FIELD OF THE INVENTION

The present invention relates to improved collectors and the use of such improved collectors in flotation processes of raw materials having a component of economic value in order to separate and recover at least some of the component of economic value.

On one form, the present invention relates to improved collectors and the use of such improved collectors in the flotation of raw materials, feed materials, ores and similar materials having a metal or mineral of economic value to assist in the separation of the metal or mineral from residual gangue thereby recovering the metal or mineral.

In one aspect, the present invention relates to the use of collectors for treating metal oxides in flotation processes so as to separate the metal oxides from the remaining material of the feed material and/or to recover at least some of the metal components from the feed material.

The present invention finds particular application as improved acid type collectors and the use of the improved acid collectors in the treatment of cassiterite so as to separate and recover tin containing oxides from the cassiterite ore using flotation processes involving the improved acid collectors.

Although the present invention will be described with particular reference to selected forms of acid collectors for recovering tin containing oxides from cassiterite ores, it is to be noted that the scope of the present invention is not restricted to the described embodiments but rather, the scope of the present invention is more extensive so as to include other forms and compounds of the collectors, the use of the various forms of the collectors to treat materials other than the described materials, the recovery of other metals or minerals of economic value from raw or feed material containing the other various metals or minerals.

BACKGROUND OF THE INVENTION

Various chemical materials have been used as collectors in flotation processes in the past to recover metal and/or mineral values. However, some of the previously used collectors have been found to be less efficient than some other collectors, sometimes considerably less efficient. One reason for previously available compounds being poor or inefficient collectors has been found to be mostly due to the inherent hydrophobicity of the raw materials being treated. The inherent hydrophobicity of the ores containing some metal oxides reduces the interaction of the collectors with ores to reduce the amount of metal oxides being separated from the remaining materials present in the feed materials. One example of this is cassiterite. Thus improved collectors are required to recover metal oxides from cassiterite, particularly economically viable amounts of metal oxides from cassiterite.

Cassiterite is one example of a raw material, i.e. an ore material that is treated with flotation collectors in flotation processes.

The flotation of tin (cassiterite) is conventionally performed using styrene

phosphonic acid (SPA), sulphosuccinamate (CA540) or sulphosuccinamate (A845). None of these collector types is particularly selective toward cassiterite and both iron and silicate minerals are routinely collected along with cassiterite. This strongly limits the tin grade, and thus the value, of cassiterite flotation concentrates.

Accordingly, it is one aim of the present invention to develop improved collectors which are more efficient in flotation processes for separating metal oxides from feed material containing the metal oxides.

It is one aim of the present invention to provide a range of chemical compounds which can be used as improved collectors for yielding high grade concentrates at high recoveries of oxide materials from waste material.

It is one aim of the present invention to provide a method of treating a feed material containing metal oxide with an improved collector in froth flotation processes to assist in separating and/or removing the metal oxide from the feed material as a precursor to subsequently efficient recovering the metal from the separated oxide.

It is one aim of the present invention to provide collectors which improve the grade of tin being recovered from cassiterite, and/or the value of cassiterite flotation concentrates.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a process for the treatment of raw materials having a component of economic value which treatment characterised in that the treatment comprises forming an aqueous slurry of the raw material, adjusting the pH of the slurry to be in the range of about 1 to 12, and adding a collector to the aqueous slurry in an amount sufficient to result in froth flotation of the material of economic value from the slurry to separate at least a proportion of the material of economic value or a material containing the material of economic value from the remainder of the slurry, wherein the collector is at least one of polycarboxylic acid or a salt thereof, or a phosphonocarboxylic acid or salt thereof, or a combination of a polycarboxylic acid or salt thereof and a phosphonocarboxylic acid or salt thereof, such that the acid is an aryl- substituted polycarboxylic acid, an aryl-substituted phosphonocarboxylic acid, or an aryl- substituted phosphono/polycarboxylic acid. According to one aspect of the present invention, there is provided a method of recovering a material of economic value from a raw material characterised in that the method comprises the steps of forming an aqueous slurry of the raw material, adjusting the pH of the slurry to be in the range of about 1 to 12, and adding a collector to the aqueous slurry in an amount sufficient to result in froth flotation of the material of economic value or of a material containing the material of economic value whereby at least a part of the material of economic importance is contained within the froth portion thereby separating the material of economic value from the raw material and treating the froth portion to recover the material of economic value wherein the collector is at least one of polycarboxylic acid or a salt thereof, or a phosphonocarboxylic acid or salt thereof, or a combination of a polycarboxylic acid or salt thereof and a phosphonocarboxylic acid or salt thereof, such that the acid is an aryl-substituted polycarboxylic acid, an aryl-substituted phosphonocarboxylic acid, or an aryl-substituted phosphono/polycarboxylic acid.

According to one aspect of the present invention, there is provided a collector which when added to a slurry containing a material of economic value results in froth flotation of the slurry to separate the material of economic value from the slurry in the froth portion characterised in that the collector is at least one of polycarboxylic acid or a salt thereof, or a phosphonocarboxylic acid or salt thereof, or a combination of a polycarboxylic acid or salt thereof and a phosphonocarboxylic acid or salt thereof, such that the acid is an aryl- substituted polycarboxylic acid, an aryl-substituted phosphonocarboxylic acid, or an aryl- substituted phosphono/polycarboxylic acid.

