title: Selective removal of 226Ra2+ from gas-field-produced waters.
abstract: The 226Ra2+ selectivity of both the self-assembled (iso)-guanosine-based systems and ionizable thiacalix[4]crown dicarboxylic acids was determined in gas-field-produced water and a metal ion-containing model solution (simulant). Seven gas-field-produced water samples have been analyzed. From a sample (K5D) with average metal ion concentrations ([metal(tot)] = 0.14 M), thiacalix[4]crown-5 dicarboxylic acid (10(-4) M) extracts 60% of the 226Ra2+ content. Extractions performed with the model solution ((M)K5D) indicate that in K5D there is significant competition in 226Ra2+ extraction due to the organic constituents of K5D, in particular with self-assembled extractants guanosine and isoguanosine. Nevertheless, all four extractants extract 226Ra2+ both from the produced water K5D and the model solution (M)K5D, even with a 100-fold excess of [metal(tot)] to [extractant]. The extracted 226Ra2+ cations could effectively be stripped from the extractants bywashing with pH 2 water. The results obtained with the extractants used, especially thiacalix[4]crown-5 dicarboxylic acid 3, clearly demonstrate the way to selectively remove Ra2+ from gas-field-produced waters.
authors.affiliation: Laboratory of Supramolecular Chemistry and Technology, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Fijs W B
authors.initials: FW
authors.lastname: Van Leeuwen
authors.forename: Cornelis J H
authors.initials: CJ
authors.lastname: Miermans
authors.forename: Hans
authors.initials: H
authors.lastname: Beijleveld
authors.forename: Tanja
authors.initials: T
authors.lastname: Tomasberger
authors.forename: Jeffery T
authors.initials: JT
authors.lastname: Davis
authors.forename: Willem
authors.initials: W
authors.lastname: Verboom
authors.forename: David N
authors.initials: DN
authors.lastname: Reinhoudt
mesh_terms: D047248:Crown Compounds / Q000737:chemistry*; D005579:Fossil Fuels; D055593:Geological Phenomena; D005844:Geology; D011886:Radon / Q000302:isolation & purification*; D014875:Water Pollutants, Radioactive / Q000302:isolation & purification*
chemical_list: D047248:Crown Compounds; D005579:Fossil Fuels; D014875:Water Pollutants, Radioactive; D011886:Radon