After water leaching of the acid baked REE concentrate, impurities such as Fe, Al, Th, and Cu are removed by neutralization with different reagents such as NaOH, Mg(OH)2, MgCO3, CaO, and CaCO3. Among all the said chemicals, lime (CaO) and limestone (CaCO3) are the preferred reagents due to their low costs. However because of calcium sulfate dihydrate (gypsum) precipitation, they are not so common in industry. One of the disadvantages of gypsum precipitation in this process is the adsorption of REE to the precipitates and loss of a proportion of REE to gypsum, which is hard to recover. In this paper, batch and continuous conditions in the impurity removal process by limestone are investigated and the differences between these two processes are examined. Based on the experiments, REE uptake by gypsum significantly increases in continuous process and different gypsum morphologies are observed.