Investigation of the adsorptive properties of filamentous fungus Aspergillus niger in the removal of 85Sr and 99mTc from aqueous solutions

This study investigates the adsorptive properties of the filamentous fungus Aspergillus niger in both isolated and lyophilized forms for the removal of 85Sr and 99mTc from aqueous solutions. The adsorption process was evaluated across a range of pH values and contact times, with a focus on understanding the kinetic behavior and efficiency of each form. For 85Sr, both forms of Aspergillus niger exhibited pH-dependent adsorption, with optimal removal efficiency occurring between pH 4 and 8. Adsorption equilibrium was achieved within 120 min, with the pseudo-second-order kinetic model providing the best fit, suggesting a chemisorption mechanism. Maximum adsorption for the lyophilized form was 68.2% at pH 4, while the isolated form reached 66.4% at pH 8. In contrast, 99mTc adsorption was minimal across all pH levels, with less than 10% adsorption observed, indicating poor affinity for the anionic pertechnetate species. The study highlights the effectiveness of Aspergillus niger in removing 85Sr from contaminated water, while also addressing its limitations in adsorbing 99mTc. These findings contribute to the understanding of biosorption mechanisms for radionuclide removal in environmental applications.