Processing Technology of Eudialithe Concentrates

Kola eudialithe concentrates contain 7-10% ZrO₂, about 2% rare earth metals, and 0·5-0·7% Nb₂O₃, and about 50% SiO₂. The rare earth fraction contains 40% of yttrium group metals including 20% of yttrium. Eudialithe is easily dissolved in acids but silica precipitates in colloidal nonfilterable form and carries away up to 40% of Zr content. In sulphuric acid leaching there is additional problem of coprecipitation of sodium-lanthanides sulphates. Solutions to these problems were proposed by adding fluoride ions to sulphuric acid:

?Output of zirconium to solution grew up to 95%.

?The rate of filtration of silica increased 100 times, the precipitate became granular and white.

?It became possible to separate heavy, quickly sedimenting double Na-Ln sulphates from light suspension of silica.

The heavy precipitate contains Na-Ln sulphates, monazite (LnPO₄ + ThSiO₄), and Na-Fe silicate eguirine. Lanthanides are dissolved by alkali or Ca-Ba-Al nitrates mixtures solutions. Then they are treated with nitric acid and any of 15 rare earth metals can be separated by well-known methods. The residue contains Nb, Ti, Mg, Ca, Fe, Si admixtures.

The zirconium sulphate acid solution is extracted with quarternary ammonium base organic solutions. Fluoride ion addition into Zr-containing organic phase increases extraction coefficients 2?3 times. The high quality silica precipitate can be used in rubber, plastics or silica gel production. After reextraction by weak HC1 solutions we obtain pure ZrO₂ product.

A scheme is proposed based on the use of standard industrial equipment and technologies.