Description:
BACKGROUND OF THE INVENTION
Complex salts, as found in saline mineral bodies such as Searles Lake, are most difficult to separate into their salable components. At temperatures from about -20° to 20° C, brine, such as the Searles Lake brine, will release most of its salable sodium salt components free of potassium values.
Under winter conditions mirabilite and natron are the principal components of this sodium salt crystallite. While this binary mixture is fairly easy to isolate from the total grouping, the separation of the components of the binary mixture, however, is more difficult to accomplish and procedures heretofore proffered have been expensive and inefficient.
SUMMARY OF THE INVENTION
It has now been found that froth flotation in an aqueous media can be utilized for the separation of mirabilite from salt mixtures, particularly natron (Na2 CO3 . 10H2 O)-mirabilite (Na2 SO 4. 10H2 O) salt systems, when there is used as the collector reagent a sulfonated hydrocarbon containing at least about eight carbon atoms, a fatty acid containing at least about eight carbon atoms or a salt of a fatty acid containing at least about eight carbon atoms.
DESCRIPTION
According to the present invention sulfonated hydrocarbons are provided as reagents for the flotation separation of mirabilite from mirabilite-natron salt complexes.
As used in the practice of this invention, the term "sulfonated hydrocarbon" means sulfonated alkenes, particularly sulfonated α-olefins and sulfonated unsaturated petroleum fractions, which are otherwise unsubstituted. Generally, the sulfonated hydrocarbons should contain at least about eight carbon atoms, preferably from about 12 to about 30 carbon atoms, and more preferably from about 20 to about 30 carbon atoms. The sulfonated hydrocarbons can be obtained by the sulfonation of the corresponding naturally occurring alkenes, naturally occurring α-olefins, α-olefins obtained by the polymerization of the lower α-olefins such as ethylene and propylene under controlled conditions, and unsaturated petroleum fractions having on an average from about eight to about 30 or more carbon atoms in the extracted molecules with sulfur trioxide in a manner set forth in French Pat. No. 1,419,652 and British Pat. specification No. 983,056, incorporated herein by reference. Illustrative, but nowise a limiting of the sulfonated hydrocarbons useful in the practice of this invention, include sulfonated pentenes, hexenes, heptenes, octenes, nonenes, decenes, undecenes, dodecenes, tridecenes, tetradecenes, pentadecenes, hexadecenes, octadecenes, nondecenes, eicosenes, heneicosenes, doeicosenes, trieicosenes, tetraeicosenes, pentaeicosenes, hexaeicosenes, octaeicosenes and like alkenes as obtained from natural and polymerization sources. The source of the hydrocarbon may be refined or crude and can contain minor amounts of other constituents which do not affect beneficiation. The amount of sulfonated hydrocarbon used as a collector reagent is not narrowly critical and can range from about 50 to about 2,000 grams, preferably from about 500 to about 1,000 grams, per ton of salt processed.
The fatty acids used as the collector reagent in the practice of this invention are saturated and unsaturated straight chain fatty acids containing about eight, preferably from about 12 to about 22 or more, carbon atoms in the chain. Illustrative, but nowise a limiting of the fatty acids which may be used in the practice of this invention are caprylic, lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidic, behenic, coco oil, tall oil and like fatty acids. The fatty acids may be used in a purified state or in a crude state as a mixture.
The fatty acid salts used in the practice of this invention are normally obtained by the neutralization of the crude fatty acids with sodium hydroxide, potassium hydroxide, ammonia and like bases.
To assist the collectors employed in this invention, there may also be present in the flotation system, secondary and tertiary alcohols or mixtures thereof. The nature and the quantity of the secondary or tertiary alcohol is not narrowly critical and there may be mentioned, as illustrations of useful secondary and tertiary alcohols; methylethyl carbinol, i-butyl alcohol, trimethyl carbinol, 2,4-dimethyl-3-ethyl-3-hexanol, methyl amyl alcohol, di-isobutyl carbinol, 2,6,8-trimethyl-4-nonanol, secondary amyl alcohol, tertiary amyl alcohol, methyl isobutyl carbinol and like secondary and tertiary alcohols. When used as assisting agents, the secondary or tertiary alcohols are normally present in an amount of from about 50 to about 150 or more grams per ton or ore solids processed.
Flotation separations of mirabilite from salt mixtures containing mirabilite and natron can be conveniently carried out using conventional flotation equipment and procedures at temperatures from about 12° C to about 30° C without loss of the crystal identity of the salts to be separated. Where a low temperature flotation separation is desired, it is merely required to provide the flotation equipment with ordinary refrigeration cooling means to maintain the processed salt within the temperature range desired. Equipment useful in the flotation separation of mirabilite from mirabilite-natron salt complexes, using the reagent collectors of this invention, include, among others, Denver and Wemco flotation systems.
