Note: Descriptions are shown in the official language in which they were submitted.
6~)8Z
MINERALS FLOTATION
The present invention relates to phosphonic acids and to the
benefication therewith of mineral ores by floation.
Hitherto, beneficiation of mineral salt ores such as barite
and fluorite has been carried out by gravity means or by flotation
techniques. In the latter techniques the ore is 3round and the
sulphide content of the ore is first removed by a flotation stage
using, for example, a xanthate as the collector. The substantially
sulphide-free ore is then subjected to a further flotation process
to bring about the flotation of the mineral salt. Among compounds
proposed for use as the flotation agent or collector are fatty
acids and petroleum sulphates and sulphonates.
One problem with these agents is that significant amounts of
collectors and depressants are needed to achieve acceptable
beneficiation~ We have found certain substituted amino phosphonates
which are highly effect,ve as flotation agents for mineral salt
ores.
The amino phosphonates are substituted amino phosphonic acids
(and their water soluble salts) having the general formula Ra
R1b R2C N(R3Po3H2)3-a-b-c especially
RN(CH2P03H2)2, where each of R, R1 and R2 is an organic
group, e.g. optionally subsituted alkyl or alkenyl group of 1-20
carbon atoms or an aryl aralkyl cycloaliphat;c or cycloaliphatic
alkyl group, and R3 is a divalent organic group, e.g. alkylene,
cyclohexyldene, alkylidene or benzylidene, each of a, b and c is O
orl , but when a is 1, b and c are 0, and when a is 0, b and c are
1. These compounds may be made by reacting a primary amine of
fonnula RNH2 or a secondary amine of forrnula R1R2NH with an
aldehyde or ketone of formula R30, in which the two valencies on
R3 are joined to the same carbon, and phosphorus acid or a
phosphorus trihalide under acid condition, and subsequently if
desired adding a base to make the salt. Where the free valencies
in the R3 group are attached to different carbon atoms, the
,~r~,
~Z160~2
compounds may be made from the amines with a haloorganyl phosphonic
acid, e.g. chloroethyl phosphonate. The substituted amino di
phosphonates, especially substituted imino bis(methylene
phosphonates) are preferred.
The present invention also provides a process for the benefi-
ciation of a mineral salt ore which comprises subjecting an aqueous
slurry of said ore at pH 1.5-11, to froth flotation in the presence
of at least one substituted amino phosphonic acid or salt thereof
of general formula RaR1bR2cN(R3P03H2)3-a-b-c and
separating a fraction comprising beneficiated mineral salt from a
second fraction depleted in said salt.
In the substituted amino phosphonate, the group R, preferably
an alkyl group, especially conta;ns 3 20 e.g. 4-20 or 4-14 carbon
atoms such as 6-12 carbon atoms; compounds in which group R has 5-
10 or9-14 carbon atoms give optimum results with the beneficiation
of scheelite ores, while compounds with R as an alkyl group of 3-9,
e.g. 3-6 carbon atoms may give optimum results for purifying barite
and fluorite ores. Thus group R may be a straight or branched
chain group and may be a propyl butyl, amyl, hexyl, heptyl, octyl,
nonyl, decy1, dodecyl group such as n propyl, isopropyl n butyl,
sec butyl, n amyl, n hexyl, n heptyl, 5-methylh2x-2-yl n-octyl, 2-
ethyl hexyl, 6-methylhept-2-yl, isononyl, n-nonyl, lauryl, cetyl,
oleyl or stearyl group; n heptyl, n octyl and 2-ethylhexyl groups
are preferred. Any branching in the chain is preferably at most 3
carbon atoms a~ay from the free valency of the R group. In the
alkenyl group the double bond is not attached to the carbon atom of
the group R bearing the free valency. The substituent in the alkyl
or alkenyl group may be an hydroxy group, an alkoxy group or
dialkyl amino group, each alkyl being of, e.g. 1-12 carbon atoms;
preferably the substituent alkyl group is an alkoxyalkyl group with
2-12 carbons e.g. 2,3,8, or 9 carbons in the alkoxy group and 2-6
carbons e.g. 2 or 3 carbons in the alkyl group, such as 3-ethoxy
608Z
-- 3 --
propyl, 3- n butyloxy propyl, 3-(2-ethylhexyloxy) propyl or 3-
(isononyloxy~ propyl groups. Example of the aralkyl group are
hydrocarbyl ones of 7-13 carbons such as benzyl, methyl benzyl and
ethyl benzyl, 1-phenylethyl and 2-phenylethyl, and hydroxy or
alkoxy (e.g. methoxy) nuclear substituted derivatives of such
hydrocarbyl groups. Examples of the aryl group are hydrocarbyl
ones of 6-12 carbons such as phenyl, tolyl, xylyl and naphthyl. The
cycloaliphatic group is usually hydrocarbyl with 5-7 carbon atoms
as in cyclohexyl, while examples of hydrocarbyl cycloaliphatic
alkyl groups are cyclohexyl methyl and 2 cyclohexylethyl.
