Construction And Catalytic Performannce Of Functional ZSM-5 Composites Synthesized From Coal Gangue

ZSM-5 is a kind of microporous material with high Si/Al ratio,large specific surface area and special pore structure.ZSM-5 have attracted a great deal of attention due to its good adsorption,selectivity and hydrothermal stability.However,the raw materials for synthesis of ZSM-5 are still relatively expensive,so it is very important to find some alternative silicon and aluminum sources.Moreover,the application of ZSM-5 in oxidative degradation of water pollutants is still not remarkable and extensive.Therefore,it is an inevitable trend for ZSM-5 to realize its application in the field of environment by means of various modification methods to improve its efficiency in wastewater degradation.Microporous and hierarchical ZSM-5 was successfully synthesized through hydrothermal method using gangue as silicon and aluminum sources.The comparison of adsorption property toward various dyes between microporous and hierarchical ZSM-5 was conducted.Furthermore,the degradation efficiency of ZSM-5 toward water pollutants was enhanced through loading metal oxide or noble metal.The modification method consisting of metal oxide and the noble metal loading to improve the efficiency of ZSM-5 in degradation of pollutants.The mechanisms of Fenton-like reaction and photocatalysis assisted SO₄^·-reaction and the recyclability of the materials were discussed.Microporous ZSM-5 was synthesized by calcination,acid leaching,alkali dissolution and hydrothermal crystallization using coal gangue as raw material.Hierarchical ZSM-5 was also synthesized in the presence of cetyltriethylammnonium bromide?CTAB?.The physicochemical properties of these two kinds of ZSM-5 were investigated by X-ray diffractometer?XRD?,specific surface area?BET?,scanning electron microscope?SEM?,transmission electron microscopy?TEM?,X-ray fluorescence?XRF?and Zeta potential techniques.The adsorption experimental results showed that these two kinds of ZSM-5 exhibited excellent adsorption performances toward positively charged dyes.This is mainly due to their rich surface negative charges,large specific surface area and unique pore structures.A series of Cu modified ZSM-5 catalysts?Cu/ZSM-5?were prepared by using ZSM-5 as support to mineralize phenol by heterogeneous Fenton-like reaction.The characterization results showed that copper existed as doping Cu ions and copper oxides on the surface of ZSM-5.There was no obvious change on MFI structure of ZSM-5 by loading modification.Catalyst 7%Cu/ZSM-5 displayed excellent degradation and mineralization properties toward phenol.It could completely degraded phenol within 30 min and the TOC removal value was 63%within 60 min.·OH and ¹O₂ played the important role in the Fenton-like reaction and the redox cycle of Cu²⁺/Cu⁺promoted the generation of active radicals.A series of copper-silver co-loaded ZSM-5 catalysts?Cu-Ag/ZSM-5?were prepared by using ZSM-5 as support to degrade tetracycline hydrochloride?TC?in through persulfate reaction under visible light irradiation.The results showed that the loading modification had no significant effect on the MFI structure of ZSM-5.The XPS analysis indicated that the silver and copper existed in the form of Ag⁰ and Cu²⁺,respectively.Catalyst 15%Cu-5%Ag/ZSM-5 displayed excellent catalytic performance toward tetracycline and it could degrade 75%TC within 60 min under visible light irradiation.The ESR and radical trapping experiments showed that·OH and SO₄^·-acted the dominant roles in the persulfate reaction system under visible light irradiation.In combination with the results of XPS,ESR,electrochemical tests and catalytic experiments,Cu⁺and Cu²⁺coexisted in the ZSM-5 support after catalytic reaction.The redox cycle of Cu⁺/Cu²⁺induced the separation and transfer of electrons and holes to produce active radicals.Noble metal Ag improved the separation and transfer of electrons and holes,which further enhanced the catalytic performance.