Comparing natural sedimentation and centrifugation of flocculated nanoparticles: Role of homogeneous polymer flocculant towards sustainable environment

• Flocculation-Enhanced Separation: Demonstrated that depletion flocculation using an anionic polymer (PSS 70K) significantly improves the sedimentation and centrifugation efficiency of Fe 3 O 4 magnetic nanoparticles. • Optimized Methods for Cost and Efficiency: Achieved highest separation efficiency (97.3 %) using low gradient magnetic separation, while identifying 400 x g centrifugation as the most cost-effective method (RM 0.02/30 min). • Sustainable Nanoparticle Recovery: The integrated approach offers an effective and environmentally safer method for magnetic nanoparticle separation, balancing performance, cost, and sustainability. Magnetic Nanoparticles (MNPs) such as Fe 3 O 4 are widely used in various industries, especially for the separation process, due to their intrinsic magnetic properties, which enhance the separation. However, these MNPs are not colloidally stable because of van der Waals forces and dipole-dipole attraction. Therefore, it must be functionalized to enhance its stability through electrostatic and steric repulsion. The functionalized MNPs are highly stable, making it difficult to separate them from the water. This may adversely affect both humans and the environment. Nanotoxicity significantly affects the release of MNPs into the atmosphere. Therefore, traditional separation methods, such as low-gradient Magnetic Separation (LGMS) and high-gradient Magnetic Separation (HGMS), have been used to separate MNPs. As previously stated, LGMS has 97 % separation assisted by depletion flocculation. Thus, the present study compares the separation feasibility of depletion-flocculation-assisted natural sedimentation and centrifugation with LGMS in terms of separation efficiency and economic pollution. Based on the present project, it is believed that LGMS is preferable for high-separation efficiency and centrifugation for cost-saving separation. This study aims to bridge this gap by comparing the efficiency and environmental impact of two scalable nanoparticle separation methods: natural sedimentation and centrifugation.