Magnetophoretic harvesting of freshwater microalgae using polypyrrole/Fe3O4 nanocomposite and its reusability

A magnetophoretic harvesting agent, a polypyrrole/Fe3O4 magnetic nanocomposite, is proposed as a cost and energy efficient alternative to recover biomass of the microalgae Botryococcus braunii, Chlorella protothecoides, and Chlorella vulgaris from their culture media. The maximal recovery efficiency reached almost 99 % for B. braunii, 92.4 % for C. protothecoides, and 90.8 % for C. vulgaris. The maximum adsorption capacity (Q (0)) of the magnetic nanocomposite for B. braunii (63.49 mg dry biomass mg(-1) PPy/Fe3O4) was higher than that for C. protothecoides (43.91 mg dry biomass mg(-1) PPy/Fe3O4) and C. vulgaris (39.98 mg dry biomass mg(-1) PPy/Fe3O4). The highest harvesting efficiency for all the studied microalgae were at pH 10.0, and measurement of zeta-potential confirmed that the flocculation was induced by charge neutralization. This study showed that polypyrrole/Fe3O4 can be a promising flocculant due to its high efficacy, low dose requirements, short settling time, its integrity with cells, and with great potential for saving energy because of its recyclability.