Process for the flotation of ores and collector for use in this process

A process is provided for the flotation of ores, wherein compounds of the formula RO-(C.sub.x H.sub.2x O).sub.n CH.sub.2 COOM, wherein R is an aliphatic residue of 8-18 carbon atoms or an alkylaryl residue having 6-12 carbon atoms in the alkyl moiety, n has an average value of 0-10 and x has a value of 2 or 3, and M is a monovalent cation, are used as collectors, together with the usual fatty acid type collectors, these collector mixtures possessing synergistic properties. Also collector mixtures for use in such a process are provided.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the flotation of ores, particularly to the 
flotation of minerals containing alkaline earth metal ions and oxidic 
copper and iron minerals, and more specifically to the use of certain 
synergistic mixtures of carboxylic acid compounds as collectors. 
2. Description of the Prior Art 
According to U.K. Pat. No. 1,355,091 a group of carboxylic acid derivatives 
containing a hydrophobic residue and having surfactant properties can be 
used as collectors for the flotation of various valuable constituents from 
ores. Although in many situations highly satisfactory results can be 
obtained with collectors of this large group of compounds, they have the 
common property that they possess a relatively strong tendency to foaming. 
This often causes an unfavorable influence on the desired separation 
during the flotation. Excessive frothing is a highly undesirable property 
in flotation practice. It results mostly into lower selectivities because 
gangue minerals are trapped in the tight froth structure. It is because of 
this difficulty that the superior activity and chemical selectivity of 
these compounds, compared with the usual fatty acid type collectors, 
cannot be utilized in practice to such an extent as would be desirable. 
The collectors of the fatty acid type are old and well-known. These 
collectors usually contain oleic acid and are often called "oleic acid", 
even though some of the commercial collectors may only contain minor 
amounts of this particular acid. Of course, one will preferably use cheap 
materials for this purpose so that sure oleic acid is never used. Some 
usual materials are commercial oleic acid, oleic acid-containing wastes, 
fatty acids from tall oil, fatty acids from fish oils and the like. In the 
present specification and appending claims these materials will be called 
either "fatty acid type collectors", or "oleic acid-containing fatty acid 
type collectors", or simply "oleic acid". 
THE INVENTION 
An object of the invention is to provide a flotation process with which 
better effectivities and selectivities are attained than with the usual 
fatty acid type collectors, avoiding at the same time the frothing 
problems of the collectors of U.K. Pat. No. 1,355,091. 
A further object is to provide collector compositions for carrying out such 
a process. 
Additional objects and advantages will become clear from the following 
description. 
SUMMARY OF THE INVENTION 
According to the invention it has been found that mixtures of compounds 
within a certain sub-group of U.K. Pat. No. 1,355,091 and fatty acid type 
collectors (oleic acid in any of its commercial forms) show a surprising 
combination of synergistic properties. Thus, the higher chemical 
selectivity and effectivity of the compounds of the U.K. patent with 
respect to oleic acid alone even though the oleic acid is used in a 
considerable excess, are maintained, whereas on the other hand the foaming 
tendency is strongly diminished. 
Accordingly, the above objects are obtained in accordance with the 
invention by using collector compositions containing as essential 
components (1) at least one compound of the formula RO--(C.sub.x H.sub.2x 
O).sub.n CH.sub.2 COOM, wherein R is an aliphatic residue of 8-18 carbon 
atoms or an alkylaryl residue having 6-12 carbon atoms in the alkyl 
moiety, n has an average value of 0-10 and x has a value of 2 or 3, and M 
is a monovalent cation, and (2) a usual oleic acid-containing, fatty acid 
type collector. 
If in the acids of the above formula the value of n is higher than 1, the 
meaning of x in the various groups C.sub.x H.sub.2x O can be the same or 
different. 
As is well-known, these ether-carboxylic acids can be prepared starting 
from an alcohol or phenol of the formula ROH. If the product to be 
prepared should have an average value of n higher than O, this starting 
product is first reacted in the usual way with ethylene and/or propylene 
oxide, whereafter the so obtained product is reacted with a salt of a 
haloacetic acid. Of course, the compounds wherein n=O, are prepared by 
reacting the starting compound ROH with the haloacetic acid salt. 