DETAILS OF ASPECTS OF THE INVENTION

Typically, the compounds of the present invention are improved collectors, particularly improved collectors in froth flotation processes for separating and/or recovering metals, minerals or the like from feed materials or raw materials. More typically, the improved collectors are more efficient collectors by improving and/or increasing the selectivity of the collectors for the particular metal or mineral of interest to be recovered, or increasing or improving the amount or yield of the particular metal or mineral being separated or recovered from the feed material or both the selectivity for and yield of the selected metal or mineral. It is to be noted that increasing the selectivity of the collectors for a selected material contained within the raw material being treated results in less unwanted material from the raw material being extracted from the raw material along with the selected material, thereby reducing the amount of subsequent separation of the unwanted material from the selected material after the selected material has been recovered. Typically, the compounds forming the collectors useful in the process of the present invention are acid compounds, including acid salts, preferably acid salts having one or more aryl group substituents in addition to the acid functionality of the compounds. More typically, the substituent aryl groups of the acids are themselves substituted to form substituted aryl groups.

Without wishing to be bound by theory, it is believed that the incorporation of one or more aryl groups, including substituted aryl groups, in the acid functionality of the

compounds of the present invention, including the aromatic ring of the aryl groups, has an important role in the activity of the collector in froth flotation processes of metal oxides, particularly cassiterite, particularly in the selectivity of the collector for the desired metal oxide.

Again, as an example, the acid compounds containing the aryl group or groups in accordance with the present invention are observed to be generally more effective as cassiterite collectors than are the more commonly used collector systems or compounds of styrene phosphonic acid which have been available previously for use as cassiterite collectors.

Collector Compounds

The aryl-substituted acid used in the process of the present invention preferably comprises any one or more of the following structural formulae:-

where n = 0 to 3

R, R', R", R"\ R"" may be H, halogen, nitro, alkyl, alkenyl, alkoxy (C-i to C ₆ , primary, secondary or tertiary), or hydroxyl.

W, X, Y and Z may be H, halogen, nitro, carboxylic acid, phosphonic acid, alkyl carboxylic acid, alkyl phosphonic acid or any of their ammonium or alkali metal salts.

The structural moiety specified as (CR"R") _n in the aforementioned structures may include alkenyl or substituted alkenyl functionalities where n is > 2. Thus, for example, (CR"R") _n may be -C(R ^a ) = C(R ^b )- or -C(R ^a ,R ^b )-C(R ^c )= C(R ^d ) - where R ^a , R ^b , R ^c and R ^d may be as for any R in the aforementioned general collector structures. Some specific examples of the compounds showing collector activity in the process of the present invention are given below:-

3-(4-methylphenyl)-3-phosphonopropanoic acid

2- (4ethoxyphenyl)propane-1 ,1 ,3-tricarboxylic acid

3- (4-methylphenyl)pentanedioic acid

2-(4-methylphenyl)ethane-1 , 1 -dicarboxylic acid

2- (4-methylphenyl)propane-1 ,1 ,3,3-tetracarboxylic acid

3- phenylpent-2-enedioic acid

The aromatic ring may be further substituted by one or two groups (R, R') in any of the available positions in the ring. Substitution in the 4-position is believed to be

advantageous from the point of view of increasing the hydrophobicity without hindering interaction of the acidic groups with the oxide surface, although this type of substitution is not essential for collector activity.

Typically, the improved collectors include the following compounds.

