| China is one of the countries with the least water resources per capita in the world.Traditional desalination technologies can alleviate the pressure of water scarcity,but with the disadvantages of low treatment efficiency and high cost.Hence there is an urgent need to develop water treatment technology with the advantages of efficient and energy-saving,and realize the recycling of useful substances.Pervaporation(PV)has the advantages of energy-saving,high efficiency,simple operation,and easy to scale up.It can not only separate organic matter from water,but also has been more and more widely studied in the field of desalination in recent years.In this paper,polyvinyl alcohol/polyacrylonitrile(PVA/PAN)membrane was selected to systematically investigated the effects of parameters such as feed concentration,feed temperature,feed flow rate,absolute pressure on the permeate side,and operating time on the desalination effect and water flux in treatment of Na Cl aqueous solution by PV process.The results showed that the concentration and temperature of feed solution have a greater impact on the water flux.The water flux decreased with the increase of the Na Cl concentration in the feed solution and increased with the increase of the feed temperature.The feed flow rate had little effect on the water flux.The water flux would decrease with the increase of the absolute pressure on the permeate side as the result of the reduction of driving force,and decrease with the extension of the operating time as the result of the increase of permeation resistance.The desalination rate of PVA/PAN PV membrane was greater than 99.80%,which showed excellent desalination performance.The operating conditions had little effect on the desalination performance of the membrane.It was the optimal operating conditions of the membrane when the feed temperature was 70?,the feed flow rate was 20 L·h-1,and the absolute pressure on the permeate side was 1 k Pa.The water flux and desalination rate of Na Cl solution with 3.5wt%treated by the membrane were 15.43kg·m-2·h-1 and 99.78%under the above conditions,respectively.The PVA/PAN PV membrane was further used for the desalination of seawater,and the results showed that the influence operating conditions on water flux and desalination effects were similar to that of Na Cl solution.However,due to a large amount of ion species and content in seawater,the membrane pollution is intensified,making the overall water flux level lower than that of Na Cl solution.The water flux of seawater desalination was 7.52 kg·m-2·h-1under the optimal operating conditions of the membrane,which was 51.3%lower than that of Na Cl solution.While the desalination rate of seawater was still greater than 99.89%.In addition,the effects of cleaning agent,cleaning interval,cleaning time and other parameters on the cleaning effect of seawater pollution membrane were also investigated in this paper.The results showed that the cleaning effect of hydrochloric acid is better than that of pure water.The cleaning effect gradually decreased as the p H of the hydrochloric acid solution increased,and the best cleaning effect was achieved when p H=2.On the other hand,the cleaning interval of the membrane was closely related to the cleaning effect,and the best cleaning interval was 2 h.Moreover,the longer the cleaning time was,the better the cleaning effect could be,and the appropriate cleaning time was 30 min. |
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