Modified hydrotalcites for enhancement of biohydrogen production

Abstract

Different hydrotalcites (HTs), namely Mg–Al HT, Ni–Mg–Al HT, magnetic Mg–Al HT, and magnetic Ni–Mg–Al HT, synthesized by a co-precipitation method were tested for their capacity to improve biohydrogen production with a wide range of doses, from 83 to 833 mg/L. Batch experiments were conducted at 37 °C using heat-treated anaerobic sludge as inoculum and sucrose as synthetic wastewater. The highest hydrogen yield was obtained around 3.37 ± 0.17 mol H2/mol sucrose added for an optimum dose of 250 mg/L Ni–Mg–Al HT. This was equivalent to 80% yield increment in relation to control. At the end of the fermentation process, sucrose was converted completely. Lactic acid (160 mg/L), acetic acid (4661 mg/L), and butyric acid (5625 mg/L) were produced as metabolites. A good performance with addition of HTs may be due to the basic property of HT and metals leaching from HTs, which may cause metabolic changes. For magnetic HTs, at optimum dose, they could be recycled three times. However, the magnetic property of such HTs was lost gradually and hydrogen yield was reduced with each run. At the third cycle, as compared to control, the obtained hydrogen yield increased 40% and 22% for magnetic Ni–Mg–Al HT and magnetic Mg–Al HT, respectively.