Effective separation of iron from titanium by transport through TOA supported liquid membrane

Separation of iron from titanium acidic solutions with tri-octylphosphine oxide (TOPO) and trioctylamine (TOA) has been investigated. TOA was found to be more selective for extraction of Fe compared with TOPO from HCI concentrations >1 M. Iron could be stripped effectively from the loaded TOA in 1 M HClO4. Parameters affecting the transport separation of iron from titanium ions have been studied using a supported liquid membrane impregnated with TOA in kerosene. HCI and HClO4 were used as feed and product solutions, respectively. Transport curves have been developed and Fe transport rate constant, k(f), together with the time of 99.9% transport, t(99.9), have been estimated. At 1 M HCI, 25 degrees C and 0.46 M TOA, Fe and Ti were practically not transported. By increasing the HCI concentration, the Fe transport was greatly improved where the t(99.9) reached 96 h at 5 M HCI. The Fe transport was further improved by rising the TOA concentration to 1.15 M and the temperature to 80 degrees C. Under these conditions about 80% of Fe was transported after only 1.5 h and the t(99.9) reached 6.4 h without any significant co-transport of Ti ions. The transport process seemed to be controlled by diffusion in the organic phase through the membrane since increasing the temperature enhanced the Fe transport. Although, direct leaching of ilmenite in HCI is known to be very limited, transport separation of Fe from the slurry by the present TOA-membrane system has lead to superior dissolution of Fe and Ti. (C) 2011 Elsevier B.V. All rights reserved.