Effects of Battery Chemical Process Liquors on Heap Bioleaching Microorganisms
Määttä, Linda (2021)
Määttä, Linda
2021
Ympäristö- ja energiatekniikan DI-ohjelma - Programme in Environmental and Energy Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2021-06-24
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202106145870
https://urn.fi/URN:NBN:fi:tuni-202106145870
Tiivistelmä
During coming thirty years, the quantity of electric vehicles will increase by eight-fold according to International Energy Agency. For the batteries of electric vehicles, metal-based battery chemicals, such as nickel and cobalt sulfate, are used as a raw material, therefore, increasing quantities of these chemicals will be needed in near future. In nickel and cobalt sulfate production process, ammonium sulfate is formed as a side product when ammonium-rich process liquors, containing ammonium sulfate, are associated with the process. These ammonium-rich side streams are a potent source of nitrogen for heap bioleaching. Therefore, in this thesis, possible negative and positive effects of ammonium sulfate (AS) bleed and feed (ammonium-rich side streams, originating from the battery chemical production process) and their constituents on biological iron and sulfur oxidation was under investigation.
The experiments of this study were performed as small-scale batch studies (shake flask). The enriched indigenous acidophilic microorganisms, present in the irrigating leach liquor obtained from a heap bioleaching plant of Terrafame Oy, were used as an inoculum. The effects of battery chemical process liquors: AS bleed and feed, and their constituents (ammonium sulfate, carboxylic acid (neodecanoid acid), Nessol D100, Cyanex 272, and Baysolvex D2EHPA), on biological iron and sulfur oxidation were investigated separately. In addition to these experiments, possible stimulatory effect of ammonium-rich AS bleed and feed, as nitrogen supplement, on biological iron oxidation was also studied.
Both AS bleed and feed process liquors negatively affected the biological iron oxidation. The process liquors resulted in a lag phase in biological iron oxidation and decrease of iron oxidation rate at concentrations higher than 2% (v/v), whereas at AS bleed and feed concentrations of 20% (v/v) and 50% (v/v), respectively, the biological iron oxidation was completely and irreversibly inhibited. With AS bleed, it was recognized that AS bleed enhanced biological sulfur oxidation at concentration of 8% (v/v) and below. The highest sulfate production yield and rate of 27% and 0.38 g/L/d, respectively, were achieved with AS bleed concentration of 4% (v/v). Ammonium sulfate concentrations higher than 20 g/L resulted in a lag phase in biological iron oxidation, whereas 250 g/L resulted in full and irreversible inhibition. Of the organic solvents (neodecanoid acid, Nessol D100, Cyanex 272, and Baysolvex D2EHPA) only neodecanoid acid affected biological iron oxidation. Neodecanoid acid resulted in a lag phase in iron oxidation with concentration of 2.5% of its water solubility (6.3 mg/L) or higher. Organic solvents Nessol D100, Cyanex 272, and Baysolvex D2EHPA were nonbioavailable for the microbial culture in experimental conditions of this study and, therefore, did not affect biological iron oxidation. In ammonium deficiency experiment, 0.079 g/L ammonium supplementation with 0.1% (v/v) AS feed, and 0.11 g/L ammonium supplementation with 0.09% (v/v) AS bleed enhanced biological iron oxidation. With 1% (v/v) AS bleed and feed concentration, the iron oxidation rate was not significantly increased. Iron oxidation rate of iron oxidizing culture, incubated in ammonium deficit medium, was 2.0 g/L/d, whereas iron oxidation rates of cultures supplemented with AS bleed or feed were over 2.3 g/L/d.
In conclusion, ammonium-rich process liquors have a potential to enhance bioleaching, however, potential nitrogen deficiency in the heap bioleaching liquors (of Terrafame) should be studied to estimate the actual demand for nitrogen supplementation. Furthermore, the battery chemical process liquors and some of their constituents may potentially inhibit heap bioleaching process. Ammonium and organic solvents, present in the process liquors, can result in drastic harmful effects in recipient waters, therefore, their release to the environment must be prevented.
The experiments of this study were performed as small-scale batch studies (shake flask). The enriched indigenous acidophilic microorganisms, present in the irrigating leach liquor obtained from a heap bioleaching plant of Terrafame Oy, were used as an inoculum. The effects of battery chemical process liquors: AS bleed and feed, and their constituents (ammonium sulfate, carboxylic acid (neodecanoid acid), Nessol D100, Cyanex 272, and Baysolvex D2EHPA), on biological iron and sulfur oxidation were investigated separately. In addition to these experiments, possible stimulatory effect of ammonium-rich AS bleed and feed, as nitrogen supplement, on biological iron oxidation was also studied.
Both AS bleed and feed process liquors negatively affected the biological iron oxidation. The process liquors resulted in a lag phase in biological iron oxidation and decrease of iron oxidation rate at concentrations higher than 2% (v/v), whereas at AS bleed and feed concentrations of 20% (v/v) and 50% (v/v), respectively, the biological iron oxidation was completely and irreversibly inhibited. With AS bleed, it was recognized that AS bleed enhanced biological sulfur oxidation at concentration of 8% (v/v) and below. The highest sulfate production yield and rate of 27% and 0.38 g/L/d, respectively, were achieved with AS bleed concentration of 4% (v/v). Ammonium sulfate concentrations higher than 20 g/L resulted in a lag phase in biological iron oxidation, whereas 250 g/L resulted in full and irreversible inhibition. Of the organic solvents (neodecanoid acid, Nessol D100, Cyanex 272, and Baysolvex D2EHPA) only neodecanoid acid affected biological iron oxidation. Neodecanoid acid resulted in a lag phase in iron oxidation with concentration of 2.5% of its water solubility (6.3 mg/L) or higher. Organic solvents Nessol D100, Cyanex 272, and Baysolvex D2EHPA were nonbioavailable for the microbial culture in experimental conditions of this study and, therefore, did not affect biological iron oxidation. In ammonium deficiency experiment, 0.079 g/L ammonium supplementation with 0.1% (v/v) AS feed, and 0.11 g/L ammonium supplementation with 0.09% (v/v) AS bleed enhanced biological iron oxidation. With 1% (v/v) AS bleed and feed concentration, the iron oxidation rate was not significantly increased. Iron oxidation rate of iron oxidizing culture, incubated in ammonium deficit medium, was 2.0 g/L/d, whereas iron oxidation rates of cultures supplemented with AS bleed or feed were over 2.3 g/L/d.
In conclusion, ammonium-rich process liquors have a potential to enhance bioleaching, however, potential nitrogen deficiency in the heap bioleaching liquors (of Terrafame) should be studied to estimate the actual demand for nitrogen supplementation. Furthermore, the battery chemical process liquors and some of their constituents may potentially inhibit heap bioleaching process. Ammonium and organic solvents, present in the process liquors, can result in drastic harmful effects in recipient waters, therefore, their release to the environment must be prevented.