Characteristics of Pollutants by Rare Earth Mine Decomposition/Purification Process, and of Treatment Technology

In this study, it was observed that the characteristics of pollutants produced during the processes of ore dressing and purification depends on the properties of rare earth and deposits from natural resources. The commercially important rare earth minerals discerned in this study were ion adsorption deposit, carbonate bastnasite and phosphate monazite. The ore dressing process for ion adsorption deposit elution was done by use of ammonium sulfate and calcination, while the process for bastnasite and monazite was smashing/grinding, gravity/magnetic separation and flotation. The process of decomposition/separation is mainly adopted for the purification process of rare-earth oxide by acid/alkali, P507 ()/oxalicacid () and carbonation and calcination. At the ore dressing process, dominant water pollutants were heavy metals, fluoride, sulphate, arsenic, and radioactive compounds, while purification process generally produced harmful gases (HF, , , CO), radioactive tailings and wastewater with heavy metals, fluoride, ammonium, radioactive materials (Th, U), and organic pollutants. Harmful gases were specifically generated from acid/alkali decomposition process while organic pollutants were originated from separation/purification process. To treat wastewater, chemical precipitation could be applied to remove heavy metal, fluoride and radioactive compounds, and stripping and struvite precipitation treated ammonium ions, while oxidation treated organic compounds.