A remotely steerable Janus micromotor adsorbent for the active remediation of Cs-contaminated water

Highlights: • Self-propelled micromotor adsorbent was developed for selective adsorption of radioactive Cs. • The random movement of the micromotor adsorbent significantly reduced the Cs cleanup time. • The micromotor adsorbent was remotely steerable and collectable using a magnetic field. • More than 98% of the radioactive ¹³⁷Cs ions were removed from solution containing competing ions. -- Abstract: We report the development of magnetically steerable self-propelled micromotors that selectively remove radioactive Cs from contaminated water. Mesoporous silica microspheres were functionalized with the highly Cs-selective copper ferrocyanide, and half of the adsorptive particle surface was then coated with ferromagnetic Ni and catalytic Pt layers to fabricate Janus micromotors. The micromotor adsorbent displayed random propulsion in an H₂O₂ solution via catalytic bubble evolution from the Pt surface, and the micromotor adsorbent self-propulsion resulted in an 8-fold higher Cs removal compared to the stationary adsorbent within one hour. The ferromagnetism of the Ni layer allowed the micromotor adsorbent to be magnetically and remotely steerable, and the propulsion speed under a magnetic field was 11-fold greater than it was in the absence of the magnetophoretic force. The adsorption of Cs by the self-propelling micromotor adsorbent and the subsequent magnetic recovery of the adsorbent enabled the successful removal of radioactive ¹³⁷Cs from aqueous solutions. More than 98% of the radioactive ¹³⁷Cs ions were removed from solution, even in the presence of competing ions, such as Na⁺ (1000 ppm).