Synthesis Of Framework Zinc-substituted A Zeolite And Its Application For Antibacterial Materials

The amount of silver load in Ag-loaded zeolite has a great influence on its antibacterial property.The antibacterial activity and durability of Ag-loaded zeolite are raised with the increasing of Ag content.The structure and property of zeolite can be changed by the zinc introduced into framework,which can improve its ion adsorption and exchange capacity.The antibacterial materials prepared using the zinc-substituted A zeolite as carrier is an effective way to solve the problems of low Ag content and poor durability in the Ag-loaded zeolite.Zinc-substituted A zeolite was prepared by the hydrothermal method and single-mode focused microwave method respectively which used sodium metaaluminate as the aluminum source,sodium silicate as the silica source,and zinc nitrate as zinc source.The effects of silica source,n?H₂O?/n?Na₂O?ratio,aging condition and crystallization condition on zinc-substituted A zeolite were investigated.The characterizations of zinc-substituted A zeolite were studied by X-ray diffraction?XRD?,X-ray fluorescence spectrometry?XRF?,X-ray photoelectron spectroscopy?XPS?,Fourier-transforminfrared?FT-IR?spectroscopy,thermogravimetric-differential thermal analysis?TG-DTA?,scanning electron microscopy?SEM?,and energy dispersive mapping X-ray analysis?EDX mapping?.The Ag-loaded zeolite was prepared by a solid phase ionic exchange approach with the zinc-substituted A zeolite synthesized by hydrothermal method as carrier.The amount of silver load in the Ag-loaded zeolite was determined by atomic absorption spectrometry?AAS?.The influence of AgNO₃ amount,reaction temperature,and reaction time on silver load in the zeolite was investigated.The antibacterial properties of Ag-loaded zeolite were estimated.The main study results are as follows:?1?The optimum conditions for the preparation of zinc-substituted A zeolite by the hydrothermal method were as follows:Zn?NO₃?₂/Al₂O₃=0.5,n?H₂O?/n?Na₂O?=35,aging temperature was 30?,aging time was 24 hours,crystallization temperature was 120?,and crystallization time was 2 hours.?2?The optimum conditions for the synthesis of zinc-substituted A zeolite by the single-mode focused microwave method were as follows:aging temperature was40?,aging time was 24 hours,microwave radiation temperature was 100?,microwave radiation power was 100 W,and microwave radiation time was 30 min.?3?It could be obtained from the analysis of XRD patterns that the zinc-substituted A zeolite was not a simple superposition of NaA zeolite and ZnO.Meanwhile the unit cell parameter of zinc-substituted A zeolite was larger than that of NaA zeolite,which illustrated that zinc was incorporated into the framework of zeolite.It could be demonstrated that the partial aluminum in the framework of zeolite were substituted by zinc during the preparation of zinc-substituted A zeolite from the XRF data analysis of zinc-substituted A zeolite and NH₄A zeolite.The zinc-substituted A zeolite and zeolite after the exchange of NaA zeolite and Zn²⁺were studied by XPS.The maximum value of high-resolution photoelectron spectra,binding energy,and FWHM of Zn(2p_3/2)in the zinc-substituted A zeolite was smaller than that of NaZn_exchA zeolite,which illustrated that zinc in the zinc-substituted A zeolite was different from the ion-exchanged zinc.Therefore,it could be proved that zinc in the zinc-substituted A zeolite was incorporated into the framework of zeolite.The wave numbers of zinc-substituted A zeolite moved in the direction of low wave numbers at the absorption peak of the stretching vibration compared with the FT-IR spectra of the zinc-substituted A zeolite and NaA zeolite,which showed that the Al³⁺in the framework of zeolite was substituted by Zn²⁺and it was incorporated into the framework of zeolite.The zinc-substituted A zeolite particles had a cubic structure,and the crystal also had a regular shape.In addition,the average crystal size of the zinc-substituted A zeolite was 300 nm with uniform distribution.Based on the elemental mapping images,O,Si,Al,Na and Zn elements were uniformly distributed in the zinc-substituted A zeolite.?4?The optimum conditions for the preparation of Ag-loaded zeolite by a solid phase ionic exchange approach with the carrier of zinc-substituted A zeolite synthesized by hydrothermal method were as follows:n?NH₄A?:n?AgNO₃?=1:1.5,reaction temperature was 350?,and reaction time was 3 hours.The amount of silver load in the Ag-loaded zeolite prepared under optimum conditions was?43.26?0.48?%.The crystal shape of Ag-loaded zeolite prepared under optimum conditions was regular,and it had a uniform distribution of particle size.The structure and morphology of the framework in the Ag-loaded zeolite were basically unchanged compared with that of the zinc-substituted A zeolite,and O,Si,Al,Na and Zn elements were uniformly distributed in the Ag-loaded zeolite.?5?Compared with the Ag-loaded zeolite prepared with the carrier of Na A zeolite,the amount of silver load in the Ag-loaded zeolite prepared with the carrier of zinc-substituted A zeolite was improved.The MIC value for Escherichia coli was 7.92ppm,the diameter of the inhibition zone was 16.74 mm,and the bactericidal rate was?99.15?0.32?%,which illustrated that the Ag-loaded zeolite had good antibacterial activity.The Ag⁺in the Ag-loaded zeolite could be released slowly in the process of antibiosis.Meanwhile,the Ag-loaded zeolite had a high amount of silver load??43.26?0.48?%?.Therefore,the durability of the Ag-loaded zeolite was improved.Referred to standard whiteboard,the color change of Ag-loaded zeolite was insignificant after UV irradiation,which indicated that the Ag-loaded zeolite had good anti-tarnish property.