Harvesting microalgal biomass using magnesium coagulation-dissolved air flotation

Xuezhi Zhang, Lan Wang, Milton Sommerfeld, Qiang Hu

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

Coagulation with magnesium was found to be more effective for harvesting microalgae Chlorella zofingiensis with dissolved air flotation (DAF) than the use of Fe3+, Al3+ or chitosan, and the required coagulant dosage was in the order Mg2+ 3+ 3+. The Mg2+ dosage required depended on the growth phases and culture medium characteristics. An early exponential culture required the highest Mg2+ dosage (226 mg g−1), while a late stationary culture required the lowest dosage (36 mg g−1). HPO4 2− and CO3 2− in the culture medium competed with the microalgal cells for Mg2+ and increased the Mg2+ dosage necessary. No Mg2+ addition was required to harvest the freshwater microalgae Scenedesmus dimorphus grown in a pond with tap water with a high Mg2+ concentration or the marine microalgae Nannochloropsis sp. The critical coagulation pH ranged between 10.8 and 11.8, with a lower pH requirement at a higher Mg2+ concentration. Magnesium hydroxide precipitated with the harvested biomass; however, over 99.5% of the precipitated Mg2+ was recovered by washing the biomass with 0.1 M HCl. Microalgal harvesting with Mg2+ did not introduce extrinsic coagulant; thus, neither the biomass nor the medium was contaminated.

Original languageEnglish (US)
Pages (from-to)43-49
Number of pages7
JournalBiomass and Bioenergy
Volume93
DOIs
StatePublished - Oct 1 2016
Externally publishedYes

Keywords

  • Biomass purification
  • Coagulant recovery
  • Flotation
  • Medium recycling
  • Microalgal harvesting

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Forestry
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal

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