Nie Xifan, Zhang Haiyang, Cheng Shaozhe, Mubashar Muhammad, Xu Cong, Li Yanhua, Tan Daoyong, Zhang Xuezhi
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Sci Total Environ. 2022 Feb 1;806(Pt 4):150901. doi: 10.1016/j.scitotenv.2021.150901. Epub 2021 Oct 12.
Foam flotation is an economical and efficient technology for microalgae harvesting. However, the mechanism of cell-collector-bubble interfacial interactions remains to be elucidated. There are two distinct hypotheses regarding the mechanism of microalgae foam flotation. In this study, the cationic surfactant N-cetyl-N-N-N-trimethylammonium bromide (CTAB), which acts as a partition between Chlorella sorokiniana cells and bubbles, is quantified and the zeta potential response of cells and bubbles after adsorption of CTAB is calculated to reveal the interfacial mechanism of the cells-collector-bubble interfacial interactions. The results indicated that more than 90% of CTAB was preferentially adsorbed on the bubbles, which reversed the surface charge of bubbles from negative (-20 mV) to positive (6.1 mV). However, only 0%-3% CTAB was observed on the microalgae cells, suggesting its limited influence on the negatively charged microalgae cells (from -22.3 to -18.6 mV). During microalgae foam flotation, the nonpolar tails of CTAB were first inserted into the bubble through hydrophobic interactions, leaving the positively charged polar heads outside; further, the CTAB-covered positively charged bubbles captured the negatively charged cells by electrostatic attraction. A feasible mechanism was proposed to understand the interfacial interaction of the microalgae cell-CTAB-bubble. By understanding the mechanism of foam flotation, efficient and cost-effective collectors and devices for microalgae harvesting using foam flotation can be developed.
泡沫浮选是一种用于微藻收获的经济高效技术。然而，细胞-捕收剂-气泡界面相互作用的机制仍有待阐明。关于微藻泡沫浮选的机制有两种不同的假说。在本研究中，对作为小球藻细胞与气泡之间的分隔物的阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）进行了定量，并计算了CTAB吸附后细胞和气泡的zeta电位响应，以揭示细胞-捕收剂-气泡界面相互作用的界面机制。结果表明，超过90%的CTAB优先吸附在气泡上，这使气泡的表面电荷从负（-20 mV）变为正（6.1 mV）。然而，在微藻细胞上仅观察到0%-3%的CTAB，表明其对带负电荷的微藻细胞（从-22.3到-18.6 mV）的影响有限。在微藻泡沫浮选过程中，CTAB的非极性尾部首先通过疏水相互作用插入气泡中，使带正电荷的极性头部留在外面；此外，被CTAB覆盖的带正电荷的气泡通过静电吸引捕获带负电荷的细胞。提出了一种可行的机制来理解微藻细胞-CTAB-气泡的界面相互作用。通过了解泡沫浮选的机制，可以开发出用于微藻收获的高效且经济高效的捕收剂和装置。
