A magnetic-responsive conical microcolumn for removing oil pollution in tubes and emulsion filtering with ultra-high separation flux†

Abstract

Micro-oil droplets and oil pollution in tubes are difficult to remove in depth. Traditional superhydrophobic–superoleophilic materials cannot reach the designated area accurately. Herein, a novel magnetic-responsive conical microcolumn was prepared by additive manufacturing integration technology. The superhydrophobic–superoleophilic conical microcolumn could absorb micro-oil droplets and clean oil pollution in closed tubes controlled by an external magnetic field with high efficiency. The geometric character significantly affects oil droplet driving behaviors. A larger aspect ratio and bottom diameter are conducive to fast oil movement with a velocity of up to 47.5 mm s⁻¹ on the conical microcolumn when the aspect ratio is 1 : 2 and the bottom diameter is 3.5 mm. After optimizing the geometric size, the conical microcolumn could absorb oil droplets of different sizes and surface energies, especially emulsified oil. Additionally, the conical microcolumns have ultra-high separation flux for various emulsions (oil-in-water: 19 894 L m⁻² h⁻¹, water-in-oil: 42 972 L m⁻²·h⁻¹) and oil type detection properties due to different oil movement velocities. Thus, the magnetic-responsive conical microcolumn is expected to be applied in droplet driving, oil pollution-cleaning, wastewater treatment, and oil type detection.