Zhang Ping, Zhu Sihan, Xiong Chao, Yan Bin, Wang Zhikang, Li Kai, Olivier Irumva, Wang Han
College of Eco-Environmental Engineering, Guizhou Minzu University, Guiyang, 550025, China.
College of Environmental and Chemical Engineering, Chongqing Three Gorges University, Chongqing, 404020, China.
Environ Sci Pollut Res Int. 2022 Nov;29(52):78809-78820. doi: 10.1007/s11356-022-21383-8. Epub 2022 Jun 14.
Algal blooms have posed great threats to livestocks and human health. Although flocculation is effective, its efficiency may hinder the direct application for algal blooms. In this study, critical (optimal) conditions and mechanisms for AlCl, FeCl, poly-aluminum chloride (PAC), chitosan, and polydimethyldiallylammonium chloride (PDADMAC)-induced flocculation of Chlorella vulgaris (C. vulgaris) were studied. Results identified the critical conditions which can cause flocculation efficiencies over 90% in 45 min for the five flocculants. Specifically, 410-mg/L doses of PDADMAC were proved to be appropriate for the treatment of C. vulgaris-induced algal blooms at pH 6.012.0. To probe the underlying mechanisms, functional groups involved in flocculation, zeta potential, and species distribution were analyzed during flocculation. FT-IR results indicated that N-H stretching in amine and C-H deformation in aliphatics were involved in algal flocculation with FeCl, and C-H deformation played an important role with PDADMAC, PAC, and chitosan. For AlCl, zeta potential and species distribution results suggested that charge neutralization and adsorption bridging were responsible for algal flocculation at pH 6~8. However, adsorption bridging and sweeping effects were the main mechanisms at pH >3 for FeCl. The flocculation mechanisms for the rest of the three polymers were charge neutralization, adsorption bridging, and sweeping. Meanwhile, all the flocculation processes followed second-order kinetics. Strong linkages were found between the rate constant, fractal dimension, and flocculation efficiency (P < 0.05). The results of critical flocculation conditions and mechanisms indicated that PDADMAC was an excellent flocculant for C. vulgaris removing and recycling, especially in water bloom treatment.
藻华对牲畜和人类健康构成了巨大威胁。尽管絮凝是有效的，但其效率可能会阻碍其在藻华处理中的直接应用。在本研究中，研究了氯化铝、氯化铁、聚合氯化铝（PAC）、壳聚糖和聚二甲基二烯丙基氯化铵（PDADMAC）诱导普通小球藻（C. vulgaris）絮凝的临界（最佳）条件和机制。结果确定了五种絮凝剂在45分钟内可使絮凝效率超过90%的临界条件。具体而言，已证明410mg/L剂量的PDADMAC适用于在pH值为6.012.0时处理由普通小球藻引起的藻华。为探究潜在机制，在絮凝过程中分析了参与絮凝的官能团、zeta电位和物种分布。傅里叶变换红外光谱（FT-IR）结果表明，胺中的N-H伸缩振动和脂肪族中的C-H变形参与了氯化铁诱导的藻类絮凝，而C-H变形在PDADMAC、PAC和壳聚糖诱导的藻类絮凝中起重要作用。对于氯化铝，zeta电位和物种分布结果表明，在pH值为6~8时，电荷中和和吸附桥联是藻类絮凝的原因。然而，在pH值>3时，吸附桥联和卷扫作用是氯化铁絮凝的主要机制。其余三种聚合物的絮凝机制是电荷中和、吸附桥联和卷扫。同时，所有絮凝过程均遵循二级动力学。发现速率常数、分形维数和絮凝效率之间存在强关联（P < 0.05）。临界絮凝条件和机制的结果表明，PDADMAC是去除和循环利用普通小球藻的优良絮凝剂，尤其是在水华处理中。
