Optimization of uranium bioreduction by shewanella RCRI7 using Response Surface Design Method (RSM) in industrial waste

Uranium compounds are toxic and radioactive. Its poisonous properties can be fatal. So, it is necessary to prevent its excessive entry into nature due to uranium's chemical toxicity and radioactivity. Waste from industrial-nuclear centers also has different amounts of uranium; therefore, the removal of this element from the effluent of these centers is essential. On the other hand, due to the importance and limited resources, uranium recovery from waste has economic value. In the present study, the Response Surface Method (RSM) based on the central composite design was used to evaluate and optimize different parameters affecting the bioremediation process of Shewanella RCRI7 in real waste. The proposed second-order model with a correlation coefficient R2 = 0.94 appropriately predicted the experimental data and the maximum uranium reduction efficiency by Shewanella RCRI7 under optimal conditions (pH = 5.7-6.5, Temperature 26.63 °C and Time 117 hours) was estimated to be about 98%. In the next step to interact between the variables, three-dimensional procedures with pH and temperature; temperature and time; pH and time interactions were obtained; finally, the uranium reduction in real effluent was investigated by XRD and spectrophotometric methods. Based on the results, Shewanella RCRI7 is determined as a valuable candidate for uranium bioreduction processes in the determined industrial wastewater. On the other hand, using the response surface methodology can provide a comprehensive understanding of the process, the mechanism of uranium bioremediation by Shewanella RCRI7, and the theoretical support for this process.