Treatment of shale gas drilling flowback fluids (SGDFs) by forward osmosis: Membrane fouling and mitigation

A polyamide thin-film composite (TFC) forward osmosis (FO) membrane was fabricated and compared to a commercially available cellulose acetate (CTA) membrane for treating shale gas drilling flow-back fluids (SGDFs). The polyamide TFC membrane outperformed its CTA counterpart in terms of pure water flux and reverse salt flux when synthetic brine was used as the feed. More severe fouling was observed for the polyamide TFC membrane as compared to the CTA counterpart when treating SGDF. Very quick buildup of fouling was identified for TFC membrane but not significant for CTA membrane. Ultrafiltration pre-treatment delayed but did not alleviate fouling formation. Surface modification of the TFC membrane by poly(ethylene gycol) (PEG) grafting resulted in reduced membrane fouling and marginal decrease in water flux. •TFC FO membrane outperformed CTA membrane in treating synthetic brine.•Severe fouling was found for TFC FO membrane in treating SGDF.•No significant fouling was found for CTA FO membrane in treating SGDF.•Ultrafiltration pretreatment only delays fouling formation of TFC membrane.•PEG grafting to the TFC membrane alleviates membrane fouling.