Magnetophoretic Harvesting of Nannochloropsis oculata Using Iron Oxide Immobilized Beads

Abstract

In this work, the harvesting of Nannochloropsis oculata microalgae through the use of nanosized Fe3O4 immobilized in polyvinyl alcohol (PVA)/sodium alginate (SA) as a flocculant (Fe3O4/PS) is investigated. Using the Fe3O4/PS immobilized beads could reduce the amount of soluble ferrous ions (Fe2+) released from naked Fe3O4 in acid treatment, leading to easy recovery. The characterization was performed under different dosages and pH values of Fe3O4/PS. The results show that the Fe3O4/PS, when applied to the algae culture (500 mg dry cell weight/L), achieves a 96% harvesting efficiency under conditions of a pH of 4 with 200 mT magnetic field intensity. Fe3O4/PS can be directly reused without adjusting the pH value. The recycled Fe3O4/PS shows stability in terms of its surface properties, maintaining more than 80% harvesting efficiency after five recycles. Magnetophoretic harvesting, using immobilized magnetic iron oxide as a particle-based flocculant, is a potential method to reduce challenges related to the cost-effective microalgae-harvesting method.

Recent Advances in Magnetic Nanoparticles and Nanocomposites for the Remediation of Water Resources

“…Testing this composite with diluted wastewater from a rare-earth processing facility demonstrated selective adsorption of rare earth elements from a mixture of ions with significant rates of recovery ranging from a measured 107% for samarium and 62% for cerium. The insertion of nanosized Fe 3 O 4 nanoparticles (size range, 2.4-2.9 nm) into polyvinyl alcohol and sodium alginate beads was reported by Kao et al [113] who used them as a flocculant for the removal of Nannochloropsis oculate algae from water. As the polymer sheath protects the magnetic core from degradation under acid conditions this provides an effective tool for the removal of algae from water.…”

The Potential of Marine Microalgae for the Production of Food, Feed, and Fuel (3F)

“…Usually, multivalent metal salts (i.e., ferric chloride, alum, etc.) and cationic polymers are used as coagulants; however, the efficacy of harvesting would depend on the cell characteristics (size, zeta potential) [216]. The ionic strength of seawater is much higher than freshwater; hence, the dosage requirement of coagulants for marine microalgae would be higher than freshwater microalgae [217].…”

Sustainable production of eicosapentaenoic acid-rich oil from microalgae: Towards an algal biorefinery

“…However, these are much more expensive than inorganic flocculants, which reduces the feasibility of industrial-scale microalgae cultivation systems. Recyclable flocculants such as magnetic nanoparticles are a cost-effective alternative (Chu et al, 2020). Electroflocculation or electrocoagulation uses metal ions released from a sacrificial electrode for flocculation.…”