| In recent years,China's increasing energy demand has promoted the rapid development of the coal chemical industry.Coal gasification technology is widely used as an environmentally friendly and efficient clean coal technology.The accompanying problem is that more and more coal gasification slags are generated during the gasification process and it is difficult to use them.Due to the differences in coal quality in different regions,the coal gasification coarse slag in Ningdong area can only be landfilled after high-level anti-seepage treatment on the ground.Such a treatment method not only wastes land resources,but also greatly increases the cost of the enterprise.More importantly,it causes great harm to the local environment and the health of the surrounding residents.In view of the above pressing problems,an efficient,economical and environmentally-friendly resource utilization method of coal gasification coarse slag is urgently needed to solve the current environmental crisis.For this reason,through the study of the physical and chemical properties of coal gasification coarse slag,a highly resourceful application scheme is determined:the characteristics of coal gasification coarse slag with high content of silicon and aluminum are used to prepare high-value-added zeolite materials.XRD,BET,F-SEM,FT-IR,TG-DSC and other technical means were used to characterize and analyze the prepared zeolite and optimize the preparation scheme.According to the characteristics of zeolite porous channels and large specific surface area,the removal effect of ammonia nitrogen in wastewater was investigated.The main research conclusions of this paper are as follows:(1)In the case of using coal gasification coarse slag,sodium hydroxide and deionized water as raw materials,without adding an aluminum source of silicon source,without adding a template agent,and when synthesizing NaP zeolite,high temperature calcination is not required.Optimized alkali melting method and one-step hydrothermal method successfully prepared FAU and NaP zeolites with a single crystal phase,regular crystal morphology,good thermal stability,large specific surface area,and dual pore structure(micropore and mesopore).The study found that Na+provided by sodium hydroxide is beneficial to promote the formation of zeolite crystals,and the molar ratio of water to silicon 60 is the key to synthesize FAU zeolites.Adjusting the molar ratio to SiO2:Al2O3:Na2O:H2o=5.2:1.0:5.0:100 is the core of the synthetic NaP zeolite.By optimizing various preparation conditions,the optimal FAU zeolite has a specific surface area of 509.88 m2/g and an average adsorption pore size of 7.61 nm.The optimal NaP zeolite has a specific surface area of 161.06 m2/g and an average adsorption pore size of 5.57 nm.In comparison,the preparation process of NaP zeolite is simpler,the production cost is cheaper,and it is easier to industrialize.It only needs to add a small amount of sodium hydroxide and trace deionized water to the coal gasification coarse slag,and it can be obtained by aging for 12 h and crystallization at 105? for 12 h.(2)Using FAU and NaP zeolites prepared under optimal conditions,the effects of various factors on the removal rate when treating ammonia nitrogen in wastewater were investigated.It is found that the removal effect and economic efficiency of NaP zeolite are significantly better than that of FAU zeolite.The double pore structure of the two zeolites and the cations present in the crystal lattice are helpful for NH4+ion exchange.When treating wastewater with a concentration of ammonia nitrogen of 100 mg/L,the optimal adsorption parameters are:the dosage of adsorbent is 20 g/L,the solution pH is 7,the shaking rate is 180 r/min,the adsorption time is 90 min,and the adsorption temperature is 25?.At this time,the optimal removal rate of NaP zeolite can reach 92.45%.This paper studies two new methods for preparing FAU and NaP zeolites,which greatly reduces the cost of preparing these two zeolites,and provides a new way for the resource utilization of coal gasification crude slag.Among them,the method of preparing NaP zeolite from coal gasification crude slag and applying it to the removal of ammonia nitrogen in wastewater has the advantages of simple process,low cost,low energy consumption and water consumption,high system integration and easy industrialization.This research solution not only solves the severe environmental problems caused by large-scale accumulation of coal gasification slag,but also greatly reduces the cost of waste disposal by enterprises,and achieves the purpose of "reat waste with waste",which has great industrial application prospects. |
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