (AM): m (DMDAAC): m (monomer B) is 70:10:20. The copolymer was used for the filtration aiding in the wet process phosphoric acid. The filtration rate of the gypsum slurry is increased by 4.8 times, and the filter cake moisture is reduced by 11.79%, with the addition of PADB. The mechanism of filtration aiding was also researched, which shows that PADB can change the mean diameter of crystals and agglomerate the tiny crystals; PADB can decrease the surface tension of the filter liquor and enhance the hydrophobicity of the gypsum.