Research on technology of copper powder production from the poor copper oresby Bio-Leaching method

52 HNUE JOURNAL OF SCIENCE DOI: 10.18173/2354-1059.2017-0054 Chemical and Biological Science 2017, Vol. 62, Issue 10, pp. 52-59 This paper is available online at RESEARCH ON TECHNOLOGY OF COPPER POWDER PRODUCTION FROM THE POOR COPPER ORESBY BIO-LEACHING METHOD Bui Van Tai 1 , Nguyen Tien Manh 2 and Bui Xuan Giap 2 1 Institute of Chemistry and Material, Academy of Military Science and Technology 2 Minerals Holding Corporation TKV, Vietnam National Coal - Mineral Industries Holding Corporation Limited Abstract. This paper describes the research on the production of copper powder from the waste ore of the copper mining process (at poor copper ore of Sin Quyen Copper Mine) by bio-leaching method using microorganisms capable to oxidize sulfide ore, separating copper in the copper salts to produce copper powder. The methods used were: UV-VIS, EDS, ICP analysis, atomic absorption to control technology bio-leaching, besides, analysis of species and density of useful microorganisms Bacillus spp and Thiobacillus ferrooxidans were carried out basing on Vietnam standards TCVN 6404, TCVN 8736. The obtained result has been a bio- leaching producing copper powder from poor ore with concentration of more than 80%. The conditions of the copper separation process are at pH = 1.5-2.5 along with air-oxygen supplementation and density of useful microorganisms > 10 3 CPU/mL. Keywords: Bio-leaching, copper ore, dissolving-separation, copper powder. 1. Introduction Copper is the industry's most important metal. In terms of volume, copper is the third metal after steel and aluminum. Copper was used by humans around 8700 BC. However, the copper mining and processing industry in the world has grown rapidly since the early 20th century. Technology producing copper metal is usually processed through a series of stages from mining, processing to enriching to increasing the content then electrolysis. In addition, it is possible to produce copper by hydrothermal method, usually using acids to dissolve ore then by electrolyzing to result in copper precipitate and purifying. In the world, an around 20% of the copper production is made from poor copper ore by biological means. Today, most of countries use the bioleaching method for mining or processing of poor copper ores [1], (see Fig.1). Bioleaching is the extraction of metals from their ores through the use of living organisms. In addition to chalcopyrite, other copper sulfide minerals such as bornite Received November 17, 2017. Revised December 8, 2017. Accepted December 15, 2017. Contact Bui Van Tai, e-mail address: bvtai2007@yahoo.com.vn Research on technology of copper powder production from the poor copper oresby bio-leaching method 53 (CuFeS4), cubannite (CuFe2S3), enacsite (Cu3AsS4), covelite (CuS) may be oxidized by bacteria to produce copper metal [2]. Fig.1 Copper bioleaching plant in Uganda Bornite Chalcopyrit Covelite For example, the reactions of chalcopyrite bioleaching may be carried out as following: Chalcopyrite leaching: (1) CuFeS2 + 4 Fe 3+ + 5 Fe 2+ + 2S 0 (spontaneous) (2) 4Fe 2+ + O2 + 4H +   ismMicroorgan 4Fe3+ (iron oxidizers) (3) 2S 0 + 3O2 + 2 H2O   ismMicroorgan 2SO 24 + 4 H + (sulfur oxidizers) Net reaction: (4) CuFeS2 + 4O2   ismMicroorgan Cu 2+ + Fe 2+ + 2SO 24 Than the copper powder may be recovered using iron fillings as following: (5) Cu 2+ + Fe 0   ismMicroorgan Cu 0 + Fe 2+ Developing countries have used a variety of copper ore processing technologies depending on the nature and content of copper. Normally with copper-enriched copper ore, copper ore is processed in the form of hydrothermal method. The poor copper ore is dissolved using sulfur oxide-capable microorganisms, bio-leaching method and then copper recovered in powder form [3]. In Vietnam now, copper production is mainly by means of heat treatment and hydrolysis from copper rich ores. Poor copper ore processing and the recovery of copper from these ores have not been still studied. Poor ore resources in mines with large reserves are increasing over time, so it is necessary to research and apply the technology of processing copper from these ore kinds. Bui Van Tai, Nguyen Tien Manh and Bui Xuan Giap 54 In this paper, a research on the production of copper powder from poor copper ore of Sin Quyen Lao Cai Copper Factory by hydrolysis method using bioleaching method was carried out. All factors such as microorganism, pH, reaction time influencing efficiency of copper powder resulting were studied in detail. 