Novel thiazidolone derivative collector for polymetallic ore

Abstract

This invention relates to a collector agent in the flotation of lead, zinc and optionally copper comprising S-alkyl-4,5-dihydro thiazole (Formula la) or N-alkyl-2- thiazolidinethione (Formula lb) or a mixture thereof wherein R1 is a C1 to C18 alkyl, C2 to C18 alkenyl, C3 to Cw cycloalkyl, C6 to C18 aryl or an alkyl ether group of the formula -(CH2)nOCH3, where n is a number from 1 to 18, such group optionally being substituted.

Description

[0001] Clariant International Ltd 1

[0002] NOVEL THIAZIDOLONE DERIVATIVE COLLECTOR FOR POLYMETALLIC ORE

[0003] Description

[0004] The present invention relates to the use of a thiazidolone derivative collector for improving a process to treat metal or mineral ores, such as lead, zinc, nickel, copper, or sulfide ores and to collector compositions that are suitably used in that process. Compared to the benchmark xanthates and sodium diisobutyldithiophosphinate, the performance of the thiazidolone derivative collector is significantly better, delivering higher recoveries for the elements of interest.

[0005] Froth flotation is a physico-chemical process used to separate different mineral particles considered economically valuable from those considered waste. It is based on the ability of air bubbles Io selectively attach on mineral particles that were previously rendered hydrophobic. The particle-bubble combinations then rise to the froth phase from where they are discharged from the flotation cell whilst the hydrophilic particles remain in the flotation cell. Hydrophobicity is induced by special chemicals called collectors. In direct flotation systems, it is the economically valuable minerals which are rendered hydrophobic by the action of the collector. Similarly, in reverse flotation systems, the collector renders hydrophobicity to those mineral particles considered waste. Product of the flotation is an ore concentrate.

[0006] The efficiency of the separation process is quantified in terms of recovery and grade. Recovery refers to the percentage of valuable product contained in the ore that is removed into the concentrate stream after flotation. In the context of this patent application the term “recovery” means the percentage of concentrated ore in relation to the total mass of the crude ore. The mass recovery Y can be calculated by the formula 100 , wherein

[0007] C = dry mass of concentrate from flotation;

[0008] F = dry mass of crude ore fed to flotation; f = feed Fe content; c = concentrate Fe content; and r = tailings Fe content.

[0009] Grade refers to the mass percentage of the economically valuable product in the concentrate after flotation, the mass of the concentrate being 100%.

[0010] A higher value of recovery or grade without compromising the other indicates a more efficient flotation system.

[0011] The air-bubbles can only stick to the mineral particles if they can displace water from the mineral surface, which can only occur if the mineral is, at least to some extent, hydrophobic. Having reached the surface, the air-bubbles can only continue to support the mineral particles if they can form a stable froth, otherwise they will burst and drop the mineral particles. To achieve these conditions, it is necessary to use various chemical flotation reagents such as frothers, collectors and modifiers as are well known in the art.

[0012] As most minerals are not water repellent in their natural state, the most important of these flotation reagents are the collectors. These collectors adsorb onto the mineral surface, rendering it hydrophobic and facilitating bubble attachment. The collectors are organic compounds which render selected minerals water-repellent by adsorption of molecules or ions onto the mineral surface, reducing the stability of the hydrated layer separating the mineral surface from the air-bubble to such a level that attachment of the particle to the bubble can be made on contact.

[0013] Collector molecules may be ionic compounds, which dissociate into ions in water, or non-ionic compounds, which are practically insoluble in water, and render the mineral water-repellent by covering its surface with a thin film. The most widely used collectors are of the sulfhydryl type, which contain a polar bivalent sulfur group. These collectors are very efficient and selective in the flotation of sulfide minerals. The most widely used of these collectors are the xanthates, dithiophosphates and dithiocarbamates. Of these, the xanthates are most important for sulfide mineral flotation.

[0014] Conventionally, collectors are added to the flotation pulp during or subsequent to grinding or during the flotation procedure itself. Collectors such as xanthates adsorb from the liquid to the sulfide mineral surface. This forms the hydrophobic identity on the sulfide mineral surface. Once in the flotation cell, this sulfide mineral is then captured by the introduced air bubbles and subsequently recovered.

