ABSTRACT
Using naked iron oxide (Fe3O4) and yttrium iron oxide (Y3Fe5O12) 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 Y3Fe5O12 nanoparticles were more efficient in microalgal biomass harvesting than Fe3O4 nanoparticles. In an effort to achieve more than 90% of harvesting efficiency, optimal dosages for Fe3O4 and Y3Fe5O12 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 Fe3O4 and Y3Fe5O12 nanoparticles increased as the pH value decreased. The experimental results also showed that under a higher pH value Fe3O4 nanoparticles were much easier to be separated from the flocs than Y3Fe5O12. 62.9% of Fe3O4 nanoparticles could be de-attached from the aggregates, when the floc pH value reached 12.3.
Acknowledgements
The authors are indebted to the following people for their assistance, input and advice (alphabetical order): Andreas Willfors, Eija Iivari, Pekka Sten, Sonja Heikkilä, Thomas Andersson. The authors would also like to thank the two anonymous reviewers for their helpful comments and suggestions that greatly improved the article.
Disclosure statement
No potential conflict of interest was reported by the authors.