Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ivb metal
Reexamination Certificate
1999-01-05
2001-10-02
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ivb metal
Reexamination Certificate
active
06296816
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a process for treating an aqueous solution of titanium sulfate and generally fits into the process for preparing titanium dioxide by the sulfuric method.
The process for preparing titanium dioxide by the sulfuric method consists of treating ilmenite and/or titaniferous slags with concentrated sulfuric acid to obtain a titanium sulfate solution, called black liquor, which is then purified by eliminating the impurities, then hydrolyzed to obtain titanium dioxide.
One of the methods of purifying black liquor is to place the black liquor in contact with an organophosphorus solvent in the presence of acid to selectively extract the titanium sulfate inorganic phase and to thereby separate the impurities from it. The titanium sulfate present in the organic phase is then regenerated into aqueous phase by placement in contact with an aqueous phase.
An aqueous solution of purified titanium sulfate is obtained through this liquid-liquid extraction process. This solution may be hydrolyzed to prepare titanium dioxide. However, this hydrolysis may be conducted only under precise conditions, particularly as concerns the titanium and sulfuric acid contents of the solution to be hydrolyzed.
It is known that the acid factor, defined as the ratio of the concentration of the active acid (free H
2
SO
4
+acid linked to titanium in TiOSO
4
form), expressed in g/l of H
2
SO
4
, to the titanium, expressed in g/l of TiO
2
, must present a low value, generally below 2.
The value of the acid factor of the final purified titanium sulfate solution may be controlled by adapting the various current flows utilized during the extraction and regeneration steps during purification. This control, however, must be precise, especially when the process for purification by extraction operates in a closed circuit, which is almost always the case.
Furthermore, under some flow conditions which permit the achievement of a good acid factor in the final solution, problems are observed in the extraction unit stages with precipitation of species containing titanium, such as (TiOSO
4
, n H
2
O), where n is between 0 and 2, at different degrees of hydration.
And finally, because of its precision, the control used does not allow the value of the acid factor of the final titanium sulfate solution to be modulated at will, thereby affecting the characteristics of the precipitated titanium dioxide.
Therefore, it is generally especially difficult to adjust the acid factor of a titanium sulfate solution during a sulfuric liquid-liquid extraction process, such that the final solution's acid factor is often too high and, if the solution is then hydrolyzed and the hydrolysate then washed and calcined, the pigment obtained is poor.
SUMMARY OF THE INVENTION
One object of the present invention is to resolve these disadvantages by offering a new purification process for a titanium sulfate aqueous solution that enables obtaining a low acid factor in the final titanium sulfate solution.
Another object is to offer a purification process for a titanium sulfate aqueous solution that makes it possible to control the acid factor by avoiding titanium sulfate precipitation problems in the battery extraction stages.
Another object is to offer a purification process for an aqueous titanium sulfate solution that makes it possible to freely modulate the value of the final acid factor.
To that end, the invention concerns an initial embodiment of a treatment process with a starting aqueous phase (SAP) containing titanium and sulfuric acid produced by the attack of sulfuric acid on titaniferous ores of the type in which the following steps are used:
an extraction step in which the starting aqueous phase (SAP) comes in contact with an organic extraction phase (OEP) containing one or a plurality of organophosphorus compounds, by means of which an organic phase containing titanium and sulfuric acid is obtained (OP);
then, a regeneration step in which the organic phase (OP) is regenerated by contact with an aqueous regeneration phase (ARP
0
), by means of which a regenerated aqueous phase (RAP
f
) containing titanium is obtained;
characterized in that it includes an additional step in which all or part of the regenerated aqueous phase (RAP
f
) is placed in contact with an organic washing phase (OWP), by means of which a treated aqueous phase (TAP) containing titanium is obtained.
The invention also concerns a second embodiment of a process for treating a starting aqueous phase (SAP) containing titanium and sulfuric acid produced by the attack of sulfuric acid on titaniferous ores of the type in which the following steps are used:
an extraction step in which the starting aqueous phase (SAP) is placed in contact with an organic extraction phase (OEP) containing one or a plurality of organophosphorus compounds, by means of which an organic phase is obtained containing titanium and sulfuric acid (OP).
a regeneration step implemented by liquid-liquid countercurrent extraction over a plurality of stages in a suitable apparatus including an initial stage in which the organic phase (OP) is introduced flowing counter to an aqueous regeneration phase (ARP
0
) introduced in the last stage of the apparatus, characterized in that an organic washing phase (OWP), containing the same organophosphorus compound(s) as the organic extraction phase (OEP) flowing counter to the aqueous regeneration phase (ARP
0
), is introduced into one or a plurality of intermediate stages flowing counter to the aqueous regeneration phase (ARP
0
).
The invention also concerns a third embodiment for treating a starting aqueous phase (SAP) containing titanium and sulfuric acid produced by the attack of sulfuric acid on titaniferous ores of the type in which the following steps are used:
an extraction step in which the starting aqueous phase (SAP) is placed in contact with ane organic extraction phase (OEP) containing one or a plurality of organophosphorus compounds, by means of which an organic phase containing titanium and sulfuric acid (OP) is obtained.
a liquid-liquid countercurrent extraction regeneration step is used over a plurality of stages in a suitable apparatus containing a first stage in which the organic phase (OP) is introduced flowing counter to an aqueous regeneration phase (ARP
0
) introduced in the last stage of the battery, characterized in that, in an intermediate stage (n) a partially regenerated aqueous phase (PRAP) is extracted, placed in contact with an organic washing phase (OWP), by means of which a partially regenerated aqueous phase (PRAP
f
), which is reintroduced at stage (n−1) of the regeneration step, is obtained.
The invention also concerns the titanium solution obtained by means of the process defined above.
Lastly, the invention concerns the process for preparing titanium dioxide in which the titanium solution is hydrolyzed, then the hydrolysate obtained is washed and calcined.
REFERENCES:
patent: 4499058 (1985-02-01), Fetoussi
patent: 4986742 (1991-01-01), Denecker
patent: 5682593 (1997-10-01), Holzner
Cordelet Frederic
Fourcot Fabrice
Griffin Steven P.
Kalow & Springut LLP
Medina Maribel
Millennium Inorganic Chemicals, S.A.
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