Effect of temperature on bioleaching of iron impurities from kaolin by Aspergillus niger fungal

ABSTRACT The microorganisms used in this study are isolates and purified strains of Aspergillus niger pistachios and NCIM 548 A. niger. All experiments, including testing of the pH, iron, citric acid, oxalic acid and sucrose concentrations in kaolin samples, were performed at temperatures of 30°C and 25°C with three repetitions. After analyzing and disinfecting the samples with distilled water on the 28th day, X-ray fluorescence (XRF) was used to analyze kaolin, especially for iron content, as well as to conduct color measurements. The results of the kaolin powder XRF showed 52% iron removal from kaolin by A. niger fungal isolated from pistachio skin after 14 days and 47.7% iron removal after 28 days at a temperature of 25°C and 33.8% iron removal after 28 days at a temperature of 30°C. The results of white measurements of treated kaolin samples showed that kaolin powders treated with A. niger pistachio skin isolate at 25°C and 30°C and A. niger NCIM 548 with fungal cells at 25°C showed the highest L* of 75.41, 74.72 and 74.49, respectively, which were increased in comparison with the L* sample of untreated kaolin, which registered 71.94. Thus, the results showed that the A. niger fungal isolated from pistachio skin at 25°C and 30°C achieved better iron removal than the other samples and that a temperature of 25°C achieved better results than a temperature of 30°C