1 Cinnamic acid

2 Phenylmalonic acid

3 2-Phenylethane-1 , 1 -dicarboxylic acid

4 2-(4-Methylphenyl)ethane-1 , 1-dicarboxylic acid

5 2-Phenylethene-1 , 1 -dicarboxylic acid

6 2-(4-Methylphenyl)ethene-1 , 1-dicarboxylic acid

7 2-(4-Ethylphenyl)ethene-1 , 1 -dicarboxylic acid

8 2-(4-Methoxyphenyl)ethene-1 , 1-dicarboxylic acid

9 2-(3,4-dimethoxyphenyl)ethene-1 , 1 -dicarboxylic acid

10 2-(4-Ethoxyphenyl)ethene-1 , 1-dicarboxylic acid

1 1 3-Phenylpentanedioic acid

12 3-(4-Methylphenyl)pentanedioic acid

13 3-(4-Ethylphenyl)pentanedioic acid

14 3-(4-Methoxyphenyl)pentanedioic acid

15 3-(4-Ethoxyphenyl)pentanediioic acid

16 3-(4-Propoxyphenyl)pentanedioic acid

17 3-Phenylpentenedioic acid

18 3-(4-Methylphenyl)pentenedioic acid

19 2-Phenylbutanedioic acid

20 2-(4-Methylphenuyl)butanedioic acid 21 (E)-2-Phenylbutenedioic acid

22 (Z)-2-Phenylbutenedioic acid

23 2-Phenylpropane-1 ,1 ,3-ticarboxylic acid

24 2-(4-Methylphenyl)propane-1 , 1 ,3-tricarboxylic acid

25 2-(4-Ethylphenyl)propane-1 ,1 ,3-tricarboxylic acid

26 2-(4-(1-Methylethyl)phenyl)propane-1 ,1 ,3- tricarboxylic acid

27 2-(4-Methoxyphenyl)propane-1 , 1 ,3-tricarboxylic acid

28 2-(4-Ethoxyphenyl)propane-1 , 1 ,3-tricarboxylic acid

29 2-(4-Propoxyphenyl_propane-1 , 1 ,3-tricarboxylic acid

30 2-(4-(1-methylethoxy)phenyl)propane-1 ,1 ,3- tricarboxylic acid

31 2-(4-Butuxyphenyl)propane-1 ,1 ,3-tricarboxylic acid

32 2-(4-Methylphenyl)propane-1 ,1 ,3,3-tetracarboxylic acid

33 N-Phenyliminodiacetic acid

34 N _I (4-Methylphenyl)iminodiacetic acid

35 N _I (4-Methoxyphenyl)iminiodiacetic acid

36 N-Benzyliminodiacetic acid

37 N-Benzoyliminodiacetic acid

38 4-Methylstyrenephosphonic acid

39 3-Phenyl-2-phosphonopropanoic acid

40 4-Phenyl-3-phosphonobutanoic acid

41 3-(4-Methylphenyl)-3-phosphonopropanoic acid

42 3-Phenyl-4-phosphonopentanedioic acid

43 3-Phenyl-4-phosphonobutanoic acid

44 3-Phenyl-2,3-diphosphonopropanoic acid

45 3-Phenyl-2-phosphonopropenoic acid

46 3-(4-Methylphenyl)-4-phosphonopentanedioic acid

47. Phenyl itaconic acid

The collector compounds are unsaturated, saturated or a combination of both. The collector compounds are mono acids, diacids, triacids or the like having one or more acid groups.

(a) Aryl substituted polycarboxylic acids

Typically, there can be a single substitution, a double substitution or a multiple substitution. Typically, if there is a single substitution, the substitution of the aromatic structure or ring forming the aryl group of the collectors is in the 4- position of the ring. Without wishing to be bound by theory, it is thought that substitution in the 4- position is advantageous by increasing the hydrophobicity without hindering interaction of the acidic groups with the oxide surface. However, other substitution patterns are possible such as 3- or 5- substitution.

If there is a double substitution, the substitution is preferably at the 3- and 5- positions. However, other combinations of substituents at different positions are possible.

The aryl substituted polycarboxylic acids may contain a heteroatom as the substituent such as for example, an N atom. However, other heteroatoms may be substituted.

In one form, the collectors are obtained from 4- substituted benzaldehydes, including 4-alkylbenzaldehydes, 4-methoxybenzaldehyde, 4-ethoxybenzaldehyde, or the like.

Typical examples of the aryl-substituted polycarboxylic acids include the following:

where R is alkoxy Ci to C ₄ , primary or secondary, or alkyl Ci to C ₃ , primary or secondary. W, X, Y, Z are carboxylic acid groups (-COOH)or H

In general, the aryl substituted polycarboxylic acids are ultimately obtained from their respective ethyl esters by hydrolysis using both acidic, or alkaline conditions.

Typical examples of aryl substituted polycarboxylic acids in accordance with the present invention are illustrated in Table 2.1. It is to be noted that the acids of Table 2.1 are merely a selection of suitable acids, without limiting the extent of the invention. Table 2.1 Correlation table of aryl-substituted polycarboxylic acids

Table 2.1 (cont.)

Table 2.1 (cont.)

(b) Aryl-substituted Phosphonocarboxylic acids

One class of the aryl-substituted acid collectors useful as collectors for metal oxides is the aryl-substituted phosphonocarboxylic acids.

The synthesis of aryl-substituted phosphonocarboxylic acids are based on reaction series similar to the reactions used to prepare the corresponding aryl-substituted

polycarboxylic acids. Condensation and/or Michael reactions produce the alkyl esters, which on hydrolysis using acidic or neutral conditions, produce the required

phosphonocarboxylic acid. Typical examples of the aryl-substituted phosphonocarboxylic acids in accordance with the present invention are illustrated in Table 3.1. Again, it is to be noted that the acids of Table 3.1 are merely representative of the types of acids that can be used in the invention. The actual acids are a selection and are not exhaustive of the types of acids or limiting of the invention.

Table 3.1 Correlation table for aryl-substituted phosphonocarboxylic acids.

Typically, selected aryl-substituted phosphonocarboxylic acids are prepared via Michael addition of ethyl cinnamate, ethyl phenylpropynoate, or their derivatives, using diethyl phosphate or triethyl phosphonoacetate as Michael donors, or similar.

Typically, the substituents of the aryl-substituted group include methyl, ethyl, propyl, butyl and the like, including isomers of such substituents or the like. Further, any member of the lower series of substituents can be used, such as for example, up to about C ₁₀ substituents, including isomers, optical isomers, conformational isomers, structural isomers, or the like.

Preferably the substituent is a methyl group. Generally, the substitution of a methyl group in the para-position of the aromatic ring has a beneficial effect on the collector ability of the polycarboxylic acids. Although the substitution of an ethyl group increases the amount of tin recovered, there is also a reduction in selectivity in some cases.

In the case of aryl-substituted phosphonocarboxylic acids, para-methyl substituted aryl substituents provide greater hydrophobicity and provide an improved balance between hydrophilic and hydrophobic portions of the collector molecules of the collectors of the present invention.

In general, the phosphonocarboxylic acids, particularly the following are more powerful collectors than their polycarboxylic acid analogues.

In one form, the phosphonic acids are more powerful collectors, due to their faster rates of adsorption on the collector surface. However, selected polycarboxylic acids have a greater inherent selectivity for cassiterite.

Typically, the concentration of the improved collectors include from about 0.25 kg collector and about 0.75 of sodium silicofluoride (SSF) per tonne of feed material.

However, some collectors exhibit improved performance at lower concentrations of SSF of about 0.33 kg/tonne and greater concentrations of collector of about 0.40 kg/t.

The stronger collectors containing para-alkoxy or para-alkyl substitution benefit from the depression of gangue materials resultant on higher concentrations of SSF. These collectors do not require as high a collector concentration as the unsubstituted collectors. High concentrations of the more powerful collectors only served to increase flotation of the gangue. The weaker unsubstituted collectors benefited from higher collector concentrations, simply due to their slow collecting action. That is, the more collector available for adsorption at the cassiterite interface, the faster the rate of flotation. These collectors are inherently more selective for cassiterite particles than the stronger collectors. Thus more collecting power is needed to float gangue materials than to float cassiterite. However, the use of SSF negates any advantage of the weaker collectors such as over the more powerful collectors.

