جستجوی مقالات مرتبط با کلیدواژه "فروشویی زیستی" در نشریات گروه "زمین شناسی"

In this study, microbial leaching of nickel from two arsenide ores (low-and high-grade samples) was precisely investigated. The microbial leaching of nickeline was accomplished with the admixture of mesophilic (Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans) cultures in shake flasks with pulp densities of 0.5, 1, and 5% for low- and high grade samples. The nickel content was over 99% dissolved by mesophilic bacteria of low-grade and high-grade samples after 10 and 28 days respectively at two 0.5% and 1% pulp densities, while the nickel content of the chemical and abiotic control tests was much lower than biotic tests (about 6.9% and 26.7% for low-grade, 10.3% and 16.9% for high-grade). This study marks the inaugural utilization of heterotrophic bacteria in such dissolution processes. Evaluation of three bacterial strains, (Bacillus cereus, Glutamicibacter nicotianae, and Bacillus zhanghouensis), revealed their proficiency in nickel dissolution from nickeline samples across a range of solid percentages (0.5%, 0.8%, 1.1%, and 3%). Notably, Glutamicibacter nicotianae demonstrated superior dissolution capabilities compared to its counterparts, resulting in 100% nickel recovery from low-grade samples and 70% recovery from high-grade samples. Control leaching experiments corroborated these findings, albeit with notably inferior dissolution rates (0.33%). Characterization of remaining samples and microbial activity was conducted through various analytical techniques including SEM-EDS, FE-SEM, and XRD analysis. The catalytic effect and galvanic interaction of different additives on the dissolution of the samples were investigated so that for the solid density of 50 grams per liter of low and high-grade samples, a specific amount of pyrite (0.75 g/L), graphite (0.8 g/L), L-Cysteine (0.48 g/L) and silver nitrate (0.0504 g/L) were added to the medium. In the low-grade sample, the nickel dissolution, all four additives in both low-grade samples with iron (II) and sulfur additives and without iron (II) and sulfur additives showed a positive efficiency so that the dissolution rate exceeded 90% on day 28. In high-grade, three of the four additives (silver-pyrite and L-Cysteine) in the high-grade sample without iron (II) and sulfur additives had a positive effect on the dissolution of nickel, and were able to increase the recovery to over 90% after 28 days, in the sample with iron (II) and sulfur additives, three additives (pyrite, silver, and L-Cysteine) had the greatest, but in the presence of iron (II) and sulfur was not benefiting but also reduced the recovery below 90%. That can be due to the high concentration of elements in the culture and its negative effect on the preformation of bacteria. In this study, mesophilic bacteria, by forming and depositing secondary arsenic minerals such as scorodite and jarosite, prepared the environment for their continued activity, which was also confirmed in the XRD analysis results.

Copper oxide ores are usually leached in sulphuric acid solution. However, it has severe adverse impact on the environment. In this study, bioleaching and leaching by citric acid, as environmentally friendly methods, are investigated. The experiments were carried out on a copper oxide ore sample containing copper content of 3.4%. This sample does not contain any energy source to grow the conventional bioleaching microorganisms (like Thiobacillusferrooxidans and Thiobacillusthiooxidans). This sample was leached by a heterotrophic bacterium, Pseudomonas aeruginosa. This bacterium produces organic acids in selected culture medium that operate as leaching agents. Leaching is investigated by citric acid, as an organic acid produced by this microorganism. The optimum bioleaching conditions were found as: glucose percentage of 6, bioleaching time 8 days and solid/liquid ratio of 1:80 and of optimum leaching conditions as: particle size range105-150µm, acid concentration of 0.2 M, 30 min dissolution time, solid/liquid ratio of 1:20 g/mL and temperature of 40°C. Under optimum bioleaching conditions 53 percent of copper was extracted and copper extraction under optimum leaching conditions was 92 percent.