Application of ZrO₂-TiO₂ composite nanofiltration membrane for treatment of simulative radioactive waste water

The radioactive waste water is generated in nuclear industry, nuclear research centers, medicine and other fields. It's harmful to living organisms, environment and natural resources. Thus, the radioactive waste water should be managed and treated well. Nanofiltration is a new kind separation technology with low-cost and high-efficiency, which ranges between ultrafiltration and reverse osmosis. In this work, TiO₂/ZrO₂ composite nanofiltration membranes with MWCO of about 500 and permeability of 270 L·m^-2·h^-1·MPa^-1 were used to remove the cobalt and strontium ions in the low-level radioactive wastewater without the addition of complexing agent. The effects of pH, transmembrane pressure and initial concentration on the permeability and retention property were investigated. It was demonstrated that the ion retention behaviors were enhanced with the increase of transmembrane pressure from 0.4 to 1.0 MPa, while the permeability changed slightly. The retention gradually increased along with the deviation from the isoelectric point (pH=7), where the retention was minimum value. Under the condition of pH=3, the retention of Co²⁺ and Sr²⁺ achieved the highest level, which was up to 99%. The ion retention and permeability decreased with the increase of initial concentration. With the operation time exceeding 2000 min, ions retention and permeability of ceramic nanofiltration membrane were almost stable. The ceramic nanofiltration membrane showed a good potential in the application of radioactive effluent treatment.