Modified PVDF ultrafiltration flat-sheet membranes for water treatment

In recent years, membranes separation processes have been increasingly used in the design and upgrade of water treatment plants to comply with the more stringent regulations and to exploit water resources of lower quality. Membrane fouling decreases the water production rate with time and is the main disadvantage of this technology. In this research, polyvinylidine (PVDF) membranes were modified using a new type of hydrophilic polyurethane additive, called L2MMs, to decrease the fouling. This hydrophilic additive migrates to the membrane surface during phase inversion and modifies the membrane characteristics. In this research, membranes were modified with different batches of two L2MMs: L2MM(PEG-200) and L2MM(PEG-600).;During filtration/fouling test with Ottawa River water (ORW), the experimental membranes showed high TOC removals (63.7% to 77.5%). Membrane incorporating L2MM(PEG-200) had higher TOC removals than those using L2MM(PEG-600). The 18%PVDF+3%L2MM(PEG-200) membranes was the best membrane since it produced the highest cumulative permeate volume, plus it fouled less and had 23% higher TOC removal than the commercial membrane.;In the first part of this work, pure water permeation (PWP) tests, contact angle measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were used to assess the impact of L2MM type, L2MM concentration and PVDF concentration on the performance and characteristics of modified PVDF membranes. The L2MMs had a significant effect on flux. Increasing the L2MM concentration improved the membrane fluxes up to a maximum and a further increase in additive concentrations resulted in a flux decrease. Both L2MM(PEG-200) and L2MM(PEG-600) increased the final PWP flux of modified PVDF membranes to 6.5 times the control membrane. Moreover, L2MM(PEG-200) increased the 100 kDa polyethylene oxide (PEO) removal from 88 to 96% compared to the control membrane. XPS analysis and contact angle measurements indicated that the L2MM(PEG-200) modified the membrane surface. L2MM(PEG-200) addition helped decrease the contact angle of the modified membranes by up to 19%.