Study On Refractory Organics Removal By Green Rust

Green rust(GR)is one kind of structural iron hydroxide with high chemical reactivity.It has great potential in water environment remediation and pollutant reduction.Sine there are few domestic researches on GR,in this study,GR was synthesized by the co-precipitation and semi-batch drop method,removal efficiency and removal influencing factors of methyl orange and nitrobenzene by GR were investigated,and reaction and removal mechanisms were analyzed.The main conclusions are as follows:(1)SEM,TEM characterization show that GR synthesized by the co-precipitation method contained a large number of acicular by-products and ferric hydroxide,while GR synthesized by semi-batch drop method had higher purity,mainly being composed of amorphous and hexagonal product;(2)Methyl orange could be effectively decolorized by GR.Under the condition that methyl orange concentration was 20mg/L and pH was 7,the removal efficiency of methyl orange reached 98%;pH had great effect on the removal efficiency.Under the condition of methyl orange concentration of 100mg/L,when the pH increased from 4 to 11,decolorization efficiency of methyl orange increased from 42% to 81%;by monitoring COD removal,decolorization efficiency variation and full wavelength scan detection during the whole reaction process,it can be concluded that methyl orange removal by GR was mainly attributed to adsorption effect and the adsorption process accords with Freundlich law.when the temperature is 20 ?,adsorption isotherm is y=0.13x+1.31;Under neutral conditions,heterogeneous Fenton system composed by GR and H2O2 was used to degrade methyl orange,the decolorization and COD removal efficiencies reached 85% and 61% respectively.Compared with traditional Fenton reaction,heterogeneous Fenton expends the reaction pH.(3)Nitrobenzene could be degraded by GR effectively,when the initial concentration of nitrobenzene was 50mg/L and the reaction condition of pH was 7,the removal efficiency reached more than 95%;pH had the great effect on nitrobenzene removal,under the condition of initial concentration of nitrobenzene 200mg/L,when pH increased from 4 to 11,nitrobenzene removal efficiency increased from 24% to 70%;By detecting COD variation and analyzing reaction product with GC-MS scan,it indicated that nitrobenzene removal by GR was reduction reaction,and the reduction product was aniline,Nitrosobenzene and so on;The XRD characterization for GR after reaction showed that the GR almost transformed into magnetite and goethite due to the redox reaction.With interlayer anions of organic anions,organic GR has more stable layer structure compared with inorganic GR.If the organic GR is used for Fenton reaction,it can keep the structure unchanged and can be reused.In this study,organic GR was synthesized and its effect on methyl orange and nitrobenzene removal was investigated.It was found that the adsorption efficiency for methyl orange and reduction efficiency for nitrobenzene was not as good as that of inorganic GR.When organic GR was used in Fenton-like reaction to degrade the above two kinds of organic compounds,almost no removal effect was observed,and further study is needed on this experimental phenomenon.