Pine Pollen-Derived Micromotors for Enhanced Heavy Metal Removal

Recent progress in manganese dioxide (MnO2)-based micro-/nanomotors has shown the immense potential of these motile devices to remediate environmental contamination. However, the production of such micromotors on an industrial scale through a facile, efficient, and reproducible process remains challenging. The present work aimed to address this issue using pine pollen (PP) grains, which are naturally-occurring and abundant. Immersing PP into a potassium permanganate solution was found to generate MnO2 nanoparticles on the grain surfaces. The distribution and amount of these nanoparticles was readily adjusted by varying the immersion time. Based on the asymmetrical PP grain shape and the catalytic effect of the MnO2, the resulting MnO2/PP composite exhibited rapid self-propulsion with a maximum speed of 360.686 μm/s (approximately eight body lengths/s) in a dilute hydrogen peroxide solution. These micromotors demonstrated heavy metal remediation performance 1.5 times greater than that of static counterparts. The composite could also be recovered and reused over three consecutive cycles while retaining its performance. The competitive cost, efficient mobility, and high heavy metal removal performance of these micromotors suggests their potential application to the remediation of heavy metal pollution.