Impact of surfactants used in oil and gas extraction on produced water treatment by membrane distillation

Produced water from unconventional oil and gas reservoirs often contains non-ionic surfactants that are added to the hydraulic fracturing fluid to facilitate water release and enhance gas production. This study investigates the impact of currently used surfactants (i.e., nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs)) and proposed alternative surfactants on the performance of membrane distillation (MD) for produced water treatment. The impact of NPEOs and OPEOs on wetting of PTFE membranes was studied as a function of their concentrations and ethoxylate (EO) chain length in a lab-scale DCMD system. Additionally, alternative surfactants, including linear alcohol ethoxylates (LAEs), branched secondary alcohol ethoxylates (BAEs), and alkyl polyglycosides (APGs), were evaluated for their potential to replace NPEOs and OPEOs. Experimental results indicate that the increase in the number of EO units in NPEOs decreased their tendency to cause membrane wetting by reducing their interaction with hydrophobic surfaces. It was also observed that LAEs and APGs that are environmentally friendly alternatives did not cause membrane wetting. This study provides valuable insights into the underlying mechanisms of surfactant-membrane interactions and offers guidelines for surfactant alternatives that can potentially improve hydraulic fracturing and lower environmental concerns while facilitating the use of MD for produced water treatment and recovery.