Preparation Of Reduced Graphene Oxide And Sodium Alginate Composite Membrane And Its Adsorption Properties Of Heavy Metal Ions

With the progress of science and technology,the rapid development of the industry has been promoted.The wastewater produced in the process of industrial production causes pollution to the environment.Especially the heavy metal ions existing in wastewater,which is non-biodegradable,and accumulated to a certain amount will cause harm to human health and the ecosystem.Therefore,the treatment of heavy metal ion in contaminated water became the focus of attention.There are many methods to remove heavy metal ions in contaminated water,such as chemical sedimentation,biological separation,electrochemical technology,membrane technology and adsorption,etc.Among them,adsorption has become a promising technology due to its high efficiency,low cost and no secondary pollution.With the rapid development of graphene,due to its excellent properties are widely used in various fields.The preparation study of graphene adsorbent is still in the initial stage.But because the hydrophobicity of the graphene membrane forms a water film in the adsorption process,which hinders its adsorption of heavy metal ions.The structural stability of the film itself is low.Thus making its application in contaminated water treatment is limited.To solve this problem,this paper studied membranes modified by crosslinking.In order to improve its structural stability and adsorption properties,the main contents of this paper are as follows:(1)In this paper,graphene oxide(GO)nano sheet was used as the substrate.Self-supported Go membranes were prepared by vacuum filtration.Self-supported reduced graphene oxide films(rGO)were prepared by the chemical reduction.The optimal condition for reduced the GO membrane is reduced concentration of 40 g L-1 and a reduction of 50 min at 80℃.The strength of five masses rGO films was 5.740,10.981,14.084,17.498 and 18.560 MPa,and the maximum adsorption capacity of rGO films to Cd2+,Cu2+ and Pb2+ was 62.37,150.08 and 170.49 mg·g-1.(2)In order to improve the hydrophobicity and structural stability of the rGO film,and to improve its adsorption,the performance of the GO film should be improved first.Adding a small amount of sodium alginate(SA)to the GO aims at promoting its adsorptive properties.But with only a weak hydrogen bond binding force between the GO and the SA,the GO/SA/Mg2+composite membrane was prepared to improve the binding force of the GO/SA membrane.The adsorptive performance of GO/SA composite membrane containing 8 wt%SA is good judging from the mixed heavy metal ion adsorption experiment.The adsorption performance of GO/SA/Mg2+ membrane containing 0.12 wt%magnesium ions is good.The intensity values of GO/SA/Mg2+ membrane is 9.370,11.701,15.842,18.430 and 19.993 MPa,respectively.The maximum adsorptive capacity of Langmuir to Cd2+and Pb2+ adsorbed by GO/SA/Mg2+ membrane reached 79.54 and 182.3 mg·g-1,respectively.(3)The GO/SA/PDA composite membrane was prepared by covalent bond crosslinking(crosslinker 1,2-Propanediamine(PDA))into GO/SA membranes.The adsorption performance of GO composite film containing 0.16 wt%ammonia is good judging from the mixed heavy metal ion adsorption experiment.The intensity values of the GO/SA/PDA membranes were 11.510,12.80,17.745,21.930 and 24.179 MPa,respectively.The maximum adsorption capacity of Langmuir to Cd2+and Pb2+ by the GO/SA/PDA membranes is 87.09 and 189.25 mg·g-1.(4)The comparison of the GO composite membrane properties crosslinking by the two methods showed that the GO/SA/PDA performed well,and the GO/SA/PDA complex membrane was then reduced to the rGO/SA/PDA composite membrane.The mass of the rGO/SA/PDA membrane was 5.4,6.5,7.7,8.9 and 10.3 mg,respectively,with strength values of 12.107,13.157,19.350,24.221 and 27.010 MPa;The rGO/SA/PDA membrane maximum Langmuir adsorption capacity for Cd2+,Cu2+and Pb2+ was 96.27,205.16 and 214.29 mg·g-1,respectively.In conclusion,GO membranes were effectively modified to the GO composite membrane by different crosslinking methods and reduced prepare into rGO composite membrane.According to the comparison of the four films,the structural stability and adsorption performance of rGO film is better than GO film,but the adsorption time of GO composite film is shorter than rGO menbrane.The composite film prepared by cross-linking modification is better than properties of pure film.Properties of GO/SA/PDA are stronger than GO/SA/Mg2+.The adsorption of the four films is mainly chemical adsorption.In addition to rGO membrane adsorption process is multilayer adsorption,and the other three films are monolayer adsorption.The results of this paper confirm that this crosslink modification method is effective and improves its structural stability and adsorption properties.Therefore,cross-modified rGO composite membrane materials provide a scientific basis and technical support for the application of environmental protection and wastewater treatment.