Enhanced Fe2+ oxidation by mixed culture originated from hot spring: Application of response surface method

Abstract

For maximum oxidation efficiency and minimum amount of jarosite, a total of 30 experimental runs were conducted and the experimental data fitted to the experimental quadratic model. The analysis of variance (ANOVA) demonstrated that the model was highly significant. Three dimensional plots were illustrated to depict the interaction between all the factors. The experimental results indicated that, the optimal conditions for the desired objects were 1.3, 7 g/l, 141 rpm and 35°C for the media initial pH, Fe²⁺ ion concentration, agitation rate and temperature, respectively. Using the regression model, a maximal oxidation efficiency of 55% and minimum jarosite precipitation of 0.34 g/l were achieved with the consideration of the optimal condition for the parameters at the end of 26 days of operation. The experiment was carried out under optimal condition and resulted in efficient oxidation and jarosite amount of 52% and 0.32 g/l, respectively. Similar values were predicted by the model. According to these results, the response surface methodology was not only applied to determine the significance information on the interaction between the factors, but also was conducted at optimal conditions for the desired objectives. It was also concluded that, the mixed culture isolated from the hot spring had the potential to oxidize ferrous to ferric irons.

Key words: Biooxidation, response surface method, jarosite,  biodesulfurization, process optimization.