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. © 2015 Elsevier B.V. All rights reserved.

A polyamide TFC membrane and CTA forward osmosis membranes were utilized to concentrate the real SGDF in comparison to the synthetic brine with similar ion concentration. It was shown that the TFC membrane was prone to be fouled very quickly when treating SGDF, but not CTA membrane. After fouling, the TFC membrane showed similar flux as CTA membrane, even though the TFC membrane outperformed the CTA A 1µm Contact angle (o) B Polyamide Polyamide 86 2.3o JSG/JSB (%) PEGylation Without PEGylation With PEGylation PEGylation 34 1.5o 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Conc. ratio Polyamide PEGylation Fig. 7. (A) An SEM image of the PEGylated TFC membrane surface and (B) contact angles of TFC membrane before and after PEGylation.