The collectors of the present invention are selective for cassiterite over silicate or silicate containing gangue materials.

Typically, the improved collectors of the present invention are poly acids having one, two, three, four or more carboxylic acid groups. Typically, the aryl substituents are arylalkyl substituents, including para-alkyl or para-alkoxy substitution of the aromatic ring.

The two types of acid functionality, phosphonic and carboxylic acids, demonstrate different collector characteristics. The use of a phosphonic acid provides stronger collecting power, that is, they collected cassiterite ore at a faster rate due to faster adsorption on the oxide surface. However, the phosphonic acid lacked the inherent selectivity of the polycarboxylic acid collector for cassiterite. The weaker polycarboxylic acid collectors are strengthened by para-substitution in the aromatic ring. This increases the power of the collector by increasing hydrophobicity.

In general, the inclusion of unsaturated bonds in the collector molecule is advantageous in affecting an increase in the dissociation of adjacent acid entities, and generation of increased rigidity in the collector. This rigidity decreases the free rotation of the aromatic ring and/or the acid units facilitating better adsorption of the acid entities. A static orientation of the aromatic ring also facilitates better association between the collector molecules via Van der Waals interactions between aromatic rings.

Incorporation of a 1 ,1 -dicarboxylic acid entity, instils increased collector activity and collectors containing this functionality are active collectors.

Inclusion of an alkyl or alkoxy substituent in the para-position of the aromatic ring provides interesting results. Alkyl substitution induces a larger change in the hydrophobicity of the collector than does alkoxy substitution. The ether linkage of the alkoxy substituent is prone to association with water molecules thus reducing its hydrophobicity, which is demonstrated by the flotation results for 2-(3,4-dimethoxyphenyl)ethene-1 ,1 -dicarboxylic acid, which has reduced collector power, although more highly substituted, when compared with the para-methoxy analogue.

The optimum choice of substituents is dependent on the collector skeleton. For collectors based on the tricarboxylic acid series, para-ethoxy substitution is the most beneficial. This provides a powerful collector with a good response to the addition of sodium silicofluoride depressant (SSF) and gave excellent selectivity in its presence. Optimum results are obtained with para-methyl substitution. Some correlation between the number of acidic groups and the nature of the para-substituent, required for reasonable collecting power exists. A balance between the hydrophilic character of the acid units and the hydrophobic character of the aromatic ring and its substituents provides good selectivity and collector strength. The larger the hydrophobic group, the more adsorption is induced at surfaces. However, if the hydrophobic group becomes too large then adsorption, and thus flotation, is less selective and gangue entrainment increases, thereby reducing the effectiveness of the collector.

In some examples of the collector, para-substitution can be replaced by interposing an extra methylene unit in the alkane section of the molecule. For example, the activity of 2- phenylbutanoic acid is less than 3-phenylprop-2-ene-1 ,2-dicarboxylic acid (phenylitaconic acid).

One of the unique characteristics of the aryl-substituted polycarboxylic acids is their ability to float large particle size cassiterite (to 0.2 mm), compared with the maximum of 0.04 mm by the use of currently available collectors. The economic implication of this result carried out on a commercial scale is substantial.

METHODS OF PREPARATION

The aryl-substituted carboxylic acids, phosphonocarboxylic acids and

polyphosphono/polycarboxylic acids can be prepared, for example, from the respective aromatic aldehydes by a series of base catalysed condensation or addition reactions, using diethyl malonate, malonic acid, diethyl phosphate, tetraethyl methylenediphosphonate, triethylphosphono-acetate or similar donors. These reactions are followed by hydrolysis of the resulting esters to form the required corresponding acids.

Raw Materials

The raw materials that are treated by the acid compounds include any suitable raw material, feed material, waste material, ores, minerals, tailings, virgin material, slags, materials containing metals, oxides and the like.

Various types of ores containing metal oxides are able to be treated in accordance with the present invention. Examples of metal oxides include the following:-

Cassiterite ores (Sn0 ₂ ) from Tasmania and New South Wales, both in Australia, Cassiterite tailings (Sn0 ₂ ) from Bolivia and China,

Wolframite ore (FeMnWo ₃ ) from Tasmania Rutile ore (Ti0 ₂ ) from New South Wales

llmenite ore (FeTi03) from Western Australia

Tantalum ore (Ta ₂ 0 ₅ ) from Western Australia

Niobium ore (Nb ₂ 0 ₅ ) from Kenya and Brazil

The materials of economic value include all oxide minerals, including metallic oxide materials or materials containing metallic oxides including precursors for and derivatives of metal containing oxide materials tin, tungsten, titanium, tantalum, niobium.

Typically, the material of economic importance is a metal or metal oxide. The improved collectors of the present invention are used for the recovery of a range of metals, minerals and the like. Typical examples of metals or metal oxides include the flotation of tantalum, niobium, titanium, tungsten oxides and the like. In addition to floating cassiterite, the collectors float wolframite (FeMnW0 ₃ ).

The collectors can be used for the flotation of zircon, rutile, monazite and other non- sulfide based ores.

