Comparative efficiency of bio-coagulants chitosan and tannin-based coagulant in coagulation-flotation separation of Chlorella sp. in saline media

Abstract

Marine microalgae are rich in valuable compounds, which cannot be commercialized due to difficulties in scaling-up. Chlorella sp. is harvested using bio-coagulants at 0−3 % salt with dissolved air flotation. Chitosan was compared with Tanfloc MTH, focusing on the algal organic matter (AOM) impact. Chitosan’s separation efficiency (η%) decreased with increasing salt concentration and by the presence of AOM. Chitosan induced moderate η% (>75 %) via bridging for 0−1 % salt media, while no mechanism caused sufficient separation at 2−3 % salt. Tanfloc MTH induced lower η% than chitosan at 0 % salt, but outperformed at 2−3 % salt. AOM hindered Tanfloc MTH efficiency, inducing >75 % only with 0.4 and 0.8 mg·mg−1 at 0−2 31 and 3 % salt, respectively. Neither coagulants are recommended for marine microalgae due to the excessively high dosage requirements. Research should focus on exploring alternative coagulants or variations of Tanfloc.