The groups Rl and R2 which may be the same or different may
be as described above for R, but preferably at least one is an
alkyl group, preferably both are alkyl groups, in particular alkyl
groups of 2-10, e.g. 3-8 carbon atoms with two alkyl groups, each
of 3-5 carbons being preferred for purifying barite and fluorite
ores and each of 4-6 carbons being preferred for purifying
scheelite ores. Thus the group R1R2N may be derived from di
alkylamines such as di butyl-, di pentyl, di hexyl-l di 2,-ethyl-
hexylamine or di cyclohexylamines~
The group R3 is a divalent organic group in which the two
free valencies may be on the same or different carbon atoms. When
they are on the same carbon atom, R3 may be an alkylidene group,
e.g. of 1-10 such as e.g. 1-3 carbon atoms as in methylene or
ethylidene or isopropylidene, a cyclohexylidene group or an
arylalkylidene group, e.g. of 7-19 carbons, e.g. a benzylidene or
tolylidene group. When the valencies are on different carbon atoms
R3 may be an alkylene group of 2-10, e.g. 2 or 3 carbon atoms or
an aryl alkylene group of 8 to 20 carbons such as 2-phenyl 1,2
ethylene sroup. Preferably R3 is a methylene group.
The water soluble salts are usually ammonium or alkali metal,
e.g. sodium or potassium salts. The compounds may be added to the
flotation medium as their free acids or as partly or completely
neutralized salts or a mixture thereof.
~z~08Z
-- 4 --
In the process used to make the compounds in which R3 has two
free valencies on the same carbon, the reagents may be heated
together at 50-150C, e.g. 50-110C, often for 0.1-4 hrs, and
often in a solvent, e.g. water. Preferably in order to stop
competing reactions between the amine and carbonyl compound, e.g.
formaldehyde, the amine and phosphorous acid and/or phosphorus
trichloride are mixed first and then the carbonyl compound added
afterwards. The reaction is performed in acid solution with the
acid, e.g. hydrochloric acid being added separately or made in situ
from the phosphorus trichloride and water. At the end of the
reaction, the product may 4e isolated as such or after treatment
with a base, e.g. ammonia or ammonium hydroxide or an alkali metal
hydroxide or carbonate, e.g. sodium hydroxide. ~owever, as the
substituted amino phosphonic acid or salts will be used in aqueous
solution, it is preferably not isolated from the aqueous reaction
product, but the aqueous solution is used as such or after dilution
~;th water.
The mineral salts, which may be beneficiated by the amino
phosphonate collectors, are slightly water soluble with a
solubility product of 10-11 to 10-4, e.g. 10-1 to 10-5.
