Process for beneficiation of phosphate and iron ores

Froth flotation of phosphate and iron ores is improved in recovery when a collector combination of a fatty acid and an alkylamidoalkyl monoester of a sulfosuccinic acid or a salt thereof is employed.

This invention relates to an improved process for the beneficiation of 
phosphate and iron ores. More particularly, this invention relates to such 
a process wherein a collector combination of a fatty acid and an 
alkylamidoalkylaminoalkyl or an alkylamidoalkoxyalkyl monoester of a 
sulfosuccinic acid or salt thereof is employed. 
Froth flotation is the principal means by which phosphate, hematite, 
magnetite and a host of other ores are concentrated. Its chief advantage 
lies in the fact that it is a relatively efficient process operating at 
substantially lower costs than many other processes. 
Flotation is a process for separating finely ground valuable minerals from 
their associated gangue, or waste, or for separating valuable components 
one from another. In froth flotation, frothing occurs by introducing air 
into a pulp of finely divided ore and water containing a frothing agent. 
Minerals that have a special affinity for air bubbles rise to the surface 
in the froth and are separated from those wetted by the water. The 
particles to be separated by froth flotation must be of a size that can be 
readily levitated by the air bubbles. 
Agents called collectors are used in conjunction with flotation to promote 
recovery of the desired material. The agents chosen must be capable of 
selectively coating the desired material in spite of the presence of many 
other mineral species. Current theory states that the flotation separation 
of one mineral species from another depends upon the relatively 
wettability of surfaces. Typically, the surface free energy is purportedly 
lowered by the adsorption of heteropolar surface-active agents. The 
hydrophobic coating thus provided acts in this explanation as a bridge so 
that the particle may be vttached to an air bubble. The practice of this 
invention is not, however, limited by this or other theories of flotation. 
Phosphate rock is a typical example of phosphate and iron ores. Typically, 
phosphate ore containing 15-35% BPL[bone phosphate of lime, Ca.sub.3 
(PO.sub.4).sub.2 ] is concentrated in very large tonnages from the Florida 
pebble phosphate deposits. The ore slurry from strip mining is sized at 
about 1 millimeter and the coarser fraction, after scrubbing to break up 
mud balls, is a finished product. The minus 1 mm fraction is further sized 
at 35 and 200 mesh. The minus 200 mesh slime is discarded. From the sizing 
operation, the +35 mesh material in thick slurry is treated with fatty 
acid, fuel oil, and caustic, ammonia or other alkaline material and the 
resulting agglomerates are separated on shaking tables, spirals, or spray 
belts. The 35.times.200 mesh fraction is conditioned with the same type of 
reagents and floated by conventional froth flotation routes. Not all the 
silica gangue is rejected by the fatty acid flotation so the concentrate 
is blunged with acid to remove collector coatings, deslimed, washed free 
of reagents and subjected to an amine flotation with fuel oil at pH 7-8. 
This latter flotation, sometimes called "cleaning", removes additional 
silica and raises the final concentrate grade to 70-75% BPL. 
Although the procedure described is effective in the beneficiation of 
phosphate and iron ores in general, there, nevertheless, exists the need 
for more effective collectors which provide increased recovery of 
phosphate and iron minerals while still providing high grade. It is 
particularly desirable to reduce the requirements for fatty acids which 
are increasingly being diverted to nutritional and other uses. In view of 
the high quantities of phosphate and iron minerals processed by froth 
flotation, such a development can result in a substantial increase in the 
total amount of mineral values recovered and provide substantial economic 
advantages even when a modest increase in recovery is provided. It is also 
highly desirable to have an efficient collector system for use at reduced 
dosage levels without sacrificing the mineral recovery performance. The 
decreases in reagent consumption are significant in view of the increasing 
diversion of fatty acids to nutritional and other uses. Accordingly, the 
provision for an improved process for beneficiating phosphate and iron 
minerals would fulfill a long-felt need and constitute a significant 
advance in the art. 
In accordance with the present invention, there is provided a process for 
beneficiating phosphate and iron minerals which comprises classifying the 
mineral to provide particles of flotation size, slurrying the classified 
mineral in aqueous medium, conditioning the slurry with an effective 
amount of a collector combination and froth floating the desired mineral 
values, said collector combination comprising from about 1 to about 99 
weight percent of a fatty acid derived from a vegetable or animal oil and, 
correspondingly, from about 99 to about 1 weight percent of an 
alkylamidoalkylaminoalkyl or an alkylamidoalkoxyalkyl monoester of 
sulfosuccinic acid of the general formula: 
##STR1## 
wherein R is a saturated or unsaturated alkyl radical of about 4 to 18 
carbon atoms, Y is --NH-- or --O--, n is an integer of from 1 to 10, 
inclusive, Z is --NH-- or --O--, p is an integer of from 0 to 9, 
inclusive, such that the sum (n+p) never has a value greater than 10, and 
X is hydrogen, alkali metal ion or ammonium ion. 
