Microalgae Recovery from Water for Biofuel Production Using CO₂-Switchable Crystalline Nanocellulose

Abstract

There is a pressing need to develop efficient and sustainable approaches to harvesting microalgae for biofuel production and water treatment. CO2-switchable crystalline nanocellulose (CNC) modified with 1-(3-aminopropyl)imidazole (APIm) is proposed as a reversible coagulant for harvesting microalgae. Compared to native CNC, the positively charged APIm-modified CNC, which dispersed well in carbonated water, showed appreciable electrostatic interaction with negatively charged Chlorella vulgaris upon CO2-treatment. The gelation between the modified CNC, triggered by subsequent air sparging, can also enmesh adjacent microalgae and/or microalgae-modified CNC aggregates, thereby further enhancing harvesting efficiencies. Moreover, the surface charges and dispersion/gelation of APIm-modified CNC could be reversibly adjusted by alternatively sparging CO2/air. This CO2-switchability would make the reusability of redispersed CNC for further harvesting possible. After harvesting, the supernatant following sedimentation can be reused for microalgal cultivation without detrimental effects on cell growth. The use of this approach for harvesting microalgae presents an advantage to other current methods available because all materials involved, including the cellulose, CO2, and air, are natural and biocompatible without adverse effects on the downstream processing for biofuel production.

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

“…In a similar cationic modification attempt, Ge et al. added CO 2 ‐switchable 1‐(3‐aminopropyl) imidazole groups to CNC to reuse the CNC‐based flocculant for harvesting microalgae . The modified CNC became acquired cationic surface charges upon CO 2 ‐treatment, allowing them to disperse in the medium.…”

Determination of Microalgal Lipid Content and Fatty Acid for Biofuel Production

“…Currently, the high costs of the important microalgal harvesting and lipid extraction processes are the primary obstacles impeding on the commercial application of microalgae-derived biofuel production [ 10 – 12 ]. For example, lipid extraction is a high-power-consumption process because lipids are stored in microalgal cells and the cell wall is a thick and rigid layer composed of complex carbohydrates and glycoproteins with high mechanical strength and chemical resistance, posing difficulties for lipid extraction [ 13 ].…”

Emerging development of nanocellulose as an antimicrobial material: an overview

“…Ge et al (2016) 106 explored the sustainability and the most efficient approach to harvest microalgae using CNC. A modification was made on the CNC by introducing a 1-(3-aminopropyl)imidazole (APIm) structure as a reversible coagulant for harvesting the microalgae.…”