The mineral salts are ones capable of being floated in froth
flotation with anionic collectors ~e.g. at 200 mg/l concentration
of collector) such as oleic acid under acid neutral and alkaline
conditions, e.g. pH 1-11, except, of course, where use of
particular conditions causes breakdown of the salt, e.g. wih metal
carbonates. The salts are preferably divalent metal salts, in
particular ones of Group 2A of the Periodic Table, e.g. with
cations of Galcium strontium or barium, or lead or magnesium. The
anionic part of the salts are usually sulphates or fluorides, but
may be carbonates, or tungstates; preferably the salts are with
divalent or monovalent anions. Preferably in the mineral salt at
least one of the cation and anion contains barium, strontium,
fluorine, lead or tungsten. Particular mineral salts are barite,
lZ~6C~IB2
-- 5 --
calcite, fluorite or fluorspar, celestite, anglesite, ~agnesite,
scheelite, of which usually all but calcite are preferentially
floated in the froth and recovered therefrom. The mineral salt ore
may contain 0.1~50% by weight of the mineral salt, e.g. 1-30~.
These mineral salt ores usually contain not only the desired salt
such as a sulphate or fluoride or tungstate, but also other mineral
salts which are usually regarded as contaminants such as calcite or
magnesite, but may be valuable, as well as undesirable compounds
such as quartz or silicates such as feldspar, mica, tourmaline and
chlorite; the flotation process enables separation of the above
desired salt from the silicates, and often from the other mineral
salts as well under the correct conditions. The mineral salts are
not metal sulphides, though these may be present in the ore. While
usually it is the mineral salt which is preferentially floated away
from the contaminants, e.g. quartz silicate, calcite, apatite or
magnesite/dolomite, in some cases, particularly with calcite e.g.
under alkaline conditions, the calcite may be preferentially
floated ahead of the m;neral salt.
~ ormally, prior to being subjected to a flotation process in
the presence of the substituted amino phosphonic acid collector,
the ore is ground and then classified at less than 800~ m, e.g.
less than 500~um. The slimes (i.e. particles of a size less than
20 or 10~um, or 5 ~m) are optionally separated, e.g by cyclone
classification technique. The ore is also normally subjected,
before or after the desliming stage, to a preliminary froth
flotation with a sulphur containing collector, e.g. a xanthate salt
such as potassium ethyl or amyl-xanthate in order to remove the
sulphide values of the ore. Thus the mineral salt ore is fine
grained, deslimed and substantially sul?hide free.
The ore in the form of an aqueous slurry usually of particles
of 10-75 ~m size is then subjected to a froth flotation process in
the presence of the substituted amino phosphonic acid or salt
o~z
- 6 -
described above. In the flotat;on cell the aqueous slurry is
treated with air to form a froth in which the mineral salt usually
becomes concentrated leaving usually a higher proportion of gangue
behind in the aqueous tailings phase. The froth is separated and
mineral salt recovered. Any suitable frothing agent may if desired
be employed to reduce the surface tension at the liquid gas
interface. Examples of frothing agents are liquid aromatic
hydrocarbons of 6-10 carbons such as benzene, toluene or xylene,
alcohols, e.g. alkanols, of 4-18, e.g. 6-12 carbon atoms, and
polyglycol ethers, polypropylene glycols, phenols and alkyl benzyl
alcohols. However, in view of the surface active properties of the
higher alkyl (e.g. 6-20 carbon) substituted aminophosphonic acids,
it is often possible to carry out the flotation without recourse to
the addition of a foaming or frothing agent. After the amino
phosphonate has been added to the slurry of mineral salt ore, there
is usually a delay, e.g. of 0.1-10 mins, e.g. 0.5-4 mins such as 1
or 2 mins to pe~it condit-oning of the ore before the start of the
frothing.
The flotation process is usually carried out at a pH of 1.5-
11, such as 5-11, normally of 8-11 and especially 9.5-11. The pH
may be adjusted by addition of an alkali (such as caustic soda) or
acid (such as sulphuric acid). In the case of mineral salt ores
which contain carbonates or phosphate, the pH is usually 5-11.
