Dewatering of phosphatic clay waste by flocculation

This work focuses on the dewatering of phosphatic clay waste of Egyptian Abu-Tartur phosphate ore by flocculation using polyacrylamides to enhance the dewatering rate and recycling of the process water. The experimental program includes sieving, hydrocyclone separation and flocculation of the overflow of hydrocyclone. Results revealed that the coarser fraction larger than 32 micron is enriched with P2O5 whereas the undersize fraction is only clay. Hydrocyclone successfully separates two cuts; the underflow fraction is enriched with phosphate while the other is just clay. By this technique, the P2O5 content is increased from 15.57 % in the feed to 26 % in the underflow cut which constitutes about 39.8 % by weight. Flocculation helps to increase both the settling rate of phosphatic clay waste and recycling the process water. The former criteria increased 37 times by using anionic polyacrylamide (A130) as compared to the natural settling rate of the same waste. Results were explained in the light of a model which suggests that the flocculation mechanism involves two stages: the first stage involves the adsorption of the reagent on the particles whereas the second forms aggregate flocs. Formation of aggregate flocs takes place by tangling the polymer molecules, so that one polymer molecule will be adsorbed at several points on the surface of the particle, leaving loops which may be of varying lengths, projecting out from the surface. Partially covered particles would collide to form bridges.