Efficient demulsification of oil-in-water emulsion triggered by pollen-based micromotors

For oil-in-water emulsion wastewaters, the primary challenge in treatment lies in demulsification due to the presence of numerous small oil droplets stabilized by emulsifiers. Toward effective demulsification, this study utilizes the naturally abundant sunflower pollen with a spiny structure and low-cost MnO 2 catalyst to construct a self-driven micromotor for rapid oil-water separation. The hollow structure of treated pollen with an opening formed during carbonization is ideal for the formation and ejection of bubbles, as evidenced by the bubble generation process inside the cavity and the bubble-propelled motion in H 2 O 2 . Surface modification with APTES and oleic acid endows the pollen-based micromotors with hydrophobic properties, enabling them to interact with the oil droplets. Leveraging self-propelled motion and micro/nanobubble production, the pollen-based micromotors can serve as active demulsifiers to bring oil droplets out from the aqueous phase and form a continuous oil layer. Influence factors including pH, temperature, and micromotor dosage are optimized, and a demulsification efficiency of over 97 % is achieved within 30 min. The proposed bio-derived micromotors offer a new platform for efficient demulsification of emulsified wastewater.