期刊
HYDROMETALLURGY
卷 146, 期 -, 页码 128-132出版社
ELSEVIER
DOI: 10.1016/j.hydromet.2014.03.015
关键词
DNPPA; Solvent extraction; Rare earths; Diluent; Temperature
Extraction behaviour of rare earths, La, Dy and Y, from hydrochloric acid medium by di-nonyl phenyl phosphoric acid (DNPPA) has been investigated over a wide range of experimental conditions such as feed acidity, feed concentration, DNPPA concentration, diluents, temperature, stripping reagents. The slope analysis method indicated the formation of [RE(HA(2))(3)] type of neutral species in the organic phase. The extraction reaction of rare earths with DNPPA was found to be exothermic with Delta H values being -10.6 kJ/mol (La), -12.9 kJ/mol (Dy) and -17.5 kJ/mol (Y). The AS values were found to be -42.5 (La), -37.3 (Dy) and -43.0 (Y) J/mol K. The free energy change (Delta G) were found to be -22 (La), -1.6 (Dy) and -4.5 (Y) KJ/mol at 303 K. Stripping of rare earth was >90% from rare earth loaded DNPPA by sulphuric acid (7 M) in a single contact at room temperature (303 K). Extraction of rare earths in different diluents followed the order: petrofin similar to dodecane > dichlorobenzene >xylene > chlorobenzene. The extraction efficiency for rare earths by DNPPA increased with increase in atomic number: La < Ce < Pr < Nd < Sm < Eu < Gd < Tb < Dy < HoY < Er < Tm < Lu. Separation factors between these metal ions were calculated and compared with extractants such as di-2-ethylhexyl phosphoric acid (D2EHPA) and 2-ethylhexyl 2-ethylhexyl phosphonic acid (EHEHPA). DNPPA was found to be stable even after 10 cycles of repeated extraction/stripping operations. (C) 2014 Elsevier B.V. All rights reserved.
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