Catalytic activity and characterization of Fe-Zn-Mg-Al hydrotalcites in biohydrogen production

Four different M2+-Mg-Al hydrotalcite (HT) materials were investigated for their effect on biohydrogen enhancement, where M2+ is Fe and/or Zn. HTs were synthesized by the coprecipitation method and characterized by infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The effect of Fe-Zn-Mg-Al HTs dose (0-833 mg/L) on hydrogen production was investigated in batch tests using sucrose-fed anaerobic mixed culture at 37 °C. The best catalytic activity was observed on Mg-Al HT at 167 mg/L with the maximum hydrogen yield of 2.30 ± 0.37 mol H2/mol sucrose, which was 44% higher than the control. The major metabolites detected in the test were acetic acid (3.6 g/L), butyric acid (4.1 g/L), and lactic acid (0.5 g/L). The basic properties of the different catalysts played an important role in stimulating or inhibiting the activity of hydrogen producing bacteria. Calcined Mg-Al HT did not promote biohydrogen production, suggesting that the catalytic enhancement was related to immobilization of bacteria in the electrostatically charged HT interlayers.