عنوان مقاله [English]
The entrance of heavy metals contaminants into the aqueous environment, due to their toxicity and the biological damages is hazardous for the human health. So the separation of them from the environment is an important subject. In this work, adsorption of heavy metals was investigated using biological method. The process of adsorption of copper and manganese using bacterium were done at different conditions (pH, temperature, and adsorbent concentration). Besides, the experimental design of Response Surface Methodology (RSM) was used to study the interactions between parameters and to draw the surface diagrams, and the estimation of the mathematical equation (absorbance versus variables) as a polynomial model. Results showed that increasing of pH up to 6 increased the bio-sorption of both Mn and Cu. Increment in temperature and adsorbent content had the same effect. Although the absorbance of Mn was a little higher than Cu, both of them showed the same changes with variables. The observed increment effects were lower at lower levels of variables and became more considerable at higher levels of variables. In each level of absorbent, with increasing of the temperature, absorbance increased which was greater at higher pH. Also, the incremental effect of pH was more remarkable at the higher bacterium concentration. The effect of each variable was influenced by another one. Using RSM, the bio-sorption amounts of both Cu and Mn were formulated versus T, pH, and adsorbent content, with a suitable accuracy and low error. In addition, the interactions between parameters were analyzed considering 3D plots and the coefficients of the achieved equations. Finally, the predicted results from the equations for the new experimental conditions were compared with the the experimental results, which showed a good agreement.