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Externally actuated active colloids for oil/water separation


In certain oil-industry-relevant scenarios, such as in the case of enhanced-oil-recovery with the deployment of surfactants, and the case of downstream production fluid handling, modified oil forms elusive emulsions, with droplets as small as a few micrometers in size, which are difficult to handle with conventional separation methods.

Herein, we present novel approaches leveraging nanotechnology toward oil-in- water separation. This research will demonstrate that the use of active colloids and/or dynamic environments can increase capture events of target material.

This work utilizes a controlled-size water droplet test—mimicking the expected volume to be encountered in microporosity regions in the oil reservoir—In conjunction with optical microscopy, to compare four approaches for oil-in-water emulsion capture. The static approach (passive diffusion), where the process took 24 hours, is used as a baseline to gauge the enhanced separation performance with respect to externally-manipulated hydrophobically-modified active colloids actuated by ultraviolet light, magnetic, and ultrasound fields. Based on the experimental results, it was found that all three external actuation methods vastly reduced the timescale of the separation process. While the ultraviolet actuation strategy ha and advantage in enhancing the kinetics of mixing, and the ultrasound actuation method exhibited advantages in collective shepherding—leading to a smaller active region for separation—and precision, it was determined that the magnetic actuation approach proved to be the fastest, most precise, and least energy intensive method for capturing oil droplets dispersed in water.

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