Kinetics of biological hydrogen production from green microalgae Chlorella vulgaris using glucose as initial substrate

ABSTRACT

In this study, the kinetics of chemical reaction was studied based on the correlation between the rate of degradation of glucose by the microalgae and the rate of hydrogen gas formation. Bio-photolysis was carried out algal strain Chlorella vulagaris in order to produce hydrogen gas (H₂) using glucose as an initial substrate. Algal strain C. vulgaris was used in this study. The strain was grown in the Bold’s basal culture (BBC) medium. Hydrogen was produced by degradation of glucose stored in a bioreactor. Produced gas was analyzed by gas chromatography (GC) to detect pure hydrogen gas production. The GC equipment was equipped with a column filled with molecular sieve 5A column containing argon as a carrier gas. During the experiment, the glucose concentration in the medium was determined by a blood-glucose analyzer. The initial glucose concentration plays an important role in the yield of hydrogen production. The results show that the highest hydrogen production over time was observed at varying glucose concentrations when the initial glucose concentration was 10 g/L. pH of medium is a critical factor in the hydrogen production process. A series of tests with pH ranging from pH 6.0 ± 0.2 to 9.0 ± 0.2 was performed. The results showed that the highest hydrogen yield was obtained by increasing the molar nitrogen and phosphate content by 10%. All experimental runs were carried out at 22°C. Essentially, the glucose uptake rate versus the hydrogen production rate is compared in this study, because the production rate of hydrogen depends on the rate of glucose depletion. For the glucose consumption, the order of reaction (n = 0.942) was first order. The reaction rate constant (k) was 7.037 × 10² s⁻¹ for the glucose consumption. For the hydrogen production, the order of reaction (n = 0.954) was also first order, while the reaction rate constant (k) was 3.890 × 10² s⁻¹ for the hydrogen production.

KEYWORDS:

• Anaerobic fermentation
• bio-photolysis kinetics
• glucose
• green microalgae
• hydrogen