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Title: Separation and recovery of radioactive and non-radioactive toxic trace elements from aqueous industrial effluents
Authors: Iyer, R H
Keywords: Industrial effluents;Liquid membrane;Recovery of elements;Supported liquid membrane;Trace elements;Track-etch membrane
Issue Date: Sep-2003
Publisher: NISCAIR-CSIR, India
Abstract: An update is presented on liquid membrane - based processes as viable and relevant alternatives to conventional approaches such as precipitation. solvent extraction, ion exchange processes and electrochemical techniques for the removal and recovery of some toxic and/or valuable trace metal ions including some actinides and fission products e.g. U, Am, Y etc and As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn etc from radioactive as well as non-radioactive aqueous waste solutions respectively. In particular, results of experiments aimed at developing supported liquid membrane(SLM)- based process using commercially available porous membranes and indigenously prepared track - etch membranes (TEMs) have been critically examined in laboratory studies to generate basic data needed to evaluate their utility for continuous operation without regeneration . These include effect of pore size, porosity, optimum pore size and the reusability. It is clearly demonstrated that indigenously prepared 10μm thick T EMs with a porosity in the range of 2-5% give comparable transport rates for metal ions-matching with that of commercial membranes of much higher thick ness (160 μm) and higher porosity of 60-85%. The smaller thickness of TEMs more than compensates for their lower porosity. It is shown that because of the ir well defined pore charactcristics TEMs could serve as model supports in SLM studies. By comparing the values of permeability coefficient (P) for TEM and polytetraflouroethylene (PTFE) supports for the transport of Pb2+ chosen as a typical divalent metal ion. and using di-2 ethyl hexyl phosphoric acid (D2 EHPA) as the carrier, it is unambiguously proved that diffusion of the metal complex across the membrane is the rate controlling step in metal ion transport in SLM-based processes. An overview of the experimental findings along with future outlook and suggestions for further work are presented in this paper.
Page(s): 1002-1011
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Appears in Collections:IJEB Vol.41(09) [September 2003]

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