Study On The Mechanism Of Treating Mining Wastewater By Metal Oxide-based Two-dimensional Materials And Three-dimensional Graphene

Different types of pollutants in mine wastewater seriously pollute water sources and ecological environment.In order to treat the mining wastewater and protect the ecological environment,this paper deals with the organic pollutants,heavy metal ions and oil substances in the wastewater.Firstly,metal oxide nanomaterials were synthesized and loaded into two-dimensional carriers to test their photodegradation performance to organic pollutants.Three-dimensional(3D)graphene is prepared by self-assembly method to treat oil substances and heavy metal ions in wastewater.The following conclusions are drawn:Nano-TiO2,ZnO and SnO2 are synthesized and loaded on two-dimensional templates such as montmorillonite,diatomite,carbon nitride and graphene oxide,respectively.Different types of composites are prepared for the degradation of organic pollutants Rh B and MB in wastewater.Compared with montmorillonite template,TiO2 loaded with 1 mg/mL GO has the best photodegradation activity.The degradation efficiency of RH B is 98.8%at 40 min and 99.3%at 30 min.Among the different templates of nano-ZnO,GO is obviously better than porous diatomite template,while the photodegradation activity of ZnO-based composites prepared by montmorillonite and g-C3N4 template is the worst.ZnO/graphene composite with 1 mg/mL GO as template has the best photodegradation activity.In addition,SnO2/graphene composite with 1 mg/mL GO as template has the best photocatalytic activity,and its photodegradation performance is better than that of SnO2/diatomite composite.It is found that the photodegradation performance of metal oxide/graphene composite is the best,even better than that of commercial P25 photocatalyst.The reason is that graphene can enlarge the light-adsorption range,and the conductive graphene also transfer photogenerated electrons on the surface of metal oxide rapidly and inhibit the recombination of photogenerated electrons and holes.Therefore,graphene-based composites have the best photodegradation activity for organic pollutants,and its performance is obviously better than other inert two-dimensional substrates.Two types of three-dimensional graphene are prepared by diffusion driven self-assembly method and hydrothermal method respectively.The adsorption capacity of 3D graphene material by self-assembly method for diesel oil,gasoline and water-diesel mixture is 123.4g/g,86.5 g/g and 3208.7 mg/g respectively,and their adsorption properties are better than those of graphene aerogel by hydrothermal method under the same conditions.The 3D graphene has an excellent repeatable adsorption performance for gasoline and diesel oil.When used for adsorbing oil substances,the C-C hexagon in 3D graphene is easier to adsorb C10?C22 long-chain diesel,which is obviously better than the adsorption of C4?C12 short chain gasoline.The better oil absorption properties of 3D graphene by self-assembly method mainly depends on its higher specific surface area and smaller pore structure.The adsorption capacity of 3D graphene materials to Pb2+,Cd2+and Cu2+is 561 mg/g,245 mg/g and 223 mg/g,which is significantly higher than graphene aerogel and two-dimensional SnO2/graphene powder.The reason can be ascribed to a large number of carbonyl,hydroxyl and other oxygen-containing groups remaining in 3D graphene sheets,meanwhile,3D graphene has a small pore size and high density,the adsorption of heavy metal ions on 3D graphene prepared by self-assembly method is considered to be a combination of physical adsorption and electrostatic adsorption.