The cation has not a large influence on the properties of the entire 
compound and they can be used in different forms such as the free acid 
form, the alkali metal salts or ammonium or substituted ammonium salts or 
amine salts. 
As fatty acid collector component one may use commercial grade oleic acid, 
but also commercial products which contain a more or less considerable 
amount of oleic acid, such as tall oil or fatty acid obtained from fish 
oils. As mentioned hereinabove, the replacement of oleic acid by such 
products is well-known and rather usual. 
The two components may be added separately to the flotation process, but 
preferably they are added as a previously prepared mixture which is much 
more practical. 
Accordingly, this invention also provides a mixture suitable as collector 
in flotations and containing as essential components the above-defined 
components (1) and (2). 
The two components may be used in amounts which can be varied within 
relatively wide limits. The ether-carboxylic acid compounds are used 
preferably in amounts of from 25 to 250 grams per ton of ore, and the 
oleic acid component can be used in amounts of from 75 to 750 grams per 
ton of ore. For obtaining the best results the weight ratio between the 
ether-carboxylic acid component and the oleic acid component should be 
from 1:15 to 2:1. If lower concentrations of the ether-carboxylic acid 
and/or lower weight ratios between the ether-carboxylic acid and the oleic 
acid component are used, the flotation properties of the collector 
mixtures are intermediate between those of the here described process and 
normal oleic acid-containing fatty acid type collectors. As a general 
rule, the weight ratio between ether-carboxylic acid and oleic acid type 
collector should not be less than 1:30, in order to obtain noticeable 
improvements. 
Dependent on the intended separation, the compositions of this invention 
may be used at pH-values of about 6-12, i.e. they may be used at any 
pH-value which occurs in practical situations. In view of the small amount 
in which the collector mixture is used with respect to the pulp, the final 
pH will depend largely on the pH-value of the pulp. Thus, the mixture of 
collectors can be added in salt form to a slurry having a pH below 7 
without materially changing this pH-value. 
Of course, the ratio between the two components will have some influence on 
the properties of the final collector mixture. The selectivity will 
increase with increasing ratios between components (1) and (2), but there 
are hardly any technical limits to the ratios, and the above stated limits 
are in fact dictated by reasons of economy. 
Of course, the selectivity of component (1) for a particular situation will 
vary with the exact nature of this component, and this should be taken 
into account, when choosing the optimum ratio between the two components. 
The collector mixtures of the present invention are especially useful for 
the flotation of minerals containing alkaline earth metal ions, such as 
apatite, fluorite, magnesite, barite, scheelite and also for the flotation 
of oxidic copper minerals and oxidic iron minerals. 
Due to the presence of component (1) the collector compositions of the 
present invention are highly insensitive to hard water, and also in this 
respect there is a synergistic action, because this insensitivity is 
substantially the same as of the ether-carboxylic acids alone, whereas 
oleic acid type collectors, as is well known, are highly sensitive to hard 
water.

The invention is further elucidated by the following examples, which, 
however, are not intended to limit the invention in any way. 
EXAMPLE 1 
The original ore was a scheelite-containing copper ore. This ore was 
subjected to a standard flotation with xanthates and frother at a high pH 
(11.5), brought about by the addition of lime (CaO) in order to float the 
copper sulfides. It was desirable to recover scheelite from the tailings 
of this flotation. The flotation of scheelite constituted a problem, 
because a good recovery of the scheelite was not possible at the high lime 
concentrations used. 
(a) Experiments with fatty acid from fish oil (predominantly oleic acid) in 
the pure form or its sodium salts at pH 11.5 did not yield any practical 
results, even not with 1500 grams per ton of original ore, and this was 
caused by the high calcium concentration. 
(b) By using the compound C.sub.8 H.sub.17 OCH.sub.2 COONa as collector in 
an amount of 250 grams per ton of original ore a recovery of 50% was 
attained of a material having a content of 20% WO.sub.3. However, the use 
of this collector also did not appear feasible for the commercial 
practice, because of the phenomenon of over-frothing. 
