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This study reports on a method for the speciation of iron in aqueous samples by the simultaneous analysis of divalent and trivalent iron ions with ion chromatography equipped with chemiluminescence detection (IC-CLD). Ferrous and ferric ions are first chelated by pyridine-2,6-dicarboxylic acid (PDCA) to form complexed anions, and separated by a mixed-bed ion-exchange column. The separated complexed ions are then detected with a CLD system containing luminol and hydrogen peroxide in a basic solution. This luminescence system has a linear dynamic range of ca. 3 orders of magnitude, with method detection limits as low as 7 μg L -1 for Fe(II) and 3 μg L -1 for Fe(III), measured in the simultaneous detection mode. This system resists interferences from common cations such as Cd, Ca, Cr, Cu, Mg, Ni, Pb, and Zn. Evaluation by analyzing real samples shows that this method is rapid, accurate, sensitive, and selective.

Strontium (Sr 2+ ) can be selectively extracted from aqueous solutions into supercritical fluid CO 2 at 60 °C and 100 atm with dicyclohexano-18-crown-6 (DC18C6) using CF 3 (CF 2 ) 6 CO 2 − (PFOA − ) or CF 3 (CF 2 ) 6 CF 2 SO 3 − (PFOSA − ) as a counter anion; at a mole ratio of Sr 2+ : DC18C6 : PFOA − = 1:10:50, the extraction of Sr (5.6 × 10 −5 M) from water at pH 3 is near quantitative whereas Ca 2+ and Mg 2+ at equal concentration are only extracted to a level of 7 and 1%, respectively; PFOSA − is an effective counter anion for selective extraction of Sr 2+ from 1.3 M HNO 3 with DC18C6 in supercritical CO 2 .Research in selective transport of metal ions in supercritical (sc)-CO 2 is of considerable current interest because of its potential applications in a variety of chemical processes which may be carried out in this environmentally friendly solvent. 1,2 Selective extraction of alkali metal and alkaline earth metal ions from aqueous solutions to organic solvents with crown ethers is well established in the literature. Extraction of these hard metal ions with crown ethers in scCO 2 is expected to be difficult because of limited solubilities of the resulting metal complexes in CO 2 . 3 It is known that fluorinated metal chelates are CO 2 -philic. 4 Thus, fluorination of ligands is one method of increasing solubility of metal complexes in CO 2 . This approach requires the design and synthesis of specific fluorinated macrocyclic compounds. Another method is to extract crown ether-metal complexes as ion-pairs into scCO 2 utilizing fluorinated counteranions. We report for the first time the successful extraction of Sr 2+ from aqueous media into scCO 2 utilizing a macrocyclic compound and a fluorinated counter anion.It is known that 18-membered crown ethers with cavity diameters in the range 2.6-2.8 Å are the most suitable hosts for Sr 2+ (2.2 Å). 5 For example, 90 Sr can be selectively extracted from nitric acid solutions with dicyclohexano-18-crown-6 (DC18C6) dissolved in a paraffinic or halogenated solvent, where nitrate serves as the counter anion. 6 This macrocyclic system is currently being evaluated for removing 90 Sr (t ½ = 30 years), a major uranium fission product, from the high level acidic nuclear wastes stored at the Idaho DOE site. However, disposal of organic liquid wastes generated from any solvent extraction process is a problem of environmental concern today because of changing government regulations. Supercritical fluid extraction provides several advantages over conventional solvent extraction including minimization of waste generation, allowing rapid separation of

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Wall thickness of siliceous MCM-41 could be controlled systematically up to 36.1 Å. A reasonable model explaining formation of thicker MCM-41 walls, not enlarging pore channel is proposed on the basis of TGA and 13 C MAS NMR data of samples. Thermal restructuring process under mild basic condition favors the silica redeposition on silica wall and building up thicker wall. Most mesostructure of calcined MCM-41 with thicker wall was retained even after hydrothermal treatment in boiling water for 14 days. To our best knowledge, the excellent hydrothermal stability of the MCM-41 silica reported herein has not been described before and facilitates practical applications of mesoporous molecular sieves in future.