Treatment of Phosphoric Acid Sludge for Rare Earths Recovery I

Abstract

A total of nine polymers were first tested. Correlations between molecular weight and sludge settling rate were identified for three types of polymers with a general trend of higher molecular weight giving a faster settling rate. Among the non-ionic polymers, the medium molecular weight polymer produced the best results (1831.88 ppm). Among the cationic flocculants, the lowest molecular weight polymer resulted in more REEs distribution (2478.81 ppm). It was concluded that the super high molecular weight of anionic flocculants works best for treating phosphoric acid sludge which resulted in REE concentration of 2568.69 ppm. Five co-polymers with different anionic ratio were tested as well. A higher anionic ratio resulted in faster settlement. It was found that the higher was the anionic ratio of the flocculant, the higher was REE concentration in the final solids and the highest anionic ratio polymer resulted in 2999.64 ppm of REE. This trend was attributed to zeta potential change due to addition of the polymer.