2. Content 2.1. Experimental method * Materials and appratus - Materials + Poor copper ore collected from the disposal of Sin Quyen Copper Plant. + Ore separation solution containing the bacteria Thiobacillus Ferroxidans used. + Industrial sulfuric acid. - Appartus + Tanks for dissolving –separation + Air compressor + Acid-resistant pumps. + Spectrophotometer: Determining the content of copper in samples. + Analytical balance, from 0 - 200 g, with error  0.1g * Experiments - Procedure producing copper powder The steps in the procedure producing copper powder using bio-leaching is presented in the Figure 2. Figure 2. Procedure producing copper powder by bioleaching - Material ore: Copper ore is selected from the disposal site of Sin Quyen Lao Cai copper mine, processed to size <15mm, sampling and analyzing the copper content before introducing into the tank. Ore sample weight is 30 kg / time. - Bio-leaching solution: Thiobacillus ferroxidans solution is taken from the discharge at the ore site of Sin Quyen copper mine in Lao Cai. Sample solutions after treatment were used for analyzing copper, iron concentration, besides, solutions were sent to determine microbial density at Institute of Biotechnology - Vietnam Academy of Sciences and Technology. - Circulation of 30 liters of sample solution containing 30 kg of ore size <15mm, reaction medium pH = 2.5, supplying oxygen 4 times a day by air compressor were carried out. Ore treatment Separation solution Control of product Bioleaching copper Removal of dirty Copper precipitate Research on technology of copper powder production from the poor copper oresby bio-leaching method 55 - After 25 days of separation, the whole solution was filtered to remove mechanical impurity, adjusting the pH of the medium to the value of 2. The iron scrape was used to clean the precipitate to obtain copper powder. Experimental process has investigated in determining some factors affecting the dissolution of copper from ore to solution such as: separation medium; time of separation; thiobacillus ferroxidans concentration and the ability of bio-leaching with providing oxygen. * Analytical methods - Analysis of copper in ore and in solution was implemented basing on Vietnam standard TCVN 3867. - Analysis of species and useful bacterial density was carried out according to Vietnam standards TCVN 6404, TCVN 8736. 2.2. Result and discusion 2.2.1. Influence of factors on bio-leaching process * Influence of pH Results of the influence of the pH on the ability of bio-leaching of ore are shown in Tables 1 and 2. Table 1. Concentration of copper and total iron in soultion after bio-leaching versus pH No. Samples Cu 2+ (g/L) Total iron (g/L) pH 1 DD 1 before bioleaching 0.100 1.5 2.0 2 DD 2 before bioleacing 0.100 1.5 3.5 3 DD 1 after bioleaching 0.115 1.70 2.5 4 DD 2 after bioleaching 0.102 1.58 3.5 Table 2. pH influence on bacterial density Samples pH Manes of bactery Unit (CFU/mL) Sample 1 2.0 Bacillus spp. 1.3105 Thiobacillus ferrooxidans 1.5103 Sample 2 3.5 Bacillus spp. 2.5103 Thiobacillus ferrooxidans 1101 Note CFU: Colony forming unit Table 1 shows that the pH of the medium influences the dissolution of the copper from the ore to the solution. When the pH of the bioleaching solution was 2, the concentration of copper in the solution increased from 0.100 g/L to 0.115 g/L, while the concentration of thiobacillus ferrooxidans in solution was kept stable (Table 2). Bui Van Tai, Nguyen Tien Manh and Bui Xuan Giap 56 * Influence of bioleaching time The results of the time effect on the ore bioleaching ability are shown in Table 3 and in Figure 3. Table 3. Copper and total iron concentration in bioleaching solution No. Time (day) Cu 2+ (g/L) Total Fe (g/L) pH 1 1 0.100 1.52 2.5 2 5 0.115 1.70 2.5 3 10 0.121 1.90 2.5 4 15 0.126 2.00 2.5 5 20 0.130 2.06 2.5 6 25 0.132 2.15 2.5 Figure 3. Copper concentration versus time The results in Figure 1 show that the reaction rate was rather slow, after 25 days, the concentration of Cu 2+ in the solution was increased to 0.132 g/L and the difference from the initial concentration was: 0.132 (g/L) - 0.100 (g/L) = 0.032 g/L. * Calculation of Efficiency of copper conversion Efficiency of copper conversion to solution