Metal-Oxide-Based Microjets for the Simultaneous Removal of Organic Pollutants and Heavy Metals

Abstract

Water contamination from industrial and anthropogenic activities is nowadays a major issue in many countries worldwide. To address this problem, efficient water treatment technologies are required. Recent efforts have focused on the development of self-propelled micromotors that provide enhanced micromixing and mass transfer by the transportation of reactive species, resulting in higher decontamination rates. However, a real application of these micromotors is still limited due to the high cost associated to their fabrication process. Here, we present FeO-decorated SiO/MnO microjets for the simultaneous removal of industrial organic pollutants and heavy metals present in wastewater. These microjets were synthesized by low-cost and scalable methods. They exhibit an average speed of 485 ± 32 μm s (∼28 body length per s) at 7% HO, which is the highest reported for MnO-based tubular micromotors. Furthermore, the photocatalytic and adsorbent properties of the microjets enable the efficient degradation of organic pollutants, such as tetracycline and rhodamine B under visible light irradiation, as well as the removal of heavy metal ions, such as Cd and Pb.

Electrochemical Deposition Tailors the Catalytic Performance of MnO2‐Based Micromotors

“…While the hydrothermal δ‐MnO 2 is characterized as ≈415 ± 107 µm s −1 and ∼421 ± 132 µm s −1 at 5% and 10% fuel respectively . The electrodeposited amorphous MnO 2 has the average speed of ≈200 ± 80 µm s −1 (equal to ≈16 body lengths s −1 ) in 5% H 2 O 2 . The average velocity of our R‐MnO 2 motors obtained from PD mode could achieve as high as 210 µm s −1 in 10% H 2 O 2 .…”

“…In principle, the catalytic activity of manganese oxide varies according to its polymorphs. As reported, commercially available ε‐MnO 2 and β‐MnO 2 micropariticles, which exhibit different motion behaviors ascribed to various particle size, shape, and morphology, have been used for the organic waste removal . Catalytic degradation and adsorptive bubble separation synergistically occurs and results in prominent decontamination efficiency.…”

“…Among a diversity of polymorphs including α, β, γ, and ε ‐MnO 2 types, ramsdellite MnO 2 (R‐MnO 2 ) has a better performance as a catalyst. Besides, rhodochrosite MnCO 3 generates as a byproduct, probably following the reaction of…”

“…Safdar et al synthesized MnO 2 ‐based micromotors with different shapes by both chemical reaction and electrochemical deposition, and found electrochemically prepared micromotors exhibit high speed but undergo self‐destruction with limited lifetime . Most recently, Fe 2 O 3 ‐decorated SiO 2 /MnO 2 microjets were obtained by chemical fabrication for the simultaneous removal of industrial organic waste and heavy metals present in wastewater …”

Visible Light Actuated Efficient Exclusion Between Plasmonic Ag/AgCl Micromotors and Passive Beads

“…They interact with their surroundings and realize various scenarios of collective behavior. Being functionalized, artificial machines at various scales have been exposed to interactive environments and used for biomedical applications, like: drug delivery, toxin removal, and environmental remediations . Recently, light‐driven nano/micromotors stimulated research on their fabrication and characterization .…”