Study on membrane pollution caused by rare earth waste water treatment by membrane electrolysis process

Abstract

ABSTRACT The membrane electrolysis technology is one of the treatment technologies for REx(CO3)y (rare earth carbonate) wastewater treatment. However, because the wastewater contains a few rare earth elements, it is easy to cause membrane contamination due to rare earth deposition on the membrane surface during membrane electrolysis treatment. This paper investigates the causes of membrane contamination caused by rare earth elements and the cleaning treatment of membranes to understand the mechanism of membrane contamination and improve membrane service life. Formation and composition of membrane pollutant produced in electrolysis process was analyzed and SEM micro-morphology analysis was done to study membrane pollutant. With the assistance of composition analysis by EDX and XRD, the main content of the membrane pollutant was determined to be RE(OH)3 amorphous precipitate. The influence of pH value of the electrolyte, the types of rare earth elements inside the electrolyte and the temperature of electrolyte on the pollution to the membrane was studied by pollutant absorption on the membrane and the ion flux change on the membrane. It was discovered that the adsorptive membrane pollution caused by Ce, Tb, and Y was relatively serious than other rare earth elements among the 16 rare earth elements, which concluded that the distribution of yttrium was higher in the heavy rare earth ore and the membrane pollution was severe when treating the smelting waste water of RE x (CO3) y produced by heavy rare earth ore by membrane electrolysis than by light rare earth ore. It was found that the mixed cleaning agent of HCl-NaClO had a good cleaning effect. The most considerable ion flux of the ion membrane after cleaning recovered to 96.5%. This study is expected to provide a valuable reference for the treatment of rare earth wastewater by membrane electrolysis.