It is to be noted in the results obtained from trials involving the use of the improved collectors that 79% tin is equivalent to 100% cassiterite and thus is the theoretical maximum grade obtainable on flotation. Process

(a) Particle Size

A typical process application for the invention may involve, in a preparatory stage, first grinding the ore sample to a size finer than 0.075mm, followed by cyclone classification of the resulting pulp, thereby removing the majority of the slime particles which are defined as particles of less than 0.005 mm in size. However, it is to be noted that the first grinding of the ore could result in coarser particles being used. Samples containing a significant proportion of sulphide minerals, such as for example, greater 1 %, are then normally subjected to a preliminary froth flotation to remove the sulphide minerals. This is one example of a pre-treatment. The resulting ore pulp is substantially sulphide free and sized in the range from about 0.005 to about 0.075mm. However, it is to be noted that the preliminary froth flotation is optional as the collectors described for use in the treatments and processes of the present invention will float metal oxides without such prior treatment or classification. It is believed that many of the collectors useful in the present invention will recover particles of cassiterite ranging from about 0.001 to about 0.25 mm, preferably from about 0.001 to about 0.15 mm, whereas known collectors tend to only recover cassiterite particles ranging from 0.002 to 0.04 mm. (b) Slurry

The aqueous slurry prepared in accordance with the process described above, which usually contains from about 20% to about 45% w/w solids, is then subjected to froth 5 flotation in accordance with the invention. However, lower amounts of solids, such as less than 20%, can be used. During flotation, the slurry is aerated to form a froth in which the metal oxide containing the metal value becomes concentrated leaving most of the gangue being of little or no economic worth in the aqueous phase. The metal oxide is recovered by collecting the froth.

i o Optionally, frothing agents may be added to the slurry if required. Not all of the collectors used in the present invention require the addition of frothing agents are not essential since suitable frothing occurs automatically with many of the collectors. Suitable frothing agents include benzene, toluene, alcohols, such as for example polypropylene glycols, polyglycol ethers, and any other reagent that reduces the surface tension at the

15 liquid/air interface.

EH

The flotation process is carried out at a pH of from about 1 .0 to about 12.0 typically at a pH of about 1 to about 8. The pH varies depending on the nature and/or composition of 20 the ore and the source of the ore. Thus, where the metal oxide is cassiterite, the process may be advantageously carried out at a pH of from about 1.5 to about 5.5, preferably from about 4 to about 5 for cassiterite. The pH is adjusted by the addition of aqueous sulphuric acid or sodium hydroxide depending upon the initial pH of the slurry. Other raw materials may require a different range of pH values.

25

Concentration

The collectors in accordance with the present invention may be employed in varying amounts depending upon the ore type. Generally, the concentration of collector is from about 50 to about 1000 g per tonne of feed ore solids in the slurry, more typically from about 30 200 to about 400 g/tonne for the cassiterite ore specified above.

The frothing step during flotation is performed for about 1 to about 90 minutes, conveniently for about 1 to about 10 minutes, and the collector may be added in various portions, for example from 1 to about 5 portions, with the oxide of interest being

concentrated in the froth which is removed after each collector addition. The collectors described for use in this invention may also be used alone or mixed with one or more other collectors, for example fatty acid collectors or alkylphosphonic acid collectors.

In order to improve the selectivity of flotation processes for some oxides, such as for example cassiterite, over gangue materials and/or to increase the recovery of the metal oxides, pretreatments and/or precleaning operation can be performed.

In one form, pretreatment involves addition of sodium silicate and/or other silicate and/or sodium fluorosilicate, such as sodium silicofluoride, and/or other inorganic salts, some organic polycarboxylic acids, or the like. Typical examples of organic salts, include salts containing Fe, Al and/or Pb cations. Typical organic polycarboxylic acids include oxalic acid and similar acids. The pretreatment may be performed prior to or as part of the process of the present invention.

In one form of the pretreatment step useful with the present invention, a

depressant, such as for example sodium fluorosilicate, may be added in quantities ranging up to about 2000 g/tonne of feed ore solids, preferably from about 100 to about 400 g/tonne. In some circumstances, it is noted that the addition of the above indicated depressant may be made concurrent with the addition of some of the collectors described for use in the present invention without any appreciable loss of grade or recovery, which is in contrast to some previously used collectors where similar concurrent additions with previously known collectors, for example, styrene phosphonic acid, resulted in substantially reduced efficiency.

In one form, the flotation process is usually, but not necessarily, run at ambient temperatures, typically in the range of about 10° to 50°, more typically in the range of 15° to 20°C.

In one form, the collectors described for use with the present invention are less sensitive, usually substantially less sensitive, to loss of flotation efficiency in the present of Ca ⁺⁺ and Fe ⁺⁺⁺ ions when compared with previously available collectors hitherto used, such as fatty acids, sulfosuccinamates and alkyl or aryl phosphonic acids.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments illustrating aspects of the invention will now be described with reference to the following non limiting examples which illustrate aspects of the invention and with reference to the accompanying drawings, in which:

Figure 1 is a graph comparing recovery rates of various collectors used in accordance with the present invention with a known commercial collector on one ore type under standard conditions, and Figure 2 is a graph comparing recovery rates of one collector used in accordance with the present invention with a known commercial collector on two further ore types under standard conditions.

Figure 3 is a schematic flow chart of one form of a test procedure.

Figure 4 is a graph comparing the amount of tin recovered of a sample of tin present in the sample for a variety of different collectors.

Examples

Various types of experimental tests were conducted to illustrate the process of the present invention. The results are presented in Table 1 as Examples 1 - 12 of the invention, with the results being also depicted in Figures 1 and 2 of the accompanying drawings.

The following tests were carried out:-

1 . Direct comparisons with a commercially available collector on one sample of tin ore under standardised conditions (Examples 1-6, Figure 1 ).

2. Direct comparisons with a commercially available collector on two further samples of tin ore under standardised conditions (Examples 7-10, Figure 2).

3. The successful flotation of tin ore significantly coarser (i.e. greater than 0.04mm) than has previously been floated (Example 1 1 , Table 1 ).

