Preparation Of Anti - Pollution Antibacterial Aromatic Polyamide Reverse Osmosis Composite Membrane

Reverse osmosis (RO) membrane separation technology has been widely used in seawater and brackish water desalination and wastewater regeneration due to the advantages of simple operation, low energy consumption, high desalination efficiency, etc, which has already become the mainstream water treatment technology. The market dominated commercial RO membrane is the aromatic polyamide membrane. However, membrane fouling has severely added the operation cost of RO technology, the preparation of antifouling RO membrane has been one of the most challenging tasks for membrane researchers at present.Improving the antifouling performance of RO membrane by means of surface modification has already been widely reported. However, the RO membrane fouling includes a variety of types such as biological pollution, organic pollution, inorganic salt deposit and so on. Most current methods reported are only aimed at one certain type, which are limited in practical applications. In this paper, Ugi four-component reaction (Ugi-4CR) was conducted as a new strategy for surface modification by simultaneously grafting hydrophilic macromolecular aldehyhyded methoxy poly(ethylene glycol) (CHO-mPEG) and amino-terminated antibacterial agent on the surface of commercial polyamide RO membrane which contains massive residue free carboxyl groups, realizing bifunctional modification in "one-pot procedure" Tris(2-aminoethyl)amine (TAEA) and sulfamethoxazole (SMZ) were chosen as two antibacterial agents to prepare two modified antifouling and antibacterial membranes: PA-g-PEG/TAEA and PA-g-PEG/SMZ. The surface chemical structure and composition of original and modified membranes were characterized using ATR-FTIR spectrophotometer and X-ray photoelectron spectroscopy (XPS) measurements. Grafting degree density was calculated by thermal gravimetric analysis (TG). The change of membrane surface morphology upon modification was observed by field emission scanning electron microscopy (FESEM) and atom force microscopy (AFM). The hydrophility of the membranes was analyzed by water contact angle (WCA) measurement.Antifouling performance was evaluated by cross-flow filtration of protein.. polysaccharide and inorganic salt solution. After 48 h of pollution, the flux decline ratio of the original membrane was 37.3% 、34.6% and 46.7%, respectively. While the two modified membranes were only attenuated by around 10.0% for any pollutant. After a short period of pure water rinsing, a flux recovery of 70.0%、 78.2% and 64.4% was obtained for original membrane, while the values were all above 95.0% for modified membranes. Antibacterial performance was evaluated by shake flask method. E.coli and S.aureus were used as model bacteria. The results showed, the original membrane had no obvious inhibitory effect on the bacteria. For PA-g-PEG/TAEA, a bacteria killing ratio of 67.9% and 78.3% was presented for the two bacteria when shook for 4 h, but when the time reached 24 h, the bacteria concentration was relatively high resulted from reproduction, the antibacterial property of the membrane was dramatically declined in this situation. For PA-g-PEG/SMZ, the superior antibacterial performance was not only obtained in low bacteria concentration, even when shook for 24 h, the bacteria killing ratio was stabilized at 98.6% and 96.3%.