Catalytic Activity Of Green Synthesized Iron Nanoparticles For Fenton-like Reaction To Degrade Dye Wastewater

Water is essential for human survival and development.A large number of industrial wastewater generated by printing factories discharging which broke the ecological balance and brought great pressure to the environment.Especially the dye wastewater,which is ranked as one of ornanic wastewater.It is difficult to degareding due to its color and it has caused serious damage to water resources with high toxicity.In recent years,Fenton technology,especially improved Fenton technology or Fenton technology combined with other technologies/methods have received many concerns in the field of sewage treatment.Fenton technology has advantages of its simple operating,wide application of pollutants and high degradation efficiency.The most common one is Fenton system with iron catalyst,which was limited by severe pH conditions and secondary pollution of iron mud.In view of the above problems,iron nanoparticles were prepared by Dimocarpus longan extract aqueous under mild and green conditions,without addition of any chemical reagents except for metallic precursors.The obtained iron nanoparticles were characterized,and its performances on methyl orange(MO)removal in Fenton-like system were investigated.Dimocarpus longan leaves in Fujian Province were selected as plant extracts.By analyzing content variation of polyphenols under different extraction condition,an optimum conditions was found to be heating at 80 ℃ for 1 hour.Then we prepared the iron nanoparticles(DL-Fe NPs)by ferric chloride and Dimocarpus longan extracts,and compared DL-Fe NPs with chemosynthesized Fe NPs by means of UV-Vis,TEM,XRD and FTIR.The results showed that DL-Fe NPs were amorphous spherical particles with average size of about 5 nm and it had good dispersibility and stability.As a Fenton catalyst,HO· was released from H2O2by DL-Fe NPs,which could degrade MO effectively.DL-Fe NPs has a better catalytic activity than chemosynthesized Fe NPs.Choosing MO as degradation substrate of Fenton catalytic oxidation system,theeffects of H2O2 dosage,concentration of catalyst,initial pH value,temperature and other factors on the degradation of MO by Fenton-like reaction were investigated.The obtained appropriate conditions were:11.1 mg/L DL-Fe NPs for the treatment of MO solution with concentration of 150 mg/L,30 ℃ and without any pH adjustment.Under this condition,MO removal rate could reach 98%in 30 min.In addition,the process is in accordance with the pseudo-first-order kinetic model and the activation energy is 41.6 kJ/mol.Based on the analysis of FTIR and the removal of MO under different reaction conditions,the process of MO degradation includes adsorption,catalysis of H2O2 to release HO·,and HO· attacking MO to break down its chemical bonds then MO decomposed into small molecules.Besides,we found that DL-Fe NPs could maintain stable in morphology,structure and catalytic activity of Fenton-like reaction in four weeks.Moreover,it can degrade a series of representative dyes,reflecting a certain degree of universality in degradation of dyes.Furthermore,DL-Fe/Ni NPs,DL-Fe/Cu NPs,DL-Fe/Pd NPs were synthesized and then added into Fenton-like system to remove MO.The results showed that DL-Fe/Pd NPs has a better performance than DL-Fe NPs.Characterizations such as UV-Vis,TEM,XRD and FTIR showed that DL-Fe/Pd NPs were amorphous spherical particles with average size of about 5 nm and had good dispersibility and stability.The effects of H2O2 dosage,catalyst concentration,initial pH value,temperature and other factors on the degradation of MO by Fenton reaction were investigated.The obtained appropriate conditions were:11.1 mg/L DL-Fe/Pd NPs(Pd wt.%=1%)for the treatment of MO solution with initial concentration of 150 mg/L,30 ℃ and without any pH adjustment.Under this condition,MO removal rate could reach 95%in 10 min.In addition,the process is in accordance with the pseudo-first-order kinetic model too and the activation energy is 34.4 kJ/mol.As Fenton catalyst,the active component in DL-Fe/Pd NPs for catalytic process is still Fe0,the incorporation of Pd does not change the mechanism of the reaction.It only played a synergistic role,which can effectively improve Fenton catalytic activity of DL-Fe NPs.