Preparation Of Modified Iron-based Composites And Their Photo-assisted Catalytic Degradation Properties Of Orange ?

With the rapid development of China's printing and dyeing industry,more and more new types of additives with complex ingredients and difficult degradation enter the water body and cause water pollution.Those printing and dyeing wastewater pose a serious threat to people's living environment and health.Due to the improvement of pollution control standard and the growing demand for environmental protection,the treatment of printing and dyeing wastewater has aroused the interests of vast scientific researchers.The photo-Fenton-like technology,which has the advantages of universal applicability and strong oxidation ability,has received widespread attention.On the basis of discussing the sources,hazards and treatment methods of printing and dyeing wastewater,this paper briefly introduces the Fenton technology with mild reaction conditions,simple operation and strong pollution control ability.Orange ? solution is selected as the simulated dye wastewater.Several heterogeneous iron-based composites were prepared by using ion doping,heterogeneous construction and composite strategies and they were used for the degradation of Orange ?.At the same time,the possible mechanism and pathway for the degradation of Orange ? were analyzed.The specific research contents are as follows:1.The Mn₃O₄-FeS₂/Fe₂O₃ composites were prepared by a solvothermal method.The effect of Mn²⁺introduction on the crystal form and morphology of the catalyst was studied.Degradation experiment results showed that the sample with a manganese-iron molar ratio of 1:2 exhibited higher activity than others.The degradation rate of 20 mg/L Orange ? reached 99.0%within 18 min under the conditions of 0.3 g/L Mn₃O₄-FeS₂/Fe₂O₃,5 mM H₂O₂ and pH=2.8.In addition,the Mn₃O₄-FeS₂/Fe₂O₃ heterostructure catalyst shows excellent stability and the ability to degrade other dyes.Fenton reaction performance was enhanced by retarding the recombination of photogenerated charge carriers and accelerating the cycle between Fe³⁺/Mn²⁺and Fe²⁺/Mn³⁺.Finally,the pathway of Mn₃O₄-FeS₂/Fe₂O₃ activated H₂O₂for the degradation of Orange ? were proposed according to the results of liquid chromatography-mass spectrometry?LC-MS?.2.The FeS₂-Fe_1-xS heterostructure catalyst was prepared by solvothermal method through adding cobalt element to change the particle nucleation process and inhibit the transformation process of pyrrhotite(Fe_1-xS)phase to pyrite?FeS₂?phase.Orange ? degradation experiments exhibited that 99.9%degradation rate was reached for 30 mg/L Orange ? solution within 15 min under the conditions of 0.2 g/L FeS₂-Fe_1-xS,2 mM H₂O₂ and pH=3.0.After eight cycles,the degradation efficiency of Orange ? can still reach 95.2%.Combined with the free radical suppression experiments and the detected intermediate products,the mechanism and pathway for the degradation of Orange ? in the FeS₂-Fe_1-xS/H₂O₂ photo-Fenton-like system were proposed.3.?-Fe₂O₃/Cu₂O?SO₄?composite catalysts were prepared by hydrothermal synthesis and calcination treatment and they were applied to the photo-Fenton-like system.Degradation experiments indicated that 98.9%degradation rate was reached for 50 mg/L Orange ? solution within 15 min under the conditions of 0.3 g/L Cu₂O?SO₄?-Fe9,3 mM H₂O₂ and pH=3.5.In the Cu₂O?SO₄?-Fe9/H₂O₂photo-Fenton-like system,the degradation rate constants of Cu₂O?SO₄?-Fe9 are 9.33and 4.07 times of Cu₂O?SO₄?and?-Fe₂O₃,respectively.The mechanism and pathway for the degradation of Orange ? were proposed based on the inhibition of active radicals,the changes in transition state of metal elements on the catalyst surface and the detected intermediate products in the Cu₂O?SO₄?-Fe9/H₂O₂ photo-Fenton-like system.