CA1216082A - Minerals flotation - Google Patents

Abstract

Abstract Ores comprising mineral salts, especially barite, fluorite or scheelite are beneficiated by froth flotation in the presence of a substituted amino phosphonic acid or salt thereof.

Description

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 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

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 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 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 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 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

Ex~mple 2 Tne tests of Example 1 were repeated with barite~ The results were as follows.

pH mg/l 2-10.5 200 2-9.5 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 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 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

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

~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

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

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

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

Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the beneficiation of a mineral salt ore which comprises subjecting an aqueous slurry thereof at pH 1.5-11 to froth flotation in the presence of at least one substituted amino phosphonic acid or salt thereof of general forumla RaRb1Rc2N(R3PO3H2)3-a-b-c, wherein each of R, R1 and R2 which are the same or different, represents an organic group R3 represents a divalent organic group and each of a, b and c represents 0 or 1, but when a is 1, b and c are 0 and when a is 0, b and c are 1, and separating a fraction comprising beneficiated mineral salt from a second fraction depleted in said mineral salt.

2. A process according to claim 1, wherein a is 1, b and c are 0 and R3 is a methylene group.

3. A process according to claim 2, wherein R is an alkyl group.

4. A process according to claim 2, wherein the mineral salt is one having a cation selected from calcium, strontium, barium and lead, and an anion selected from sulphate, fluoride, carbonate, tungstate and phosphate, but excluding calcium phosphate.

5. A process according to claim 3, wherein the mineral salt is at least one of barite and fluorite and the beneficiated salt fraction is recovered from the froth.

6. A process according to claim 5, wherein R is an alkyl group of 3-12 carbon atoms.

7. A process according to claim 6, wherein the mineral salt ore is subjected to froth flotation at pH 3-11 in the presence of an alkyl imino bis methylene phosphonic acid or salt thereof in which the alkyl group has 6-9 carbon atoms.

8. A process according to claim 7, wherein the flotation is at pH
8-11.

9. A process according to claim 5, wherein the mineral salt ore comprising barite and fluorite is subjected to froth flotation at pH 9.5-11 in the presence of a salt of an alkyl imino bis (methylene phosphonic acid) in which the alkyl group has 7-9 carbon atoms and a beneficiated salt fraction enriched in barite is recovered from the froth.

10. A process according to claim 3, wherein R is an alkyl group of 6-12 carbon atoms.

11. A process according to claim 1, wherein a mineral salt ore comprising scheelite is subjected to froth flotation at pH 8-11 in the presence of an alkyl imino bis methylene phosphonate wherein the alkyl group has 9-13 carbon atoms.