4. The successful flotation of another metal oxide material (Example 12).

Table 1

Ex. Collector Amoun Conditioning pH Flotation Cone. Assay Dist.

t

Added time (mins) Time No %Wt %Sn Sn% g/t (min)

1 styrene 280 10 4.5 3 1 6.1 15.8 84.5 phosponic 60 4.5 3 2 5.0 2.2 9.7 acid 60 4.5 6 3 7.9 0.37 2.5

60 4.5 6 4 4.1 0.16 0.6

Tailings 76.9 0.04 2.7

997.0 gm 100.0 (1.14) 100.0

2 2-(4-methylphenyl) 400 1 1 4.5 2 1 1.4 46.3 56.8 ethane-1 , 50 2 4.5 2 2 0.8 30.2 21.2

1-dicarboxylic 30 2 4.5 3 3 0.8 13.7 9.6 acid 20 1 4.5 3 4 0.6 6.2 3.2

Tailings 96.4 0.1 1 9.2

100.0 (1.14) 100.0

3 2-(4methylphenyl) 400 10 4.5 2 1 2.0 25.6 52.2 butanedioic acid 100 - 4.5 2 2 1.4 17.4 24.9

60 - 4.5 3 3 1.9 6.5 12.5

40 - 4.5 3 4 1.2 2.25 2.8

Tailings 93.5 0.08 7.6

987.5 gm 100.0 (0.98) 100.0

4 3-(4-methylphenyl) 280 10 4.5 3 1 2.4 33.5 70.4 pentanedioic acid 60 - 4.5 3 2 1 .5 9.9 13.0

60 - 4.5 6 3 3.6 2.8 8.8

60 - 4.5 6 4 2.7 0.6 1.4

Tailings 89.8 0.08 6.4

100.0 (1.14) 100.0

Table 1 (cont.)

3-(4-methylphenyl) 4.5 2 1 3.5 23.6 80.4

-3-phosphonopropanoioc 4.5 2 2 2.6 4.3 10.9 acid 4.5 3 3 2.6 0.99 2.9

4.5 3 4 1.3 0.39 0.5

Tailings 90.0 0.06 5.3

983.6 gn 100.0 (1 .03) 100.0

2-(4-ethoxyphenyl) 4.5 2 1 1.7 51.8 80.2 propane-1 , 1 , 3- 4.5 2 2 0.7 18.7 1 1.9 tricarboxylic acid 4.5 3 3 0.5 6.3 2.9

4.5 3 4 0.3 3.9 1.1

4.5 2 5 0.2 2.5 0.5

Tailings 96.6 0.04 3.4

1000.28 100.0 (1 .10) 100.0 styrene phosphonic 4.5 3 1 6.1 15.8 84.5 acid 4.5 3 2 5.0 2.2 9.7

4.5 6 3 7.9 0.35 2.5

4.5 6 4 4.1 0.16 0.6

Tailings 76.9 0.04 2.7

997.0 gm 100.0 (1 .13) 100.0

2-(4-ethoxyphenyl) 4.5 2 1 1.4 41.6 53.5 propane-1 , 4.5 2 2 10. 28.4 26.1

1 , 3-tricarboxylic 4.5 3 3 0.9 1 1.3 9.4 acid 4.5 3 4 0.6 5.7 3.1

Tailings 96.1 0.09 7.9

982.1 gm 100.0 (1 .09) 100.0

Table 1 (cont.)

9 styrene phosphonic 180 10 4.5 2 1 2.8 18.9 61.9 acid 50 1 4.5 2 2 1.4 1 1.4 18.7

30 1 4.5 3 3 1.5 5.05 8.9

20 1 4.5 3 4 1.8 1 .85 3.9

Tailings 92.5 0.06 6.6

1 101 . Ogm 100.0 (0.85) 100.0

10 2-(4-ethoxyphenyl) 180 10 4.5 2 1 2.0 29.5 80.3 propane-1 , 1 , 3- 22 2 4.5 2 2 1.1 6.45 9.7 tricarboxylic acid 12 2 4.5 3 3 1.0 1 .85 2.6

10 2 4.5 3 4 0.9 0.70 0.9

Tailings 95.0 0.05 6.5

1 135.7gm 100.0 (0.73) 100.0

1 1 2-(4-ethoxyphenyl) 410 15 4.5 2 1 4.9 62.4 50.0 propane-1 , 1 , 3- 70 2 4.5 2 2 2.4 57.4 22.5 tricarboxylic acid 70 2 4.7 3 3 1.4 42.5 9.7

70 2 5.0 3 4 1.0 30.5 5.0

Tailings 90.3 0.86 12.8

725.5 gm 100.0 (6.1 1 ) 100.0

%WO Dist'n

3

W0 ₃ %

3-(4-methylphenyl) 4.5 3 1 0.8 32.8 50.5 pentanedioic acid 4.5 3 2 0.6 20.6 24.0

4.5 6 3 0.3 13.9 8.0

4.5 6 4 0.2 6.5 2.5

Tailings 98.1 0.08 15.0

953.2 100.0 (0.52) 100.0

All tests completed at room temperature

Performance aspects of embodiments in accordance with the present invention is illustrated by comparing the performance of specific collectors with that of a commercially available collector on a sample of tin ore prepared under standard test conditions. The ore sample (from Cleveland Tin Ltd, Tasmania) collected for this purpose was prepared by crushing to minus 3.35 mm, and riffled into 1.5 kg sub samples. In each of Examples 1 to 5:- a. The ore was ground in a laboratory ball mill to give a product which was 89% finer than 0.075 mm and 53% finer than 0.038 mm.

