Abstract
During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable properties of high hydraulic performance combined with high membrane fouling resistance. This project employs the vapor induced phase separation (VIPS) technique to develop a hydrophilic polyvinylidene fluoride (PVDF) membrane with polyethylene glycol (PEG) as an additive for produced water treatment. Results show that thanks to its slow nonsolvent intake, the VIPS method hinders additive leaching during the cast film immersion. The results also reveal that the exposure of the film to the open air before immersion greatly influences the structure of the developed membranes. By extending the exposure time from 0 to 30 min, the membrane morphology change from typical asymmetric with large macrovoids to the macrovoid-free porous symmetric membrane with a granular structure, which corresponds to 35% increment of steady-state permeability to 189 L·m−2h−1bar−1, while maintaining >90% of oil rejection. It was also found that more PEG content resides in the membrane matrix when the exposure time is extended, contributes to the elevation of surface hydrophilicity, which improves the membrane antifouling properties. Overall results demonstrate the potential of VIPS method for the fabrication of hydrophilic PVDF membrane by helping to preserve hydrophilic additive in the membrane matrices.
Highlights
Oil and gas are some of the most important industries to supply energy demands
The results suggest a strong effect of exposure time on the resulting polyvinylidene fluoride (PVDF) membrane morphology
The immobile structure pre-formed on top of the cast film during the exposure time acted as a barrier for polyethylene glycol (PEG) that hindered its leaching during the immersion
Summary
Oil and gas are some of the most important industries to supply energy demands. they are accountable for water contamination during the refinery and/or production operation. One of the most common methods to produce hydrophilic property from hydrophobic polymer-based membranes (such as PVDF) is by incorporating hydrophilic additive in the dope solution. It is one of the simplest and straight forward ways to enhance membrane hydrophilicity [10,11]. To minimize the PEG additive leaching, this study employs a simple and yet effective VIPS method to develop hydrophilic PVDF-based membranes with desirable properties for PW treatment. We hypothesize that extending the exposure time of cast film under a humid atmosphere before immersion in coagulation would facilitate the formation of the immobile membrane layer on top of the cast film that hinders the mobility of PEG molecules to the nonsolvent which hold the hydrophilic additive from leaching [7]. Membrane performance for PW treatment, as well as their antifouling properties, were investigated
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