Study On Anti-fouling Nanosized Silica/PVDF Composite Membrane

Membrane separation is a new unit operation which can be effectively used in deep treatment for sewage. But the membrane has a tendency to be contaminated in ultrafiltration. So it is urgent to prepare novel membranes with good anti-fouling performance.Anti-fouling membrane was fabricated with polyvinylidene fluoride (PVDF) as membrane-forming material, which has a perfect chemical stability and thermal stability. N, N-dimethyl acetamide (DMAc) was used as solvent and polyethylene glycol (PEG400) as pore-inducing reagent in this thesis. Hydrophilicity and mechanical strength of the membrane was improved by adding nanosized silica modified withγ- aminopropylthriethoxysilane to the casting solution. The so prepared membrane was found to be effective for disposing sewage.First, the effects of operating conditions such as PVDF concentration, PEG400 content, evaporating time and coagulation bath temperature on the performance and properties of membrane were investigated. The proper conditions of membrane-forming technology were established, which involved PVDF concentration of 18wt. %, PEG400 content of 10wt. %, 5 seconds evaporating time and 30℃for coagulation bath.Then, the effects of adding inorganic particles to casting solutions on membrane properties were studied. A method to modify nanosized silica withγ- aminopropylthriethoxysilane as coupling reagent was established. Membrane prepared with so modified nanosized silica as additive has a good mechanical stress, tenacity, hydrophilicity and retention.Anti-fouling performance of the composite membrane was simply investigated. The hydrophilicity of composite membrane was improved by adding nanosized silica, which could make contributions to membrane anti-fouling performance.The original ideas of this paper include the following parts: First, a new method for dispersing nanosized silica to casting solution was established. Particles dispersed by this method don't reunite with each other. Membrane prepared with such particles has a good separating performance. Second, it is supposed that the following two factors make main contribution to membrane performance:(1)chemical bond between nanosized silica and polyvinylidene fluoride; (2) hydrophilicity of nanosized silica.