These compounds may be employed in amounts depending upon the
content of the ore of the mineral salt to be recovered and the
presence of interfering ions and/or minerals, increases in all of
which necessitate increases in amount of collector. Usually at
least an effective amour,t of the collector is used. Generally the
concentration Ot the amino phosphonate collector in the slurry is
25-500, e.g. 50-500 or 150-300 mg/l. The amount of collector based
on the solids content of the slurry, may be 50-1000 5 per tonne of
lZl~C18
7 -
ore, e.g. 100-600 9, especially 20~-500 9, per tonne of ore solids
in the slurry in the first flotation treatment to which the ore has
been subjected, Thus if the ore is subjected to a froth flotation
to remove sulphide then the amount of amino phosphonate is
expressed per tonne of the ore going into that sulphide
pretreatment. Likewise if there is no prior froth flotation to
remove sulphide then the amount of amino phosphonate is expressed
per tonne of ore going to the first amino phosphonate flotation.
The solids content of the slurry is usually 20-45~ by weight. The
frothing step may be performed for 1-60 rnins, e.g. 1-10 mins.
Once the mineral salt has been floated it remains on the
surface of the liquid in the flotation vessel in the form of a
froth which may be removed by mechanical means and the ~ineral salt
recovered therefrom. ~ence in that process the aqueous slurry of
ore is subjected to a froth flotation process which produces a
froth comprising a purified mineral salt fraction of higher mineral
salt content than in the ore and an aqueous phase comprising
tailings of lower mineral salt content than the ore. It is
possible, e.g. in the case of ores comprising calcite and a mineral
salt, which floats less well than calcite, for the froth to
comprise the lower purity fraction with calcite and the aqueous
phase to comprise the higher purity mineral salt fraction. In the
general case therefore the froth flotation process produces 2
phases, a froth phase of product of one purity of mineral salt and
an aqueous phase of product of a second purity of mineral salt, and
the phases are separated and the product of higher purity of
mineral salt is recovered.
~ hen the desired product is in the froth phase the collector
may De added in more than 1, e.g. 2-4 portions, with the froth
being separated after each addition, the froth fractions being
successively less purified with respect to gangue materials. This
technique may be advantageous when the collector concentration is
Z
low giving high selectivity, but low recovery in each step; keeping
the collector concentration low and adding more successively can
give overall high recovery as well as the high selectivity.
Some of the substituted amino phosphonic acid collectors, e.g.
those in which the group R is an alkyl group of 6-9 carbon atoms,
may show a selectivity in froth flotation for the mineral salts
over silicates such as tourmaline and/or chlorite, both often
occurring with mineral salts. Thus differential froth flotation
can be used to purify the ore.
The substituted amino phosphonic acid collectors may be used
alone or mixed with one another or mixed with other collectors such
as fatty acid salts, e.g. as oleic or linoleic acid salts or an
alkyl phosphonic acid, e.g. as octyl phosphonic acid or styrene
phosphonic acid or sulphonates or sulphates, e.g. alkyl
sulphcsuccinates or alkyl sulphosucc~na~atee.
In order to improve the selectivity of the flotation for the
mineral salts over gangue materials and/or to increase the recovery
of mineral salts, pretreatments and/or precleaning operations may
be performed. Examples of pretreatment are attrition, conditioning
with the amino phosphonate and/or depressants for, e.g. iron, and
addition of sodium silicate as a depressant for iron silicates;
prewashing with dilute acid may be used with salts stable thereto
to help reduce any adverse influence of iron on the flotation. The
precleaning operation is part of the froth flotation involving the
amino phosphonate with the first froth flotation operation giving a
first froth and a first tailings and the first froth being diluted
with water and then refrothed to give a second purer froth and a
second tailing. The mineral salt content of the second froth is
recovered and the second tailings are recycled to the first froth
flotation step or to the step of slurrying the ore. Solids are
separated or allowed to separate from the first tailings and the
:lZ~082
g
aqueous mother liquor recycled to the first or second froth
flotation step. If desired, a third flotation step may be
performed. In each froth flotation step the flotation may take
place in 1 or more cells in parallel; usually in the first rougher
flotation step 3-8 such as 4-6 cells are used while 1 or 2 cells
may be sufficient for the second and any subsequent steps. In
order further to aid selectivity (i.e. upgrading of the ore), any
or each froth flotation step may include deep froth flotation, in
which only the uppermost part of the froth (with the highest
enrichment) is removed, with the rest of the froth being recycled
to the froth flotation cell from whence it came.
