3,4-(METHYLENEDIOXY)BENZYL ACRYLATE ACRYLIC-ACID COPOLYMERS AS SELECTIVE PH-CONTROLLED FLOCCULANTS FOR FINELY DIVIDED TITANIUM MINERALS

Fully synthetic tailor-made radical copolymers of 3,4-(methylenedioxy)benzyl acrylate with acrylic acid afforded excellent pH-controlled selective flocculation of aqueous ultrafine dispersions of the titanium minerals rutile and ilmenite. Sedimentation experiments proved that the copolymers, characterized by osmotic molecular weights in the range of 35 000-476 000 Da, produced stable, well separable flocs with rutile or ilmenite at acidic pH while they did not flocculate gangue minerals such as quartz. They showed the distinctive, very useful property of reversibly changing their effect from flocculation to dispersion or neutral by changing the pH. The formation of flocs is interpreted on the basis of a preliminary gathering process of the particles determined by the pH-dependent alteration of the particle surface solvation carried out with the copolymer.