| In recent years,the development of high-tech,electronic information manufacturing industry has also achieved rapid growth,resulting in the growth of the electroplating wastewater it produces.According to incomplete statistics 2017 wastewater discharge reached 69,966.1 million tons.If these wastewaters containing heavy metals are not effectively treated,they will inevitably cause irreversible pollution to the environment due to the enrichment characteristics of heavy metals.Therefore,the treatment and recovery of heavy metals in wastewater has become a topic of concern and a hot spot.Scholars have taken different research approaches on how to effectively and efficiently recycle heavy metals in wastewater,and the main methods for treating electroplating wastewater are physical methods,chemical methods,bioremediation methods,and physical-chemical methods,each of which has its own advantages and disadvantages at present.However,the superiority of the membrane method for treating heavy metal ions in wastewater has gradually emerged in the process of development,as the membrane preparation process is simple,reusable and has a small footprint without secondary pollution.In this experiment,citric acid modified β-cyclodextrin modified graphene oxide(CA-CD/GO)hybrid membranes were prepared by sol-gel method to recover Cu(II),Ni(II)and Pb(II)from electroplating wastewater.In this experiment,β-cyclodextrin was first modified by hydrothermal method using citric acid and then cross-linked with graphene oxide and silane coupling agent(WD-51)to prepare the hybrid film,and the prepared citric acid-modified cyclodextrin(CA-CD)material and the prepared hybrid film were characterized and analyzed using cold field emission scanning electron microscope,energy spectrum analyzer,surface roughness tester,thermogravimetric analyzer and infrared spectrometer.characterization and analysis.The adsorption performance of the prepared CACD/GO hybrid membranes was investigated for Cu(II),Ni(II)and Pb(II)under controlled p H,temperature,time and concentration conditions,and the experimental data were used to study the adsorption mechanism of CA-CD/GO hybrid membranes during the adsorption process.kinetics to study the adsorption process of CA-CD/GO hybrid membrane is following the pseudo-second-order kinetic model,further proving that the membrane is adsorption of metal ions is chemisorption;using the relationship between concentration and adsorption amount to study the adsorption isotherm model,by comparing the Langmuir adsorption isotherm model and Freundlich adsorption isotherm model,the A～F hybrid membrane is more consistent with the isotherm adsorption model of L,indicating that the adsorption belongs to monolayer adsorption,G hybridized membrane is more consistent with F isothermal adsorption model,and surface G is multilayer adsorption.Among them,the value of 1/n of G membrane is 1.389,which is greater than 0.5,indicating that the rate of adsorption is the slowest;using the relationship between temperature gradient and adsorption,the thermodynamic model is explored,and based on the Gibbs free energy change(△G<0),standard enthalpy change(△H>0)and standard entropy change(△S>0)it can be further concluded that the CA-CD/GO hybrid membrane for Cu(II),Ni(II)and Pb(II)metal ions is a non-spontaneous adsorption reaction,and the membranes can enhance the adsorption of Ni ions on the hybrid membranes by appropriate temperature increase within the controlled temperature range.After the adsorption mechanism of the hybrid membrane was clearly explored,it was further explored that the adsorption capacity of the hybrid membrane was generally enhanced when the environment of the adsorbed water in which the hybrid membrane was located was oscillatory,and it was also explored that the hybrid membrane had preferential selective adsorption for Cu(II)when multiple metal ions coexisted.Finally,desorption experiments of the hybrid membranes were conducted to investigate the reusability of the hybrid membranes by using hydrochloric acid,nitric acid,EDTA and mixed solutions of hydrochloric acid and silane coupling agent to desorb the adsorbed hybrid membranes,respectively. |
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