Intensification of zirconium and hafnium separation through the hollow fiber renewal liquid membrane technique using synergistic mixture of TBP and Cyanex-272 as extractant

The novel synergistic mixture of TBP and Cyanex-272 is used as the extractant in the hollow fiber renewal liquid membrane (HFRLM) technique for Zr/Hf separation. The effects of the chemical and operational parameters such as HNO₃ concentration in the donor phase, NH₄F concentration in the acceptor phase, Cyanex-272 and TBP concentration in the liquid membrane phase, the lumen and shell side flow rates, and aqueous/organic volume ratio on the mass transfer and separation performance of HFRLM method were investigated. The obtained results reveal the intensification potential of proposed HFRLM technique for selective extraction of Zr over Hf with separation factor higher than 100. The HFRLM method provides two times higher mass transfer flux in comparison with hollow fiber supported liquid membrane (HFSLM). Also, the HFRLM method shows satisfactory stability for 700 min of continuous operation. The Zr ion transport through the LM phase follows the coupled co-transport mechanism and the diffusion in the renewal layer is recognized as the rate-controlling step in the HFRLM process. Moreover, the Zr mass transfer coefficient and molar flux in the HFRLM method are calculated in the range of 1× 10^-8 to 8.4× 10^-7 m·s^-1 and 4.9× 10^-6 to 20.1 ×10^-6 mol·m^-2 s^-1, respectively.