b. The ground product was deslimed in two stages of cyclone classification to reject particles of 0.005 mm and below.

c. The sulphides present in the ore samples were removed from the deslimed feed in a separate pretreatment step in the ore samples comprising flotation after pH modification of the feed ore with sulphuric acid to pH 5.0, activation and 3 minutes conditioning with 100 g/tonne copper sulphate, 3 minutes conditioning with potassium amyl xanthate collector, and 0.5 minutes conditioning with 20 g/t of a frothing agent of trade name AF65. d. The remaining material which had been deslimed by the sulphides being removed was then prepared for tin flotation by five minutes conditioning with 300 g/t sodium silicofluoride after pH modification to 4.5 with sulphuric acid. e. Example 1 : The pre-conditioned material was then conditioned for ten

minutes with 280 g/tone styrene phosphonic acid (the commercial collector), 0.5 minutes conditioning with 10 g/t of AF65 frother and 3 minutes flotation with air. The process of collector frother addition is repeated with four upgraded tin concentrates in total being removed for 2-3, 2-3, 3-6, 3-6 minutes of flotation time for each concentrate respectively. The material remaining is the flotation tailing devoid of tin. The process conditions, collector amounts, flotation times and results are set out in Table 1.

f. Examples 2 to 6: The same procedure as indicated in paragraph (e) above was carried out with examples of collectors in accordance with the invention, by substituting them for the commercial collector of Example 1 . The inventive collectors, process conditions and results are set out in Table 1.

The effect of using collectors in accordance with the present invention on different tin ore types is illustrated in Examples 7-10. In this case, performance of one of the inventive collectors is compared against that of the commercial collector under similar conditions for two ore types from Cleveland Tin Ltd, Tasmania (ore type A) and from Ardlethan Tin, New South Wales (ore type B). The results for the two tests on the Cleveland ore are given as Examples 7 and 8 and the Ardlethan ore as Examples 9 and 10. The procedure carried out in Examples 7 to 10 is identical to that for Examples 1 to 6 with the conditions and results being as set out in Table 1 .

Another illustration of embodiments in accordance with the present invention is their performance in the flotation of coarse (greater than 0.040 mm) tin minerals, as specified in Example 1 1 . The sample used was the feed to the gravity cleaning section (from Cleveland Tin Ltd, Tasmania) which was 19.9% finer than 0.2 mm and 13.4% finer than 0.038 mm. The size by size recovery (given in Table 2) shows successful flotation of tin at sizes greater than 0.150 mm. The procedure carried out in Examples 1 1 is identical to that for Examples 1 to 6 with conditions being as set out in Table 1.

Table 2

Size by Size Recovery Data, Example 1 1

Coarse Tin Flotation

Size (mm) Feed Concentrates

%wt %Sn Sn Dist %wt %Sn Sn Recovery

+0.212 7.4 4.87 5.6 0.4 8.8 9.1

0.212-0.150 12.5 5.25 10.2 0.8 51.3 63.2

0.150-0.106 16.3 4.77 12.1 1.2 56.5 86.7

0.106-0.075 20.8 4.29 13.9 1.4 59.3 93.3

0.075-0.053 19.6 4.38 13.4 1.4 59.2 96.3

0.053-0.0.8 10.0 7.94 12.4 1.1 64.6 98.3

-0.0.8 13.4 15.54 32.4 3.4 60.8 99.3

Total 100.0 (6.42) 100.0 9.7 (58.1 ) 87.7

In example 6, an ore sample was taken directly from the milling circuit feed at Cleveland Tin Ltd, Tasmania. The sample was reground to minus 0.075 mm and floated under standard conditions, with the procedure being identical to that in Examples 1 to 6 and the conditions and results being as set out in Table 1.

In one aspect, the compounds forming the collectors in accordance with the present invention can be used to concentrate other raw materials or feed materials, such as for example, other oxide minerals, from gangue. This application is illustrated in Example 12. The feed is a sample of wolframite (FeMnW0 ₃ ) ore which has been floated in accordance with the procedure given for Examples 1-6, with the conditions and results being as set out in Table 1.

The results given in Table 1 for Examples 1 to 6 are summaried in graphical form in Figure 1. This shows the cumulative grade of concentrate against the recovery of tin achieved for Examples 1-6. The points refer to the concentrates collected with the point on the right hand of the curve referring to concentrate 1 , the next referring to concentrate 1 plus concentrate 2 and so on. The fourth point on the left of the curve represents the final grade and recovery achieved in the test.

Similar grade/recovery curves are shown for Examples 7-10 in Figure 2, in which the responses of one of the collectors in accordance with the present invention with that of the standard commercial collector on the two different tin ore types under similar conditions are shown. In both cases, significantly higher initial and final grades and recoveries were achieved with the collector of the invention.

Examples T01 to T09.

With particular reference to Figures 3 and 4, a further investigation into the collectors of this invention are described.

Two collectors and SPA were tested using a sample of Renison tin float feed collected from the operating plant specifically for this purpose. Two SPA tests were performed as baselines and then a number of RTD collector tests were performed in comparison.

Results indicate greatly enhanced performance for the RTD collector types tested. The improvements are in the range of twice the concentrate tin grade at similar tin recovery to the concentrate. Results indicate that this is due to the enhancement of selectivity against iron with <10% recovery to concentrate compared to around 50% for SPA. Thus, the collectors of the invention are more selective in recovering tin, and not contaminant material.

A bulk sample of Renison plant "tin float feed" damp cake was received for preparation and testing. The sample was repulped and pulp aliquots filtered, washed and sealed in one litre containers for individual flotation tests.

Figure 4 outlines the testing procedures performed in this example.

