Study On Treatment Of Dyeing And Finishing Waste-water By Membrane Distillation Technology Based On PVDF Nano-fiber Membrane

The issue of dyeing waste-water is related to environment. It has become a focus recently.The problem of large-scale dyeing and finishing waste-water has been a national concern.Effective treatment of dyeing waste-water is extremely critical for the protection of ecology and environment. Traditional methods of dyeing and finishing waste-water treatment are biological,physical, chemical and so on. In this paper, research object is dyeing finishing waste-water. This paper makes systematic and further research on the factors which affecting heat transfer mechanism of vacuum membrane distillation process.Vacuum membrane distillation is one of membrane distillations. It is a new technology of membrane separation. The main components of the membrane distillation process are hydrophobic and porous membrane, steam separator, steam generator, steam collection device.The experiment can separate gas from liquid by hydrophobic porous membrane material. The gas is pulled by a vacuum pump to the vapor cooling system, collected by this equipment. The whole process is similar to vacuum distillation. Films are made by the polyvinylidene fluoride(PVDF).Films used in the process exhibit good hydrophobicity, acid and alkali, stable physical and chemical properties, toughness. Participating in market competition, films power to low cost relatively. It is an ideal material used in the field of vacuum membrane distillation.Taking into account the adequacy of the heat transfer process, the cross-flow module adopted on this experiment. The factors that affected the results are reviewed by experiments of mono-factors. First, NaOH solution is used in experiment. This thesis has successively investigated the effect of experimental temperature, feed flow rate on the experimental results.The best experimental conditions are selected. Then we deal with simulate dyeing and finishing waste-water. Finally, dyeing and finishing waste-water from factory treated by experiment. In vacuum membrane distillation experiments we found that with increasing temperature,the membrane flux obtained increasing gradually; the membrane flux increasing gradually wih feed flow rate, but the rate of increase is slowing. With the feed concentration increases, the membrane flux obtained reduced gradually, and the rate of decrease is faster. Experimental results show that the the retention rate can be control above the range of 99.9% by vacuum membrane distillation. Under the condition of temperature 80℃, circulating water flow rate of450ml/min, mass fraction of impurity is 1%, the largest pure water flux is 6kg/(m2·h). Purified water minimum conductivity is16μs/cm. This paper examines the mechanism of membrane’s pollution. Experimental results show that the membrane surface solute will precipitate to form a solid thin film layer, which leads to membrane flux decline. Using hydrochloric acid and water rinse film material, flux will recover more than 80%.In summary, this paper discusses the use of PVDF nano-fiber membrane systematically.Getting achievements through membrane distillation technology to solve problem of dyeing waste-water. Studies show that vacuum membrane distillation process of dyeing waste-water has good feasibility.