(c) In this experiment a mixture of 200 grams/ton of the compound of part 
(b) and 100 grams/ton of the fatty acid salt of part a) was used. A 
recovery of 60% was obtained of a material containing 25% of WO.sub.3. 
However, this time no trouble with over-frothing was experienced, and 
accordingly a clear synergistic effect was obtained. 
EXAMPLE 2 
A phosphate ore of magmatic origin was used containing about 7% of P.sub.2 
O.sub.5 with a gangue of mainly silicates and Fe-minerals. A requirement 
for a good flotation is that the floated material should have a content of 
at least 36% of P.sub.2 O.sub.5. In all experiments the pH had been 
adjusted at 10.2 with the aid of sodium carbonate. Due to this calcium was 
precipitated which amounts to a dehardening of the water. 
(a) 750 grams/ton of a tall oil distillate was used containing principally 
fatty acids. The recovery was 84% and the floated material contained over 
36% of P.sub.2 O.sub.5. 
(b) 150 grams/ton was used of a product having the formula C.sub.14 
H.sub.29 --(OC.sub.2 H.sub.4).sub.n OCH.sub.2 COONa, wherein n had an 
average value of 2. The recovery was 87% of a product containing 33% of 
P.sub.2 O.sub.5. In this experiment difficulties were experienced by too 
much frothing, which resulted in a lower selectivity. 
(c) A mixture of 200 grams/ton of the tall oil distillate of part (a) and 
100 grams/ton of the compound of part (b) was used as collector. Again a 
recovery of 87% was obtained with a P.sub.2 O.sub.5 content of floated 
material of over 36%, but this time without difficulties caused by too 
much frothing. 
EXAMPLE 3 
The original ore contained about 55% of fluorite with as gangue SiO.sub.2, 
CaCO.sub.3 and BaSO.sub.4 ; the BaSO.sub.4 was previously floated with 
alkyl sulphate. The remaining material was used for flotation experiments 
with the aim of recovering fluorite. The requirement for the floated 
fluorite is that it should be at least 97% pure. 
(a) Commercial oleic acid was used in an amount of 250 grams/ton (of the 
original ore) at a pH of 8, using tannins (500 grams/ton) to depress the 
calcite. The recovery was 80% and the floated material contained over 97% 
of fluorite. 
(b) This experiment was carried out at a pH of 6 using as collector 100 
grams/ton (of original ore) of oleyl-(OC.sub.2 H.sub.4).sub.n OCH.sub.2 
COOH, wherein n has an average value of 6. The recovery was 93% and the 
floated material contained over 97% of fluorite. The collector was added 
as the sodium salt. 250 Grams/ton tannin proved to be sufficient to 
depress the calcite. Remark: The pH-value of 6 was chosen for this 
experiment, because it is an optimum for the use of this material (the pH 
was adjusted to the desired value of 6 with H.sub.2 SO.sub.4). At higher 
values excessive frothing causes the flotation to be unfeasible for 
practical purposes. However, the pH of 6 is generally unpractical for 
using in flotation plants, because almost all flotations, and in this case 
the previous flotation with alkyl sulphate, are carried out at much higher 
pH-values. 
(c) This experiment was carried out again at pH 8 at a tannin consumption 
of 500 grams/ton. The collector was a mixture of 90 grams/ton of the oleic 
acid of part (a) and 30 grams/ton of the oleyl compound of part (b). The 
recovery was 91.5% and the floated product contained more than 97% of 
fluorite. Remark: Although the recovery was a fraction lower than in 
experiment (b) the process of experiment (c) is much more acceptable in 
actual practice, because no exceptional pH has to be used. Moreover, the 
cost of the collector mixture of experiment (c) is lower than that used in 
experiment (b). 
