Degradation Of Methylene Blue Based On Fe Sustained-release Fenton Process

Fenton process is widely used to treat organic wastewater with high chromaticity,high toxicity,poor biodegradability due to its strong oxidation and fast reaction.However,it is difficult to recycle and produces iron-containing sludge,hindering the engineering application.In order to solve these problems,a heterogeneous Fenton process was proposed on the degradation of dye wastewater in this study.In this paper,oolitic hematite and Yeshan limonite were used as solid iron sources,zero valent iron?ZVI?,hematite sulfide?SH?,zero valent iron sulfide?SZ?and limonite sulfide?SL?were prepared by hydrogen reduction and sulfurization as heterogeneous catalysts.XRD,XPS,FTIR and SEM were utilized to analyze the crystal structure,phase composition and microstructure of samples.Methylene blue?MB?was chosen to be the target pollutant,ZVI,SH,SZ and SL were as catalysts to catalyze hydrogen peroxide.The influence factors and mechanism of degradation of MB using these catalysts were discussed.The main research results are as follows:?1?The activation of hematite was conducted via thermal treatment in hydrogen atmosphere to form ZVI.The results showed that the degradation effect was the best when the ZVI dose is 69 mg/L,H₂O₂ concentration is 5.0 mmol/L and initial p H is 3.0,approximately 100%of colour was removed,and 47%TOC removal was achieved.The BMG kinetic model can describe the degradation of MB well.Furthermore,after cycled7 times,the decolorization efficiency had decreased by 6%,which implies an excellent stability.The mechanism analysis showed that Fe²⁺released by ZVI catalyzed H₂O₂,and the generation of HO·is important and was essential in the degradation of MB.?2?The activation of oolitic hematite,ZVI and Yeshan limonite were conducted via thermal treatment in hydrogen sulfide atmosphere to obtain SH,SZ and SL.The results showed that SH dose is 200 mg/L,H₂O₂ concentration is 12.5 mmol/L;SZ dose is 150mg/L,H₂O₂ concentration is 12.5 mmol/L;SL dose is 50 mg/L,H₂O₂ concentration is 1.0mmol/L,and the degradation effect was the best when the p H value was 3.The degradation efficiency increased along with increasing reaction temperature and the degradation process of MB followed the first-order kinetic model.Each system can continuously released Fe²⁺under acidic conditions and quenching experiments showed that the HO·produced by the system was the main reason for the degradation of MB.Moreover,the degradation efficiency?80%,90%,90%?remained pretty well after the running 5 cycles,exhibiting high recycling performance.?3?Combined with the experimental results of chapter 3 and chapter 4,through the comprehensive comparison of MB decolorization efficiency,p H value adaptability,TOC removal and other related parameters and in combination with the reaction rate?k₁?of first-order kinetic parameters,catalyst dose,H₂O₂ concentration and reaction time,the catalytic capacity of ZVI,SH,SZ and SL is from strong to weak:SL>ZVI>SZ>SH.Through XRD results in the chapter 4,limonite is an iron manganese mineral with nanostructure,low crystallinity and high activity,which is the reason why the catalytic effect of SL is better than that of ZVI,SZ and SH.