USE OF NON OXIDANT BIOCIDE FOR THE SELECTIVE RECOVERY OF VALUABLE METALS IN A FROTH FLOTATION PROCESS

Abstract

The present invention relates to a method for the selective recovery of valuable metal minerals in a froth floatation process using a non-oxidizing biocide.

Claims

1. A process to recover a metal of value from an aqueous pulp, comprising: i. contacting an aqueous pulp with a biocide, wherein the aqueous pulp comprises a metal ore; and, ii. thereafter recovering the metal of value by subjecting the aqueous pulp to froth flotation.

2. The process according to claim 1, wherein the biocide is selected from the group consisting of 2,2-dibromo-2-cyanoacetamide, glutaraldehyde, and mixtures thereof.

3. The process according to claim 1, wherein the biocide is 2-dibromo-2-cyanoacetamide.

4. The process according to claim 1, wherein the metal of value is selected from the group consisting of copper, molybdenum, zinc, gold, nickel, lead, tungsten, and mixtures thereof.

5. The process according to claim 4, wherein the metal of value is copper.

6. The process according to claim 5, wherein productivity is greater than 90% for the copper from the aqueous pulp.

Description

EXAMPLES

Example 1. Measuring Bacterial Contamination in Copper Mining Process

[0012] Eight samples of slurry/water were collected using sterile flasks from different process points at a mining company in Chile (see Table 1). This plant processes raw material consisted of tailings from two different sources. The plant follows a typical extraction process for copper concentrate (911 MetallurgistA Practical Guide to Mineral Processing Engineering https://www.911metallurgist.com/blog/copper-process-flowsheet-example. Accessed on Jul. 12, 2017) with the exception of having two aforementioned raw material streams processed in parallel through primary, secondary grinding and rougher flotation (after which the streams are combined).

[0013] After sampling, water phase was separated from suspended solids by decantation for 10 min and analyzed using the Luminultra ATP QGA test-kit, a 2.sup.nd Generation Adenosine Triphosphate (ATP) measurement tool for low-solids water-based samples (ASTM D4012 compliant) (https://www.luminultra.com/qga/). The levels of ATP allow for the estimation of microbe levels in the samples. In addition, the viable counts of microorganisms in the decanted aqueous phase samples were determined using a most probable number (MPN) method in 96-well microtiter plates with serial dilution across the plate using a robotic automated system (Cochran, W. G. Estimation of Bacterial Densities by Means of the Most Probable Number. Biometrics, 1950, p. 105-116. Rowe, R., Todd, R., Waide, J. Microtechnique for Most-Probable-Number Analysis. Applied and Environmental Microbiology. 1977, 33, 675-680). Trypticase Soy Broth (TSB) was used as culture media for the MPN method and readings were performed after 48 h incubation at 37 C. Summary of samples and corresponding bacterial levels are summarized in Table 1.

TABLE-US-00001 TABLE 1 Samples collected and analyzed for bacterial contamination Estimated Viable Viable Counts Total counts from Sample Sampling point ATP from ATP MPN # in the process (pg/mL) (CFU/mL) (CFU/ml) 1 Raw Material 1 2087 2.1 10.sup.6 5 10.sup.5 5 10.sup.6 2 Raw Material 2 2980 3.0 10.sup.6 5 10.sup.5 5 10.sup.6 3 Feed of Rougher Flotation 5830 5.8 10.sup.6 5 10.sup.5 (Raw Material 2 stream) 5 10.sup.6 4 Tailings of Rougher 4815 4.8 10.sup.6 5 10.sup.5 Flotation 5 10.sup.6 (Raw Material 1 stream) 5 Rougher concentrate- 5749 5.7 10.sup.6 5 10.sup.5 combined streams 5 10.sup.6 6 Final concentrate-4.sup.th 176 1.8 10.sup.5 5 10.sup.5 cleaner 5 10.sup.6 7 Water from thickeners 12165 1.2 10.sup.7 5 10.sup.5 5 10.sup.6 8 Fresh water 169 1.7 10.sup.5 5 10.sup.2 5 10.sup.3

