Study On The Photoelectro Catalytic Degradation Of Environmental Pollutants Carbofuran And Rhodamine B

Nowadays, the kinds and discharge of sewage and industrial wastewater are increasingrapidly and their composition become more complex, which contains a lot of refractoryorganic pollutants. Carbofuran and Rhodamine B are typical forms of organic syntheticpolymer pollutants. Due to a wide use of these pesticides and organic dyes in recent years, thedamages caused by carbofuran and rhodamine B increased increasingly. Hence, it is urgent todevelop rapid easy-to-use, robust, and cost-affective techniques for the removal of carbofuranand rhodamine B in water. Nanomaterials, due to their large specific surface area, small size,excellent optical properties, have unique advantages in the fields of environmental toxicorganic pollutants degradation. In this paper, we have studied the applications ofnanomaterials in the field of catalytic degradation of pollutants, which could be divided intothree aspects as follows:（1） In this paper, the degradation of carbofuran with graphene oxide-ferroferricoxide-hemoglobin （GO-Fe₃O₄-Hb） composite in an electrochemical-enzyme system wasreported. The graphene oxide-Fe₃O₄-hemoglobin composite was fabricated by a two-stepprocess. First, graphene oxide-Fe₃O₄（GO-Fe₃O₄） composite was prepared via a simple andeffective chemical precipitation method. Then, hemoglobin was covalently immobilized ontothe graphene oxide-Fe₃O₄by glutaraldehyde （GA）. The prepared grapheneoxide-Fe₃O₄-hemoglobin composite was added into a membraneless electrochemical reactorto form an electrochemical-enzyme system for carbofuran degradation. Results indicated thatcarbofuran can be easily degraded by electro-enzymatic method. Under the optimumconditions, the removal efficiency of carbofuran was about94.6%. The grapheneoxide-Fe₃O₄-hemoglobin composite showed improved enzyme thermal stability and had awide active pH range. Furthermore, the graphene oxide-Fe₃O₄-hemoglobin composite can beeasily separated under a magnetic field from the reaction solution, which greatly decreases thecost of the enzyme in the practical applications.（2） Ag₂WO₄/Zn-Cr layered double hydroxides （LDHs） composite has been successfullysynthesized via a facile anion-exchange precipitation reaction method by adding AgNO3solution into WO4anions intercalated Zn-Cr LDHs suspensions. X-ray diffraction （XRD）,field emission scanning electronic microscope （FESEM）, X-ray photoelectron spectroscopy（XPS）, and Fourier Transform Infrared （FT-IR） were used to characterize the products. It wasfound that Ag₂WO₄particles were highly dispersed on the surface of Zn-Cr LDHs materialson a large scale. The photocatalytic degradation studies on Rhodamine B （RhB） indicate that Ag₂WO₄/Zn-Cr LDHs composite shows much higher visible-light-driven photocatalyticactivities for degradation of organic pollutants than Ag₂WO₄and Zn-Cr LDHs. The possiblephotocatalytic mechanism is also discussed. This work provides a facile approach to fabricatenovel types of visible-light-induced photocatalysts for environment treatment.（3） A novel composite photocatalyst Ag/AgCl/Zn-Cr layered double hydroxides （LDHs）was prepared by a facile anion-exchange precipitation method via the reaction of Zn-Cr-ClLDHs and AgNO3, during which Cl anions in the interlayer of LDHs are consequentlyreleased and reacted with Ag ions to form AgCl. X-ray diffraction （XRD）, field emissionscanning electronic microscope （FESEM）, transmission electron microscopy （TEM）,high-resolution transmission electron microscopy （HRTEM）, Fourier Transform Infrared（FT-IR） and UV-vis diffuse reflectance spectra were used to characterize the products. It wasfound that Ag/AgCl particles were uniformly grown on the surface of Zn-Cr LDHs materialson a large scale, and the composite shows well visible-light absorption ability. Thephotocatalytic degradation studies on Rhodamine B （RhB） indicate that Ag/AgCl/Zn-CrLDHs composite shows enhanced visible-light photocatalytic abilities for degradation oforganic pollutants than Ag/AgCl and Zn-Cr LDHs. The photocatalytic mechanism wasanalyzed by active species trapping experiments. It revealed that the h+and O2are the twomain reactive species for RhB degradation by Ag/AgCl/Zn-Cr LDHs composite, and theproportion of h+greatly increases compared to that of Ag/AgCl and Zn-Cr LDHs, indicatingthat an efficient charge separation is crucial for the enhancement of the photocatalyticactivities. This work provides an approach to fabricate novel types of visible-light-inducedcomposite photocatalysts for environment treatment.