Group 3 yttrium

Scandium is very widely but thinly distributed and its only rich mineral is the rare thortveitite, Sc2Si20v (p. 348), found in Norway, but since scandium has only small-scale commercial use, and can be obtained as a byproduct in the extraction of other materials, this is not a critical problem. Yttrium and lanthanum are invariably associated with lanthanide elements, the former (Y) with the heavier or Yttrium group lanthanides in minerals such as xenotime, M "P04 and gadolinite, M M SijOio (M = Fe, Be), and the latter (La) with the lighter or cerium group lanthanides in minerals such as monazite, M P04 and bastnaesite, M C03F. This association of similar metals is a reflection of their ionic radii. While La is similar in size to the early lanthanides which immediately follow it in the periodic table, Y , because of the steady fall in ionic radius along the lanthanide series (p. 1234), is more akin to the later lanthanides. 

E. Morrice, B. Porter, E. A. Brown, C. Wyche and R. G. Knickerbocker, Electrowinning Cerium Group and Yttrium Group Metals, U. S. Bureau of Mines, Rept. Invst. No. 5868,1961. 

Limited research studies [6] show that the minerals from the yttrium groups can be recovered using alkyl hydroxamate collectors which form complex reactions with REO. 

Figure 24.4 Generalized flowsheet for beneficiation of yttrium group of minerals using flotation.

This hydroxamate is selective towards calcite, fluorite and sericite. The yttrium group minerals that contain zircon also have highly complex mineral compositions. These ores contain fergusonite, euxenite and priorit besides other minerals that contain REO. Such deposits are found in Northern Canada (Thor Lake). 

In the case of REO-containing zircon, there is a strong relationship between zircon recovery and the recovery of REO from the yttrium group of REOs. This relationship is illustrated in Figure 24.6. 

In a number of cases, the REO from the yttrium group contains significant amounts of pyrochlore and/or tantalum columbite. Both minerals usually float with the zircon and REO minerals. 

Sm, Eu and Gd can be concentrated by crystallization through double magnesium nitrates, followed by crystallization of bismuth magnesium nitrates [30]. Sm and Eu are then removed by a proceedure based on valence change, and Gd is recovered by bromate crystallizations. Yttrium group earths may be conveniently separated by bromate crystallization. 

Double sulphate precipitation is one of the most common methods used in industry for the separation of cerium group from yttrium group rare earths. Various other precipitants such as chromates, double chromates, ferrocyanides, phosphates etc. have been tried. 

Scadden and Ballou [62] have employed add phosphates for the first time, and reported the preferential extraction of the yttrium group rare earths in di-w-butyl phosphoric acid (w-C4H90)2P0(0H) over the lower Z rare earths. 

Lanthanides of the yttrium group and tin were investigated by Burgett and Fritz [646] with the use of decafluoroheptane-3,5-dione and dibutyl sulphoxide. An aqueous solution of lanthanides of pH 5.5 was extracted with a cyclohexane solution of both reagents in an amount three times higher than the total contents of the metals. Under these conditions, almost quantitative extraction of these elements was achieved. 

Class II. The Yttrium Group, of general formula M2Pt3(CN)12. 2lHaO.—These are rhombic, red in colour with a green reflex. Their densities and crystallographic constants are as follow ... 

The values of pfor a regular octahedron, A E and 14 A Dq for the case of complex formation between rare earth ions and ethylenediaminetetraacetate obtained by calculations [16] are given in Table 3.7. The data show that the calculated values of 14ADq are fairly constant for the cerium group of elements, followed by a decrease for the yttrium group of elements. 

The above order pertains to the cerium group of elements. The order changes for the yttrium group of elements and appeal s to be as shown below ... 

Ketelle, B.H. and Boyd, GE. (1947) The exchange adsorption of ions from aqueous solutions by organic zeolites. IV. The separation of tiie yttrium group rare earths. Journal of the American Chemical Society, 69 (11), 2800-2812. 

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