Examples of the beneficiatioon that may be perfonmed with
amino diphosphonates with group R an alkyl of 7-9 carbons and the
specific conditions, are the froth flotation of barite or fluorite
away from silicates at pH 2-11, away from quartz silicates and
magne,ium carbonate and/or calcium carbonate and/or apatite at pH
9-11, away from quartz and magnesium carbonate at pH 3-11 and a~ay
from calcium carbonate and/or apatite at pH 2-4; amounts of 20-100
or 20-50 mg/1 or 100-1000 g/tonne of amino diphosphonates with
group R representing an alkyl group of 4-9 carbons, in particular
n-butyl, amyl or n-hexyl groups are preferred, while n heptyl, n-
octyl or 2-ethylhexyl groups for R often give benefit. Separation
of barite or fluorite from gangue especially apatite at pH 3-11 may
also be performed with the amino diphosphonates in which R is
butyl, as may separation of barite from fluorite with that amino
diphosphonate at pH 9.5-11, though in the latter case the order of
flotation may depend on the degree of crystallinity of the barite
and fluorite, the former otherwise having the greater tendency to
float. Separation of scheelite from silicates and quartz may be
performed with the above preferred amino diphosphonates in which ~
is an alkyl group of 7-9 carbons. Scheelite may also be separated
from silicates and quartz at pH 3-11, such as, 3-9;5, e.g. 3-7 or 8-10.5,
with longer chain amuno diphosphonates in which R is an aIkyl group of
9-13 carbon atoms, in particular, isononyl and n-dodecyl groups.
i .
lZ1~12
- 10 -
While scheelite can be floated from silicates with the long
chain alkyl am;no diphosphonates, the scheelite often contains
barite and/or fluorite and/or calcite which is preferentially
flotated with those compounds. To overcome this problem, the
barite/fluorite/calcite may be floated in a pretreatment step with,
e.g. a lower alkylamino bis methylene phosphonate ,
to leave in the tailings the scheelite and silicates, and then thP
tailings may be treated with the long chain alkylamino compounds to
float the scheelite and leave the silicates in the tailings.
The invention is illustrated in the following examples, in
Examples 1-6 of which the term "full flotation'` in these examples
means that the agglomerated particles of minerals are carried to
the surface of the liquid with some retention of them at the
surface, and the term "three quarters flotation" means that the
agglomerated particles are carried to the surface of the liquid,
but with no retention thereof at the surface.
Examp~e 1
Vacuum flotation tests were carried out in 30 ml glass tubes
attached to a vacuum pump. Samples (200mg) of pure fluorite
mineral of 150-75~ size were mixed with aqueous solutions t25ml) of
the pH 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5,
8.0, 8.5, 9.0, 9.5, 10.0, containing the collector specified below.
After 10 minutes, a vacuum was applied to the tubes and flotation
was then assessed to have occured when flocculated mineral was
observed to have been floated by the precipitated air bubbles. The
collector was of formula RN (CH2 P03Na2)2 where R was n-octyl.
The minimum amount of the collector needed to effect full flotation
of the mineral at each of the quoted pH's was noted.
pH mg/l
2-10.5 100
3-10 50
4-10 20
4.5-11 10
lZl~i08Z
- 11 -
Ex~mple 2
Tne tests of Example 1 were repeated with barite~ The results were
as follows.
pH mg/l
2-10.5 200
2-10 100
2-9.5 20
2-10.5 10
Exam~e 3
In a similar manner to that of Example 1~ a sample of scheelite
(calcium tungstate) was tested in the vacuum flotation apparatus.
