David Wesley Lipp

Low molecular weight polyacrylamide-based polymers as modifiers in phosphate beneficiation

Abstract The phosphate industry currently uses several natural polymers such as starch and guar as modifiers to achieve better separation of phosphate from silicates and carbonates. These natural products have many drawbacks: poor selectivity, low performance/dosage ratio, instability and sensitivity to aging, batch variability in composition, and deleterious down-stream effects. Several new, synthetic, low molecular weight polymers have recently been developed as cost-effective alternatives to natural products. These polymers have not only overcome many of the problems associated with natural products, but also have high activity and selectivity. The approach used in designing the synthetic polymers was to incorporate functional groups that would adsorb selectively on the mineral surface thereby rendering it hydrophilic. The phosphate modifier (depressant) developed recently is a low molecular weight polyacrylamide containing both hydroxyl and carboxylic acid functional groups. This polymer has provided excellent selectivity in the separation of apatite from siliceous gangue. The role of this and related polymers in the selective cationic flotation of quartz from apatite is discussed in this paper. The structure-activity relationships have been studied by determining the modifier activity of a range of polyacrylamides containing hydroxyl, carboxyl or carboxymethylol groups.