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

A magnetophoretic harvesting agent, a polypyrrole/Fe 3 O 4 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/Fe 3 O 4 ) was higher than that for C. protothecoides (43.91 mg dry biomass mg −1 PPy/Fe 3 O 4 ) and C. vulgaris (39.98 mg dry biomass mg −1 PPy/Fe 3 O 4 ). 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/Fe 3 O 4 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.