| The per capita possession of water resources in our country is small.While water resources are scarce,water pollution is becoming more and more serious.Therefore,it is very important to use effective methods for water treatment.Membrane separation technology,as one of the water treatment methods,has great development prospects.However,the low strength of hydrophilic membranes,easy pollution,and poor hydrophobicity of hydrophobic membranes hinder the further development of membrane separation technology.Therefore,this article focuses on improving membrane technology and membrane modification,essentially improving membrane performance,and preparing separation membranes with excellent comprehensive performance.This paper mainly carried out the following aspects of work:1.Using polysulfone(PSF)as the membrane material,through the phase inversion method,four factors and five-level orthogonal experiments were designed based on polymer concentration,casting solution temperature,air bath time and coagulation bath temperature to optimize the membrane production process.Membrane strength,membrane pores,and membrane flux are the response indicators,and the best process parameters are obtained using range and average analysis and verified.Studies have shown that the effects of various factors on the membrane structure and performance are significantly different.Through comprehensive consideration and balancing the advantages and disadvantages of each performance,the final process parameters for the best membrane performance are:the polymer concentration is 22%,and the casting solution temperature is 60℃,the air bath time is 150 s,and the coagulation bath temperature is 25℃;and through verification,it is found that the performance of the membrane prepared under the best process parameters is better than the average performance of the membrane prepared by the orthogonal experiment2.Using modifiers polyvinylpyrrolidone(PVP),polyethylene glycol(PEG-400)and sucrose fatty acid esters(SE)to hydrophilically modify polysulfone membranes under optimal process parameters,and studying the pairs of modifiers’influence to membrane structure and its performance.The hydrophilic modification results show that the three modifiers have improved the hydrophilic properties of the membrane,of which SE is the most obvious.When the amount of SE added is 0.4%,the contact angle decreases from 86°to 54°,and the hydrophilic performance is significantly enhanced..At the same time,the addition of SE has a positive effect on the toughness of the polysulfone membrane.When the addition amount is 0.2%,the elongation at break reaches 180%.3.By studying the effects of different molecular weights of polyvinylidene fluoride(PVDF)and the concentration of ethanol in non-solvents on membrane performance,prepareing polyvinylidene fluoride membranes with excellent hydrophobic properties and compareing them with other commercial membranes.The research results show that the structure,hydrophobic properties,and pore size distribution of membranes prepared by PVDF of different molecular weights are quite different,nd the difference of mechanical properties is small.Under the same polymer concentration,the viscosity of the casting solution formulated in the membrane material of the model PVDF-6020 is lower than that of PVDF-1015.The concentration of ethanol in the non-solvent has a greater impact on the performance of the membrane.As the concentration of ethanol in the non-solvent increases,the hydrophobicity of the membrane increases significantly.When the ethanol concentration is 99%,the membrane contact angle reaches 144°,but due to the large membrane pore size,it is not conducive to practical applications;when the ethanol concentration is 75%,the membrane contact angle is 138.9°,and the pore size is appropriate;compared with commercial membranes It can be seen that the membrane prepared when 75%ethanol is used as the non-solvent in this study has better hydrophobic properties. |
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