Reducing oil and grease on-site in real offshore oilfield-produced water through feasible adsorption-desorption cycling

Although produced water treatment is witnessing an increasing demand worldwide, conventional treatments are limited, marginally aiming at water-soluble pollutants. Here, we develop a cycling adsorption process, targeting water-soluble compounds and mapping the conditions to yield oils and grease content in real water matrix below the legislation requirements, allowing full adsorbent reuse through a feasible offshore route. The adsorption performance was evaluated in terms of pH, adsorbent concentration, and contact time, while the desorption performance was assessed in terms of eluent type, concentration, and contact time. The polymeric resin MN 202 presents an excellent ability to remove oil and grease from the real produced water matrix, and acid pHs favored the process. The adsorption equilibrium is reached after 12 h, with an oil and grease removal of 92 % at pH 5, presenting multilayer adsorption during the process, with an influence of external diffusion governed by hydrophobic and electrostatic interactions. In the desorption process, CH3O- species, originated by NaOH's solubilization in methanol, enables complete adsorbent regeneration in 2 h. The adsorption-desorption cycling is stable, and the adsorbent microstructure assessment indicates no significant changes in the resin surface due to adsorption-desorption runs.