| Zeolite as microporous material with abundant pore structure and regular pore distribution, it has widely applied in the fields of catalysis, adsorption, separation, photoelectric materials, and functional materials etc. Therefore, zeolite created the inestimable value for social development. In the long-term practice activities, people have a better knowledge of the nature of the microporous zeolite and its performance in the aspects of adsorption and ion exchange. So far, there have been 225 zeolites with different topological structure were synthesized, and laid the theoretical basis for the development in the field of zeolites. In order to expand the application fields of zeolites, different objects can form composite materials with zeolite. It showed some unique properties in the optical, electrical and magnetic fields. The diversity of zeolite synthesis, can be exploited to design and obtain high performance composite materials with novel structure in the aspect of material forming and composite material preparation.Using cheap low-grade kaolin mineral as raw material for preparing molecular sieve is an important direction of kaolin research in recent years, which is also the efficient use of China’s rich reserves of low grade kaolin mineral resources.Fly ash is a kind of solid waste pollution. In the process of the discharge, there may be toxic trace elements enrichment in flue gas material. Using fly ash as raw material to Synthesis of zeolite, not only can provide low cost, good performance adsorbents for heavy metal wastewater treatment, but also to achieve the fly by waste of resource utilization, bring environmental and social benefits.In this paper, cheap low-grade kaolin resources and solid waste fly ash were used as raw material resources.With the hydrothermal synthesis method was used to carry out the study on the synthesis of zeolite.The magnetic carrier technology put the magnetic properties of Fe3O4 materials into molecular sieve for the preparation of magnetic zeolite Materials. From technological difficulties of preparation, quality materials characterization, heavy metal adsorption properties and so on. A series of studies of zeolite and magnetic zeolite were conducted. The paper discusses the factors affecting the synthesis of zeolite and magnetic zeolite through kaolin and fly ash. From the aspects of structure, properties and applications of indicators compared the quality of synthetic zeolites and zeolite magnetic. Moreover, XRD, SEM, TEM, BET and VSM were used to study the change regulation of zeolite and magnetic zeolite in the process of synthesis and application.The innovations of this paper were as folloes::1. Using low-grade kaolin resources as raw material without adding any source of silicon and aluminum source conditions. The 3A zeolite was synthesized by one-step successful preparation through the method of salt calcination.Avoid tradition complex method of synthesis 3A zeolite.that was first to synthesis 4A zeolite then through ion exchang to gei 3A zeolite.2. Kaolin and Fly ash used as raw material, by the method of direct calcination and magnetic carrier technology to prepare preferable at constant temperature hydrothermal conditions to prepare preferable magnetic 4A zeolite and magnetic P zeolite. This method aimed to obtain cheap and facile magnetic zeolitet.3. U The solid waste resource fly ash was used as the raw material with the method of direct calcination at constant temperature hydrothermal conditions to prepare pure P zeolite, which possesed high degree of crystallinity.The main results of this paper were as follows:1. By using XRD, XRF,FT-IR. TG and SEM analysis measures to test the selected raw kaolinite. Chemical analysis revealed that the composition of kaolinite (SiO2 37.57 wt.%, Al2O3 34.73 wt.%, TFe2O3 3.22 wt.%, TiO2 2.99wt.%). By calculation shows Si/Al ratio of approximately 2. The Si/Al ratio under conditions was appropriate for the preparation of 4A zeolite. And the content of impurities in raw materials of iron and titanium is little. There is no need to iron removal treatment and it can be directly synthesized. Phase analysis shows kaolin containing mainly kaolinite, illite, albite, gibbsite, and a small amount of quartz. Kaolinite content of which is greater than 80%, indicating a high proportion of the kaolinite content was suitable for the preparation of molecular sieve product. From the result of thermal analysis, before temperature of 250℃ the adsorbed water was gradually discharged. At the temperature of 250-500℃ non-bridge-hydroxyl started to prolapse was gradually discharged. After 600℃, the crystal structure of kaolin has been completely collapsed and a new phase was generated. From the result of SEM analysis, kaolin was a false six square type