Preparation Of Polypropylene Homogeneous Ion Exchange Membrane And Its Application In Electrodialysis

One of today's major industrial pollutants is the discharged wastewaters,and the heavy metal ions in wastewaters can cause serious damage to people,soil and microorganisms.Electrodialysis technique is an economic and practical method for removing heavy metal ions in wastewater.It can achieve the concentration of metal ions and the recycling of water at the same time without causing secondary pollution.It has shown a wide range of application fields and prospects.In this thesis,the laboratory-made polypropylene homogeneous ion exchange membrane was used in the laboratory-built electrodialysis device for the concentration and separation of cupric ions in wastewater,which indicates certain practical value.Firstly,the fluorine-containing acrylate,together with acrylic acid(AA)and methacrylamide propyl trimethyl ammonium chloride(MAPTAC)respectively,was grafted onto polypropylene non-woven fabric under ultraviolet irradiation.Meanwhile,their corresponding polymer solutions(PAA and PMAPTAC)were prepared in the absence of crosslinkers.Secondly,the two resultant polymer solutions were coated on the counterpart surfaces of the grafted polypropylene nonwoven fabrics respectively,and thus the polypropylene homogeneous cation exchange membranes and anion exchange ones were made respectively.The influences of the amount of monomer,cross-linker and photo-initiator on the grafting rate of two kinds of modified non-woven fabrics were mainly investigated.Thirdly,the measurement and analysis techniques,such as infrared spectroscopy,scanning electron microscopy,thermogravimetry,water content,ion exchange capacity,water contact angle and tensile test were employed to characterize the structure and properties of the two kinds of ion exchange membranes.Finally,the cation exchange membrane was applied to the electrodialysis device for cupric ions concentration and separation.Through the data analysis of the pH,conductivity,energy consumption and copper ions concentration of each water chamber in the experiment setup,the effectiveness of homogeneous and commercial heterogeneous cation exchange membranes were compared by using electrodialysis to treat copper ions wastewater.The main conclusions were found as follows:(1)The optimal grafting rate was 169.4%at the monomer AA content of 34.4%,while the optimal grafting was 343.5%at the monomer MAPTAC content of 30.7%.(2)When the content of photo-initiator BP increased,the grafting increased first and then decreased.The maximum grafting rate of AA was 189.1%at the BP content of 3.1%;the optimal grafting of MAPTAC was 370.8%at BP content of 3.7%.(3)Keeping AA and MAPTAC concentrations unchanged,the grafting rate increased first and then decreased with the increase of crosslinker.The maximum grafting rate of AA was 268.1%at the crosslinker of 6.1%,whereas the highest grafting rate of MAPTAC was 334.0%at the crosslinker of 7.1%.(4)The results of scan electron microscope,infrared spectroscopy,and thermogravimetry showed that AA,MAPTAC and fluorinated acrylate were successfully grafted onto the PP macromolecular chains.(5)The results of the surface contact angle of the ion exchange membrane showed that the membrane hydrophobicity increased with the increase of fluoroacrylate.(6)The ion exchange capacity,water content,and the mechanical strength shared similar tendency with monomer concentration.Namely,they all increased with monomer concentration initially and then leveled off.However,the areal resistance of the membrane first decreased and then remained unchanged.(7)The results of electrodialysis showed that the removal rate of cupric ions with homogeneous membrane was better than that with heterogeneous one.When the cathode solution was hydrochloric acid,both the metal ions removal and current efficiency of homogeneous membrane were higher than those of heterogeneous one.In this thesis,the polypropylene nonwoven was grafted under UV irradiation and coating,and the resultant homogeneous cation exchange membranes were applied to the electrodialysis device to remove copper(?)ions,and good separation efficiencies were achieved.It is of great significance to expand the output of PP nonwovens and promote the transformation and upgrading of nonwovens industry.