Polyamide Forward Osmosis Membrane: Synthesis, Characterization and Its Performance for Humic Acid Removal

In this research, modification on the ultrafiltration (UF) membrane by synthesis of a thin layer of polyamide selective layer was designed for high performances of forward osmosis (FO) water treatment. Two monomers, m-Phenylenediamine (MPD) and Trimesoyl chloride (TMC) with different concentrations of MPD (2.0% w/v and 1.0% w/v) were reacted with TMC (0.15% w/v) for interfacial polymerization (IP) reaction to form a thin polyamide selective layer. The polyamide FO membrane prepared was characterized by using the Field Emission Scanning Electron Microscope (FESEM) and contact angle measurement. Forward osmosis membrane performances in terms of water flux (L/m2hr) and humic acid rejection (%) were evaluated in order to obtain the best performances of the FO membrane. It has been demonstrated that the result of membranes with a MPD concentration of 2.0% w/v revealed a large number of fully sponge-like structures and possess high hydrophilic properties. Moreover, experimental results clearly demonstrated that the 60s reaction time of the polyamide FO membrane with MPD of 2% w/v exhibited a lower water flux of 1.98 L/m2.h and the highest humic acid rejection (99.2%) when 2.5M of sodium chloride (NaCl) was used as draw solution. Compared to the 60s reaction time of the polyamide FO membrane prepared with a MPD concentration of 1.0% w/v with the same concentration of feed and draw solution exhibiting a higher water flux of 3.80L/m2, a lower humic acid rejection with 95.4% of salt rejection was observed. It is found that the overall characterization and performance of the polyamide FO membrane is mainly due to the formation and thickness of the thin polyamide layer that plays an important role in facilitating a high water flux in forward osmosis for humic acid removal.