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

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, 10-250ppm, and 2min, 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 216ppm 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.