The process of the present invention by its use of the specified collector 
combination provides superior results in the froth flotation of phosphate 
and iron ores than obtained with either component alone and leads to high 
recovery and grade at lower dosage requirements. In preferred instances, 
fatty acid requirements can be reduced by 50% while still maintaining high 
mineral recovery and grade. 
In carrying out the process of the present invention, a phosphate and iron 
mineral is selected for treatment. Such minerals include phosphate, 
hematite, magnetite, and the like, that are conventionally processed by 
froth flotation using an acid collector. The selected mineral is screened 
to provide particles of flotation size according to conventional 
procedures. Generally, the flotation size will encompass from about 35 to 
200 mesh particles. 
After the selected mineral has been sized as indicated, it is slurried in 
aqueous medium and conditioned with an effective amount of the collector 
combination. Generally, the effective amount will be found in the range of 
about 0.1 to 2 pounds per ton of ore although variations outside this 
range may occur due to the specific ore processed, the quantity and nature 
of gangue material, the particular collector combination being used, the 
particular values of recovery and grade desired and the like. Phosphate 
and iron minerals, in general, are floated at a pH value in the range of 
about 6.0 to 12.0, preferably about 8.0 to 10.0. Suitable additional 
additives such as pH regulators, frothers, fuel oil, and the like, may be 
added in conjunction with conventional procedures. 
After the slurry has been conditioned as indicated, it is subjected to 
froth flotation following conventional practice. The desired mineral 
values are recovered with the froth and the gangue remains behind. 
The process of the present invention uses as the mineral collector a 
combination of about 1 to about 99 weight percent of a fatty acid derived 
from a vegetable or animal oil and, correspondingly, from about 99 to 
about 1 weight percent of an alkylamidoalkylaminoalkyl or an 
alkylamidoalkoxyalkyl monoester of a sulfosuccinic acid of the general 
formula (I). Illustrative compounds of this formula include: 
##STR2## 
and the corresponding free acids, potassium salts and ammonium salts. 
The fatty acid employed in the collector combination is one derived from a 
vegetable or animal oil. Illustrative vegetable oils include babassu, 
castor, Chinese tallow, coconut, corn, cottonseed, grapeseed, hempseed, 
kapok, linseed, wild mustard, oiticica, olive, ouri-ouri, palm, palm 
kernel, peanut, perilla, poppyseed, Argentine rapeseed, rubberseed, 
safflower, sesame, soybean, sugarcane, sunflower, tall, teaseed, tung and 
ucuhuba oils. Animal oils include fish and livestock oils. These oils 
contain acids ranging from six to twenty-eight carbon atoms or more which 
may be saturated or unsaturated, hydroxylated or not, linear or cyclic and 
the like. 
A preferred collector combination is one containing about 90 to 97 weight 
percent of fatty acid and, correspondingly, about 10 to 3 weight percent 
of the specified monoester of sulfosuccinic acid or salt thereof.

The invention is more fully illustrated in the examples which follow 
wherein all parts and percentages are by weight unless otherwise 
specified. Although the invention is illustrated with phosphate rock as 
typical of phosphate and iron ores, it is to be understood that similar 
benefits will be obtained with phosphate and iron ores in general. The 
following general procedure was followed in the froth flotation examples 
which follow. 
GENERAL PROCEDURE 
Rougher Float 
Step 1 
Secure washed and sized feed, e.g., 35.times.150 mesh screen fractions. 
Typical feed is usually a mixture of 23% coarse with 77% fine flotation 
particles. 
Step 2 
Sufficient wet sample, usually 640 parts, to give a dry weight equivalent 
of 500 parts. The sample is washed once with about an equal amount of tap 
water. The water is carefully decanted to avoid loss of solids. 
Step 3 
The moist sample is conditioned for one minute with approximately 100 cc of 
water, sufficient caustic as 5-10% aqueous solution to obtain the pH 
desired (pH 9.5-9.6) a mixture of 50% acid and fuel oil and additional 
fuel oil as necessary. Additional water may be necessary to give the 
mixture the consistency of "oatmeal" (about 69% solids). The amount of 
caustic will vary from 4 to about 20 drops. This is adjusted with a pH 
meter for the correct endpoint. At the end of the conditioning, additional 
caustic may be added to adjust the endpoint. However, an additional 15 
seconds of conditioning is required if additional caustic is added to 
adjust the pH. Five to about 200 drops of acid-oil mixture and one-half 
this amount of additional oil is used, depending on the treatment level 
desired. 
Step 4 
Conditioned pulp is placed in an 800-gram bowl of a flotation machine and 
approximately 2.6 liters of water are added (enough water to bring the 
pulp level to lip of the container). The percent solids in the cell is 
then about 14%. The pulp is floated for 2 minutes with air introduced 
after 10 seconds of mixing. The excess water is carefully decanted from 
the rougher products. The tails are set aside for drying and analysis. 
Step 5 
The products are oven dried, weighed, and analyzed for weight percent 
P.sub.2 O.sub.5 or BPL. Recovery of mineral values is calculated using the 
formula: 
##EQU1## 
wherein W.sub.c and W.sub.t are the dry weights of the concentrate and 
tailings, respectively, and P.sub.c and P.sub.t are the weight percent 
P.sub.2 O.sub.5 or BPL of the concentrate or tails, respectively. 
