Using magnetic materials to harvest microalgal biomass: evaluation of harvesting and detachment efficiency

• Published in: Environmental technology 2019-04, Vol.40 (8), p.1006-1012
• Main Authors: Zhu, L.-D., Hiltunen, Erkki, Li, Zhaohua
• Format: Article
• Language: English
• Subjects: Algae; Biomass; biomass production; Chlorella vulgaris; Efficiency; Flocculants; Flocculation; Harvesting; Iron oxides; Magnetic materials; Magnetics; magnetophoretic harvesting; Microalgae; Nanoparticles; pH effects; Separation; Yttrium
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2017.1415379

Using naked iron oxide (Fe 3 O 4 ) and yttrium iron oxide (Y 3 Fe 5 O 12 ) nanoparticles as flocculants, the harvesting efficiency of Chlorella vulgaris biomass was investigated. The harvesting process includes two steps, which are the separation of microalgae from the culture solution with the magnetic nanoparticles and then the separation of the algae from the magnetic nanoparticles. The optimal dosages and pH values for the magnetic harvesting of microalgal biomass were determined. Results showed that Y 3 Fe 5 O 12 nanoparticles were more efficient in microalgal biomass harvesting than Fe 3 O 4 nanoparticles. In an effort to achieve more than 90% of harvesting efficiency, optimal dosages for Fe 3 O 4 and Y 3 Fe 5 O 12 to harvest microalgal biomass were 10 and 2.5 g/L, while the appropriate pH values were 6.2 and 7.3, respectively. The harvesting efficiency of Fe 3 O 4 and Y 3 Fe 5 O 12 nanoparticles increased as the pH value decreased. The experimental results also showed that under a higher pH value Fe 3 O 4 nanoparticles were much easier to be separated from the flocs than Y 3 Fe 5 O 12 . 62.9% of Fe 3 O 4 nanoparticles could be de-attached from the aggregates, when the floc pH value reached 12.3.