The amount of the collector needed to effect three quarters
flotation of the mineral ~t the pH figures quoted were noted and
was found to be 200 mg/l at pH 4.8-7.5.
eomparative-Examples
In a similar manner to that of Example 1, the flotation propert;es
of various gangue minerals often associated with the minerals of
Example 1-3 were also tested. The minerals were dolomite, calcite,
apatite, garnet, tourmaline, chlorite, quartz. The amounts of
co11ector needed for three quarters flotation of the mineral at the
pH f;gures were as follows,
pH
mgtl ~olomite ealcite Apatite earnet Tourma~ine ehlorste
2~Q 4.5-8 2.5-10 2.5-9 2-8 2-7 2-11
100 5-8 3-10 3.5-8.8 2-7 2-6.5 3-8
5.5-8 3.5-9.5 4.2-8.2 2-7 2-6 4-7
6.5-7.53.8-8.5 5.5-6.5 2-8 2-6
- 4.2-7.5 - 2-7 2-5.8
82
- 12 -
The results for full flotation of the minerals were as follows
pH pH pH
mgltl ~alcite ~arnet Tourmaline
200 3-6 2-7 2-4. 1
100 4-5 2-6 2-4. 1
2-6
2-7
Essentially no flotation occurred at pH 2-11 wi th amounts of
collector of 200 mg/l or less with quartz.
Thus the minerals of Examples 1-3 may be separated from quartz by
flotation, and the minerals of Examples 1 and 2, from apatite and
dolomite at above pH 9, e.g. 9-11.
~xamples-4,5 an 6;~
The experiments of Examples 1-5 were repeated using as collector N-
n- butyl imino bis methylene phosphonic acid or n-hexyl imino bis
methylene phosphonic acid (each being as the di sodium salt in
aqueous solution). The results were as follows.
.
Bartte E~amp7e~4;5
n butyl compound - Three quar~ers flotation of the mineral at pH 2-
11 and 10-200 mg/l col7ector and full flotation of the mineral at
DH ~-S and 75-100 mg/1 collector.
n hexyl compound - Three quarters flotation of the mineral at pH
2.5-10 at 200 mg.l, and pH 2.5-11 at 10-100 mgtl collector. Full
flotation of the mineral at pH 3-8 at 200 and 100 mg/l, pH 3-8.3 at
50 mg/l, pH 3-9 at 20mg/1 and pH 3.1-9.4 at 10 mg/1.
'.
~2~08Z
- 13 -
Flaorite^Example 6,7
n butyl compound - Three quarters flotation of the mineral at pH 2-
9.5 at 10-200 mg/l and full flotation of the mineral at 3.3-6.6 at
200mg/1, pH 3.5-6.8 at 100 mg/l, pH 3.8-6.8 at 50 mg/l, at pH 4-7
at 20 mg/l and pH 4.5-7.1 at 10 mg/l.
n hexyl compound - Three quarters flotation of the mineral at pH 2-
10.4 at 10-200 mg/l and full flotation of the mineral at pH 2-9.3
at 200 mg/l, pH 2.8-9.3 at 100 mg/l pH 2.9-9.5 at 50 mg/l, pH 2.9-
9.7 at 20 mg/l and pH 2.9-9.9 at 10 mg/l.
Comparison of the results for barite and fluorite compared to those
of calcite, dolomite and apatite below with the n butyl and n hexyl
compound show that the fluorite, but especially the barite may be
preferentially float~d at a pH above 9.5, e.g. 9.5-11.
~omparative Examples
The experiments of Examples 4-7 were repeated with each of apatite,
calcite and dolomite. The results were as follows.
Apat~te
With the n butyl compound there was no flotation at pH 2-11 and 10-
200 mg/l collector. With the n hexyl compound, there was three
quarters flotation of the mineral salt at pH 4-7.8 at 200 mg/l,
4.4-7.4 at 100 mg/l and pH 5.5-7 at 50 mg/l.