EXAMPLE 4 
A magnesium ore was used containing about 45% of magnesite with principally 
SiO.sub.2 and dolomite as gangue. The experiments were carried out at a pH 
which had been adjusted with NaOH at 11.0, using sodium hexametaphosphate 
as a dolomite depressant. Experiment (a) collector: commercially available 
tall oil distillate, predominantly containing fatty acids. This distillate 
was of different quality than that of Example 2. It was used in an amount 
of 450 grams per ton of ore. The magnesite recovery was 83% and the 
floated product contained 90% of magnesite, the remainder being 
predominantly dolomite. 
(b) A mixture of 150 grams/ton of the crude tall oil of part (a) and 150 
grams/ton of C.sub.6 H.sub.13 OCH.sub.2 COONa was used as collector. This 
time the recovery was 90.5% at a comparable concentrate grade. 
EXAMPLE 5 
The starting ore contained PbS and ZnS, together with barite as principal 
economical constituents. The PbS and ZnS were removed by a usual xanthate 
flotation. The tailing of this flotation contained about 20% barite, the 
remainder being predominantly iron minerals and silicates. It was desired 
to recover as much as possible of this barite by flotation. The flotation 
of the barite was carried out at pH 7.5. 
(a) 300 grams/ton of original ore of the same tall oil as in Example 2 (as 
sodium salt) was used as collector. The recovery of barite was 78% and the 
floated material contained 96% of barite. 
(b) A mixture of 150 grams/ton of the tall oil of part (a) with 30 
grams/ton of nonylphenyl-OCH.sub.2 -COONa was used as collector. The 
recovery was 87% and the floated product contained 96% of barite. 
EXAMPLE 6 
The original ore was a copper ore containing both sulphidic and oxidic 
copper minerals. The copper sulphides were first removed as far as 
possible by a usual flotation with xanthate. The remaining material 
contained oxidic copper minerals, intergrown to a large extent with the 
gangue minerals. In order to recover the oxidic copper minerals at the 
highest possible grade the material should be crushed again, in order to 
arrive at the oxidic copper from the gangue. However, it is desirable to 
carry out this recrushing treatment with as little of the original 
material as possible, and to this end a flotation is used with the aim to 
obtain a material of which the particles contain a reasonable percentage 
of copper so that recrushing of these particles will be worthwhile. The 
flotation experiments of this example were carried out at pH 8.5. 
(a) As collector 650 grams/ton of original ore of commercial sodium oleate 
was used. The recovery was 57% and the floated material contained 10.9% of 
Cu. 
(b) 300 grams/ton of original ore of dodecylphenyl-OCH.sub.2 COONa were 
used as collector. A copper recovery of 67% was obtained and the floated 
material contained 9.2% of Cu. However, the use of this collector did not 
appear quite feasible in practice because of overfrothing. 
(c) A mixture of 350 grams/ton of the commercial sodium oleate with 140 
grams/ton of the dodecylphenyl compound of part (b) was used as collector. 
This time a recovery of 70% was attained and the concentrate graded 9.7% 
of Cu. This time no difficulties by over-frothing were experienced so that 
this collector mixture is more suitable for actual practice. 
EXAMPLE 7 
The starting product was an iron ore originally containing about 2% of 
P.sub.2 O.sub.5 with as gangue minerals principally silicates and small 
amounts of CaCO.sub.3. The iron constituents were present largely as 
magnetite and were removed for the greater part magnetically. A flotation 
was now carried out with the aim of recovering as much as possible 
apatite. The flotations were carried out at pH 9.0 (adjusted with NaOH). 
(a) 275grams/ton of original ore of fish oil fatty acid were used as 
collector. The recovery was 70% at a grade of 24.5% of P.sub.2 O.sub.5. 
(b) As collector a mixture was used of 140 grams/ton of the fish oil fatty 
acid of part (a) and 70 grams/ton of C.sub.8 H.sub.17 OCH.sub.2 COONa 
(same product as in Example 1). A recovery of 75% was obtained and the 
floated product contained 31.0% of P.sub.2 O.sub.5. 
EXAMPLE 8 
The ore used for the flotation was a fluorite ore containing about 35% of 
fluorite with ankerite, calcite and silicates as principal gangue 
minerals. The flotation experiments were carried out at a pH which had 
been adjusted at 10.2 with sodium carbonate, whereas dextrin was used as a 
depressant for gangue minerals. 
