| Microbial oxidation of ferrous iron may be available alternative method of producing ferric sulphate, which is a reagent used for removal of H2S from biogas. The technics includes three parts: desulfurize, regeneration and sulfur separation. In the regeneration reactor, the Thiobacillus ferrooxidans helped to oxidize the ferrous iron into the sulfate iron as the catalyst. In the process the most important is the continuity and the speediness of the reaction. For practical use of this process, different methods were used to immobilize the Thiobacillus ferrooxidans cells augmenting the cell density and accelerating the reaction. In case of that the upper bioreactor work capacity was obtained to achieve the successfully continuous operation. In this study, the immobilization methods, the culture medium and the bioreactor system were researched respectively.The alginate calcium carrier was used firstly to entrap the microbe cells to evalue the immobilization effect. The results showed that when the alginate concentration was 2 %(W/V), the ferrous sulphate diffusion rate was confirmed to be maximum with the effective diffusion coefficient 2.183×104cm2·min-1 using computer simulating. Meanwhile the effect of calcium chloride on the effective diffusivity was neglectable. Then confirming the concentrations of alginate and calcium chloride were 2 %(W/V) and 4 %(W/V) respectively, changing the initial ferrous iron and the kalium dibasic phosphate concentration and adding the active carbon in the gel to improve the oxidation rate of ferrous iron. The results showed that the oxidation rate was maximum(0.27 g·L-2·h-1) and it would take 50h to oxidize completely in the condition of initial ferrous iron concentration 5g/L with the entrapped cells concentration of 15g/L alginate solution. When the initial ferrous iron concentration were 8g/L the time would cost 60h for the oxidation. Besides the addition of the active carbon could accelerate the oxidation of the ferrous iron from 0.55 g·L-1·h-1 to 0.78 g·L-1·h-1. But the kalium dibasic phosphate would quicken the ferrovanadium deposition which obstruct the foramen of the gel resulting in the bio-cycle decrease.In order to decrease the deposition in the bioprocess, the growth process of Thiobacillus ferrooxidans in different initial pH value and cultivation condition has been studied. It was showed that when the pH value higher than 1.6, the oxidation could maintain the stabilization but the more deposition would happen as the pH value increased. In the condition of the pH value 1.8, different nitrogen resources such as (NH4)2HPO4, NH4Cl, NH4NO3 and (NH4)2SO4 were analysed. It was found that the optimal nitrogen resource was (NH4)2HPO4 in the condition which there were the minimal deposits 0.78 g·L-1 with the stabilized ferrous iron oxidation rate. It was also showed the less deposition as the (NH4)2HPO4 concentration decreased. When the concentration was 0.5g/L, the deposition in the bioprocess could be negligible. So the optimum mudium was (NH4)2HPO4 0.5g/L, CaNO3 0.01g/L, KCl 0.1g/L, MgSO4 0.2g/L, FeSO4·7H2O 44.3g/L.To enhance the bacteria oxidation ability, the Thiobacillus ferrooxidans cells were cultivated in the packed-bed bioreactor filled with spills carriers. All experiments were conducted under the following conditions: fenous iron concentration, 10g/L; pH, 1.8; temperature, 30℃. Experimental evidence verified that the average oxidation rate of ferrous iron were advanced from 0.4 g·L-1·h-1 to 1.0 g·L-1·h-1 after cells immobilization on the carriers. As the increasing of aeration rate, the oxidation rate would increase in intensity with the maximum average rate 4.86 g·L-1·h-1 under the aeration rate 1.4L/min. Size of the carriers was also found to influence the oxidation rate. The much more Thiobacillus ferrooxidans cells preferred to be absorbed in the small size carriers attributed to the bigger surface. So the average oxidation rate of the ferrous iron was increased to 2.36 g·L-1·h-1. In this study, the suitable dilution rate was also described to get the best oxidation ability. Finally it was showed that the maximum oxidation rate was 5.68 g·L-1·h-1 when the microbe cells were supported by smaller size carriers, and the optimum dilution rate was 0.9h-1 with the ferrous iron conversation 65%.
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