after 25 days of bioleaching: - The copper in ore: 30 (kg) × 0.13 (%) = 3.9 (g) - The copper dissolution: (0.132 - 0.100) × 30 (L) = 0.96 (g) => Efficiency of copper conversion (0.96/3.9) × 100 = 24.6 (%) * Effect of bacterial density The results of the effect of bacterial concentration of Thiobacillus Ferroxidans on the ore bioleacing ability are shown in Tables 4 and 5. Research on technology of copper powder production from the poor copper oresby bio-leaching method 57 Table 4. Bacterial density Sample Bacterial density Unit (CFU/mL) M 1. Before Bioleaching Total aerobic microorganisms 2.4105 Bacillus spp. 1.2104 Thiobacillus ferrooxidans 2101 M 2 Before Bioleaching Total aerobic microorganisms 1.3105 Bacillus spp. 1.2104 Thiobacillus ferrooxidans 1.5103 M 1 After bioleaching Total aerobic microorganisms 2.7103 Mold 0 Bacillus spp. 1.1 103 Thiobacillus ferrooxidans 2.4101 M 2 After bioleaching Total aerobic microorganisms 1.1102 Mold 0 Bacillus spp. 1.3104 Thiobacillus ferrooxidans 1.2103 Table 5. Copper and total iron concentrations before and after bioleaching No. Sample Cu 2+ (g/L) total Fe (g/L) pH 1 M1 Before bioleaching 0.100 1.50 2 2 M2 Before bioleaching 0.100 1.50 2 3 M1 After bioleaching 0.106 1.62 2.5 4 M2 After bioleaching 0.116 1.75 2.5 Thiobacillus ferrooxidans bacterium density affects the dissolution of copper from ore to solution. As the tables above show, the higher the bacterial density, the faster the dissolution time of copper is in the solution. Therefore, for the copper ore bioleaching process to be effective, the bacterial concentration of Thiobacillus ferrooxidans must be at least 10 3 CFU / mL. * Influence of air Results of the effect of supplemental air during on the bioleaching are shown in Table 6. Bui Van Tai, Nguyen Tien Manh and Bui Xuan Giap 58 Table 6. Influence of microbial density when with and no air additions Samples Air Microorganisms Unit (CFU/mL) M 1 No air addition Total aerobic microorganisms 2.710 3 Mold 0 Bacillus spp. 1.110 3 Thiobacillus ferrooxidans 2.4101 M 2 Air addition Total aerobic microorganisms 1.110 2 Mold 0 Bacillus spp. 1.3104 Thiobacillus ferrooxidans 1.2103 The data in the table above show that the microbial density is strongly reduced for non-oxygenated samples, while sample 2 supplemented with air of microbial density maintained steady. 2.2.2. Recovering copper powder from solution The after bioleaching solution, the ferrous metal scrap was used for producing copper as following CuSO4 + Fe = FeSO4 + Cu Copper powder is resulting in under pH = 2, in H2SO4 acid, iron scrap used is cleaned with 3% sulfuric acid for the reaction time of 2 days, stirring reaction to separate the copper layer from iron. After the experiment, the product was washed, cleaned and dried, weighted and analyzed and presented as follows, Table 7. Table 7. Copper recovery results from iron scrap No. Solutions before bioleaching Copper powder Efficiency (%) Cu left (gCu/L) V (L) (gCu/L) Metal (g) Q (g) HL (%) Metal (g) 1 30 1.52 45.6 52.52 80.51 42.30 92.72 0.11 Using iron shavings, copper powder can be obtained with content of more than 80% Cu from bioleaching solution; Copper recovery rate from solution reaches ≈ 93 %. The copper content left in solution was 0.11 g/L. 3. Conclusion - The process of producing copper powder from the poor copper ore has been studied by bioleaching using of thiobacillus ferrooxidans. Research on technology of copper powder production from the poor copper oresby bio-leaching method 59 - The conditions for the bioleaching of copper from ore have been established: - pH of the medium: 1.5 - 2.5; Density of Thiobacillus ferrooxidans: > 10 3 CFU/mL; Addition of air oxygen into the bioleaching process - From copper ores with a content of 0.13% of Cu, prepared copper metal powder resulted in over 80% Cu. This product can be used for the next metallurgical stage to produce copper sheets or other products used for domestic production or export. This method is usefully applied for manufacturing copper powder from the poor ore containing copper sulfide, reducing environmental pollution due to not using many chemicals and do not emit SO2. REFERENCES [1] Bioleaching Mining Sustainable. Mission 2015. [2] D. Barrie Johnson, 2013. Established, Evolving and Emerging Biotechnologies. Mining and Microbiology, Mission. [3] Andrew Gipson, 2008. Copper Mining Using AcidoThiobacillus. Mission.