Construction Of Composite Hydrogel Filter Membrane And Purification Of Oily Wastewater

With the prosperity and development of marine economy,the pollution of oily wastewater from ships has become increasingly serious,which has caused serious harm to human health and ecological environment.Membrane separation technology plays an important role in the field of oily wastewater because of its environmental friendliness,simple operation process and high efficiency.Polyvinyl alcohol hydrogels have attracted much attention due to their advantages of easy modification,rich functional groups and low preparation cost.However,polyvinyl alcohol hydrogel also has the disadvantages of low porosity,poor oil resistance,poor thermal stability and low separation efficiency,which limits its application in the study of oily wastewater purification.In order to meet this challenge,this thesis uses polyvinyl alcohol as raw material,using chitosan and hydrotalcite to modify and optimize it,and used freezing-salting out strategy to optimize the pore structure of hydrogel filter membrane,and applies it to the purification of ship oily wastewater.The main research contents are as follows:(1)Polyvinyl alcohol hydrogel(PVA)was prepared by a simple and feasible method using polyvinyl alcohol as raw material.The PVA hydrogel was characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).The oil-water separation performance of PVA hydrogel filter membrane for oily wastewater was investigated.The results show that the PVA hydrogel filter membrane has excellent separation effect on oil-water mixture,and the separation efficiency reaches 99.58%.At the same time,it has certain separation ability for oil-in-water emulsion in oily wastewater,and the separation efficiency reaches 68.45%.(2)In order to further improve the separation effect of PVA hydrogel filter membrane on oil-in-water emulsion,a polymer hydrogel filter membrane(PVA-CS)was synthesized by in-situ one-step method using polyvinyl alcohol and chitosan as raw materials.The effect of salting-out time on oil-water separation performance in oily wastewater was studied by SEM and FTIR.The results showed that the PVA-CS hydrogel filter membrane had excellent purification effect on the oil-in-water emulsion in ship oily wastewater,and the purification efficiency and membrane flux reached 99.87%and 587.65 L m-2h-1bar-1,respectively.The number of cycles was 6 times.It overcomes the shortcomings of low flux,incomplete separation and uneven pore of PVA hydrogel filter membrane,and provides a theoretical basis for the popularization and application of polyvinyl alcohol and chitosan.(3)In order to further improve the mechanical strength and recycling performance of PVA-CS membrane,a new composite hydrogel filter membrane(PVA-CS-LDH)was synthesized by using polyvinyl alcohol.chitosan and hydrotalcite as raw materials,and PVA-CS blend matrix was intercalated into the interlayer of hydrotalcite(LDH).The characterization analysis and mechanical property test were carried out,and the effects of different factors on the purification performance of oily wastewater were investigated.The results show that the separation efficiency of PVA-CS-LDH membrane for oil-water emulsion in ship oily wastewater is as high as 99.99%.At the same time,it has excellent purification effect on heavy metal ions in ship oily wastewater,and the filtration efficiency reaches 97.44%.The cycle performance reaches 10 times.Compared with PVA-CS,PVA-CS-LDH filter membrane can not only purify oil-water emulsion in oily wastewater.but also has excellent purification performance for metal ions.More importantly,the mechanical strength and reusability of PVA-CS-LDH filter membrane have been greatly improved,which broadens new ideas for the field of marine oily wastewater treatment.