Flocculation showed the potential for harvesting microalgae at a low cost. The inorganic flocculant (AlCl₃) and organic flocculant (chitosan) are two representative and common flocculants, which were suited for different conditions (pH, salinity, and cell density). To investigate the effects of the three factors on the flocculation performance of the two flocculants, especially for the interaction effects among these factors, single-factor experiments and response surface methodology (RSM) were conducted. The results indicated that AlCl₃ performed better under alkaline conditions, whereas chitosan showed better performance at acidic pH. Salinity had little influence on the flocculation efficiency (FE) of AlCl₃. By contrast, increasing salinity reduced the FE of chitosan, especially above 8.4 g/L. As cell density increased, the optimal dosage of AlCl₃ increased to a constant ~ 26 g/L. In contrast, the optimal dosage of chitosan continuously increased within the studied range. Also, RSM revealed significant interaction effects of [salinity][cell density] for AlCl₃, due to which AlCl₃ showed a good flocculation performance under either high cell density or high salinity conditions but poor with both high together. Significant interaction effects of [salinity][cell density] for chitosan was observed, and one of the two factors hence alleviated the negative influence from the other. Considering their performance under the different condition and the interaction effects, dual flocculation with AlCl₃ + chitosan on multiplex conditions was evaluated, and the results indicated that higher FE with wider applicability could be achieved with lower dosages of the dual flocculant compared with utilization of the two flocculants individually under most of the conditions.

絮凝显示出以低成本收获微藻的潜力。无机絮凝剂（AlCl ₃）和有机絮凝剂（壳聚糖）是两种代表性的常见絮凝剂，适用于不同条件（pH，盐度和细胞密度）。为了研究这三个因素对两种絮凝剂絮凝性能的影响，特别是对于这些因素之间的相互作用，进行了单因素实验和响应面方法（RSM）。结果表明，AlCl ₃在碱性条件下表现更好，而壳聚糖在酸性pH下表现出更好的性能。盐度对AlCl ₃的絮凝效率（FE）影响很小。相反，增加盐度会降低壳聚糖的FE，尤其是在8.4 g / L以上时。随着细胞密度的增加，AlCl ₃的最佳剂量增加至恒定〜26 g / L。相反，壳聚糖的最佳剂量在研究范围内不断增加。同样，RSM揭示了[盐度] [细胞密度]对AlCl _3的显着相互作用，这是由于AlCl ₃在高细胞密度或高盐度条件下均表现出良好的絮凝性能，但在高细胞密度或高盐度条件下均表现差。观察到[盐度] [细胞密度]与壳聚糖有显着的相互作用，因此这两个因素之一缓解了彼此的负面影响。考虑到它们在不同条件下的性能以及相互作用的影响，对AlCl ₃ +壳聚糖在多重条件下的双重絮凝进行了评估，结果表明，与较低的用量相比，使用较低剂量的双重絮凝剂可以获得更高的FE和更广泛的适用性。在大多数情况下，两种絮凝剂分别存在。