Removal Of 4-chlorophenol In Aqueous Solution By Aluminum-iron Alloy Particles

Halogenated aromatic compounds have been widely used with the rapid development of industry and agriculture.These compounds are highly toxic and have adverse impacts on the environment.They have been discharged into the environment by direct or indirect ways such as evaporation,container leakage,sewage discharge,pesticide usage,product incineration.Oxidative degradation of 4-chlorophenol using aluminum-iron alloy in the presence of dissolved oxygen was investigated.Adsorption,reductive dechlorination by Al-Fe alloy and the direct oxidation of O₂ were found to be negligible in the process.The degradation of 4-CP was inhibited significantly when methanol existed in the solution as OH scavenger,verified ·OH was the activated oxygen species that degrades 4-CP.Because of the massive microscopic galvanic cells formed spontaneously between aluminum and iron within Al-Fe alloy,thus enhancing the electron transfer ability,it was more readily to transfer electrons from alloy to dissolved 02 and in situ generated H2O₂.And the ·OH could be in situ generated by Fenton reaction between H2O₂ and Fe2+ and by reaction between Al and H2O₂ under acid condition.Alloy Al-Fe 10?WAl:WFe=90:10?has a distinct advantage for the removal of 4-CP over Fe,Al or Al/Fe10?physical mixing?.The optimum experimental conditions for the Al-Fe alloy/O₂ system were as follows:Al-Fe10 alloy without pretreatment?40-60 mesh?,addition amount of alloy 5 g·L-1,4-CP initial concentration 50 mg·L-1,initial pH 2.5 and temperature 25±1?.Under these conditions,the removal rate of 4-CP reached 94.6%after 5 h.The robustness of alloy over repeated use of Al-Fe 10 alloy provided further evidence of the stability properties of the alloy,which was conducive to practical use..The simple kinetic analysis showed that the degradation of 4-CP was more consistent with the zero-order kinetics.In the process of studying the reaction kinetics model,the kinetic model of degradation of 4-CP including alloy amount,initial concentration of solution,pH value and temperature was calculated.In this paper,GC-MS and ion chromatography analysis of the product were tested,suggesting that 4-chlorocatechol degradation pathway and hydroquinone degradation pathway were both existed in the oxidation of 4-CP.Al-Fe alloys were used to remove the 4-CP under continuous operation system.Under the optimum conditions,the system reached a stable removal rate 96%,and the system can keep such a high removal rate continuously for one week,which proves the stability of the alloy properties and the feasibility of the experimental device.