Preparation Of PVDF-g-PAA Modified Ultrafiltration Membrane And Its Application In Dye Wastewater Treatment

With the rapid development of the textile industry,a large amount of dye wastewater without proper treatment will be produced,which will be harmful to the environment and human beings.Membrane separation technology has been paid more and more attention because of its mild separation conditions and simple process,and it has no phase change in the separation process.Howe ver,the conventional membrane separation is based on the principle of aperture sieve.The charged modified ultrafiltration membranes are prepared by us.The retention and concentration of the anionic dye Congo red(C R)are obtained by the electrostatic force of charged membrane and the charged dye.As the same time,it combined with micellar enhanced,the removal of MB are acquired by the solubilization from micellar to cationic dye methylene blue(MB).The main results are as follows:1 Through the initiation of 2,2'-azobisisobutyronitrile activated by ozone,the PVDF-g-PAA copolymer was prepared by using PVDF as the matrix polymer and DMAc as the solvent.The maximum substitution of carboxyl was 12.4% when the molar ratio of PVDF and acrylic acid was 1:6.The series of different charge and diameter of PVDF-g-PAA with PVDF blend negatively charged modified ultrafiltration membrane were prepared by immersion precipitation phase inversion method.The charge and structure parameters of electronegative ultrafiltration membrane were investigated.The experimental results show that with the increase of amount of PVDF-g-PAA in the blend,the aperture of the modified membrane increased,as well as the porosity,pure water flux,hydrophilicity,ion exchange capacity increased;The section was transformed from the dead end of the tear to the profile type,the spongy support layer is loose and has a large number of loose pores.The flow potential E and Zeta potential were all negative,and the absolute value of Zeta increased with the increase of solution pH.2 The cationic dye methylene blue(MB)and anionic dye Congo red(CR)were chosen as typical representative of different types of charged dyes.The static adsorption experiments showed that the charged membrane has good adsorption for MB,the maximum adsorption capacity reached 10.06mg/g,but has no adsorption for CR,basically.The p H and ionic strength of the solution affect the adsorption capacity of MB,which is due to the electrostatic force between the charged membrane and MB.The interception experiments show that the intercept of charged membrane for MB can be obtained in the former 50 min,because of the electrostatic adsorption of negatively charged ultrafiltration membrane on MB.But the interception rate decreased when the adsorption reached saturatio n,However,the the retention rate of charged membrane for CR can maintain around 96%,and played a certain role in concentration.The ionic strength of solution had the charge shielding effect to the charged membrane,which cased the,electrostatic repulsion of both weaken and the retention rate of CR decreased.Compared with membrane pore size,the influence of the loading capacity of the blend ultrafiltration membrane on the retention rate of CR is relatively large.3 The MB wastewater was treated by the solubilization of micelle informed using twelve sodium dodecyl sulfate(SDS),combined with the interception role negatively charged ultrafiltration membrane When the concentration of MB and SDS is 10 mg/L and 8mmol/L in the stock solution,respectively,the concentration of MB in the concentrated solution was the highest,the amount of SDS was the least,the interception rate was the highest.The NaC l of the solution can increase the solubilization ability of the SDS micelle,but it also has the electrostatic shielding effect on the membrane,which results in the decrease of the retention rate.