Bare Iron Oxide Nanoparticles for Magnetic Harvesting of Microalgae: From Interaction Behavior to Process Realization

Abstract

Microalgae continue to gain in importance as a bioresource, while their harvesting remains a major challenge at the moment. This study presents findings on microalgae separation using low-cost, easy-to-process bare iron oxide nanoparticles with the additional contribution of the upscaling demonstration of this simple, adhesion-based process. The high affinity of the cell wall for the inorganic surface enables harvesting efficiencies greater than 95% for Scenedesmus ovalternus and Chlorella vulgaris. Successful separation is possible in a broad range of environmental conditions and primarily depends on the nanoparticle-to-microalgae mass ratio, whereas the effect of pH and ionic strength are less significant when the mass ratio is chosen properly. The weakening of ionic concentration profiles at the interphase due to the successive addition of deionized water leads the microalgae to detach from the nanoparticles. The process works efficiently at the liter scale, enabling complete separation of the microalgae from their medium and the separate recovery of all materials (algae, salts, and nanoparticles). The current lack of profitable harvesting processes for microalgae demands innovative approaches to encourage further development. This application of magnetic nanoparticles is an example of the prospects that nanobiotechnology offers for biomass exploitation.

Immunomagnetic Separation of Microorganisms with Iron Oxide Nanoparticles

“…Bare iron oxide nanoparticles (BIONs) with 5-50 nm size can be used for e.g. protein purification [13,14], enzyme immobilization [15] and harvesting of algae [16]. Usually, the nanoparticles are embedded in polymers and used as superparamagnetic microbeads (0.1-100 µm) and are further modified with functional group to anchor an immunoactive group, such as an antibody [17].…”

Interaction Analysis of Commercial Graphene Oxide Nanoparticles with Unicellular Systems and Biomolecules

“…[4,[13][14][15], as suitable carriers for enzymes of industrial interest. Similarly, applications for the use of these types of nanomaterials for the immobilization of prokaryotic and eukaryotic microorganisms have been investigated [11,[16][17][18].…”

Microalgae Harvesting: A Review

“…Commercial application of microalgae include food supplements, animal feed, biofuel production [11] [19], pharmaceutical industry, cosmetics products, natural pigments as well as they can produce different kinds of carotenoid, enzyme polymer, lipid, natural dye, peptide, toxin and sterols, which are used in several industrial products [37]. In addition, microalgae have the potential to accumulate high-value substances such as omega-3 fatty acids, vitamins and antibiotics [14] [45].…”

“…The main advantages of magnetic separation processes are the high efficiency and the low operating costs, together with simple and fast processing. The idea of using magnetic material to process algae and to apply some form of magnetic separator is not new, probably dating back half a century when separation was incorporated into wastewater treatment [14]. Magnetic separation is a simple separation process.…”

“…This application of magnetic nanoparticles is an example of the prospects that nanobiotechnology offers for biomass exploitation. The high affinity of the cell wall for the inorganic surface enables harvesting efficiencies greater than 95% for Scenedesmus ovalternus and Chlorella vulgaris [14]. Fe3O4 particles synthesized by chemical co-precipitation were efficient in harvesting the freshwater algal species Botryococcus braunii and Chlorella ellipsoidea [26] [45].…”