Efficient Removal of Pb(II) from Aqueous Systems Using Spirulina-Based Biohybrid Magnetic Helical Microrobots

Wastewater remediation toward heavy metal pollutants has attracted considerable attention, and various adsorption-based materials were employed in recent years. However, it is still challenging to explore low-cost and high-efficient adsorbents with superior removal performance, nontoxicity, flexible operation, and good reusability. Herein, Fe₃O₄- and MnO₂-loaded biohybrid magnetic helical microrobots (BMHMs) based on Spirulina cells were presented for the first time, and their performance on Pb(II) removal was studied in detail. Intracellular synthesis of Fe₃O₄ and MnO₂ nanoparticles into Spirulina cells was successively conducted to obtain the BMHMs with superparamagnetism and high surface activity. The BMHMs could be flexibly propelled under magnetic actuation, and collective cork-screw spinning was performed to enhance fluidic diffusion with intensive adsorption. Rapid and significant removal of Pb(II) in wastewater was achieved using the swarming microrobots, and a high adsorption capacity could be reached at 245.1 mg/g. Moreover, the BMHMs could be cyclically reutilized after simple regeneration, and good specificity toward Pb(II) was verified. The adsorption mechanism was further studied, which revealed that the pseudo-second-order kinetics dominated in the adsorption process, and the Langmuir isothermal model also fitted the experimental results well. The intriguing properties of the BMHMs enable them to be versatile platforms with significant potentials in wastewater remediation.