[0015] According to the state of the art, in the separation of ores containing lead, zinc and copper, lead and zinc have been floated by first floating the copper and lead in the presence of a depressant for the zinc, this depressant also being a depressant for iron sulfides which is present in the gangue, such as sodium cyanide or zinc sulfate (or both in a combination colloquially called Complex). The depressed zinc remains in the slurry for the next flotation stage where it will be reactivated and floated in a zinc concentrate where typically another flotation reagent (copper sulfate) is used as surface activator (surface chemistry change without physical attachment of the reagent) for zinc.

[0016] Xanthates and thiol compounds can be oxidized and the obtained dixanthogens and similar products of the oxidation are themselves collectors.

[0017] Some limited attempts have been made to utilize these oxidation products as the principal collectors and prior art includes the deliberate electrochemical oxidation of xanthates to dixanthogens before their addition to flotation cells or conditioning tanks.

[0018] Aryasuta Nayak, M. S. Jena & N. R. Mandre (2022) Beneficiation of Lead- Zinc Ores - A Review, Mineral Processing and Extractive Metallurgy Review, 43:5, 564-583 teaches in its chapter 3.5.1 .5. commonly used collectors for the Zn / Pb flotation. Xanthates are the collectors with the most widespread use.

[0019] This invention relates to the differential flotation of ores containing at least lead and zinc, and more particularly of ores containing at least lead, zinc and copper. It was the object of this invention to find a collector for the Zn / Pb flotation that may replace xanthates. This invention seeks to provide a collector to selectively recover lead in a primary flotation, leaving zinc sulfides in the tailings that subsequently will be recovered in a secondary flotation stage.

[0020] Zinc recovery on the primary concentrate (lead or copper & lead concentrate) is needed to be as low as possible because it decreases the lead grade of the concentrate due to its readily floatable characteristic (zinc sulfides). Additionally, any content of zinc in the lead (or copper & lead) concentrate will not create value and it will be considered a zinc loss in the overall flotation process. Adequate zinc depression by the effect of depressants previously mentioned, leave it available to be floated in a later stage.

[0021] The present invention is based on the discovery that, if in the primary flotation stage of lead (or copper & lead) a more selective collector against zinc is used at the same dosage and together with the same type of depressants and sequence of addition, then lead recovery will maintain in the same levels and zinc will be depressed more efficiently. This can be quantified by same or higher recovery of lead, lower recovery of zinc to the lead (or copper & lead) concentrate and a higher grade (content as weight percentage of the slurry weight) of zinc in the slurry that remains for a second flotation stage.

[0022] For the secondary flotation stage (zinc flotation) no change is necessary on the reagents or dosages of them, as it will be more zinc available in the slurry, zinc recovery will increase in percentage as mass of metal produced in the zinc concentrate produced from said slurry. This invention relates to a collecting agent, or collector agent, for the flotation of lead, zinc and optionally copper.

[0023] In a first embodiment, this invention provides a collecting agent comprising S-alkyl- 4,5-dihydro thiazole (Formula la) or N-alkyl-2-thiazolidinethione (Formula lb) or a mixture thereof wherein R1 is a Ci to Cis alkyl, C2 to C18 alkenyl, C3 to C18 cycloalkyl, Ce to Cis aryl or an alkyl ether group of the formula -(CH2)nOCH3, where n is a number from 1 to 18, such group optionally being substituted.

[0024] The alkyl and alkenyl groups may be linear or branched. The alkyl and alkenyl groups may be substituted or unsubstituted. In a preferred embodiment, the alkyl and alkenyl groups contain 2 to 8 carbon atoms.

[0025] The cycloalkyl group may be substituted or unsubstituted. The cycloalkyl group contains preferably 3 to 8 carbon atoms. The cycloalkyl group may be bonded to the rest of the molecule directly, or through a non-cyclic carbon atom, i.e. through a carbon atom in a side chain of the cycloalkyl group.

[0026] The aryl group may be substituted or unsubstituted. The aryl group may be bonded to the rest of the molecule directly, or through a non-cyclic carbon atom, i.e. through a carbon atom in a side chain of the aryl group. The aryl group contains preferably 6 to 12 carbon atoms.

