A one-step preparation of superhydrophobic stainless steel mesh and application in raffinate cleaning technology as a coalescer for contaminated organic-water separation

Improving raffinate oil-water separation efficiency and simplifying the production process of coalescing material are both in great demand but remain difficult. In this study, a superhydrophobic stainless steel surface was created using a simple one-step electrodeposition process in an electrolyte solution comprising nickel chloride (NiCl 2 ·6H 2 O), stearic acid, and ethanol. The surface shape, chemical content, and superhydrophobic property were studied using a scanning electron microscope (SEM), Fourier-transform infrared (FT-IR) spectrometer, energy dispersive spectroscopy (EDS), and contact angle measurement. The cotton-like microstructure, comprised of crystals of Ni metal and Ni(CH 3 (CH 2 ) 16 COO) 2 , demonstrated outstanding acid and alkaline resistance with a maximum surface contact angle of 166.8°. The oil-water separation performance of raffinate was tested in a mixer-settler, and the separation efficiency ranged from 75% to 80% in a P507 + Kerosene/water system, based on Chemical Oxygen Demand (COD) indicating its potential applicability in the solvent extraction process. A high-speed camera was also used to observe the coalescing behavior of oil droplets in water. • The maximum contact angle of superhydrophobic SS surface reached 166.8°. • The water contact angles exceed 150° respecting to the pH level from 1 to 13. • The phase separation efficiency could reach almost 80% when the raffinate flows through a 12-layers coalescer. • The coalescing process of an oil droplet on the electroplated fiber was captured every 0.0033 s by a high-speed camera.