Effect of ultrasonic treatment parameters on acidophilic microorganisms for bacterialchemical leaching

This study investigates the impact of ultrasonic irradiation on the population of acidophilic chemolithotrophic bacteria at the Shanuch deposit, since ultrasonic treatment has a positive effect on the rate of bacterial-chemical leaching of ores. The bacterial culture under investigation includes species such as Acidithiobacillus thiooxidans, A. ferrooxidans and Sulfobacilus thermosulfidooxidans, which are crucial for bioleaching processes. In the experiments, the bacterial suspension was subjected to ultrasonic treatment at various time intervals (1, 3, 5, 10, 15, 20, and 30 minutes) with different vibration intensities (4.2, 7.2, and 11.0 W/cm2) and different feeding modes. Topdown and bottom-up feeding modes were examined, conventionally known as counter-current feeding modes. The results indicate that increasing the intensity of ultrasonic treatment beyond 4.2 W/cm2 and prolonging the exposure time significantly reduced the number of bacteria in the mixed culture isolated from the Shanuch deposit ore. Notably, bacteria that are typically resistant to adverse environmental factors such as high temperature and acidic conditions were less tolerant to ultrasonic irradiation. At an intensity exceeding 11 W/cm2, the bacterial count decreased by up to 99.9 % after prolonged exposure. The pH and Eh values of the suspension remained stable throughout the experiments, suggesting that ultrasonic irradiation had minimal impact on these environmental parameters. Overall, the study found that ultrasonic treatment effectively reduced bacterial counts in the mixed culture, with the reduction effect becoming more pronounced with increased duration and intensity of the irradiation.