(a) 800 grams/ton of the same tall oil distillate as used in Example 4 was 
used as collector. The recovery was 89% and the floated material contained 
96.5% of CaF.sub.2, 2.1% of carbonates and 1.0% of SiO.sub.2. 
(b) A mixture of 200 grams/ton of the tall oil distillate of part (a) and 
200 grams/ton of C.sub.8 H.sub.17 O-CH.sub.2 -COONa was used as collector. 
The recovery was 91% and the floated material contained 97.8% of 
CaF.sub.2, 1.3% of carbonates and 0.7% of SiO.sub.2. 
EXAMPLE 9 
A fluorite ore was used containing about 65% of fluorite with as gangue 
minerals quartz and mica. The flotation experiments were carried out at a 
pH-value of 8.5. 
(a) 425 grams/ton of the same tall oil distillate as in Examples 4 and 8 
were used as collector. The recovery was 94% and the floated product 
contained 94% of fluorite. It should be remarked that this is a too low 
grade which is caused by the mica in the gangue. 
(b) A mixture of 150 grams/ton of the tall oil distillate of part (a) and 
75 grams/ton of myristyl-(OC.sub.2 H.sub.4).sub.n -OCH.sub.2 COONa, 
wherein n has an average value of 2, was used as collector. This time the 
recovery was 95% and the floated material contained over 97% of fluorite. 
EXAMPLE 10 
The starting product was a copper ore containing both sulphidic and oxidic 
copper minerals. The sulphidic copper minerals were first removed by a 
standard flotation with xanthates. The aim of the present experiments was 
to recover as much as possible of the oxidic copper minerals. The 
experiments were carried out at a pH which had been adjusted at 10.5 with 
NaOH. 
(a) The same tall oil distillate as in Examples 4, 8 and 9 was used as 
collector in an amount of 500 grams/ton of original ore. The recovery was 
65%, and the floated material contained 25% of Cu. 
(b) A mixture of 300 grams/ton of original ore of the above tall oil 
distillate with 100 grams/ton of original ore of oleyl-(OC.sub.2 
H.sub.4).sub.n OCH.sub.2 COONa, wherein n has an average value of 6, was 
used as collector. The floated product again contained 25% of Cu, but this 
time the recovery was 78%. 
EXAMPLE 11 
The original ore contained both barite and fluorite as valuable 
constituents. First the barite was floated with an alkyl sulphate type 
collector. The tailings of this flotation contained about 25% of fluorite 
with SiO.sub.2 as the principal gangue mineral. It was desired to recover 
the fluorite in a purity of at least 97% (according to usual 
specifications). 
(a) 500 grams/ton of ore of a commercial available twice distilled tall oil 
fraction, predominantly containing fatty acids, was used as a collector at 
pH 8. The recovery was 85% and the floated product contained over 97% of 
fluorite. 
(b) 125 grams/ton of original ore of hexylphenyl-O-CH.sub.2 COOH was used 
as the collector at pH 6 (adjusted with H.sub.2 SO.sub.4). This pH had 
been chosen after previous experiments had shown that this was the optimum 
pH for this flotation. The collector was added as the sodium salt to the 
acidic pulp. The recovery was 93%, and the floated product contained again 
over 97% of fluorite. Although the recovery has increased, the pH of 6 
which, as stated already hereinabove, is rather exceptional in flotation 
practice, means a serious drawback for actual application. 
(c) A mixture of 200 grams/ton of original ore of the tall oil distillate 
of part (a) and 80 grams/ton of original ore of the compound of part (b) 
was used as collector, this time at pH 8 again. The same recovery was 
attained as in part (b), i.e. 93%, and the floated product contained over 
97% of fluorite. 
EXAMPLE 12 
A fluorite ore was used containing about 40% of fluorite which was 
intimately intergrown with the SiO.sub.2 gangue. Consequently, the ore was 
ground to a relatively fine size distribution. The flotation experiments 
were carried out at a pH which had been adjusted at 10 with sodium 
hydroxide. 
