Effect of additive and coagulation bath temperature on structure and properties of HDPE membranes via thermally induced phase separation

Membrane separation technology as an effective and energy-saving method is playing an important role in solving water crisis. High-density polyethylene (HDPE) with excellent comprehensive performance is an ideal material for the preparation of separation membrane. However, it is susceptible to fouling during separation process owing to its inherent hydrophobicity and is difficult to prepare HDPE porous membranes with uniform pore size distribution. In this work, HDPE membranes with improved hydrophilicity and uniform pore size distribution were successfully prepared via thermally induced phase separation with white oil as diluent. Meanwhile, ethylene–vinyl acetate (EVA) and polyethylene glycol (PEG20000) as hydrophilic polymer additives were added, while silica nanoparticles (SiO2) or multilayer graphene oxide were used as hydrophilic inorganic additives respectively. In particular, the influence of additives and coagulation bath temperatures on the properties of the membranes were investigated in detail. The hydrophilicity of the HDPE membranes was improved, and the thickness of the dense skin layer decreased effectively with the addition of 5% EVA, 5% PEG20000 and 2% SiO2. The pure water flux (407.63 L·m–2·h–1) was about 7.65 times higher than the pure HDPE membrane. In particular, the appropriate increase in the coagulation bath temperature was conducive to crystal growth and diluent aggregation. Furthermore, the mean pore size, porosity, and pure water flux all increased significantly, while the BSA rejection ratio decreased slightly. The prepared HDPE membranes showed high rejection ratio (> 99.9%) for the carbon ink particles, long-term and cyclic filtration stability, and excellent corrosion resistance to the aggressive chemical solutions.