CO₂ controlled flocculation of microalgae using pH responsive cellulose nanocrystals

Area of Science:

• Biomaterials Science
• Environmental Biotechnology
• Microalgae Cultivation

Background:

• Cellulose nanocrystals (CNCs) are sustainable nanomaterials with tunable properties.
• Developing efficient and environmentally friendly methods for microalgae harvesting is crucial for biofuel and bioproduct applications.
• Surface modification of CNCs can impart novel functionalities for specific applications.

Purpose of the Study:

• To synthesize imidazole-functionalized cellulose nanocrystals (ImCNC).
• To investigate the pH-responsive behavior of ImCNCs.
• To evaluate the efficacy of ImCNCs for the flocculation of Chlorella vulgaris using CO2.

Main Methods:

• One-pot grafting of imidazole functionalities onto cellulose nanocrystals.
• Characterization of surface charge properties across a pH range.
• Assessing flocculation efficiency of Chlorella vulgaris using ImCNCs and CO2 induction.
• Evaluating the compatibility of ImCNCs with microalgae during cultivation.

Main Results:

• Successfully grafted imidazole onto CNCs with a degree of substitution (DS) up to 0.06.
• ImCNCs exhibited pH-responsive surface charge: positive below pH 6 and negative above pH 7.
• Achieved up to 90% flocculation efficiency for Chlorella vulgaris at a 200 mg L(-1) dose.
• Demonstrated good compatibility of ImCNCs with microalgae during cultivation.

Conclusions:

• Imidazole-functionalized cellulose nanocrystals are effective pH-responsive flocculants for Chlorella vulgaris.
• The use of CO2 for pH adjustment offers a sustainable approach for inducing flocculation.
• ImCNCs hold potential for developing reversible flocculation systems in microalgae cultivation.