Treatment of Simulated Radioactive Waste Liquid by Air-Gap Membrane Distillation

Abstract

The treatment of simulated radioactive wastewater by air-gap membrane distillation process was conducted. The membrane flux and rejection rates of Cs+, Sr2+, Co2+ and UO2+2 were used as indexes to evaluate the performance of PTFE, PVDF and PP hydrophobic membranes. The effects of feed temperature, feed flow rate and air gap thickness on membrane flux and the rejection rates were discussed. The results show that the feed temperature has the most significant effect on the membrane flux. Increasing the feed temperature can significantly increase the membrane flux. The membrane flux of PTFE membrane with a pore size of 0.22 μm increases from 4.79 kg/(m2·h) to 16.24 kg/(m2·h), when the feed temperature increases from 60 ℃ to 90 ℃. Increasing the feed flow rate can notably increase the membrane flux in the lower feed flow rate range. But with the increase of feed flow rate, the increase rate of membrane flux is slowing down. Increasing the air gap thickness decreases the membrane flux. Within the experimental conditions, the process conditions have no obvious effect on the rejection rate. Among the above three hydrophobic membranes, the PTFE membrane with a pore size of 0.22 μm has the best rejection performance with the rejection rate above 99.97%. The PTFE membrane with a pore size of 0.22 μm is more suitable to be applied to treat radioactive wastewater by the membrane distillation process.

Keywords

• air-gap membrane distillation
• membrane material
• membrane flux
• rejection rate
• influencing factor