| With the development of the society,the social medicine and chemical industry constantly expand.The demand of p-Nitrophenol(PNP),known as the pharmaceutical intermediates and fine chemical products,is increasing dramatically,which is associated with a large number of wastewater containing PNP discharged into the ecological environment and caused serious pollution of surface water and groundwater,even destruction of the ecological environment seriously.The PNP is widely used and has rich sources but is difficult to degrade account for the the conjugate effect of nitro,hydroxyl and benzene ring.Also the degradation products of nitroso and hydroxylamine are cancerogens.The gaseous PNP can be adsorbed by respiratory system and skin which may lead to giddy,vertigo and skin empurples.It can lead to respiratory obstruction,lower blood pressure,weakened pulse and even death at high concentration of PNP.In addition,PNP can be enriched in aquatic organism which is difficult to remove and can cause severely damage to the ecology.Therefore,it is of great significance to explore a safe,efficient,and stable method for removing PNP.As a green and efficient material,nano-Zero-Valent Iron(nZVI)has been increasingly used to remove many environmental pollutants as heavy metals,halogenated organic,aromatic organic and so on.However,due to easy agglomeration,loss,and oxidation,it has greatly limitation on its development and practical application.The sulfidation of nZVI(S-nZVI)can not only improve the reaction activity but also weaken the oxidation.Additionally,bentonite is a kind of non-metallic minerals with strong ion exchange and large specific surface area.China possess rich bentonite in reserves and has a long history of development and utilization.The loading of nZVI onto bentonite can increase its stability and the dispersion of nZVI particles and weaken its agglomeration effect,which can greatly increase the practical application value of nZVI.The commonly used methods for removing PNP are physical,biological,and chemical methods now.The physical methods mainly include:adsorption method and extraction method,biological methods mainly include:biofilm method and activated sludge method and chemical methods as the most common method contain electrochemical oxidation,advanced oxidation and catalytic addition.Each method has its own advantages and disadvantages.It is necessary to choose suitable methods according to local conditions to achieve efficient and practical results.The main research contents of this paper include:preparation of s S-nZVI supported on bentonite and the influence of different S/Fe molar ratio,loading rate on the activity of the material,through specific surface area,scanning electron microscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy to characterize the properties of the composite.In addition,the influence of the composite on the removal of p-nitrophenol was studied under different conditions,and its removal mechanism was preliminary discussed by full wavelength scanning and gas chromatography-mass spectrometry(GC-MS).The main results are as follows:(1)The composite material has the strongest reactivity when the molar ratio of S/Fe is 0.0112 and the loading rate is 50%.(2)The rate of removal rate of PNP by bentonite-supported S-nZVI gradually decreased with the increasing pH.(3)Sodium sulfate can promote the removal of PNP by bentonite-supported s S-nZVI.(4)The hydroxyl radicals were generated during the removal process and participate in the removal of PNP reaction.(5)Bentonite-supported S-nZVI can reduce PNP to p-aminophenol and also can oxidize p-aminophenol to p-benzoquinone.(6)The composite material has a certain adsorption effect on the removal of PNP. |
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