Study On Synthesis Of Zeolite From Fly Ash And Its Application

In recent years,the preparation of zeolite molecular sieve from fly ash is a hot topic in the research of high value utilization of fly ash.In this study,fly ash is used as raw material..A zeolite molecular sieve adsorbent for treating methylene blue and methyl orange wastewater is developed by microwave-assisted heating and chemical modification methods.The aim is to reduce cost and make the best use of fly ash.Firstly,the influence of preparation process on zeolite adsorption performance was studied.The optimum process conditions were determined by orthogonal experiment.The fly ash raw material was ball milled and added acid to remove impurities.Then fly ash zeolite was synthesized by microwave-hydrothermal method,and the synthesized fly ash zeolite（FZ）was modified by CTAB to obtain CTAB modified fly ash zeolite（CFZ）.It is found that FZ has a good removal effect on methylene blue,but almost no adsorption capacity on methyl orange.On the contrary,the adsorption ability of CFZ to methyl orange is higher,but the adsorption ability to methylene blue is decreased.When the ratio of liquid to solid is 9:1,alkali 2 mol/L,crystallization time 2 h and crystallization temperature 105℃,the adsorption capacity of the two zeolites is up to optimum.At this time,the removal rate of FZ to methylene blue is 99.14%,and that of CFZ to methyl orange is 98.40%.Secondly,the adsorption characteristics of synthetic zeolite were analyzed.The adsorption process of the two zeolites conform to the quasi second-order kinetic equation,and the main control step of adsorption rate is liquid membrane diffusion.The isothermal adsorption process of the two zeolites are consistent with the Langmuir model.According to Langmuir isothermal adsorption equation,the theoretical maximum adsorption capacity of FZ for methylene blue is 35.370 mg·g^-1,and that of CFZ for methyl orange is 49.875mg·g^-1.XRD,FT-IR,SEM,BET and other analysis methods were used to analyze the structure and adsorption mechanism of zeolite synthesized before and after CTAB modification.The main composition of the synthesized fly ash zeolite is Na P zeolite,and it also contains some unreacted quartz,mullite and amorphous materials.The pore size and specific surface area of the CTAB modified zeolite are narrowed,but the crystal form is not changed.As far as FZ is concerned,methylene blue cation can be adsorbed directly by ion exchange with metal cation on zeolite surface.As for CFZ,the hydrophobic membrane formed on the zeolite surface can dissolve the organic association compound formed by CTAB and the anionic dye methyl orange.Thus the adsorption capacity for methyl orange is improved.Taking the project with an annual output of 10000 tons（5 000 tons of fly ash zeolite and 5000 tons of CTAB modified fly ash zeolite respectively）as an example,the economic benefit and environmental impact analysis were carried out.It shows that this technology has good economic and environmental benefits,and has a good promotion prospect.The results of this work provide theoretical support for the selection of adsorbents for printing and dyeing wastewater.It has wide application prospect,high economic and environmental benefits.