More fouling resistant modified PVDF ultrafiltration membranes for water treatment

Polyvinylidene fluoride (PVDF) membranes were modified using L2MM, a new type of hydrophilic polyurethane additive, to improve membrane performance. Membranes were prepared using 15 and 18%PVDF and small weight percentages (i.e., 1.5 and 3%) of L2MM. Their fouling resistance was evaluated by filtration/fouling tests with Ottawa River Water (ORW) using membranes incorporating two different types of L2MMs (L2MM(PEG-200) and L2MM(PEG-600)). For comparisons a commercial membrane (HFM-180) was also tested. A PVDF membrane prepared with 3% L2MM(PEG-200) which produced the highest cumulative permeate volume, had a lower flux reduction and its TOC removal was 24% higher than the HFM-180 membrane. L2MM produced more hydrophilic PVDF membranes which had pure water permeation (PWP) rates up to 128% greater than the control PVDF membranes. Many of the L2MM blended membranes had significantly higher total organic carbon (TOC) removals than the HFM-180 membrane tested (64–67% versus 46%). Modeling of the flux decline suggested the membranes fouled via a combination of pore blocking and cake filtration; scanning electron microscopy (SEM) of the fouled membrane surface confirmed the existence of a cake layer.

► L2MM lowered the contact angles of PVDF membranes and significantly improved their performance.
► In river water filtration the best modified PVDF membrane had final fluxes up to 144% higher than the controls.
► L2MM blended membranes had high river water NOM removals, much higher than the commercial membrane tested.
► The best modified PVDF membrane fouled significantly less than the other membranes including the commercial membrane tested.
► PVDF membranes made with L2MM(PEG-200) were more hydrophilic and performed better than those made with L2MM(PEG-600).