Selective Transport of Silver Ions Through Crown Ether Supported Liquid Membranes

Mohammad Waqar Ashraf¹, A. A. Al-Thukair¹ and M. H. Al-Malack²*  

¹Department of Chemistry, King Fahd University of Petroleum and Minerals Dhahran- 31261 (Saudi Arabia) ²Centre for Environment and Water, KFUPM, Daharan- 31261 (Saudi Arabia)

The silver content of environmental samples is being increased with the increasing use of silver compounds and silver containing preparations in industry. Silver can enter environment via industrial waters because it is often an impurity in copper, zinc and antimony ores. Recent information about the interaction of silver with essential nutrients, especially Se, Cu, vitamin E and Vitamin B12, have focused attention on potentially toxic nutrients. Thus, separation and recovery of silver ion are of increasing interest. Supported liquid membrane technology has been recently recognized as promising tool for selective separation of metal ions from aqueous solutions. In the present work, a supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is developed. The SLM used is a thin porous polypropylene (PP) membrane impregnated with hexathiacyclooctadecane (C12H24S6) dissolved in alcohol. Crown ether acts as a specific carrier for the uphill transport of Ag+ ion and its natural complex through SLM. In the presence of thiosulfate ion as a stripping agent in the strip solution, transport of silver occurs almost quantitatively after three hours. The performance of two different membrane materials is compared. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ni2+, Cu2+, K+, Cd2+ and Cr3+ ions were investigated.

Selective transport; Silver ions; Crown ether; Supported liquid membrane