Preparation And Permeation Of Functional Graphene Oxide Membranes

With the growth of population and the rapid development of industry and agriculture,the scarcity of fresh water has become a risk and challenge.The treatment and reuse for waste water,which produced in industrial and agricultural,became one of the effective means to cope with the shortage of water.Sewage treatment methods include chemical precipitation,adsorption,ion exchange,biological treatment and membrane separation.The membrane separation technology is one kind of important and effective methods in water treatment field due to its simple process and easy to control.However,there are several inevitable technical drawbacks in water treatment,such as chlorine resistance,stain resistance,stability,etc.Graphene and its derivatives have been attracted wide attention as one new type of membrane materials in water purification for unique two-dimensional structure,their outstanding physical properties,and chemical stability.Graphene oxide（GO）is a very promising membrane material.GO can be stacked to form two-dimensional nanochannels between GO layer,which can be used as channel passing through molecular,ion and organic compound.In addition,GO,owning a large number of oxygen-containing functional groups on the edges and surfaces,could be modified by various functional groups.The characteristics of GO membrane can be enhanced,such as selectivity,water flux,antifouling properties and stability.Therefore,GO was modified in this paper to study the permeation behavior of metal ions and organic compound.There is three parts in this paper.β-CD-GO was prepared by GO modified withβ-cyclodextrin（β-CD）and used to explore the permeation behavior of phenol in the first part.GO composite membranes were synthesized by GO cross-linked with amino acids in second part.The rejection rates of three composite membranes to alkali metals,alkaline earth metals and transition metals are studied.GO,reduced graphene oxide membrane（RGO）and ethanediamine modified GO membranes（EDA-GO）were used to permeate UO₂²⁺and Th⁴⁺.Firstly,the interlayer spacing and water flux ofβ-CD-GO increases gradually with the additionβ-CD increases.The concentration of phenol and the thickness of membrane affect phenol permeation amounts.There was no effect to phenol permeation when metal ions were added in phenol solution.The pH effect to phenol permeation is complicated.Phenol had larger permeation amount than benzenediol and the separation ratio between them was 1.3.Graphene oxide membrane was fabricated onto a nylon membrane by vacuum filtration method and cross-linked by amino acids（L-alanine,L-phenylalanine,serine）.The rejection rate of alkaline through the composite membranes were over 94%,and decreases when H⁺neutralized the electronegativity.The rejection rates to alkaline earth and heavy metal are over 97%and 95%,respectively.Metal ions could be inserted into GOM layers,which enlarged the interlayer spacing and neutralized negative potential of GOM.The rejection rate to metal ions deceased as negative potential decreased.GO,RGO and EDA-GO were used to research the permeation behavior of UO₂²⁺and Th⁴⁺.It is found that RGO had the maximum permeation of UO₂²⁺and Th⁴⁺and EDA-GO had the maximum separation ratio.The permeation of UO₂²⁺and Th⁴⁺through EDA-GO increases when the temperature increases.The permeation of UO₂²⁺and Th⁴⁺was the biggest when the driving liquid is 1M HNO₃.The effect of NaNO₃ was big to UO₂²⁺permeation and small to Th⁴⁺permeation.