Effects of phosphate and carbonate on photo-fermentative hydrogen production of biomass straw

Abstract: For the study of phosphate and carbonate on the effect of photo-fermentation hydrogen production process, and based on the enzymatic hydrolysis of corn stalk pretreated for hydrogen producing substrate, in this paper, hydrogen production, pH value, ORP value and hydrogen production kinetics were analyzed under different concentrations of phosphate (K2HPO4) and carbonate (NaHCO3). The concentration of K2HPO4 was respectively 5, 10, 15, 20, 40 and 60 mmol/L, the concentration of NaHCO3was respectively 5, 10, 15, 20, 25 and 30 mmol/L, and the untreated group was the control group. The results showed that phosphorus in KH2PO4 was involved in biological growth, metabolism and energy transfer during microbial growth. Phosphorus is an important element in the process of biological growth and metabolism, while the phosphate also has a certain pH buffering capacity. The appropriate concentration of K2HPO4 can promote activities of photosynthetic bacteria to produce hydrogen, but also effectively buffer the pH value of the reaction system. When the concentration of K2HPO4 was 10mmol/L, the hydrogen yield was (40.65±0.35) mL/g, it increased significantly by 28.48% compared with control group, and the effect of promoting photo-fermentative hydrogen production was best. The final pH was 6.37±0.02, significantly higher than that of the control group of 6.06±0.03, indicating phosphate can effectively buffer the pH value of the reaction system. The results of kinetic characteristics of hydrogen production under different concentration of K2HPO4 showed that the suitable concentration of K2HPO4 increased the maximum hydrogen production potential and maximum hydrogen production rate, shortened the delay time of hydrogen production, when the concentration of K2HPO4 was10mmol/L, the maximum hydrogen production potential and the maximum hydrogen production rate were the highest, and the hydrogen production delay time was shorter, which was respectively 40.81 mL/g, 1.87 mL/(h•g) and 2.85 h. The appropriate concentration of NaHCO3 can promote photosynthetic bacteria to produce hydrogen, but also effectively buffer the pH value of the reaction system. When the concentration of NaHCO3 was 5 mmol/L, the hydrogen yield was 37.46±1.40 mL/g. It increased significantly by 18.39% compared with control group, and the effect of promoting photo-fermentative hydrogen production was best, and the final pH value was 6.26±0.04, which was significantly higher than that of the control group of 6.06±0.03. The results of kinetic characteristics of hydrogen production under different concentration NaHCO3 showed that the suitable concentration of NaHCO3 can improve the maximum hydrogen production potential and the maximum hydrogen production rate, but would delay hydrogen production, when the concentration of NaHCO3 was 5mmol/L. With this concentration, the maximum hydrogen production potential and the maximum hydrogen production rate were the highest, the hydrogen production delay time was relatively short, which was respectively 37.26 mL/g, 1.92 mL/(h•g) and 5.11 h. The study can provide a scientific reference for the further improvement of the technology of hydrogen production from straw biomass.