Scenedesmus obliquus recovery using polyacrylamide and chitosan: an optimization study.

Synthetic or natural cationic polymers, such as polyacrylamide and chitosan, are exploited as coagulants due to their characteristics, such as a high positive surface charge. Due to variations in culture conditions, such as species and cell concentration, different interactions of coagulants with microalgae occur, affecting the efficiency of biomass recovery. Thus, in this study, the separation efficiency of biomass of the microalgae Scenedesmus obliquus was evaluated by coagulation-flocculation with the synthetic polymer polyacrylamide and natural polymer chitosan to optimize the dose and pH by means of a rotational central composite design. Biomass removal efficiencies greater than 90% and greater than 70% were observed for the synthetic polymer and chitosan, respectively. Notably, the reduced optical density and biological nature of microalgae make the use of response surface methodology challenging. Optimal regions with doses of 12.8 mg of synthetic polymer and 5.0 mg of chitosan were obtained per liter of microalgae sample. An optimal pH of 6.5, falling within the natural range of culture conditions was indicated for both coagulants, minimizing reagent costs. The interaction with microalgae and the potential application of chitosan and other natural coagulants that are efficient and economically viable should be explored. [ABSTRACT FROM AUTHOR]