The effect of PEO and organic sulfonates on phosphogypsum filtration has been evaluated using high-dolomite phosphate ore in a multistage batch mineral dissolution and filtration process. Results show that PEO and organic sulfonate compounds increase the rate of filtration. A thorough analysis of parameters that affect filtration was conducted to isolate the mechanism(s) by which the additives enhance the rate of phosphogypsum filtration. The analysis of the data indicates that both PEO and organic sulfonate compounds delay the measurable onset of phosphogypsum crystal nucleation. Results also suggest that the PEO alters the rate of phosphogypsum nucleation by associating with calcium ions and acting as an effective buffer. The reduced rate of nucleation is believed to be responsible for the observed increase in particle size and the corresponding increase in the rate of phosphogypsum filtration,