Flocculation optimization of microalga Nannochloropsis oculata

Area of Science:

• Marine biology
• Biotechnology
• Chemical engineering

Background:

• Efficient harvesting of microalgae like Nannochloropsis oculata is essential for biofuel and bioproduct applications.
• Flocculation is a cost-effective method for algal biomass concentration, but requires optimization.
• Cationic salts such as aluminum sulfate (AS) and ferric chloride (FC) are commonly used flocculants.

Purpose of the Study:

• To investigate and optimize the flocculation of Nannochloropsis oculata using aluminum sulfate (AS) and ferric chloride (FC).
• To develop predictive models for maximizing the final solid concentration of algae (SCA) under various conditions.
• To evaluate the trade-offs between SCA and biomass recovery rate.

Main Methods:

• Single-factor experiments and response-surface-methodology (RSM) were employed.
• Second-order polynomial models were established to analyze the effects of initial algal biomass concentration (IABC), pH, and flocculant dose (FD).
• Model predictions were validated through experimental results.

Main Results:

• Solid concentration of algae (SCA) was favored by low pH, though this negatively impacted biomass recovery.
• A positive stoichiometric relationship was observed between flocculant dose (FD) and initial algal biomass concentration (IABC).
• Optimal flocculation conditions predicted maximum SCAs of 32.98 g/l with AS and 30.10 g/l with FC.

Conclusions:

• The developed models accurately predict optimal flocculation conditions for Nannochloropsis oculata.
• Aluminum sulfate (AS) and ferric chloride (FC) are effective flocculants for concentrating Nannochloropsis oculata biomass.
• The study provides a framework for optimizing algal harvesting processes using chemical flocculation.