Synthesis Of 4A Zeolite From Coal Gangue And Its Adsorption On Fluorine-containing Wastewater

4A zeolite, which doesn't pollute the environment, is a kind of artificial synthesized zeolite with higher ion exchange performance and adsorption performance.The solid waste-Coal gangue will produce great harm to the environment because of discarding and accumulation. However, Coal gangue has a large number of SiO2 and Al2O3, which can be used as the raw material for the synthesized zeolite. This subject use coal gangue to synthesize zeolite 4A by adopting the stepwise method of dissolving silicon and aluminum in the hydrothermal synthesis, which needs no adding sources of silicon and aluminum. It provides a new way of easy method and high maneuverability for the synthesis of 4A zeolite from coal gangue. Along with industrial development, industrial fluoride wastewater and some of drinking water exceeded the standard, which will seriously be harm to the environment and human health if we not handled properly. Use the synthesized zeolite 4A to treat fluoride wastewater and explore its adsorption properties and characteristics can not only to provide an effective adsorption material for the treatment of fluoride wastewater, but also to achieve the environmental protection purpose.First, this subject explore the influencing factors of extracting effective silicon and aluminum components of coal gangueand the crystallization conditions influencing on the synthesized product. Results of the synthesis experiments are as follows.The group of kaolinite, quartz and other inert ingredients will transform into metakaolin and other active ingredients after overheating activation of coal gangue.The characterization of the coal gangue transforms into Na2SiO3and NaAlSiO4 after heatingthe activated gangue and Na2CO3 under a mass ratio of 1:1.3, high temperature of 830? and melting time of lh.Then, the molten product is mixed with water with the solid-liquid ratio of 1:30 and mixed time of 1h, and Na2SiO3 is almost completely dissolved in the water by characterization. Later, the desilication rock is mixed with 3mol/L NaOH solution with the temperature of 60? and time of 1h, and soNaAlSiO4is almost completely dissolved. Finally, put the aluminum silicon solution under aging and hydrothermal crystallization for synthesized zeolite. Zeolite 4A is generated with a short crystallization time, andsodalite needs longer crystallization time. The obtained crystallization time of zeolite 4Ais 4h and the synthesis of Sodalite is 16h.Then, explore the adsorption of fluorine to zeolite 4A synthesized from coal gangue. Results of the adsorption experiments are as follows. The initial pH of the solution has a great influence on the defluorinating efficiency to the synthetic zeolite, and the optimal pH range is 4-6. With the increase of the mass ratio of solution to zeolite, the quantity of fluorine adsorption increases, while the defluorinating rate decrease slowly. It can not only improve the quantity of fluorine adsorption, but can guarantee a greater defluorinating rate when the ratio of solution to zeolite is 50:1. The unit fluorine adsorption is increasing to varying degrees with the increase of initial concentration. The adsorption of fluorine to the synthetic zeolite has a certain concentration limit range for the higher concentration fluoride, while the adsorption effect is better to the lower fluoride concentration. The fluorine adsorption increases faster during the early reaction, while the removal amount increases slowly with the longer adsorption time, and finally it tends to a stable equilibrium. And the fluoride removal process complied with the pseudo-second-order model and the Fleundlich isothermal adsorption model, indicating that the adsorption process is a chemical and multilayer adsorption.Finally, explore the adsorption of fluorine to zeolites modified by ferric chloride and calcium hydroxide solution. The optimum conditions of zeolite modified by ferric chloride are the Fe3+mass fraction of 0.05% and modification time of 2h, and optimum conditions by calcium hydroxide are the Ca(OH)2 mass fraction of 7% and modification time of 2h. The defluorinating effect of zeolite modified by calcium hydroxide is higher than the ferric chloride. The fluorine content can reach the primary standard of industrial waste water discharge in our country after using the zeolite modified by calcium hydroxide, and when the initial concentration of fluorine is 500mg/L, it can reach the secondary standard of industrial waste water discharge. When the initial concentration of fluorine is less than 400mg/L, the content of fluorine can only reach the secondary standard after using the zeolite modified by ferric chloride.