Study On The Preparation Of PVDF Membrane Modified By Nanocomposites And Its Distillation Performance

The wastewater treatment capacity is facing arduous challenges,because of emissions of domestic sewage and industrial wastewater,and the frequent occurrence of offshore oil spills.There are some difficulties and low efficiency in the treatment of wastewater which owns high oil content and high salinity.Membrane distillation is a new water treatment technology which combines distillation with membrane separation.It has a broad application prospect in the fields of seawater desalination,oil-water separation and so onIn this paper,CTS-SPFO-SiO2 nanocomposites which were prepared by hydrophilic material method using chitosan(CTS),SPFO and SiO2 nanoparticles as modified materials,were sprayed on one side of polyvinylidene fluoride(PVDF)membrane to prepare super hydrophilic/underwater super hydrophobic oil membrane.The composite membrane was applied to the direct contact membrane distillation(DCMD)experiment in the treatment of oily wastewater.The main contents and results are as followsThe single factor gradient experiments were carried out for the treatment of concentrated brine solution by DCMD.The influences on the permeate flux were discussed,which caused by the change of the concentration of the feed solution,the temperature of the cold side and the hot side,the flow rate of the cold side and the hot side.It was concluded that increasing the temperature of the hot side was the most effective way to improve the permeate flux,and proved that the temperature difference between the two sides of the membrane was the driving force of the membrane distillation experimentThe contact angle measurement,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)were employed to test the surface properties of the composite membrane and the original PVDF membrane.The successful synthesis of the three modified materials was verified.The Micro-Nanostructure necessary to hydrophilicity was observed on the surface of the composite membrane.The characteristic of super hydrophilic in air and super hydrophobic in water of composite membrane was reflected by surface wettability analysisThe super hydrophilic/underwater super hydrophobic composite membrane was applied to the treatment of high salt water solution.The hydrophobicity of the basement membrane was not changed by single-sided coating.The composite membrane showed similar desalination ability to the original PVDF membrane.The membrane distillation performance of the composite membrane was analyzed in the treatment of diesel salty wastewater.The experimental results show that the composite membrane owns strong oil resistance and more excellent membrane distillation performanceCurrent results provided an important theoretical basis for the industrial development of direct contact membrane distillation.