Example 2. Evaluating Bacterial Impact on Flotation Process

[0014] To evaluate bacterial impact on flotation process, artificially contaminated water was produced and compared to clean tap water. Each water sample from the cited mining company (example 1) was swabbed and streaked on Tryptic Soy Agar (TSA) solid culture media plates and incubated at 37 C. After one week colonies from these plates were transferred to a liquid culture media TSB (Difco) and grown for 72 hours at 37 C. A new streak was done on the solid TSA media obtaining 100% of plate cover after incubation at 37 C. for 48 hours. All the plate surface was scrapped and suspended in a saline solution (4.5%) 3 days before the beginning of flotation trials. 4 mL of bacterial pool (3.410.sup.5 CFU/mL) were added to 5 L of tap water and this was used as contaminated water.

[0015] A copper-mine ore (chalcopyrite, CuFeS.sub.2) previously extracted from Raw Material 2 region was crushed and primarily ground. Samples were sieved through Tyler, size 10, mesh using a sieve shaker. About 1 kg of this solid was secondarily ground using 22.23 cm17.15 cm laboratory ball mill, containing 10 kg of 2.54 cm metal balls at 70 rpm for 30 minutes. The process was carried out in the presence of 500 mL water (tap or contaminated), diesel oil (15 g/ton) and a primary collector from Mathiesen MATCOL D-101 (modified dithiocarbamate) at 38 g/ton to generate a particle size (P80) of 180 m. The resulting ore pulp was treated with a biocide (Aqucar GA 50, Dow Chemical Co. or Aqucar DB 20, Dow Chemical Co.), at 100 ppm dosage for 10 minutes (for tap water and contaminated water control samples this step was omitted), and transferred to an Agitair LA-500 Laboratory Flotation Cell filled with water up to 2,700 mL and mixed for two minutes to homogenize, generating a pulp of approximately 31% solids. A secondary collector AX-343 (potassium amyl xanthate plus sodium isobutyl xanthate) was added at 12 g/ton as well as a blend of frothers at 12 g/ton, consisting of 55% methyl isobutyl carbinol (Dow Chemical Co.), 40% Flomin F810 (SNF FloMin, Inc.), 5% Mathiesen DF-1012 (Mathiesen Corp.). Initial pH was maintained at 10.0 via addition of lime and the pulp was conditioned for 20 minutes.

[0016] The concentrate was collected by hand scraping the froth from the pulp surface once every 10 seconds for a total flotation time of 12 minutes at 1,440 rpm. Resulting concentrate and the tailings were filtered under vacuum, dried in an oven at 80 C. and analyzed by atomic absorption spectroscopy. Results are presented in table 2. Grade is defined as percentage of the metal on the concentrate and recovery is defined as percentage of the metal in the original feed that is recovered in the concentrate. Productivity for both metals is calculated by multiplication of corresponding grade and recovery values for treated metal divided by the equivalent operation for the tap water sample values (normalized to 100%).

TABLE-US-00002 TABLE 2 Metallurgic balance for rougher flotation using artificially contaminated tap water treated with organic biocides 10 min before flotation Contaminated Contaminated Water + Tap Contaminated Water + 100 ppm Water Water 100 ppm GA DBNPA Cu Grade, % 9.19 8.10 8.32 9.49 Cu Recovery, % 88.3 88.3 88.0 87.2 Cu Productivity 100% 88.1% 90.2% 102% Fe Grade, % 19.8 15.3 17.2 17.8 Fe Recovery, % 46.7 43.5 44.7 43.0 Fe Productivity 100% 72.0% 83.1% 82.8%

[0017] Treatment with both biocides, glutaraldehyde and DBNPA, showed improvement in copper grade compared to untreated contaminated water samples. DBNPA was the only biocide able to return copper productivity to the level of a tap water, while keeping lower recoveries and grades of the undesirable iron when compared with tap water condition.