| The acceleration of the industrialization process has made high salinity wastewater treatment an urgent problem to be solved for sustainable development and environmental protection.The commonly used methods for treating high salinity wastewater include conventional treatment methods,concentration technology,and zero-emission technology.Membrane distillation is a new technology that combines membrane and thermal methods,which can be used as terminal concentration and zero emission technology.It has been initially applied in seawater desalination and later used in industrial high sallinity wastewater treatment and other fields due to its low energy consumption,high recovery rate,efficient concentration and wastewater reduction,which causes people's concern about its large-scale application.In order to popularize the membrane distillation process,one of the cores is to develop a membrane which is easy to manufacture with low cost,high flux,anti pollution and good stability.In this research,a simple and economic way to prepare superhydrophobic electrospinning nanofiber membrane was studied,and its treatment of high salinity wastewater in membrane distillation was tested and analyzed.Firstly,this research used electrospinning to prepare polyacrylonitrile nanofiber membrane with high porosity,and then used the cyclization and oxidation reation happened in the high temperature oxidation at 250? to make the polyacrylonitrile turn from chain structure to ladder structure,leading to the change of morphology and the enhancement of performance.The joints of fibers were strengthened,which is similar to the phenomenon of "welding".After that,using hydrothermal method to successfully load ?-Fe OOH particles on the fiber,increasing the membrane fiber roughness.Finally,the use of low surface energy substances such as fluorosilane and silicone to construct a super-hydrophobic surface.The prepared FAS-PDMS@Fe OOH@SPAN membrane had super-hydrophobic properties with a contact angle of 155.43 °,and it also exhibits good hydrophobic properties for contaminants such as acids,alkalis,humic acids,and surfactants.The prepared super-hydrophobic nanofiber membrane was used in a direct contact membrane distillation unit to treat simulated high salinity wastewater,and the effects of the feed liquid salt concentration,temperature difference,and p H on its operating efficiency were analyzed.The experiments showed that the prepared membrane used in tests can reach an average water flux of 24.74 L m-2 h-1 and salt rejection of 99.997% when it was operated for 8 hours under the conditions of feed solution sodium chloride concentration of 7 wt%,feed liquid temperature of 80? and permeate temperature of 15?.In order to test the long-term operation of FAS/PDMS@Fe OOH@SPAN membrane,the membrane distillation test was carried out at the salt concentration of 10 wt% for 63 consecutive hours.The average flux reached to 25.13 L m-2 h-1,and the salt rejection had been above 99.997%,which showed the potential of long-term treatment of high salinity wastewater.Finally,by analysing and comparing the engineering economic,it can be seen that membrane distillation technology has the economic advantages of low investment and operating cost,small footprint,etc..While preparing membrane for membrane distillation technology with excellent performance and stable operation,the development and manufacture of supporting equipment can promote membrane distillation technology to become a promising new technology for high saltinity wastewater treatment as soon as possible. |
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