Preparation Of Novel Metal Oxide Nanomaterials For The Adsorption And Degradation Of Dyes

With the rapid development of the global economy and modern industry, waterpollution problems have become increasingly prominent, and have become a great problemin the world. Water pollutants, especially for the drainage of dye wastewater have become atremendous harm to human and eco-environment. Therefore, in order to protect humanhealth and eco-environment so as to realize the sustainable development, it is of greatsignificance to effectively deal with these dyes wastewater.In order to remove the dye pollutants from the wastewater, some physical, chemical,biological methods (such as adsorption, ion exchange, chemical catalytic oxidation,biodegradation, photocatalysis and nanofiltration, etc.) have been widely studied. Adsorption,photocatalysis and advanced oxidation processes which were used in this paper are threeeffective treatment of dye wastewater. However, there are still some problems existed inthese three methods, i.e.low adsorption capacity, difficult recovery, and lowutilization rate oflight and poor stability.Therefore, based on a large amount of existing literatures, the preparation of severalnovel metal oxide nanomaterials as high efficient, environmental sewage treatment agentscan effectively improve some disadvantages of the above-mentioned adsorbent and catalyst.Also, in this paper, we carried out a systematic study on the structure, morphology, growthmechanism, performances and other aspects of the nanomaterials‘preparation. Based onexperimental researches and the study of the mechanism, the main studies of this paper areas follows:(1) A series of CoFe2xMxO4(M=Al3+, In3+and Cu2+) ferrites were synthesized by afacile hydrothermal method, and their adsorption capacity of the Congo red were compared.On the premise of spinel structure, the coercive forces and adsorption capabilities of thedoped CoFe2O4ferrites are significantly enhanced. Compared with the magnetic properties of pure cobalt ferrite, we speculate that the Al3+ion occupied on the tetrahedral A‘siteswhile both In3+and Cu2+ions occupied on octahedral B‘sites. Physical adsorption is themain adsorption property. It is first reported that coercive field of magnetic material showsmore important influence on the adsorption capacity than that of specific surface area. Watermagnetized mechanism was proposed to explain the relation between the coercive field andadsorption capacity. The as-prepared CoFe2xMxO4ferrites with excellent magnetism can beused as a reusable absorbent for fast, convenient, and highly efficient removal of dyes fromthe wastewater. In the all samples, In3with the largest coercive force of2014.2Oe possessedthe highest CR adsorption capacity (605.4mg g1).(2) A facile hydrothermal method combined with a mild ultrasonic means has beendeveloped for the fabrication of magnetically recyclable thin-layer MnO2nanosheet-coatedFe3O4nanocomposite. The photocatalytic studies suggest that the MnO2/Fe3O4nanocomposite shows excellent photocatalytic efficiency and stability simultaneously for thedegradation of methylene blue (MB) under UV-vis light irradiation. Magnetic measurementsverify that the MnO2/Fe3O4nanocomposite possesses ferromagnetic nature, which can beeffectively separated for reuse by simply applying an external magnetic field afterphotocatalytic reaction. Moreover, its well acid-resistance and stable recyclability are veryimportant for the future practical application as photocatalyst.(3) A general one-pot hydrothermal synthesis was used to prepare Mn3O4reducedgraphene oxide (rGO) hybrid with narrow size-distribution and good dispersion.Its potentialapplication inheterogeneous activation of peroxymonosulfate (PMS) to degrade an azo dye(Orange II) was carefully investigated. Compared with single Mn3O4or rGO, theMn3O4rGO hybrid shows a much higher catalytic activity due to synergistic catalysis. And,100%decomposition could be achieved in90min with30mg·L1of Orange II,0.05g·L1of Mn3O4rGO, and1.5g·L1of PMS. In addition, the degradation mechanism of Orange IIby Mn3O4rGO/PMS system was proposed. Meanwhile, inductively coupled plasmaanalysis revealed that the leach of manganese ions was low. Through the stability test, thehybrid catalyst exhibited stable performance even after four successive runs of regeneration.