and the crystal type is preferable.2. There are three main methods to calcine kaolin in this paper. They are the direct calcination method, alkali calcination method and salt calcination method respectively. Direct calcination method mainly focuses on the calcine products at different calcine temperature. The phase and morphology of calcine kaolin at different calcination temperatures were analyzed by XRD and SEM. Preparation of 4A molecular sieve through the experiment of calcined kaolin system. The calcination temperature obtained direct calcination method is appropriate in 700℃. At this point kaolin has been completely transformed into amorphous metakaolin. With the increase of the calcination temperature, XRD pattern of the calcined kaolin substantially unchanged. However, there was quartz diffraction pattern peaks in the calcined kaolin until the temperature was increased to calcination at 1000℃. This indicates that the crystal structure of quartz did not change after high-temperature treatment. All the calcination time was united to 4 hours. Kaolin and sodium hydroxide were mixed before calcination to get the caustic calcined kaolin. The optimum calcination temperature and time used in the direct method to obtain the high-temperature calcination treatment. In order to examine the different amounts of co-calcined kaolin with an alkali relationship. The phase and morphology of calcined product were analyzed by XRD and SEM. Co-calcined product was actually sodium silicate and sodium aluminosilicate. Therefore, alkali calcination was actually the product of sodium silicate and sodium aluminosilicate hydrothermal reaction for the preparation of molecular sieve. Salt calcination method is the primary method of calcined kaolin one step preparation of 3A zeolite molecular sieve. Calcining mixture of kaolin and potassium chloride mixture before calcination, the product is used for preparing the 3A zeolite.3. The calcined kaolin came from three calcining method were prepared as hydrothermal reaction. Influence factors of direct calcination hydrothermal reaction for the preparation of molecular sieve was mainly discussed, including the concentration of NaOH. aging temperature of the reaction system and the crystallization temperature. The prepared molecular sieve obtained the optimum preparation process through XRD, SEM and other analytical tools. According to the different calcination temperature synthesis of 4A molecular sieve XRD analysis, the calcination temperature of kaolin can synthesize 4A zeolite at 500-900℃. It can be seen from SEM analysis that only in the calcination temperature of 700℃. synthetic zeolite sample as a whole more regular shape with uniform size, the particle size is about 2μm, well dispersion, and calcium ion exchange capacity available to 350mg/g- dry. Molecular sieve prepared by alkali calcination is the mixture of molecular formula of X zeolite and P zeolite. Through the XRD software to calculate the X zeolite content was about 80%. Salted calcined product prepared primarily for the preparation of zeolite 3 A. Through the XRD analysis of the preparation of 3 A zeolite, it can be observed that the patterns of 3A and 4A molecular sieves prepared almost the same. This also demonstrated that the potassium ion as a counter cation of the zeolite molecular sieve characteristic diffraction peaks did not change and skeletal structure remains unchanged. The structure of the zeolite was characterized by XRD, the added potassium ions exist only in 4A zeolite pore or cage and its skeletal structure did not change. SEM analysis showed that the product sample 3A molecular sieve particle size uniform, smooth surface. The prepared molecular sieve product by TG test analysis,4A molecular sieves for the heat treatment temperature should better not higher than 500℃. TG analysis showed the sample at 139.5℃ had a very strong endothermic valley accompanied by significant weight loss. Between the temperature of 100-200℃, there was the main loss of free water. Between the temperature of 200-400℃, the structure of adsorbed water and coordinated water gradually discharged. After the temperature of 500℃, non-bridge-hydroxyl started to prolapse, and zeolite crystal structure gradually collapses. Between the temperature of 900-1000℃, there wasjust a little exothermic peak between the differential thermal curve but weight loss without changes, which indicated that the crystal structure of kaolin has been completely collapsed and a new phase was generated. Therefore, zeolite heat treatment temperature should be lower than 500℃. Infrared analysis of molecular sieve indicated that band shape of the same type of molecular sieve was substantially the same infrared spectra.4. Characterization of selected fly ash by means of XRD, XRF, FT-IR, TG and SEM analytical methods, fly ash contained silicon and aluminum (Si 52.40 wt.