EXAMPLE 1 
Following the general procedure, Florida pebble phosphate rock was froth 
floated following conventional procedures using a fatty acid derived from 
tall oil in conjunction with No. 5 fuel oil at pH 9.0 as a control 
standard. As an example of the invention, a collector combination 
consisting of 92% of tall oil fatty acid and 8% of a sulfosuccinate of the 
structure: 
##STR3## 
was employed in conjunction with fuel oil. Results and test details are 
given in Table I. 
TABLE I 
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FLOTATION OF PHOSPHATE ROCK 
Dosages Weight BPL Improvement 
Fatty Acid Additive 
Fuel Oil 
Recovery 
% BPL Recovery 
Over Fatty 
Example 
(lbs/ton) 
(lbs/ton) 
(lbs/ton) 
(%) Feed 
Tail 
Conc. 
(%) Acid (%) 
__________________________________________________________________________ 
Compara- 
0.44 -- 0.44 13.65 18.64 
10.93 
67.45 
49.38 -- 
tive 
1 0.405 0.035 
0.44 17.98 17.89 
6.78 
68.58 
68.92 39.6 
__________________________________________________________________________ 
EXAMPLES 2-5 
Following the general procedure outlined above, Florida pebble phosphate 
rock was froth floated following conventional procedures using a collector 
combination consisting of 90% tall oil fatty acid and 10% of an 
alkylaminoalkyl monoester of a sulfosuccinate of the structure: 
##STR4## 
was employed in conjunction with fuel oil. Results and details are given 
in Table II along with comparative examples. 
TABLE II 
__________________________________________________________________________ 
FLOTATION OF PHOSPHATE ROCK 
Collector 
Fuel Oil 
Dosage 
Dosage 
Weight 
Assay % BPL 
BPL Recovery 
Example 
Ratio* 
(lbs./ton) 
(lbs./ton) 
Recovery 
Feed 
Tail 
Conc. 
% 
__________________________________________________________________________ 
Comp. A 
100/0 
0.3 0.6 0.08 14.31 
14.30 
22.32 
0.12 
2 90/10 
0.3 0.6 18.31 15.09 
4.6 
61.89 
75.10 
Comp. B 
100/0 
0.4 0.8 4.41 14.66 
12.70 
57.19 
17.20 
Comp. C 
100/0 
0.4 0.8 6.15 13.33 
10.32 
59.21 
27.32 
3 90/10 
0.4 0.8 21.15 15.70 
3.53 
61.08 
82.27 
Comp. D 
100/0 
0.5 1.0 18.89 15.28 
7.18 
50.07 
61.89 
4 90/10 
0.5 1.0 19.82 14.99 
3.31 
62.26 
82.30 
Comp. E 
100/0 
1.0 2.0 25.06 15.58 
2.82 
53.72 
86.43 
5 90/10 
1.0 2.0 23.03 14.60 
1.79 
57.41 
90.56 
__________________________________________________________________________ 
*Weight percent of fatty acid to alkylamino monoester of sulfosuccinate. 
EXAMPLE 7 
Following the procedure of Examples 2-5 in every material detail except 
that an alkylaminoalkyl monoester of a sulfosuccinate of the structure: 
##STR5## 
was employed, substantially equivalent results were obtained. 
EXAMPLE 8 
Following the procedure of Examples 2-5 in every material detail except 
than an alkylaminoalkyl monoester of a sulfosuccinate of the structure: 
##STR6## 
was employed, substantially equivalent results were obtained. 
EXAMPLE 9 
Following the procedure of Examples 2-5 in every material detail except 
that an alkylaminoalkyl monoester of a sulfosuccinate of the structure: 
##STR7## 
was employed, substantially equivalent results were obtained. 
EXAMPLES 10-13 
The procedure of Examples 2-5 is followed in every material detail except 
that the ratio of the fatty acid to the alkylamino monoester of the 
sulfosuccinate is varied to show more clearly the synergistic effect. 
Results and details are given in Table III. 
TABLE III 
__________________________________________________________________________ 
FLOTATION OF PHOSPHATE ROCK 
Collector 
Fuel Oil 
Dosage 
Dosage 
Weight 
Assay % BPL 
% BPL 
Example 
Ratio* 
(lb./ton) 
(lbs./ton) 
Recovery 
Feed 
Tail 
Conc. 
Recovery 
__________________________________________________________________________ 
10 100/0 
0.5 1.0 18.89 15.28 
7.18 
50.07 
61.89 
11 90/10 
0.5 1.0 19.82 14.99 
3.31 
62.26 
82.30 
12 50/50 
0.5 1.0 23.72 15.03 
1.46 
57.22 
90.30 
13 0/100 
0.5 1.0 22.15 15.09 
2.85 
55.23 
81.08 
__________________________________________________________________________ 
*Weight percent of fatty acid to alkylamino monoester of a sulfosuccinate