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Harvesting of Chlorella vulgaris using Fe3O4 coated with modified plant polyphenol

Zhao, Yuan, Wang, Xiaoyu, Jiang, Xiaoxue, Fan, Qianlong, Li, Xue, Jiao, Liyang, Liang, Wenyan
Environmental science and pollution research international 2018 v.25 no.26 pp. 26246-26258
Chlorella vulgaris, X-ray photoelectron spectroscopy, chemical bonding, harvesting, iron oxides, magnetic separation, neutralization, pH, polyphenols, thermogravimetry, ultrasonic treatment, zeta potential
The Chlorella vulgaris harvesting was explored by magnetic separation using Fe₃O₄ particles coated with the plant polyphenol chemically modified by a Mannich reaction followed by quaternization (Fe₃O₄@Q-PP). The –N(R)₄⁺ and Cl–N⁺–C perssad of the Q-PP were linked to the Fe₃O₄ particles by N–O bonds, as suggested by the X-ray photoelectron spectroscopy spectra. The thermogravimetric analysis displayed the mass percentage of the Q-PP coated on the Fe₃O₄ surface was close to ~ 5%. Compared with the naked Fe₃O₄ particles, zeta potentials of the Fe₃O₄@Q-PP particles were improved from the range of − 17.5~− 25.6 mV to 1.9~36.3 mV at pH 2.1~13.1. A 70.2 G coercive force was obtained for the Fe₃O₄@Q-PP composite, which demonstrated its ferromagnetic behavior. The use of Fe₃O₄@Q-PP resulted in a harvesting efficiency of 90.9% of C. vulgaris cells (3.06 g/L). The Fe₃O₄ particles could be detached from the cell flocs by ultrasonication leading to a recovery efficiency of 96.1% after 10 cycles. The recovered Fe₃O₄ could be re-coated with Q-PP and led to a harvesting efficiency of 80.2% after 10 cycles. The magnetic separation using Fe₃O₄@Q-PP included charge neutralization followed by bridging and then colloid entrapment.