Synthetic shale gas produced water pre-treatment via ultrafiltration membranes enhanced with polydopamine-coated hydroxylated 2D boron nitride nanosheets

Shale gas produced water (PW), a byproduct of oil and gas extraction, contains harmful contaminants that pose serious environmental risks, especially to marine ecosystems. Effective pre-treatment is crucial to mitigate these impacts. This study investigates the development of polyethersulfone (PES) ultrafiltration (UF) membranes enhanced with polydopamine (PDA)-coated hydroxylated hexagonal boron nitride nanosheets (HhBN) for PW purification. HhBN nanosheets was synthesized via calcination, followed by acid-washing for surface functionalization, and subsequently coated with PDA to improve compatibility within the PES matrix. Membranes were fabricated using the non-solvent phase inversion method, incorporating PDA-HhBN loadings ranging from 0.1 to 0.5 wt%. The modified membranes demonstrated improved wettability, permeance, and overall performance in PW purification. The modified membrane with 0.2 wt% PDA-HhBN (UF02) achieved the highest pure water permeance of 466.1 L.m⁻².h⁻¹.bar⁻¹ (LMH/bar), a 1.81-fold increase over the unmodified membrane (UF00). During PW filtration, UF02 exhibited permeances of 155.4–286.3 LMH/bar, compared to 53.2–171.8 LMH/bar for UF00 over 1-h filtration period. Additionally, UF02 showed a flux recovery ratio of 87.6 % after five filtration cycles, compared to 56.7 % for UF00, indicating enhanced fouling resistance. The irreversible fouling ratio dropped significantly from 23.6 % in UF00 to 2.8 % in UF04. The modified membranes achieved over 99 % rejection of oil, turbidity, along with slight reductions in salinity and total dissolved solids. These enhancements attributed to the improved hydrophilicity and mechanical strength provided by the PDA-HhBN composite. Overall, the incorporation of PDA-HhBN significantly enhanced the performance of PES UF membranes, positioning them as promising candidates for shale gas PW pre-treatment.