Patent ID: 6171506
Filing Date: 2001-01-09
Classification: B01D,C02F

Abstract:
A process of thickening an aqueous suspension of mineral solids having a mineral solids content of at least 5 g/l and not more than 125 g/l, by sedimentation comprising adding to the suspension a water-soluble anionic bridging polymeric flocculant having intrinsic viscosity of at least 5 dl/g and a water-soluble cationic polymeric flocculant,allowing the solids to settle under gravity so as to form a lower underflow fraction containing a concentration of solids greater than that of the suspension and an upper overflow fraction containing a concentration of solids lower than that of the suspension and removing the underflow fraction,characterized in that the anionic and cationic flocculants are added to the suspension as an aqueous composition formed by blending 1 part by weight of the cationic polymeric flocculant with 2 to 99 parts by weight of the anionic polymer floccculant and sufficient water to give total polymer concentration of below 5 wt % and under conditions whereby counter-ionic precipitation can occur and in the aqueous composition substantially all of the anionic polymeric flocculant which is not precipitated by the cationic polymeric flocculant is in solution and during addition of the aqueous composition to the aqueous suspension of mineral solids the suspension is subjected to low shear so that counterionic precipitation can occur.