~alcite
N-butyl compound - Three quarters flotation of the mineral at pH
4.8-& at 200 mgil, pH 5.8-7.2 at lG0 mg/l, pH 5.6-6.9 at 50 mg/l,
pH 5.8-6.7 at 20 mg/l and pH 6-6.7 at 10 mg/l collector.
n-hexyl compound - Three quarters flotation of the mineral at pH 6-
9 at 200 mg/l, pH 6-8.9 at 100 mg/l, pH 6.2-8.7 at 50 mg/l, pH 6,3-
8.4 at 20 mg/l and pH 6.6-8.0 10 at mg/l.
8,Z
- 14 -
~olomite
n-butyl compound - Three quarters flotation of the mineral at pH
5,5-6.3 at 200 mg/l only.
n- hexyl ccmpound - Three quarters flotation of the mineral at pH
4.8-7.6 at 200 mg/l9 pH 5-7.3 at 100 mg/l and pH 5.7-7 at 50 mg/l.
E~amp7es-8~9
The experiments of Example 1 were repeated with scheelite as in
Example 3, and iso nonylimino bis methylene phosphonic acid and
also with n-dodecyl imino bis imino methylene phosphonic acid, in
each case added as their di sodium salts (in aqueous solution). The
results were as follows.
iso nonpl compound
Three quarters flotation of the mineral at pH 3-9.5 at 200 mg/l, pH
3.3-8.5 at 100 mg/l, but not below 70 mg/l at pH 2-11.
n-dodec~l compound
Three quarters flotation of the mineral at pH 6-11 at 200 mg/l, pH
2-11 at 100 mg/l, pH 2-7 at 50 mg/l, pH 2-5.7 at 20 mg/l and pH 2-
4.7 at 10 mg/l, and full flotation of the mineral at pH 6-7.3 at
200mg/l, pH 3.1-7.3 at 100 mg/l and pH 3.1-3.6 at 50 mg./l.
~,
lZ~O~Z
- 15 -
In Examples 10-13, the expression kg/tonne used ir conne~tion with
amounts of modifier or collector etc. means the amount expressed
per tonne of the original ore sample before grinding.
Example 10
A lkg sample of barite ore from England containing about 40.5~
barite and also silicates, sulphide, calcite and a small amount of
strontionite, was beneficiated as follows. The ore of particle
size passing a 1.7 mm screen was wet ground in a rod mill in 50
solids aqueous slurry for 15 minutes. The pulp obtained was
deslimed three times in a laboratory cyclone to separate slimes of
nominal 0.01 mm size. The resulting slurry which was at pH 8.5 was
diluted with water to a 30X solids slurry and then pretreated to
remo~e sulphides by conditioning for 3 minutes with 0.1 kg/tonne of
copper sulphate, added in aqueous solution followed by 5 minutes
cond~tioning with 0.02 kg/tonne sodium isopropyl xanthate~ then a
polypropylene gylcol frothing agent, sold under the trade name DOW
250, in amoun~ of 0.008 kg/tonne was added and the resulting s1urry
subjected to froth flotation with air. The froth, whioh cor.tained
sulphide, was separated from the aqueous slurry. The pH of the
aqueous slurry was adjusted to 10.0 by addition of sodium hydroxide
solution and then three portions of the collector, n-octyl iminobis
(methylene phosphonic acid) (added as -I sodium salt in aqueous
solution) were added followed by 2 minutes conditioning and froth
flotation with air after each addition to give Concentrates 1, 2
and 3, the froth flotat~on being for 3 minutes for Concentrate 1
and 2 minut2s for each of Concentrates 2 and 3. In each addition,
an amount of colle~tor of 0.2 kg/tonne was used. The froth was
separated afte~ each addition of collector and dried, weighed and
analysed for barium and strontium as ~ere the final tailings. The
results were as fo1lows.
~ Dist. ~ Stront- ~ Dist.
