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BACKGROUND: Liquid-liquid extraction is widely used for the separation of rare earths, among which synergistic extraction has attracted more and more attention. Numerous types of synergistic extraction systems have been applied to rare earths with high extraction efficiency and selectivities. In the present study, mixtures of sec-octylphenoxyacetic acid (CA12, H 2 A 2 ) and 1,10-phenanthroline (phen, B) have been used for the extraction of rare earths from nitrate medium. The stoichiometry of samarium(III) extraction has been studied using the methods of slope analysis and constant molar ratio. The possibility of using synergistic extraction effects to separate rare earths has also been studied.

A method based on ultrasound-assisted cloud point extraction (CPE) was developed for the determination of phenolic compounds in water samples by high-performance liquid chromatography coupled with diode array detection (DAD) (HPLC-DAD). A nonionic surfactant, Tergitol 15-S-7, was chosen as the surfactant. The parameters affecting the CPE efficiency, such as Tergitol 15-S-7 concentration, salt concentration, extraction temperature, incubation time, centrifugation time, ultrasonic time, sample pH, and dilution solvent were systematically evaluated and optimized. Under the optimum experimental conditions, the linear regression coefficients of the standard curves were greater than 0.9986 and the limits of detection were in the range of 1.7-6.0 μg/L. The method was shown to be reproducible and reliable with intraday and interday relative standard deviations lower than 4.0 and 5.8%, respectively. The recoveries for the addition of different concentrations of phenolic compounds to water samples were in the range of 81.1-109.4%.

BACKGROUND: Synergistic extraction has been proven to enhance extractability and selectivity. Numerous types of synergistic extraction systems have been applied to rare earth elements, among which sec-nonylphenoxyacetic acid (CA100) has proved to be an excellent synergistic extractant. In this study, the synergistic enhancement of the extraction of holmium(III) from nitrate medium by mixtures of CA100 (H 2 A 2 ) with 2,2 -bipyridyl (bipy, B) in n-heptane has been investigated. The extraction of all other lanthanides (except polonium) and yttrium by the mixtures in n-heptane has also been studied.