[0027] The alkyl ether group is represented by the chemical formula -(CH2)nOCH3 where n in a preferred embodiment varies from 2 to 12. Most preferably, R1 is an alkyl group with 2 to 8, particularly 3 to 6 and exemplary 4 carbon atoms.

[0028] In the collecting agent, the individual amounts of S-alkylated (la) and N-alkylated (lb) species can vary from 0 to 100 %. Preferred are mixtures where S-alkylated- 4,5-dihydro thiazole (la) is predominant. Particularly, the individual amount of S- alkylated-4,5-dihydro thiazole (la) is 80 wt.-% or higher, preferably 90 wt.-% or higher. Particularly, the individual amount of N-alkylated-4,5-dihydro thiazole (lb) is 20 wt.-% or less, preferably 10 wt.-% or less. More particularly, the individual amount of S-alkylated-4,5-dihydro thiazole (la) ranges from 80-99 wt.-% and the individual amount of N-alkylated-2-thiazolidinethione (lb) ranges from 1-20 wt.-%. Exemplary amounts are 85-98 wt.-% S-alkylated-4,5-dihydro thiazole (la) and 2-15 wt.-% N-alkylated-4,5-dihydro thiazole (lb), or 88-97 wt.-% S-alkylated-4,5-dihydro thiazole (la) and 3-12 wt.-% N-alkylated-4,5-dihydro thiazole (lb), and 90-96 wt.-% S-alkylated-4,5-dihydro thiazole (la) and 4-10 wt.-% N-alkylated-4,5-dihydro thiazole (lb).

[0029] The compounds according to Formulae la and lb can be synthesized according to the following route.

[0030] Solvent Water

[0031] Catalyst: NaOH

[0032] Examples

[0033] Example 1 :

[0034] Sample characterization

[0035] A dry ore sample was mechanically prepared by grinding. The sample contained Cu: 0.06 wt.-%; Pb: 1 .13 wt.-%; Zn: 1 .75 wt-%; Ag: 0.006 wt.-%.

[0036] Reagents

[0037] For the standard (comparative) test the reagents used were

[0038] Sodium Cyanide, Zinc Sulphate Depressants

[0039] Potassium Amyl Xanthate Collector

[0040] Copper sulphate, Surface activator for zinc on second stage

[0041] Methyl Isobutyl Carbinol and Frother

[0042] Na Diisobutyldithiophosphinate Collector

[0043] The inventive collector tested in this study, partly referred to as JEF-311 , was a compound according to Formulae 1a and 1 b, wherein R1 was a n-butyl group. The weight ratio between Formula 1a and Formula 1b was 0.85 to 0.15.

[0044] Flotation Tests

[0045] Laboratory tests were done with 1 Kg ore charges prepared at 100% -10# (-2 mm). Standard grinding is P80 of 180 pm, grinding time was determined for a standard ball mill (8”x 8”) with 7.3 Kg of grinding media at 67% solids. Grinding time was estimated in 7 minutes and 19 seconds with a nonlinear function regression.

[0046] Flotation stages rougher and scavenger were applied on the bulk concentrate and also for Zn flotation as represented on figure 1 . Bulk means the first stage of flotation, Zn flotation is the second stage as shown in Fig. 1 .

[0047] The first series of results (figure 2) consisted in ZnSO4 dosage variation using the standard primary collector (Na Diisobutyldithiophosphinate). It was observed a proportional response of Pb recovery with ZnSO4 dosage, increasing from 79.5% at 200 g / t to 83.3% al 600 g / t. For Zn 200 g / t dosage of ZnSO4 did not have an efficient rejection in bulk flotation with 84.3%, by increasing to 400 g / t and 600 g / t similar results were obtained with 54.7% and 52.2% respectively. For Cu recovery was 71.7% when 200 g / t of ZnSO4 was used, increasing dosage to 400 g / t or 600 g / t recovery value stabilizes around 79% but it has to be taken in count the very low feed grade. Cu and Pb rejection during Zn flotation stage was good all dosages of ZnSO4, although Zn recovery was very low for 200 g / t ZnSO4 dosage with a value of 10.4%, when dosage was increased to either 400 g / t or 600 g / t this value can grow to 36.7% and 39.1 % respectively but is still a low recovery.

