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Long-chain poly-arginine functionalized porous Fe3O4 microspheres as magnetic flocculant for efficient harvesting of oleaginous microalgae

Liu, Pei-Rui, Wang, Ting, Yang, Zi-Yu, Hong, Yu, Hou, Yang-Long
Algal research 2017 v.27 pp. 99-108
Chlorella, active sites, adsorption, arginine, flocculation, harvesting, hydrogen bonding, iron oxides, microalgae, molecular weight, porosity
Considering the porous characteristics of magnetic porous Fe3O4 microspheres, this study aims to utilize long-chain poly-arginine (PA) to obtain PA-modified porous Fe3O4 microspheres (p-Fe3O4@PA). The microspheres possessed a loose porous structure on the surface, and the average pore size was 224.2Å. The harvesting efficiency for Chlorella sp. HQ improved markedly compared with that of p-Fe3O4 after modification with three PAs with different molecular weights. p-Fe3O4@PA-2 (PA molecular weight: 15,000–70,000) had the best performance with a decreasing dosage from 300mgL−1 to 10mgL−1. The results indicated that PA modification at a higher molecular weight could promote microalgae adsorption, whereas PA modification of an excessively high molecular weight (>70,000) was not conducive to microalgae harvesting. The modification percentage of p-Fe3O4@PA (57.9%) provided abundant adsorption media and active sites for Chlorella sp. HQ adsorption. Bridging flocculation and hydrogen bonding between Chlorella sp. HQ and p-Fe3O4@PA greatly enhanced harvesting efficiency. In addition, the p-Fe3O4@PA could maintain good cycling stability because of the relatively large size of the microspheres.