PDA Composite Membranes And Their Antifouling Properties

Membrane bioreactor (MBR) has been widely applied in wastewater treatment and water purification due to the advantages of smaller footprint, better effluent qualities and higher sludge concentration. Unfortunately, the high cost of the membrane materials and membrane fouling are critical challenges and barriers to the improvement of MBR systems.In order to control membrane fouling, PDA was used to modify different membranes in this work and their antifouling properties were investigated. The work mainly includes three parts:(1) To develop a high flux and antifouling membrane to be used in membrane bioreactor for water pretreatment, a low cost polyester filter cloth was modified by coating with polydopamine (PDA), based on the easy self-polymerization and strong adhesion characteristics of dopamine (DA) under mild conditions. The most reasonable modification conditions are1.5g/1DA concentration and24h coating time. There was142.67%increment of the stable flux for the PDA modified membrane under the best conditions compared with that of the original membrane. The results of the long term experiments in MBR indicate that the membrane modified by PDA reduced the membrane fouling in active sludge, especially the irreversible fouling.(2) Through addition of PDA into PVDF casting solutions, PVDF/PDA blend membranes were prepared by phase inversion techniques. The effects of the blending ratio and PDA concentration on the antifouling properties of the membranes were also investigated. When the PDA concentration was0.3%, the flux of the blend membrane was increased from56.19L/(m2·h) of blank membrane to69.63L/(m2·h). The flux recovery ratio of the PVDF/PDA membranes were both above90%, compared with68.5%and56.4%of the controlled PVDF membranes in the filtration test.(3) PDA was used to increase the dispersibility of nano-TiO2for preparation the PVDF composite membrane with high hydrophilicity. PDA-TiO2/PVDF membrane was peraration and the different conditions were tested. When the best ratio of PDA/TiO2was3:20and the concentration of the additives was2%. Compared with the PVDF membrane, the flux of the modified membrane in suspenstin solusion increased42.82%under the best conditions.