| With the development of industry,water pollution is becoming more and more serious.There are a wide variety of toxic heavy metal ions in the water,causing huge hidden dangers to the ecological environment and human health.Hexavalent chromium ions,coming from various industrial activitys like printing and dyeing industry,tanning industry,electroplating etc.,are discharged into water in large quantities,and enriched by the earth’s water cycle and food chain,and finally,they enter the ecosystem and the human body.Hexavalent chromium ions are highly toxic and carcinogenic,and therefore have great harm to the ecological environment and human health.It is found that the toxicity of hexavalent chromium ions is five hundred times great than the trivalent chromium,but trivalent chromium is the essential element for human,so how to reduce the hexavalent chromium ions into low-priced trivalent chromium and gathering is an effective way to solve the pollution of hexavalent chromium ions in wastewater.In this paper,two new types of adsorbents were prepared and their characteristics were characterized.Adsorption experiments were carried out using potassium dichromate as chromium source,and the adsorption principle was explained.The main contents of this paper are as follows:Firstly,GO/MnO2 was prepared by hydrothermal deposition using graphene oxide as a substrate,magnetic separation was performed by introducing Fe3O4,and GO/MnO2/Fe3O4/PPy was prepared by polymerization pyrrole monomer under acidic condition through polymerization reaction.The results of SEM and TEM showed that PPy was coated on the surface of MnO2 nanowires to form core-shell structure.The XRD data showed that GO/MnO2/Fe3O4/PPy had great crystallinity.FT-IR data shows that there were many functional groups on the surface.Chromium ion concentration can be detected by the intensity of absorption peak at 540nm after dyeing through UV.The XPS data prove that there are various elements present in the product,and the hexavalent and trivalent chromium elements were found before and after the adsorbent adsorbed.It is proved that the adsorbent principle is mainly to reduce the hexavalent chromium to the low toxicity trivalent chromium,and the intensity peak of the N element greatly decreases after the adsorption,indicating that the nitrogen group in the material has made a major contribution to the reduction process.The adsorption isotherm and kinetic data fit well with the Langmuir adsorption isotherm and the per-second-order kinetic equation,and the equilibrium adsorption capacity is about 374.5mg/g.Subsequently,we used polyvinyl alcohol particles to prepare polyvinyl alcohol microspheres.With the modification of polyethyleneimine,we found that it has excellent adsorption and degradation performance for hexavalent chromium ions in water,and the chemically modified polyvinyl alcohol microspheres are filled into a thin PVA film made by 5%(MW)polyvinyl alcohol solution,and it can separate easily from the solution.This material was characterized by SEM and FT-IR to verify their morphology and the types of functional groups they carried.Adsorption isotherms and kinetic data all show that they are consistent with Langmuir isotherms and per-second-order kinetic equations,and it has excellent performance in practical applications.Finally,the adsorption principle of the two materials is put forward based on the changes of the XPS data before and after the adsorption.The experimental data also verify our hypothesis.It is hoped that these two kinds of adsorbent materials with excellent degradation performance will make a certain contribution to the future treatment of heavy metal ion wastewater. |
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