PURIFICATION OF SPHENE CONCENTRATE TO REMOVE PHOSPHORUS IMPURITY
863
titanium phosphates, i.e., to lower degree of purifica-
tion to remove phosphorus. Therefore, 2% hydro-
chloric acid was taken for the treatment in order to
reduce the degree of sphene decomposition. The fine-
ly ground sphene concentrate was processed using
the procedure described above. The results of the ex-
periments are presented below
CONCLUSION
The efficiencies of purification of the sphene conc-
entrate to remove a phosphorus impurity with hydro-
chloric and sulfuric acids are close, but preference
should be given to hydrochloric acid, which rules
out any contamination of the concentrate with sulfur
impurity and makes it possible to reduce the expen-
diture of water for washing by a factor of 2 3.
Treatment time, h
1
2
3
Residual content of P2O5, wt % 0.14 0.029 0.024
ACKNOWLEDGMENTS
Comparison with the data in Table 4 shows a con-
siderably higher efficiency of purification to re-
move phosphorus for the finely ground sphene con-
centrate.
The study was financially supported by the pro-
gram Leading Scientific Schools (grant no. NSh-
4383.2006.3).
The final stage in preparation of the sphene concen-
trate is its washing with water to remove the mother
liquor. Because of the low solubility of the precipi-
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1
tated calcium sulfate ( 2 g l ), its removal by wash-
ing requires a water volume exceeding that of the acid
by a factor of 6 8. At the same time, the expenditure
of water to removal of chloride and nitrate ions by
washing is 2 3 times smaller than that for calcium
sulfate.
The problem of utilization of solutions formed in
decomposition of fluorapatite and washing solutions
requires an additional analysis. One of suggestions
is to purify the sphene concentrate in fluidized-bed
apparatus, which will enable fuller consumption of
the acid and lower expenditure of water for washing
of the purified concentrate. In this case, the acid will
be consumed nearly completely. With hydrochloric
acid used for purification, the waste solution will be
a solution of CaCl2, which can be utilized, e.g., by
electrodialysis [6, 7].
With sulfuric acid used for purification to remove
phosphorus, the forming finely crystalline CaSO4 will
be carried away from the apparatus by the washing
solution and then can be separated by hydroclas-
sification, which was confirmed in the stage of
pilot industrial tests at Apatit Open Joint-Stock
Company.
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 6 2007