Efficient magnetic flocculation for microalgae harvesting using a novel composite flocculant of Fe3O4-based starch-grafted-cationic polyacrylamide
Bingcong Zhang, Bifei Mao
Abstract
As a flocculant for algae harvesting, a novel magnetic starch-grafted-cationic polyacrylamide composite (MAG@ST-g-CPAM) was developed in this study, and the harvesting efficiency of the composite was assessed with comparison to starch, Fe 3 O 4 magnetite nanoparticles , cationic polyacrylamide and starch-grafted-cationic polyacrylamide. The feeding ratios for flocculant synthesis were optimized, and impacting factors were examined. Magnetic particles were recovered for cyclic use, and the effect of MAG@ST-g-CPAM flocculation on water reuse was examined. The results showed that MAG@ST-g-CPAM flocculation successfully achieved harvesting efficiencies of 93.2 % and 97.3 % at doses of 25 mg/L and 30 mg/L, respectively, which were superior to those of other flocculants. The optimized feeding ratio of acrylamide:Fe 3 O 4 :starch was 6:4:3. The late exponential algal growth solution with a pH range of 5–6 was most favorable for algae flocculation. A total of 93.7 % of Fe 3 O 4 magnetite nanoparticles was recovered at pH = 3, and flocculation facilitated the reuse of water by effectively eliminating fulvic acids from the culture solution. This study demonstrated that MAG@ST-g-CPAM is a promising flocculant for algae harvesting.