(a) 475 grams/ton of ore of commercial sodium oleate were used as 
collector. The recovery was 79%, and the floated material contained over 
97% of fluorite. Losses of fluorspar were mainly due to very fine 
particles. 
(b) A mixture of 325 grams/ton of the sodium oleate with 125 grams/ton of 
nonyl-phenyl-OCH.sub.2 -COONa was used as collector. The recovery this 
time was 89% and the floated product again contained over 97% of fluorite. 
EXAMPLE 13 
The original starting product was a barite-containing ore grading about 30% 
of barite. According to a known method the crushed ore was upgraded by a 
dense medium separation (with ferro silicon slurry), wherein the light 
silicates were separated for the greater part. In this way a concentration 
of the ore to about 80% of barite was obtained. This preconcentrated ore 
was used for the flotation experiments. These experiments were carried out 
at a pH which had been adjusted at 10.5 with NaOH. 
(a) 750 grams/ton of original ore of commercial oleic were used as 
collector. The recovery was 95% and the floated material contained 96% of 
barite. 
(b) 300 grams/ton of original ore of dodecylphenyl-(OC.sub.2 H.sub.4).sub.n 
OCH.sub.2 COOH, wherein n has an average value of 10, were used as the 
collector. The recovery was 97.5%, and the barite content of the floated 
material was 95%. It appeared that this collector was not feasible for 
practical purposes, because of excessive frothing, resulting into lower 
grades by the mechanically floated gangue particles. 
(c) A mixture of 125 grams/ton of original ore of the oleic acid and 250 
grams/ton of original ore of the dodecylphenyl compound of part (b) was 
used as collector. The recovery was 96% and the floated material contained 
97.5% of barite. This time no excessive frothing occurred. 
EXAMPLE 14 
A fluorite ore was used containing about 70% of fluorite with as gangue 
minerals principally SiO.sub.2 with small percentages of CaCO.sub.3 and 
CaSO.sub.4. The flotation experiments were carried out at pH 8. 
(a) Commercial oleic acid in an amount of 1000 grams/ton of ore was used as 
the collector. The recovery was 93% and the floated material contained 
more than the required 97% of fluorite. 
(b) A mixture of 275 grams/ton of ore of the oleic acid with 100 grams/ton 
of ore of dodecylphenyl-(OC.sub.2 H.sub.4).sub.n OCH.sub.2 COOH, wherein n 
has an average value of 10, was used as collector. At this much lower 
collector consumption again a recovery of 93% was obtained, and the 
floated material again contained over 97% of fluorite. 
EXAMPLE 15 
A sedimentary phosphatic ore containing 18% of P.sub.2 O.sub.5 was floated 
after desliming by conventional methods at pH 10 with NaOH, using a 
mixture of petroleum sulfonate and fatty acids as collectors. The rougher 
concentrate was cleaned and recleaned. 
(a) As the fatty acid collector 1000 grams/ton of flotation feed of a crude 
tall oil was used. A concentrate grading 31.5% of P.sub.2 O.sub.5 was 
obtained at a flotation recovery of 89%. 
(b) 500 grams/ton of crude tall oil and 100 grams/ton of C.sub.14 
[(OC.sub.3 H.sub.6)-(OC.sub.2 H.sub.4)].sub.n -OCH.sub.2 COOH, wherein n 
has an average value of 4, consisting of 2 units of propylene oxide and 2 
units of ethylene oxide, were used as collector. At this reduced collector 
consumption a high recovery of 93% was obtained and the grade even 
amounted to 32.4% of P.sub.2 O.sub.5. 
(c) 500 grams/ton of crude tall oil and 20 grams/ton of the compound 
described under (b) resulted in a flotation recovery of 89% at a grade of 
32.1%. Remark: In practice, the most desired collector recipe strongly 
depends on prices of phosphate concentrates at different grades and 
collector costs. 
Evidently, various modifications can be made in the light of the discussion 
and disclosure hereinabove without departing from the scope thereof.