Effect of ferrous iron concentration on anaerobic bio-hydrogen production from soluble starch

Both batch experiments (initial pH value was 7.0 and 8.0, respectively) were conducted to convert soluble starch to hydrogen at 35∘C. Anaerobic mixed bacteria acclimated with soluble starch was used as inoculum. At initial pH=8.0pH=8.0, the H2H2 yield significantly increased from 106.4 to 274.0 ml/g starch with increasing iron concentration from 0 to 200 mg FeSO4/lFeSO4/l. When iron concentration continued to increase from 200 to 4000 mg FeSO4/lFeSO4/l, iron inhibition did not happen. On the contrary, hydrogen production was efficiently accelerated. Here, lag-phase time and end time all had about 22 h shortened. However, corresponding cumulative H2H2 volumes were adjacent to the maximum value (225 ml) required at [FeSO4]=150mg/l. As for pH 7.0 systems, though flocculation still appeared, superfluous iron (over 800 mg FeSO4/lFeSO4/l) slightly inhibited hydrogen production. The difference in two strains of iron experiments resulted from the variance in initial solubility of iron under various initial pH values. The experiment results show that superfluous soluble iron shows slightly inhibitive influence on H2H2 production, and that the optimum soluble iron concentration is 150 mg FeSO4/lFeSO4/l from soluble starch (10.0 g/l). Furthermore, the effect of the starch concentration (5.0–40.0 g/l) on hydrogen production also was investigated under 150 mg FeSO4/lFeSO4/l. The result shows that high starch concentration has no remarkable effect on H2H2 production. The maximum cumulative hydrogen was 260.5 ml at starch concentration of 20 g/l.