Abstract :
The tetrad effect in the variation with atomic number Z of partitioning between organic phase and water phase and of coprecipitation from aqueous solution for the lanthanides (III, Lns3+) was found and confirmed in 1960s and 1990s, respectively [D.F. Peppard, G.W. Masom, S. Lewey, J. Inorg. Nucl. Chem. 31 (1969) 2271; D.F. Peppard, G.W. Mason, S. Lewey, J. Inorg. Nucl. Chem. 27 (1965) 2065; D.F. Peppard, A.A. Bloomquist, E.P. Horwitz, S. Lewey, G.F. Mason, J. Inorg. Nucl. Chem. 32 (1979) 339; I. Fidelis, S. Siekierski, J. Inorg. Nucl. Chem. 28 (1966) 185; L.J. Nugent, J. Inorg. Nucl. Chem. 32 (1970) 3485; C.K. Jørgensen, in: K.A. Gschneider Jr., L. Eyring (Eds.), Handbook of the Physics and Chemistry of Rare Earth, vol. 3, North-Holland, Amsterdam, 1991, Chapter 23; I. Kawabe, Geochem. J. 26 (1992) 369; R.D. Shannon, Acta Crystallogr. A 32 (1976) 751; I. Kawabe, A. Ohta, S. Ishii, M. Tokumura, K. Miyaushi, Geochem. J. 33 (1999) 167; I. Kawabe, A. Ohta, N. Miura, Geochem. J. 33 (1999) 181; I. Kawabe, Geochem. J. 33 (1999) 267; A. Ohta, I. Kawabe, Geochem. J. 34 (2000) 439; A. Ohta, I. Kawabe, Geochem. J. 34 (2000) 455; I. Kawabe, Geochem. J. 33 (1999) 349; I. Kawabe, T. Toriumi, A. Ohta, N. Miura, Geochem. J. 32 (1998) 213]. In 2002, the tetrad effect in the adsorption of Lns3+ at solid–water interface was reported [A. Ohta, I. Kawabe, Geochem. J. 34 (2000) 455; I. Kawabe, Geochem. J. 33 (1999) 349]. Is this effect more likely to occur in liquid–liquid and precipitate–liquid systems? Is this effect is an intrinsic property of the 4f electron elements in adsorption systems from aqueous solutions? Based on the available experimental data of adsorption systems from aqueous solutions from our laboratory and other laboratories [I. Kawabe, T. Toriumi, A. Ohta, N. Miura, Geochem. J. 32 (1998) 213; F. Coppin, G. Nerger, A. Bauer, S. Castet, M. Loubet, Chem. Geol. 182 (2002) 57; M. Majdan, S. Pikus, A. Gladyysz-Plaska, L. Fuks, E. Zieba, Colloids Surf. A 209 (2002) 27; Z.Y. Tao, X.K. Wang, X.X. Dai, J.Z. Du, Appl. Radiat. Isot. 52 (2000) 821; J.Z. Du, X.X. Dai, X.K. Wang, Z.Y. Tao, J. Radioanal. Nucl. Chem. 230 (1998) 129; X.K. Wang, W.M. Dong, H.X. Zhang, Z.Y. Tao, J. Radioanal. Nucl. Chem. 250 (2001) 491; J.Z. Du, X.M. Yin, X.K. Wang, X.X. Dai, X. Zhang, T.Y. Sun, Z.Y. Tao, Adsorp. Sci. Technol. 15 (1997) 341; X.K. Wang, W.M. Dong, Z.Y. Tao, Colloids Surf. A 223 (2003) 135; D. Koeppenkastrop, E.H. Decarlo, Chem. Geol. 95 (1992) 251; D. Koeppenkastrop, E.H. Decarlo, M. Roth, J. Radioanal. Nucl. Chem. 152 (1991) 337] and the theoretical analyses of coulombic interaction, hydration energy and chemical energy, it may be concluded that this effect may be more likely to occur in liquid–liquid and precipitate–liquid systems than in adsorption systems from aqueous solutions and that though refined spin-paring energy theory (RSPET) [I. Kawabe, Geochem. J. 26 (1992) 369; I. Kawabe, A. Masuda, Geochem. J. 35 (2001) 215] provides a theoretical basis of the tetrad effect, the occurrence of this effect in the adsorption systems from aqueous solutions depends mainly on many external factors, because the adsorption mechanisms of Lns3+ from aqueous solution are obviously more complex than those in the liquid–liquid and precipitate–liquid systems. The tetrad effect in the adsorption of lanthanides (III) from aqueous solution awaits further theoretical and experimental developments.
