Study On Adsorption Of Fluoride In Drinking Water By Zeolite Molecular Sieve Modified By Micron Zirconia Composite

Fluorine is a non-metallic element widely used in daily life and one of the indispensable trace elements in the human body.About 90%of the fluorine in drinking water can be absorbed by the body,so drinking water becomes the main channel for human body to take fluoride.Appropriate intake of fluoride is beneficial to the human body.Excessive intake can cause fluorosis,such as dental fluorosis and skeletal fluorosis.The high-fluorine groundwater formed in China due to natural geological conditions is mainly distributed in North China,Northwest China,Northeast China and Huanghuai Plain.In addition,with the development of smelting aluminum plants,ceramic glass,semiconductor manufacturing,phosphate fertilizer industry,etc.Unreasonable emissions have also caused fluorine pollution in more and more areas of water.At present,China's conventional water treatment process has a poor ability to remove fluorine,and it has been unable to meet the effluent quality requirements of the drinking water hygiene standard GB5749-2006.In this study,the use of micron-sized zirconia for the strong adsorption of fluorine,while using the stable structure of zeolite molecular sieve and rich pores,the two are combined to make a new type of zeolite molecular sieve/micron zirconia water treatment material.To improve the treatment efficiency of fluoride in water by traditional techniques,the research content of the thesis mainly includes the following three parts:Optimization of preparation of zeolite molecular sieve/micron zirconia composite adsorbent:In this study,a micron zirconia crosslinked zeolite molecular sieve was used to prepare a composite adsorbent for removing fluoride ions from water by optimizing the zeolite molecular sieve/micron zirconia composite adsorbent.Preparation process parameters:hydrochloric acid concentration,mass ratio of micron zirconia to zeolite molecular sieve,preparation temperature and preparation time,determine the optimal preparation parameters of zeolite molecular sieve/micron zirconia.The optimal preparation method is as follows:the hydrochloric acid concentration is 8%,the mass ratio of the micron zirconia to the zeolite molecular sieve is 0.8/1,the preparation temperature is 10?,and the preparation time is 10 h.Specific surface area?BET?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?EDS?,fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?and thermal weight?TG?features were used to analyze the surface and structural characteristics of the zeolite molecular sieve/micron zirconia.The results show that the zeolite molecular sieve/micron zirconia has a larger specific surface area than the zeolite molecular sieve,and its surface is concave and convex,and can simultaneously detect the characteristic groups of the micro-zirconia and zeolite molecular sieves Zr-OH,Zr-O,X-OH,X-O₄?X is Si,Al?etc.XRD indicates that the introduction of micron zirconia greatly changes the structure of the zeolite molecular sieve itself,TG analysis shows that the introduction of micro-zirconia has a certain effect on the crystallization water content of the zeolite molecular sieve itself,and the thermal stability is increased.Study on the influencing factors and regeneration of zeolite molecular sieve/micron zirconia composite adsorbent:The static adsorption test was used to simulate the fluoride-containing raw water with sodium fluoride,and the differences including dosage,adsorption time,p H value,and adsorption temperature were studied.The influence of factors on the adsorption effect.The experimental results show that the optimal dosage is 2 g/150 m L;the adsorption saturation has basically been reached at 8h;when the p H is between 5?6,the adsorbent has a good effect on removing fluoride ions;the adsorption temperature is in the range of 5?25?,the effect of removing fluoride ions increases with increasing temperature.When the fluoride ion concentration in the raw water is 4?5 mg/L,the zeolite molecular sieve/micron zirconia dosage is 2 g/150 m L,the adsorption time is 8 h,the p H value is 6.5,and the temperature is 25?,The removal rate of fluoride ions reached the maximum,which was 95.36%,and the adsorption capacity also reached the maximum,which was 0.36 mg/g.Optimum regeneration conditions for fluoride ion-saturated zeolite molecular sieve/micron zirconia:Put 2.0 g of fluoride ion-saturated zeolite molecular sieve/micron zirconia in 100 m L of Na OH solution with a total molar concentration of 1.0 mol/L of cations at a speed of 130 r/min,shake at 30?for 12 h,then rinse the regenerated adsorbed particles with deionized water and bake at 60?for 5 h to obtain regenerated composite adsorbed particles.The removal rate and adsorption capacity of the regenerated adsorbed particles to fluoride ions reached 80.02%and 0.293 mg/g,respectively.Adsorption mechanism of zeolite molecular sieve/micron zirconia composite adsorbent:The adsorption kinetics,adsorption isotherm and adsorption thermodynamics of zeolite molecular sieve/micron zirconia composite adsorbent for fluoride ion were studied.The experimental results show that the reaction of zeolite molecular sieve/micron zirconia to remove fluoride ion conforms to the Lagergren quasi-secondary kinetic model;the adsorption conforms to the Freundlich adsorption isotherm equation,which is multi-layer adsorption;the adsorption thermodynamics result indicates that the zeolite molecular sieve/molecular sieve adsorbs fluorine.The process of ions is a spontaneous endothermic reaction.The zeolite molecular sieve/micron zirconia composite adsorbent adsorbed by fluoride ion was analyzed by SEM-EDS,FTIR and XRD.The results showed that the morphology and structure of the micro zirconia/zeolite molecular sieve composite adsorbent did not change greatly before and after the adsorption of fluoride ion.It still maintains the basic skeleton of the tetrahedron;it mainly relies on the coordination exchange of Zr-OH and Zr-O with fluoride,and generates new characteristic groups such as Zr-F and[Zr F₅]^-.The results of preparation and mechanism analysis of zeolite molecular sieve/micron zirconia composite adsorbent can provide technical reference and theoretical support for the treatment of high fluoride water.