Systhesis Of Magnetic Zeolite4A Based On Kaolin And Its Application In Removing Of Ammonia-nitrogen

Zeolite4A behaves excellent properties of adsorption, iron-exchange andcatalysis in the macro due to its unique pore structure arising from aluminosilicateframework. So it has been widely used in many fields such as environmentalprotection, daily chemicals, processing and catalysis in oil, and many other areas.However, there are two problems in the application process of zeolite4A. It is noteasy to separate quickly with organization and the other is the high cost whenzeolite is synthesized by chemical raw materials directly. In this dissertation,magnetic zeolite4A was synthesized ueing hydrothermal method based on kaolinand its application in removing of ammonia wastewater was investigated in detailsto preparate magnetic zeolite4A with a low cost and has a good property inremoving of ammonia nitrogen in wastewater and can bereused. The effects ofhydrothermal synthesis conditions on the molecular4A were studied by using XRD,SEM, FT-IR and the influence of Fe₃O₄loading on morphology of magnetic zeolite4A was also analyzed. Furthemore, the effects of reaction conditions on removal ofammonia nitrogen were studied, and the mechanism of ammonia adsorption onmagnetic zelite4A was discussed. In addition, the effect of Fe₃O₄content onremoval of ammonia nitrogen was analyzed. The main results are as followed.1、 The morphology and properties of synthetic products were greatlyinfluenced by SiO₂/Al₂O₃, Na₂O/SiO₂, H₂O/Na₂O and crystallization temperatureand time. Meanwhile the results of orthogonal experiments indicated the optimalpreparation conditions of4A zeolite were SiO₂/Al₂O₃=2.3:1, H₂O/Na₂O=50:1,Na₂O/SiO₂=1.4:1and crystallization time8h. Besides, SiO₂/Al₂O₃and reactiontime were regarded as the major influencing factor. Moreover calcium ion exchangecapability and water static adsorption capacity were319.91mgCaCO₃·g^-1and23.02%, respectively, after synthesis in optimal conditions.2、Synthetic Fe₃O₄was approximate spherical paticles of nanometer. Thepsrticles of Fe₃O₄distributed uniformly and can be combined with zeolite bychemical bond making them not easy to be oxidized. Meantime the morphology ofmagnetic zeolite was changed by adding Fe₃O₄particles, but it didn’t damage theframework structure and pore characteristic of zeolite. Furthermore calcium ionexchange capability and water static adsorption capacity were respectively 303.39mgCaCO₃·g^-1and21.67%when Fe₃O₄content comes to4.48%.3、The removal efficiency of ammonia nitrogen on zeolite was affected by pH,temperature, initial concentration, adsorption time and the content of Fe₃O₄almosthas no effect on it. Moreover ammonia nitrogen adsorption capacity of zeolite andmagnetic zeolite （4.48%of Fe₃O₄content） were10.53mg/g and10.47mg/g,respectively. The adsorption equilibrium time is about45min when temperature andinitial concentration of ammonia nitrogen were20℃and50mg/L, respectively. Inaddition, three isotherm adsorption models were used and the results showed thatthe Langmuir-Freundlich isotherm has a good agreement with the adsorption results.Meanwhile, the results of Lagergren quasi second-order rate equation fittingshowed that adsorption rate was controlled by the chemical adsorption.