Enhanced performance of salt-induced Pluronic F127 and bentonite blended polyvinyl chloride ultrafiltration membrane for the processing of oilfield produced water

Pluronic F127 blended polyvinyl chloride (PVC) ultrafiltration (UF) membranes using different loading of inorganic salts (like NaCl, KCl, NH₄Cl, MgCl₂ and CaCl₂) in casting solution involving N-methyl-pyrrolidone solvent are prepared for the cleaning of oilfield produced water with 200 ppm oil concentration. The effect of salt loading in casting solution on the performance of blended PVC membranes is studied by determining the thermodynamic and kinetic effect, membrane hydrophilicity, morphology, pure water flux, oilfield produced water permeate flux, oil rejection and fouling resistance ability. A better performing membrane is obtained using KCl in polymer casting solution involving PVC-14.0 (g), NMP-80.0 (g), Pluronic F127-5.0 (g) and KCl-1.0 (g) with enhanced (i) pure water flux (i.e., 607.8 L m⁻² h^-1), (ii) produced water permeate flux (i.e., 265.7 L m⁻² h^-1) and (iii) oil rejection (> 92.8 %) with higher fouling resistance (i.e., flux recover ratio > 71.65 %) when trans membrane pressure is kept at 100 kPa, compared to PVC UF membranes involving CaCl₂, MgCl₂, NaCl and NH₄Cl salts in casting solution. The addition of bentonite nanoclay in Pluronic F127 and KCl-induced PVC casting solution has a significant impact to improve the UF performance and results super-hydrophilic membrane with water contact angle < 10°. An enhancement in pure water and oilfield produced water permeate flux by 42.25 % and 37.61 %, respectively, with oil rejection > 92.0 % is obtained over UF membrane without bentonite.