Microalgae harvesting includes conventional methods like centrifugation, sedimentation, and filtration, as well as advanced methods like flocculation, magnetic nanoparticle, and flotation. Biomass recovery using centrifugation is high but high gravitational force can alter the cell structure. Sedimentation is one of the most useful methods in wastewater microalgae harvesting, though it is applicable to large-cell microalgae (>70 μm). Filtration is a low-cost method and easy to process; however, fouling and clogging can result in low yield. Among several techniques, flocculation is one of the most effective and economical approaches for biomass harvesting. Nanomaterial-based flocculants are considered due to their efficiency and reusability. Nanoparticle-based flocculants have gained attention in recent years due to their unique properties, such as high surface area, small size, and enhanced reactivity. These nanoparticles can be engineered to interact with microalgal cells, causing agglomeration and facilitating the separation of biomass from the culture medium. Studies have demonstrated that using nanoparticle-based flocculants can significantly improve the efficiency of microalgae harvesting compared to traditional flocculation methods. This review emphasizes the mechanism of flocculation, types of flocculation, the dosages of flocculants, and the flocculation recovery efficiencies. The role of green routes in synthesizing nanoparticles for the advancement of flocculation technique is especially highlighted in this article for the sustainable biodiesel production from microalgae. Thorough evaluations, encompassing techno-economic and life cycle assessments, play a crucial role in appraising the economic feasibility and environmental ramifications of biofuels derived from microalgae. This article provides an overview of flocculation methods suitable for microalgal harvesting, their mechanisms, advantages, and drawbacks.

微藻收获包括离心、沉降和过滤等传统方法，以及絮凝、磁性纳米颗粒和浮选等先进方法。使用离心的生物质回收率很高，但高重力会改变细胞结构。沉淀是废水微藻收获中最有用的方法之一，尽管它适用于大细胞微藻（> 70 μm）。过滤是一种低成本方法，且易于加工；然而，结垢和堵塞会导致产量低。在多种技术中，絮凝是生物质收获最有效和最经济的方法之一。基于纳米材料的絮凝剂因其效率和可重复使用性而受到考虑。近年来，纳米粒子絮凝剂因其独特的性能而受到关注，例如高表面积、小尺​​寸和增强的反应活性。这些纳米粒子可以被设计为与微藻细胞相互作用，引起团聚并促进生物质从培养基中分离。研究表明，与传统的絮凝方法相比，使用纳米颗粒絮凝剂可以显着提高微藻收获的效率。本文重点介绍了絮凝机理、絮凝类型、絮凝剂用量和絮凝回收效率。本文特别强调了绿色路线在合成纳米粒子以促进絮凝技术进步中的作用，以实现微藻可持续生产生物柴油。全面的评估，包括技术经济和生命周期评估，在评估微藻生物燃料的经济可行性和环境影响方面发挥着至关重要的作用。本文概述了适合微藻收获的絮凝方法、其机制、优点和缺点。