Journal
JOURNAL OF CLEANER PRODUCTION
Volume 344, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jclepro.2022.131042
Keywords
Microalgae harvesting; Flocculation; Cationic starch; Tannin; Dissolved extracellular organic matter; Bound extracellular organic matter
Categories
Funding
- Natural Science Foundation of China [21506103]
- Sichuan Province Science and Technology Support Program [2019YJ0399, 21ZDYF3503]
- Sci-ence Research and Innovation Team Project of Neijiang Normal Uni-versity [18TD05]
- National Undergraduate Innovation and Entrepreneurship Training Program of China [X2020078, X2020100]
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In this study, a novel tannin-based flocculant (TCCs) was synthesized and successfully grafted onto cationic starch-based flocculants (CCs). Various analyses confirmed the grafting of tannin onto the CCs skeleton. TCCs exhibited excellent harvesting performance at low dosages and had better reflocculation ability. The introduction of tannin allowed TCCs to combine with specific proteins and form compact flocs, leading to dosage savings and improved harvesting efficiency.
Owing to low cost and excellent biodegradability, cationic starch-based flocculants (CCs) have been researched in the field of harvesting microalgae, however lacking of targeted affinity to microalgae cells limited their flocculation performance. In present study, tannin was used in the synthesis of a novel CCs grafted tannin-based flocculant (TCCs). SEM, XRD, FTIR, H-1-NMR, zeta potential and UV-Vis analysis proved the successful graft of tannin on CCs skeleton. TCCs exhibited outstanding harvesting performance at 4.0 mg/L dosage, much better than CCs (20.0 mg/L) and flocs formed by TCCs possessed higher reflocculation ability. The flocs size, flocs shape and zeta potential changing regulation indicated that both CCs and TCCs can flocculate microalgae cells through charge neutralization and bridging flocculation. To further explore the flocculation mechanisms, effects of flocculants on microalgal dissolved and/or bound extracellular organic matter were systematically tested. Results suggested that the introduction of tannin make TCCs targeted to combine with proteins in the bound extracellular organic matter and then form compact flocs through hydrogen bonds and hydrophobic bonds, thus saving the flocculant dosage and improving the harvesting efficiency. Additionally, harvesting per ton microalgae by TCCs costs only 19.4 USD, which is more economic saving than CCs and some traditional flocculants.
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