[0048] The second series of results (figure 3) belongs to the dosage variation of ZnSC with JEF-311 used as primary collector. For bulk flotation Pb and Cu recoveries did not seem to have any clear relation with ZnSO4 dosage and values were on the range 79.4%-81 .4% for Pb and 67.6%-82.2% for Cu. In Zn rejection relationship between Zn recovery with ZnSCM dosage was evident decreasing its value from 64.7% at 200 g / t to 14.2% at 600 g / t. For Zn flotation stage a clear improvement again is seen starting with 29% recovery at 200 g / t of ZnSO4 to raise to a value of 77.3% with 600 g / t.

[0049] When Zn recovery was analyzed in bulk flotation but also in Zn stage, it was seen the response is proportional to the dosage of ZnSO4 for all collectors but not on the exact same amount (figure 4), this created different dosages curves for each collector and each result on Zn bulk rejection induced the contrary effect on the following Zn flotation stage i.e. , better Zn rejection in bulk provided more Zn available to be recovered in Zn stage. Regarding Zn recovery at bulk stage standard collector curve showed improvement when ZnSO4 dosage increases, although recovery stabilizes only at a value slightly of higher than 50% at maximum dosage, while collector JEF-311 can reach as high as 77%.

[0050] Finally, if we analyze Zn flotation stage there was a notorious effect of the amount of available Zn (rejected on bulk stage) increasing Zn recovery. For this reason, Zn recovery curves for each collector have the inversed order if compared with the previous stage meaning. In Fig. 4, the comparative collector Na-DTPN is represented by the upper graph on the left (bulk) and by the lower graph on the right (Zn recovery). The inventive collector JEF-311 is represented by the lower graph on the left (bulk) and by the upper graph on the right (Zn recovery). It can be seen clearly that the inventive embodiment on the left allows to lower the Zn recovery further when a depressant is added at increasing concentrations, compared to the comparative embodiment that will level out. Similarly, in Zn recovery (graphs on the right) the inventive embodiment allows for an increase in Zn recovery at increasing depressant concentrations, while the comparative embodiment leads to a levelling out of the Zn recovery.

[0051] This result is obtained with ZnSO4 as depressant but will be the same for other depressants.

[0052] Abbreviations in the figures:

[0053] Z-11 potassium amyl xanthate

[0054] AP-3418 sodium diisobutyldithiophosphinate

[0055] MIBC Methyl isobutylcarbinol

[0056] Cone. Ro. Rougher concentrate

[0057] Cone. Scv. Scavenger concentrate PAX potassium amyl xanthate

[0058] JEF-311 inventive collector

Claims

Patent Claims1 . Collector agent comprising S-alkyl-4,5-dihydro thiazole (Formula la) or N- alkyl-2-thiazolidinethione (Formula lb) or a mixture thereofwherein R1 is a Ci to Cis alkyl, C2 to C18 alkenyl, C3 to C18 cycloalkyl, Ce to Cis aryl or an alkyl ether group of the formula -(CFhjnOCHs, where n is a number from 1 to 18, such group optionally being substituted.

2. Collector according to claim 1 , wherein R1 is alkyl.

3. Collector according to claim 2, wherein R1 has 2 to 8 carbon atoms.

4. Collector according to one or more of claims 1 to 3, which comprises a mixture of the compounds according to Formula 1 a and Formula 1 b in a weight ratio from 80 to 99 wt.-% Formula 1 a and 1 to 20 wt.-% of Formula 1 b.

5. A process for the flotation of lead, zinc and optionally copper ore, the method comprising subjecting an ore comprising lead, zinc and optionally copper to a first flotation stage, wherein a depressant for zinc is present, and as a collector the collector agent according to one or more of claims 1 to 4 is present, and subjecting the flotation phase comprising the depressed zinc ore to a second flotation stage, wherein a depressant for zinc is present, and as a collector the collector agent according to one or more of claims 1 to 4 is present.

6. Use of a collector according to one or more of claims 1 to 4 in the separation of ores comprising lead, zinc and optionally copper.

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