Removing heavy metal ions from wastewater by Chlorella sorokiniana coupled to manganese-doped magnetic ferrite nanoparticles

In this study, we investigated the benefit of combining Chlorella sorokiniana with manganese-containing ferrite nanoparticles (NPs) for heavy metal removal and cell harvesting. Our results demonstrate that the combination of non-toxic nanoparticles significantly enhances the heavy metal removal capacity of C. sorokiniana without affecting its growth. The microalgae combined with NPs was able to sequester Cr⁶⁺, Co²⁺, and Ni²⁺ from aqueous solutions and could remove these metals at a higher adsorption capacity and within a relatively short time than their individual counterparts, indicating a synergistic effect between the algal cells and the nanomaterials, where bioadsorption and chemisorption were the main players. Both biosorption and chemisorption capacities were found to be the highest for single-metal systems and decreased when coexisting ions were present in the solution. The adsorption of the heavy metals evaluated was better described by the pseudo-second order model than the pseudo-first order model, indicating that chemisorption dominated over physisorption. These characteristics suggest that the combination of biosorbents with nanosorbents is a promising approach for the treatment of water contaminated with heavy metals making this process more efficient, economical, sustainable, and clean.