%, Al 18.09 wt.%, Fe 0.42 wt.%, Ti 4.33% wt.%). Si/Al ratio was about 5. Only from the chemical point of view. Neimeng fly ash is suitable for the preparation of P type molecular sieve. The phase analysis showed that fly ash was mainly amorphous. There’s a small amount of crystalline substances such as anatase, quartz and mullite. Titanium exists in anatase, thus did not participate in the the preparation process of the molecular sieve.5. Fly ash calcination treatment used the two methods, including direct calcination method and alkali calcination method. Direct calcination method mainly focuses on the calcine products at different calcine temperature. It was obtained that the calcination temperature was 800℃ and calcining time was 4 hours suitable for experimental needs. Calcination temperature and time of alkali calcination method and direct calcination method were identical. The influence of the adding amount of fly ash and sodium hydroxide on the calcination product was studied. The calcined product was analyzed by XRD shows that in the experimental process used in the calcination temperature conditions, organic matter in fly ash can be removed by calcination. The structure and phase of fly ash did not change and calcined raw ash anatase and quartz did not change. Through the XRD analysis of fly ash after alkali after calcination, the organic impurities of fly ash can be removed. And fly ash and alkali at high temperature could produce acid sodium and silicon aluminum silicate.6. Two kinds of fly ash were synthesized by calcining experimental molecular sieve. The impact factors of suitable hydrothermal experimental conditions to produce direct calcination P zeolite are the hydrothermal temperature, the hydrothermal time and the alkali concentration. Based on the hydrothermal synthesis product analysis as can be seen by XRD analysis at the time when the reaction temperature was between 80℃ -100℃, preparation of P zeolite can be achieved. The molecular sieves under conditions of the hydrothermal reaction temperature of 95℃ and 100℃ produced higher XRD peak. Taking all the factors into account, the hydrothermal synthesis temperature chose 95℃. Alkali concentration experiments, through XRD and SEM analysis, it can be able to synthesis P zeolite in 2 mol·L-1, with the increase of the concentration of alkali crystal morphology also gradually complete. When the reaction of alkali concentration products between Smol·L-1-Smol·L-1, XRD diffraction peak was high and electron microscope morphology better. When the alkali concentration increased 6 mol·L-1, from the SEM diagram can be seen in the crystal surface will have some no reaction substances exist. Therefore, the appropriate alkali concentration was between 3mol·L-1 -5mol·L-1. P zeolite was prepared by alkaline elution method, which was carried out under the influence of silica to alumina ratio of regulation to verify the material conditions of different silica to alumina ratio of zeolite hydrothermal products. Silica to alumina ratio in the range of tests selected for 2.5-6.5. Through XRD and SEM analysis shows that the synthesis of P zeolite molecular sieve suitable silicon aluminum ratio is 4.5-6.5. When the ratio of silicon and aluminum was 2.5-4.5, X zeolite was generated. When the ratio of silicon and aluminum was 4.5-6.5, phase pure of P zeolite was generated. P zeolite was prepared by TG analysis, shows that the temperature of the high temperature treatment of producing P zeolite cannot be higher than 500℃. From the result of TG curve analysis, sample has a very strong endothermic valley around 139.5℃ accompanied by significant weight loss. Between the temperature of 100-300℃, it was mainly the loss of free water. Between the temperature of 300-500℃, the structure of adsorbed water and coordinated water gradually discharged. After the temperature of 500℃, non-bridge-hydroxyl started to prolapse, and zeolite crystal structure gradually collapses. Between the temperature of 900～1000℃, there was a small exothermic peak between the differential thermal curve but weight loss without changes, which indicated that the crystal structure of P zeolite has been completely collapsed and a new phase was generated.7. There are two main methods for the preparation of Fe3O4 magnetic particles, including organic suspension polymerization and chemical co-precipitation method. Two methods were prepared magnetic Fe-04 particles. The magnetic susceptibility of suspension polymerization product of Fe3O4 material was 37.277 emu/g. The magnetic susceptibility of chemical co-precipitation product of Fe3O4 material was 75.771 emu/g with coercivity 30.08 Oe. Preparation of magnetic 4A molecular