We~ ht ~ X Barite of Barite ionite Strontionite
9 _ _
Conc. 1 37.9~ 67.3 63.0 3.1 74.4
Conc. 2 11.50 44.7 12.7 1.8 13.1
Conc. 3 5.89 46.2 7.8 1.6 7.0
Talin s 43.66 15.3 16.5 0.2 5.5
g ~
100.00 (40.5) 100.0 1.58 100.00
121~)8Z
- 16 -
Example 11
The procedure of Example 10 was repeated using a fluor;te ore from
England contain;ng about 38.4~ calcium fluoride, as well as
sulphide~ silicates and calcite, and with flotation of the flusrite
at pH 9.5 instead of pH 10Ø The three cor,centrates and tailings
were dried, weighed and analyzed for calcium fluoride. The results
were as follows.
~ Distribution
Weigh~ ~ ~ CaF ~ of CaF ~__
Concentrate 1 32.08 83.1 69.38
Concentrate 2 13.05 70.8 24.05
Concentrate 3 4.85 26.7 3.37
Tailings _ 50.02 2.5 3.20
.
100.00 (3B.4) 100.00
Example 12
The procedure of Example 11 was repeated with a different collector
for the fluorite namely n-hexyl iminobis (methylene phosphonic
acid) (added in aqueous solution of a sodium salt) and addition of
that collector according to th~ following regime; 2 minutes
conditionlng with 0.2 kg/tonne collector and then froth flotation
to produce negligible floated matter, 2 minutes conditioning with
0.2 kg/tonne collector and flotation to give a froth (Concentrate
1) followed by addition of 0.2 kg/tonne collector and flotation to
give Concentrate 2, addition of a further 0.2 kg/tonne of collector
and frothing which gave no flotation of solids and, finally,
addition of a further 0.2 kg./tonne of collector and flotation to
give a froth (Concentrate 3) and tailings. The results were as
follows.
~ Concentration
Weight ~ ~ CaF ? of CaF ?
Concentrate 1 22.60 92.4 54.47
Concentrat~ 2 14.24 91.3 33.91
Concentrate 3 5.22 62.6 8.52
railin~s 57O94 2.05 3.10
10Q.00 (38.3) 100.00
12~ 3Z
- 17 -
Example 13
A lkg sample of scheelite ore from Spain containing about 0.53X W
and also silicates (especially mica~ and quartz was beneficiated as
follows. The ore of particle size passing a 1.7mm screen was wet
ground for 25 minutes in a rod-mill in 50~ solids aqueous slurry
containing 0.5 kg/tonne sodium silicate. The pulp obtained was
deslimed three times in a laboratory cyclone to separate slimes of
nominal 0.01 mm size from an aqueous slurry. The pH of this slurry
was adjusted to 10.0 with sodium hydroxide, the slurry diluted to a
30~ solids concentration and then to it was added 0.1 kg/tonne of
the collector n-dodecylimino bis (methylene phosphonic acid) (added
in aqueous solution as a sodium salt) with 2 minutes conditioning
followed by 2 further portions of the same amount of the same
collector each with 2 minutes conditioning. The slurry was then
subjected to froth flotation with air, but without the need for
added frothing agent to form a rougher froth concentrate and
roushef aqueous tailings wh~ch ~ere separated. The rougher
concentrate was reslurried to a 10~ solids slurry at pH 10.0 and
refrothed with air to glve a flrst froth concentrate and first
cleaner tailings which was separated. The first froth concentrate
was reslurried to a 10~ solids slurry at pH 10.0, 0.05 kg/tonne of
sodium silicate addea and the slurry refrothed with air to give a
second froth concentrate and second cleaner tailings~ which were
separated. The recleaner concentrate, first and second cleaner
tailings and rougher tailings were each dried, weighed and analyzed
for W. The results were as follows.
~ Distribution
Welght ~ ~ W of W
Recleaner Concentrate 4.78 7.34 66.77
Second cleaner ta~ling 5.44 1.11 11.49
First cleaner tailing 6.49 0.99 12.23
Rougher railing 83.29 _0.06 9.51
100.00 (0.53) 100.00
