The Interaction Of Polysulfone Ultrafiltration Membrane And Low Molecular Weight Organics And Surfactant

As a new approach of separation, purification and concentration, membrane technology is widely used in many fields because of its obvious advantages. Fouling and degradation of membrane are the bottlenecks of the application of membrane in separation. The interaction between molecules in feed solution and materials of membrane is the key of the research of membrane fouling and degradation.In this paper, using polysulfone membrane, four low-molecular-weight organic systems of alcohol, aldehyde, acid and phenol mixed with water were selected to study the impact of low-molecular-weight organic solute on the ultrafiltration process. The results showed that, water resistance of the membrane was 0.32 times than that of its own; In accordance with the fouling factor, the order of the fouling degree of four low-molecular-weight organic solution of alcohol, phenol, acid, aldehyde with water was as follow: methanol solution <phenol solution <formic acid Solution <formaldehyde solution. Fouling of phenol solution to membrane was serious than methanol solution, this may be due to that phenol is a weak acid and hydrophobic of phenyl is stronger than that of methyl. Formic acid is a strong acid, the attractive interaction between electronegative carboxylic ion and membrane aggravated the fouling of membrane. This lead to the decrease of flux. Degeneration of protein caused by formaldehyde increased the fouling of membrane.According to surfactant's special nature, surfactant SDS and CTAB were selected to study the impact of low-molecular-weight organic solute on ultrafiltration in presence of surfactant and the interaction between membrane's fouling surface and the solute were also studied. The results showed that surfactant affected membrane's flux in many accesses. Firstly, the decrease of surface tension can reduce membrane's fouling and increase the water flux. Secondly, critical micelle formed after the addition of surfactant, which can be intercepted by membrane. With the increase of CMC, the flux reduced. Thirdly, if there was charge in surfactant, the electronic interaction can also change the flux. Because of the above causes, the flux differed from different feed solutions.Experiment results showed that, When SDS joined the four organic solvents, the flux reached its maximum in critical concentration, which means the smallest fouling of the membrane. For methanol solution, SDS had no effect of reducing fouling, which was more obvious in acid and aldehyde solutions. For CTAB, the flux of methanol solution and phenol solution reached its maximum at half of CMC concentration, while formic acid Solution and formaldehyde solution at CMC concentration. In alcohol, phenol, acid systems, fouling factors were close to 0.36, but formaldehyde solution had special effect of reducing fouling of membrane. The comparison of the effect of two added surfactant showed that cationic surfactant was superior to the anionic surfactants.Humic acid was used to simulate wastewater to foul pollute the membrane. Through further observation and analysis of the above systems, the following results were obtained: Based on the removal of organic matter, knowing that organic material in humic acid first adsorbed in membrane hole, making it narrowing, thus increased the organic matter interception, and then a layer cake formed and aggravated the membrane fouling. With the adding of surfactant in humic acid, hybrid solution's flux reduced, fouling factors increased, so the addition of surfactant couldn't improve fouling. From the fouling factors we could see, CTAB got light fouling than SDS.Comprehensive factors were considered, the surfactant of membrane had beneficial effects on organic wastewater of low molecular weight under experimental conditions, but membrane fouling becomes more serious for the system of humic acid. It presents different results in the different feed solution, resulting from comprehensive function of multiple factors. In this paper, the results and inference of preliminary exploration to establish the base of subsequent work.