Study On The Performance Of NF Membrane And Application To Dye Industry

Polysulfone was chosen as the porous substrate for its excellent properties, cheap price and availability. By fabricating an ultra thin functional layer on the polysulfone substrate through interfacial polymerization taking piperazine as the monomer in aqueous phase, trimesoyl chloride as the monomer in organic phase and triethylamine as the proton acceptor, high performance nanofiltration composite membranes were prepared, and its separating behaviors and operation conditions were investigated systematically. The process of combing ultrafiltration and nanofiltration(UF/NF) to treat dye wastewater was designed and put into practice. The pilot test proved the process successful: the wastewater after treatment became decontaminate, and the production line is pollution free.The research is conducted in the following four aspects:1. Substrates with different molecular weight cut-off (MWCO) were subjected to coating, one with 6,000 and the other with 20,000, According to performance tests, the latter produced composite membranes far better than the former.2. The separating behaviors of the composite membrane were investigated systematically using various salts such as NaCl, KCl, Na₂SO₄, MgCl₂, CaCl₂ and MgSO₄, the highest rejection is to Na₂SO₄, the second to MgSO₄, the third to MgCl₂ and CaCl₂, and the lowest to KCl, NaCl, being 99%, 98%, 70%, 60%, 15% and 10% respectively.3. Mother liquid of the dye intermediate was treated by the combining process of UF/NF, the content of NaCl in the mother liquid was efficiently reduced and the effective contents of dye increased from 75% to 83%.4. Wastewater of the dye intermediate was treated by the combining process of UF/NF, COD after treatment was around 200, which meet the National effluent standards of wastewater. The nanofiltration condense solution can be recycled to production making the production line pollution free.