Optimization of efficient lead removal by Bacillus sp. Strain STG-83 using response surface methodology for bioremediation of contaminated wastewater

Environmental hazards of wastewater containing metals, including lead, have attracted researchers' attention on their cleanup using novel methods such as bioremediation. In the present study, the biosorption ability of lead by Bacillus sp. Strain STG-83 was evaluated. Response surface methodology with central composite design by the Design Expert software was used to optimize parameters such as pH, biomass concentration, and initial lead concentration. The results showed that the quadratic model proposed by Design Expert software with a correlation coefficient of R2=0.9938 predicted the process behavior properly; lead biosorption by the bacteria was optimized at pH=4.5, initial concentration of lead 297.95 mg. L-1, and the amount of adsorbent 1 g.L-1, which is equal to 149.595 mg. g-1 dry weight. Also, the experimental data were fitted with Langmuir and Freundlich isotherms. The results showed that the Langmuir model is more suitable with R2=0.961. Kinetic studies showed that adsorption capacity reached its maximum value within 5 minutes. Ultimately, due to the valuable potential of this bacterium in rapid and high biosorption of lead, Bacillus sp. strain STG-83 is introduced as a valuable bacterial sorbent for lead bioremediation processes and performance of response surface methodology in modeling and optimizing lead biosorption process by Bacillus sp. strain STG-83 is confirmed.