| Industrial waste acid mainly comes from pharmaceutical,dye,electroplating,metallurgy and other industries.If these waste acid solutions which are highly corrosive are discharged without treatment,it leads to not only a waste of natural resources but also a great threat to the environment,soil and water sources.Therefore,the discharged acid waste liquid must be purified,and the useful resources within it must be reused and recycled.Diffusion dialysis,as a membrane separation method with low energy consumption and environmental friendliness,plays an important role in waste acid recovery.At present,the membranes used for acid recovery by diffusion dialysis can be divided into dense anion exchange membranes and porous anion exchange membranes.The recovery efficiency of the dense anion exchange membrane is high,but the ion mobility is low and the time consumption is long.The porous anion exchange membrane can show a higher permeability for different ions but a lower recovery efficiency than the dense membrane,leading to lower purity of the separated acid,which requires further purification.Therefore,a porous polyimide anion exchange membrane was prepared as a substrate and coated with a thin layer of graphene oxide?GO?for diffusion dialysis recovery of acid.With a large specific surface area,GO can be readily used for forming a large area of interlocked lamellar film,and its surface contains a large number of carboxyl,hydroxyl and epoxy groups,which are easy to be chemically modified.Another part of this thesis is the preparation of quaternized graphene oxide,which has anion exchange properties and is then assembled into a two-dimensional membrane.Acid recovery by diffusion dialysis can be realized by using the ordered channels of the two-dimensional membrane.The first chapter is the preparation and application of graphene oxide-polyimide?P84? composite membrane.The mixture of GO and ethylenediamine?EDA?is suction filtered to the surface of the P84 anion-exchange membrane by vacuum filtration,and then chemically cross-linked by heating to prepare a composite membrane?GO-P84?.The properties of these membranes are characterized,including water content,membrane morphology and ion exchange capacity.The GO is chemically cross-linked by ethylenediamine,which provides the stability necessary for the layered GO nanosheets for overcoming their inherent dispersibility in the water environment.The properties of these membranes are characterized,including water content,membrane morphology and ion exchange capacity.The composite membrane is used to treat simulated titanium dioxide industrial waste acid?H2SO4/Fe SO4?by diffusion dialysis,and also used to separate hydrochloric acid from organic acidic liquid?HCl/Gly?containing hydrochloric acid and glyphosate.The results showed that the GO-P84composite membrane had a high acid permeability to the acid system and could effectively realize the separation of the acid/salt mixture.In the second chapter,the surface charge characteristics of GO are chemically modified and then the modified GO membrane is used for diffusion dialysis.The quaternized graphene oxide?QGO?is prepared by dehydration condensation reaction between GO and quaternary ammonium ionic liquid IL-NH2.The surface of QGO is grafted with positively charged groups,leading to anion exchange characteristics and good water solubility.The membrane is characterized by X-ray diffraction?XRD?,Zeta potential and Field emission scanning electron microscope?FESEM?,and the separation performance of the membrane is investigated by diffusion dialysis of H2SO4/Fe SO4system.The results show that the dialysis coefficient of QGO with different ammonium ratio varies from 0.0059 m/h to 0.0082 m/h,the separation factor ranges from 36.7 to24.0,and hence the separation efficiency is higher than that of GO membrane?dialysis coefficient:0.00070 m/h,separation factor:15.0?.The results show that QGO membrane,as a modified two-dimensional material membrane,has excellent separation performances. |
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