Synthesis Of Low-cost SUZ-4 Zeolite And Its Performance Of Removing Organic Dye

With the rapid development of China's printing and dyeing industry,a large amount of printing and dyeing wastewater is inevitably generated in the process of dye synthesis and processing.The composition of the wastewater is complex,and the substances are toxic,harmful and not easily degraded,which poses a serious threat to the ecological environment and human health.At present,adsorption is widely used in the treatment of printing and dyeing wastewater due to its advantages,such as good treatment effect,convenient operation,little space and low investment.Due to its unique pore structure and large specific surface area,zeolite has become one of the most concerned adsorbent in the field.However,the high cost of zeolite preparation severely restricts its application in the wastewater treatment,due to large amount of adsorbent required.Therefore,it is imperative to replace chemical raw material by cheaper silicon and aluminum sources to reduce the preparation cost of zeolite.In this paper,SUZ-4,a new type zeolite,is investigated by using industrial waste,coal fly ash and silica fume as raw materials.The low-cost SUZ-4 zeolite can be synthesized in one-pot,and its adsorption performance for removing methylene blue in printing and dyeing wastewater is investigated.The main contents of the thesis are as follows:(1)Using coal fly ash and silica fume as raw materials,the SUZ-4 zeolite was synthesized by the seed method.By optimizing the experimental conditions,suitable synthesis conditions for high crystallinity SUZ-4 zeolite are as follows:when the addition amount of seed crystal is 17 wt.%,and the crystallization temperature is 150 o C and the crystallization time is 96 h,the range of Si O₂/Al₂O₃ratio is 21.2-26.2,the range of KOH/Si O₂ ratio is 0.37-0.42.(2)Using silica fume as the silicon source and tetraethylammonium hydroxide(TEAOH)as the template agent,SUZ-4 zeolites with different morphologies were prepared by adjusting the system pre-crystallization time and the amount of ethyl acetate added.When the amount of ethyl acetate added was 0mL,the resulting SUZ-4 zeolite sample was rod-like.When the addition amount of ethyl acetate increased to 1 mL,the morphology of the obtained SUZ-4 zeolite became from dandelion-like to chrysanthemum-like and further to pompon-like,as the pre-crystallization time increaed from 12 h to 24 h,and extended to 48 h.When the amount of ethyl acetate added was more than 1 mL,the SUZ-4 zeolite cannot be obtained.(3)Combining various characterization methods,the formation mechanism of the SUZ-4 zeolites with different morphology is proposed.During the different pre-crystallization stages,amount of crystal nuclei with certain number and size were formed under the action of the template agent(TEAOH).When ethyl acetate was added,the template agent was ineffective immediately imputed by acetic acid produced by the hydrolysis of ethyl acetate,and no more crystal nucleus was generated in the system.At the same time,the crystal nuclei formed in the pre-crystallization stage were self-assembled into spheres in the form of"tip-to-tip"under the action of ethanol,another hydrolysate,to minimize the activation energy of the crystal surface.Hence,SUZ-4 zeolites with different morphology were formed by assembling the crystal nuclei with different number and size produced by different pre-crystallization stages.(4)The adsorption capacities of the low-cost SUZ-4 zeolite prepared with fly ash and silica fume as raw material and the commercial one prepared with chemical agent as raw material were compared.When the concentration of methylene blue is 200 mg/L,the dosage of SUZ-4 zeolite is 200 mg,and pH=7,the adsorption amounts are respectively 41.23 and 42.68 mg/g for the two zeolites,which are almost the same.(5)The adsorption capacity of the common rod-like and dandelion-like SUZ-4 zeolite was compared.The effects of initial concentration,pH value,adsorption time and adsorption temperature on the adsorption capacity of the two kinds of SUZ-4 zeolites were discussed.The experimental results showed that under the above adsorption conditions,the adsorption capacity of dandelion-like SUZ-4zeolite is significantly better than that of ordinary rod-like one.Based on the adsorption mechanism study,it is found that the adsorption processes of the two kind zeolites to methylene blue conform to the Langmuir model,which is a single-layer adsorption,that both conform to the pseudo-second-order kinetic model,and the adsorption is a spontaneous irreversible exothermic process.