Rapid separation of microalga Chlorella vulgaris using magnetic chitosan: Process optimization using response surface methodology

ABSTRACT

Microalgal flocculation using magnetic chitosan was evaluated as a technique to rapidly settle Chlorella vulgaris cells. Magnetic chitosan particles were synthetized using chemical coprecipitation of Fe²⁺ and Fe³⁺ ions by NaOH in the presence of chitosan followed by treatment under hydrothermal conditions. Using general full factorial experimental design, the influential range of solution pH, flocculant dosage, and settling time were determined to be 6–8, 10–250 ppm, and 2 min, respectively. Parallel flocculation experiments employing pure chitosan and magnetic chitosan were conducted in the influential range of factors, resulting in maximal efficiencies of 46% and 91.4%, respectively. The results of the second-order factorial design followed by response surface methodology (RSM) helped the second-order polynomial function to predict an optimum separation efficiency of 94% with a flocculant dosage of 216 ppm and pH = 7.23, which was verified by experimental results. This paper presents for the first time to our knowledge the optimization of C. vulgaris separation with magnetic chitosan particles in magnetic fields under a series of pHs, dosage, and time conditions.

KEYWORDS:

• Algae harvesting
• Chlorella vulgaris
• magnetic chitosan
• particles
• response surface methodology

Acknowledgments

The authors would like to acknowledge University of Tehran for their full financial support. Conception of the study, whole experiments, data interpretation, and statistical analysis were performed at University of Tehran.

LSU Agricultural Center and LSU Biological & Agricultural Engineering Department are acknowledged for assistance with re-writing parts of the manuscript. Published with the approval of the Director of Louisiana Agricultural Experiment Station as Manuscript # 2015-232-21029.

The authors also want to express their gratitude to Dr. Hossein Delavari Amrei and Farbod Rahimi for their valuable support on this study.