sieve experiment mainly preparation the optimum process conditions of 4A molecular sieve by kaolin. In the preparation of alkaline elution conditions, introduced the chemical co precipitation of magnetic Fe3O4 particles to synthesize the magnetic 4A zeolite. The magnetic susceptibility of the product was 4.5364 emu/g with coercivity 16.744 Oe. By XRD analysis showed that the preparation of magnetic 4A zeolite possessed a high degree of crystallinity. Introduced Fe3O4 phase did not affect its cubic symmetry. That did not affect the skeletal structure of 4A zeolite. Moreover, the peak of the Fe2O3 generation due to the oxidation of Fe3O4 was not observed. That in the process of synthesis of Fe3O4 was not oxidized. By the analysis of transmission electron microscope, magnetic 4A zeolite cubic body contours and crystal shape was more complete. And the 4A molecular sieve compared to its edges became smoother with the particle size was about 400nm. Fe3O4 magnetic nanoparticles partially adhered to the surface of the product, more serious phenomenon of reuniting did not appear. It was mainly present between the molecular sieve particles and more evenly distributed. It can also be seen that unlike the mechanical mixture, the Fe3O4 particles were uniformly distributed in the zeolite and did not exist in isolation Fe3O4 particles or aggregates. The main producing the optimal process condition of P zeolite with fly ash system was used to produce P zeolite which was introduced during the preparation of Fe3O4 magnetic materials. The magnetic susceptibility of the product was 11.990 emu/g with coercivity 20.67 Oe. The XRD analysis showed that the preparation of magnetic P zeolite possessed a high degree of crystallinity. Introduced Fe3O4 phase did not affect the skeletal structure of P zeolite. By the analysis of transmission electron microscope, magnetic P zeolite was ball-shaped profile and crystal shape was more complete. And the 4A molecular sieve compared to its edges became smoother with the particle size was about 0.2-1.0 μm. Fe3O4 magnetic nanoparticles partially adhered to the surface of the product, more serious phenomenon of reuniting did not appear. It can also be seen that the Fe3O4 particles were uniformly distributed in the zeolite and did not exist in isolation Fe3O4 particles or aggregates.8. The sixth chapter investigates the zeolite adsorption properties of products prepared in the experiment. Through static adsorption method, The capability of 4A zeolite, P zeolite, magnetic 4A zeolite, magnetic P zeolite to remove heavy metal ions Cu2、Cr+、Pb2+、Cd2+、Ni2+ were studied. The results showed that the adsorption effects of four kinds of zeolite materiala for heavy metal ions Cu2+、Cr3+、Pb2+、Cd2+、Ni2+ were underperforming when pH was less than 2. On top of that, when the pH value was 4, the adsorptive capacity of Cu2+were 47.20 mg/g,49.70 mg/g,43.98 mg/g, and 46.55 mg/g respectively, the adsorptive capacity of Cr3+were 53.26 mg/g, 50.76 mg/g,50.92 mg/g, and 46.89 mg/g respectively, the adsorptive capacity of Pb2+were 43.36 mg/g,45.04 mg/g,39.70 mg/g, and 41.18 mg/g respectively, the adsorptive capacity of Cd2+were 49.26 mg/g,46.00 mg/g,48.76 mg/g, and 43.54 mg/g respectively, the adsorptive capacity of Ni2+were 45.40 mg/g,44.96 mg/g,42.96 mg/g, and 43.77 mg/g respectively. Apart from that, samples were analyzed by EDS for 4A zeolite and P zeolite after the adsorption of heavy metals. After adsorption, zeolite surface deposited a layer of heavy metal ions. But the morphology of the zeolite did not change and it can be reused after desorption.9. Through the analysis of the results of experiment and characterization study of the preparation of zeolite, it can be concluded that the mechanism of preparation of 4A zeolite and P zeolite was the solid phase transformation mechanism. The general formation process of zeolite could be seen according to the TEM images. The mechanism of magnetic zeolite preparation was Fe3O4 material loaded on the crystal surface of zeolite in the forming process of zeolite. According to TEM analysis, magnetic zeolite material was made from the outer layer of zeolite crystal which was loaded nanoscale Fe3O4 magnetic material.This paper discussed the synthesis of the 4A zeolite and P zeolite with kaolin and fly ash used as the raw materials. On this basis, the preparation of the magnetic zeolite was further studied.The results of this paper will contribute to the recovery and application of heavy metal in the field of molecular sieve adsorbent material. Diversity of zeolite synthesis strategy can be used to designed and obtained molecular zeolite composite materials with novel structure in the forming and composite material preparation process. |
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