Separation of ammonia from radioactive wastewater by hydrophobic membrane contactor

• The hydrophobic membrane contactor (HMC) was used to remove ammonia.
• The ammonia removal efficiency could reach above 90%.
• The ammonia mass transfer coefficient increased with increase of feed velocity.
• The HMC is a promising way to remove ammonia from radioactive wastewater.

The radioactive wastewater produced in the manufacturing process of UO2 kernel for high temperature gas-cooled reactor (HTR) contains high concentration of ammonia. The ammonia has to be removed effectively for further treatment of the wastewater. In this study, the hydrophobic membrane contactor (HMC) was adopted to remove and recover the ammonia from radioactive wastewater at room temperature. The operating parameters such as feed velocity and initial ammonia concentration were determined. In addition, the effect of wastewater composition on ammonia separation was studied. The experiment results showed that ammonia removal efficiency could reach above 90% after 120 min operation when pH was not adjusted. While the initial pH of wastewater was adjusted to 12.0, ammonia removal efficiency could reach above 95%. The ammonia mass transfer coefficient increased with increase of feed velocity and tended to an asymptotic value when the feed velocity reached 0.049 m/s. When the initial ammonia concentration was 2211.6 mg/L, 5864.6 mg/L and 23,898.7 mg/L, the ammonia removal efficiency was 95.0%, 94.2% and 94.1%, respectively after 120 min operation, i.e. the initial concentration of ammonia in wastewater had almost no effect on ammonia separation. In addition, the coexisting substances, such as urea and tetrahydrofurfuryl alcohol (THFA), also had no effect on ammonia separation. The HMC is a promising way to separate ammonia from radioactive wastewater.