Magnetic separation for high efficiency harvesting of microalgal cells

C. Guo
Institute of Process Engineering, Chinese Academy of Sciences,
China

Keywords: microalgal cells, havesting, magnetic nanoparticles

Summary:

Microalgae are recognized as a promising resource to produce biofuel that is renewable and environmentally friendly energy. Microalgae harvesting remains a challenge due to small cell size, low cell density in water, and large amount of water to remove. Among recent techniques for microalgae harvesting, magnetic separation with magnetic nanoparticles provides a promising method because of simple operation, fast separation, low running cost and energy saving. Here we report an efficient magnetic separation technology using Fe3O4 nanoparticles harvesting marine or fresh water microalgae from culture broth. Recovery capacity of these nanoparticles was affected by microalgal growth phase and reached the peak value when the microalgal growth reached its maximal biomass. The recovery efficiency of microalgal cells from the culture medium reached more than 95% within 4 min. Electrostatic attraction and cell aggregation was beneficial for harvesting the algal cells. Reuse of the culture medium obtained from magnetic separation gave similar biomass production in comparison with that from centrifugation separation after 5 recycles. A magnetic separator, which consisted of permanent magnet drum, separation chamber and scraper blade, was applied for efficient microalgae harvesting. The harvesting efficiency of Chlorella ellipsoidea cells reached more than 95% within forty seconds in each batch operation of microalgae harvesting. In the continuous operation of microalgae harvesting, the harvesting efficiency decreased with increasing the liquid flow rate through the separation chamber and remained more than 95% at the liquid flow rate less than 100 mL/min. The developed magnetic separator together with functional magnetic nanoparticles provided a promising method for efficient microalgae harvesting in practice.