SAMPLE PREPARATION

A single bulk sample of Renison plant "tin float feed" damp cake was received. The sample was repulped and pulp aliquots filtered, washed and sealed in one litre containers for individual flotation testing. FLOTATION REAGENTS USED

The following reagents were used in this test program:

SIBX, collector, Sodium Iso Butyl Xanthate which is supplied by Orica of Australia

MIBC, frother, methyl Iso butyl Carbinol, which is supplied by Shell SPA: Styrene Phosphoric Acid, commercial grade powder, ex India RTD1544: Cassiterite collector which is 2-(4-ethoxyphenyl)propane-1 ,1 ,3- tricarboxylic acid trisodium salt

RTD1500: Cassiterite collector, which is 2-(4-ethoxyphenyl)propane-1 ,1 ,3- tricarboxylic acid.

FLOTATION ROUTINE

Cassiterite flotation tests were performed under the following conditions:

Collector: mix precise 1 % solutions day before test, allow to agitate gently overnight.

Flotation rougher performed in a 3.8L Agitaire style laboratory cell, 32% solids. Pulp pH: 6.5 monitored and adjusted with H2S04 as required.

Pulp conditioned with 20gpt SIBX for 2 minutes. Frother: MIBC 50gpt.

Scavenger float for sulphides.

Pulp pH: 5.0 monitored and adjusted with H2S04 as required.

Pulp conditioned with 200gpt SSF for 10 minutes.

Pulp conditioned with 200gpt COLL for 15 minutes.

Rough in three stages with further two 150gpt additions and conditioning.

A single 2.7L cleaner float performed on combined rougher concentrate

Pulp pH is monitored and adjusted with H2S04 as required.

No collector addition in cleaner stage. Float three concentrates.

Air rate, time and wet weight are recorded for each concentrate.

Products filtered and dried for weight determination and analysis. TESTS PERFORMED

Table 4: Test Summary: Flotation Tests

FLOTATION TESTING

Table 5 indicates the tests performed for each type.

Table 5: Flotation Tests Performed

Results clearly indicate much improved selectivity performance for the RTD collectors. At 80% tin recovery to concentrate the RTD collectors yield a product of at least twice the tin grade. Table 6 indicates the deportment of iron to rougher and cleaner products for each test. This clearly indicates the reason for the enhanced tin grades evident in the RTD collectors. Iron (mainly present as siderite - an iron carbonate) is recovered to concentrate to a very limited extent, the collectors identified as T03 and T04 average 7% iron recovery compared with 51 % iron recovery for the SPA tests.

Table 6

Test Modifier Collector Dose Ro Cone Ro Cone CI Cone CI Cone

(gpt) Fe(%) Rec(%) Fe(%) (Rec(%)

T01 SSF SPA 550 20.3 57.4 22.0 52.4

T02 SSF SPA 550 19.9 57.4 21.7 50.5

T03 SSF 1544 575 14.2 16.4 13.5 1 1.6

T04 SSF 1544 375 9.2 7.2 7.1 3.4

T05 Na2Si03 1544 500 1 1 .5 3.7 7.1 0.6

T06 Na2Si03 1544 300 7.9 4.7 3.5 0.9

T07 Na2Si03 1544 450 9.0 7.7 6.1 2.6

T08 Na2Si03 SPA 300 20.5 48.4 22.5 40.1

T09 SSF 1500 500 12.8 13.2 10.3 7.6

Table 7.1 Example T01

Float Celt fteaand Power

Rt5US]tii3.r Start

C!ean If Finisrt

aao fcWhit

Table 7.2 Example T02

Table 7.3 Example T03

Table 7.4 Example T04

Table 7.5 Example T05

Example T06

Table 7.7 Example T07

Table 7.8 Example T08

Table 7.9 Example T09

Results of the tests are provided in Figure 4 which is a graph of the amount of tin recovered expressed as a percentage as a function of the amount of tin actually present in the sample being tested. As can be seen from Figure 3, as the amount of tin present in the sample being tested increases, the amount of tin being recovered reduces, sometimes dramatically so, as is illustrated by collectors T01 SPA, T02 SPA, and T08 SPA C12, all of which are collectors not in accordance with the present invention, i.e. currently available collectors. However, the collectors identified as T03 RTD 1544 SSF, T04 RTD 1544 Na ₂ Si0 ₃ , T07 RTD 1544 C12 and T09 RTD 1500 SSF all exhibit relatively higher recovery amounts of tin as the amount of tin in the samples increases. This is particularly noticeable at amounts in excess of 20% of tin in the samples where from at least about 85% and higher amounts are recovered using these collectors which are in accordance with the present invention. The high recovery amount of over 80% is maintained to about 40% of tin present in the sample apart from collector T09 RTD 1500 SSF which reduces to about 70% which is still very high compared to prior art collectors which reduce to about 50% recovery amount for samples having about 30% tin only.

It is to be noted that the collector identified as RTD 1500, being collector T09 RTD 1500 SSF of Figure 3, is 2-(4-ethoxyphenyl)propane-1 , 1 , 3-tricarboxylic acid and the collectors identified as RTD 1544, being collectors T03 RTD 1544 C12, are 2-(4- ethoxyphenyl)propane-1 , 1 , 3-tricarboxylic acid tri-sodium salt. Both of these collectors are in accordance with the present invention and exhibit improved collector properties in froth flotation of tin as demonstrated by the results of Figure 4.

It will be appreciated that the Examples of the present invention described herein are given solely to illustrate the invention and not to limit. On reading this description, those knowledgeable in the art may become aware of modifications and variations not disclosed herein but falling within the general ambit of the invention. Such modifications and variations are to be considered as part of the invention.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.