Removal Of Nitrobenzene In Wastewater By Zeolite-supported Nanoscale Zero-Valent Iron/Ni

Nitrobenzene(NB)has wide range of applications,but,because of its high toxicity,stable properties and resistance to biological degradation of NB,it has serious harm to the environment.The conventional treatment process for NB wastewater has many problems,such as high cost,difficulty,unstable effect and secondary pollution.nanoscale Zero-Valent Iron(n ZVI)has a significant effect on NB wastewater treatment,and the cost is controllable.The degradation product is aniline which can be easily degraded by microorganisms.However,due to its strong activity,high surface energy and ferromagnetism,n ZVI is prone to agglomeration and oxidation,which reduces its reaction performance and affects its application in environmental governance.The stability and reactivity of iron nanoparticles can be improved by some modification methods.In this paper,zeolite supported nanoscale Zero-Valent Iron(n ZVI-Z)was prepared by impregnation-liquid phase reduction method using activated zeolite as carrier and polyethylene glycol 4000(PEG-4000)as dispersant.Then Zeolite supported nanoscale Zero-Valent Iron/Ni(n ZVI/Ni-Z)was prepared by double-solvent impregnation-liquid phase reduction method after the doping of Ni to optimize n ZVI-Z.The morphology,structure and chemical composition of the two materials were characterized by various means,and the removal effect of NB on the two materials was investigated.The main results were as follows:(1)The two materials were characterized by XRD,SEM,BET,XPS,FTIR and other means.The characterization results of n ZVI-Z showed that zeolite as the carrier could effectively weaken the agglomeration of n ZVI particles,and the n ZVI particles were uniformly distributed on the zeolite material in the form of small balls or short chains.The specific surface area of the synthesized n ZVI-Z material was large;Iron was oxidized to a lesser degree and mainly existed in the form of zero valence.The results of n ZVI/Ni-Z characterization showed that the n ZVI/Ni bimetal had good dispersion and was uniformly loaded on the surface of zeolite in the form of small spherical particles.The specific surface area of the synthesized n ZVI/Ni-Z material was slightly higher than that of n ZVI-Z,and the reactivity was improved.Iron and nickel existed mainly in the form of zero valence(2)The experiment of NB removal showed that n ZVI-Z composite material has an excellent effect on NB removal compared with n ZVI and zeolite.Under the experiment conditions of Fe loading 20%,dosage 2.0 g/L,initial concentration of NB20 mg/L,initial p H 7.0,temperature 25 ℃,reaction time 60 min,the NB removal rate of n ZVI-Z was 92.2%.The composite of n ZVI/Ni-Z with higher reactivity was prepared by introducting Ni to form nano-bimetal.Under the experiment conditions of Fe loading 20%,Ni loading 1%,dosage 2.0 g/L,initial concentration of NB 20 mg/L,initial p H 7.0,temperature 25 ℃,reaction time 60 min,the NB removal rate of n ZVI/Ni-Z was 94.8%,the amount of Ni metal dissolved in the solution was very small,and the amount of Fe metal dissolved in the solution decreased significantly compared with n ZVI-Z,which proved the stability was improved.The results of the repeatability experiment showed that n ZVI/Ni-Z has better reusability and stability.NB degradation products were detected by gas chromatography-mass spectrometry(GC-MS).It was concluded that the final product of NB degradation was aniline,and NB,phenylhydroxylamine,azobenzene and azobenzene oxide were the intermediate products of the reaction.NB was degraded by n ZVI/Ni-Z through reduction,in which n ZVI was the electron donor and Ni was the reaction catalyst.In conclusion,the composite n ZVI-Z has good dispersion and high reactivity;and the reaction performance and stability of the composite doped with Ni are improved,and n ZVI/Ni-Z has great potential in the treatment of NB wastewater.