The flotation separation of mirabilite, according to the present invention, can be effectively carried out at slurry solid contents up to about 40 percent by weight or more, although it is preferred for efficiency to carry out the flotation at a salt solids content between about 20 to 30 weight percent. The salts may be conveniently treated as obtained from the source. However, it is preferred to wash the salts to remove organics and bitterns which can reduce the efficiency of the collector reagent employed.
It is also within the ambit of this invention to separate mirabilite from more complex salt mixtures such as those containing mirabilite, natron, halite, borax and other minor sodium salts. In such systems, sulfonated hydrocarbons or fatty acids are used to separate, by flotation, a mirabilite rich constituent from a natron rich constituent and other flotations using different reagents may be used to fractionate the natron and mirabilite respectively from the rough constituents.
The following examples are illustrative of the flotation separations which can be carried out according to the practice of this invention.
EXAMPLE 1
A binary mixture containing 55 percent by weight mirabilite and 45 percent by weight natron separated from a harvest of salts obtained by cooling Searles Lake brine to -5° C were slurried in a brine saturated with mirabilite and natron salts at a solids concentration of 25 percent by weight. Froth flotation separation was made using, as the flotation collector, α-eicosene in an amount equivalent to 500 grams per ton of salt solids processed. The flotation was carried out at a temperature between about 5° and 20° C in a Denver Cell.
There was obtained a float containing 72.0 weight percent mirabilite and 28.0 weight percent natron, entrainment free, and a residue containing 44.6 weight percent mirabilite and 54.4 weight percent natron. In this separation 32.2 percent of the contained mirabilite was recovered.
EXAMPLE 2
Using the procedure set forth for example 1 a salt grouping comprising mirabilite, natron and halite obtained in a crystallization of Searles Lake brine at -5° C was treated in a froth flotation apparatus using Witco LOCS, an aklyl aryl petroleum sulfonate prepared by Witco Chemical Company, in a concentration equivalent to 700 grams per ton of salt solids processed. Table I shows an analysis of the system before and after flotation, in which there was a yield of 45 percent mirabilite from the salt system at a mirabilite purity of 75.2 percent. ##SPC1##
EXAMPLE 3
The float obtained in Example 2 was subjected to a cleaner flotation using only the entrained collector as the flotation reagent. Table II contains an analysis of the system before and after flotation in which there was obtained a mirabilite yield in the float of 67.6 percent. ##SPC2##
EXAMPLE 4
A salt mixture containing 50 percent by weight mirabilite and 50 percent by weight natron was suspended in a liquor containing 10.0 percent sodium sulfate and 15.0 percent sodium carbonate at a slurry density of 25 percent. The mixture of salts was separated in a Denver Cell using as the collector Petronate HL, a sulfonated petroleum fraction having a molecular weight range from 440 to 470 and an empirical formula of C26 H42 SO3 Na and manufactured and sold by Sonneborn Division of Witco Chemical Company. At a concentration equivalent to 200 grams per ton of salt solids, a float containing 90 percent mirabilite and 10 percent natron and a residue composition containing 61.4 per cent mirabilite and 39.6 percent natron was obtained.
EXAMPLE 5
The procedure of Example 4 was repeated except that the collector concentration was increased in two successive portions to an equivalent of 250 grams per ton of salt solids. The first float had a composition of 97.1 percent mirabilite and 2.9 percent natron, and the second float had a mirabilite purity of 95 percent. The composition of the residue was 61.4 percent mirabilite and 39.6 percent natron.
EXAMPLE 6
The procedure of Example 4 was repeated except that the collector concentration was increased to an equivalent of 650 grams per ton of salt solids. The composition of the float obtained had 94.4 percent mirabilite and 5.6 percent natron by weight. The residue contained 54.5 percent mirabilite and 48.5 percent natron by weight.
EXAMPLE 7
The procedure of Example 4 was repeated except that there was used as the collector Petronate CR, a sulfonated petroleum fraction having a molecular weight between 490 and 510 and an empirical formula of C30 H50 SO3 Na and manufactured by Sonneborn Division of Witco Chemical Company, in a concentration equivalent to 1,000 grams per ton of salt solids. The float was determined to have a mirabilite concentration of 81.7 percent and a natron concentration of 18.3 percent by weight.
EXAMPLE 8
A salt grouping obtained by cooling Searles Lake brine was subject to flotation in a Denver Cell using as the collector Petronate HL in a concentration equivalent to 650 grams per ton of salt solids. The float had a mirabilite purity of 94.4 percent. An analysis of the system before and after flotation appears in Table III. ##SPC3##
EXAMPLE 9
The procedure of Example 8 was repeated except there was used as the collector Neofat 255, a stripped coco fatty acid chiefly containing groups having 12, 14, and 16 carbon atoms in the chain and manufactured by Armour Chemical, in an amount equivalent to 100 grams per ton of salt solids processed and, as the promotor, methyl isobutyl carbonate in an amount equivalent to 100 grams per ton of salt solids processed. The float obtained had a composition of 68.7 percent mirabilite and 31.3 percent natron.