Study On Preparation And Performance Of PAMAM/TMC Reverse Osmosis Composite Membrane

On treating the oily waste water, the traditional method is replaced by the membrane technology with low energy consumption and simple process. Forseparating stable oily/salineemulsion (size of oil droplet<1μm), the ultrafiltration membrane or nanofiltration membrane can’t reject the oil and salts in one single pass. The reverse osmosis membrane with good ability to resist oil pollution could achieve the goal to get water recycling, and alsomaintain good performance in a long time. So we synthesized PAMAM(OG) molecular with branched structure. By interfacial polymerization of PAMAM (0G) and TMC, the PAMAM/TMC reverse osmosis membrane was prepared. Also, the surface structure and composition of membrane was characterized by SEM, FTIR-ATR, AFM and contact angle. The separation performance of Na2SO4, MgCl2, MgSO4, NaCl and different size of oil/saline water system was tested, respectively. Then, the condition to prepare the PAMAM/TMC membrane, such as reaction time, concentration of monomers, was optimized and the influence of operating conditions was investigated. Additionally, the resistance to oil, chlorine, acid and alkali of PAMAM/TMC membrane was investigated. Detailed, results were as follows:(1) Through the divergent approach, the PAMAM (OG) was synthesized by Michael addition reaction and amidate condensation reaction with the raw material of ethanediamine and methyl acrylate. The structure of PAMAM (OG) was confirmed to consist with the expected structure by FTIR and Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF). Also, the result of Free Standing experiment showed that as the monomer of water phase, PAMAM (OG) could react with TMC to form a thin selective membrane.(2) The PAMAM/TMC composite membrane was prepared by interfacial polymerization with the polysulfone supporting membrane. The characterization results showed that the thickness of formed selective membrane was about200nm. With20nm roughness and40°of contact angle, the surface was very smooth and hydrophilic. For the performance of PAMAM/TMC membrane, the rejection of NaSO4, MgCl2, MgSO4and NaCl was higher than85%. Also to separate the stable oily/saline water of300nm, the rejection of oil and NaCl was about99%and89.3%respectively, the water flux was18.39L/(m2·h).(3) The optimization results of preparation condition were as follows:the reaction time was180s, the concentration of PAMAM was2.4%(w/v), the concentration of TMC was0.1%(w/v), the temperature of heat treatment was60℃. Additionally, some operation conditions, such as the operating pressure, the pH of feed water, could influence the performance of membrane. As the operating pressure increased from1.2MPa to2.8MPa, the water flux was doubled to27L/(m2·h). The performance of membrane was stable when the pH of feed water was7to9and the flux was about18L/(m2·h), the rejection of NaCl was89%.(4) To separate stable oily/saline emulsion, the PAMAM/TMC membrane had great ability to resist oil and keep good performance. After running for24h, the flux decreased about3%, the rejection of oil and salt was98%and88%, respectively. Also, the good ability to resist chlorine, acid and alkali of membrane of PAMAM/TMC membrane was showed by investigation.