| In recent years,Ningdong coal gasification has developed rapidly in China.However,the amount of solid waste from coal gasification residue is huge and difficult to use.Coal gasification slag is the product of high temperature gasification of coal in reducing atmosphere(CO,H2)with calcium carbonate added at about 1500℃.It is mainly composed of inorganic and amorphous glassy substances,containing a certain amount of water and some residual carbon.Its physical and chemical properties are different from those of traditional solid wastes such as fly ash.The existing fly ash recycling technology can not solve the problem of gasification slag recycling.At present,the main treatment method of Ningdong coal gasification slag is landfill,which wastes land resources and seriously affects the environment and economic benefits of enterprises.Therefore,it is necessary to carry out targeted resource utilization of Ningdong coal gasification slag.In this paper,the coal gasification coarse slag as the research object,put forward an economic,environmental protection utilization way.The traditional synthesis of zeolite usually uses pure chemical reagent or strong acid and alkali solution,accompanied by wastewater pollution,high cost and other problems.Zeolite material was prepared from coarse slag which is rich in silicon and aluminum.The prepared material was analyzed by XRD,bet,f-sem,FT-IR and other technical means,and the removal effect of simulated wastewater was explored.(1)Sod zeolite was synthesized from coal gasification slag,NaAlO2,NaOH and deionized water.Without any surfactant as template,high temperature calcination and acid pickling,simple hydrothermal method was used to adjust the Si/Al ratio of 1.5 and react in 4.5m sodium hydroxide solution with solid-liquid ratio of 1:1.5.The crystallization temperature was 120℃ and the crystallization time was 12 h The effects of Si/Al ratio,alkali concentration,solid-liquid ratio,crystallization time and crystallization temperature on the type and structure of synthesized zeolites were studied.The prepared SOD zeolite was analyzed by various characterization techniques.The specific surface area of SOD zeolite synthesized from coal gasification slag can reach 25.74 m2/g,and the average adsorption pore size is 8.34 nm.The removal of heavy metal lead from waste water by SOD zeolite synthesized from coarse coal gasification slag was studied.According to the adsorption principle of SOD zeolite prepared in the optimal environment,the effects of the amount of zeolite needed for adsorption,pH of waste liquid,adsorption time of zeolite for heavy metal elements,adsorption temperature of zeolite and other factors were studied,and the best economic and feasible removal scheme was determined.(2)ZSM-5 zeolite was synthesized from coarse coal gasification slag,Na2SiO3,TPABr and deionized water by hydrothermal method at 160℃for 72 h by adjusting SiO2:Al2O3:Na2O:H2O:TPABr=25:1.0:2.0:1100:0.4.The effects of template amount,alkali amount,H2O amount,crystallization temperature and crystallization time were studied.The ZSM-5 zeolite was characterized by various characterization techniques.The traditional preparation of ZSM-5 zeolite is usually washed with acid solution to remove impurities.Caustic soda stimulates the activity of silicon and aluminum,which leads to high cost,accompanied by strong acid and alkali wastewater and low alkali utilization rate.We use the silicon and aluminum contained in the coal gasification slag without acid washing and alkali fusion.Instead of alkali fusion,Na2Si03 is used instead of NaOH on the raw materials.It not only complements the silicon source,but also reduces the cost and reduces the alkali pollution.Na2SiO3 promotes the depolymerization and transformation of aluminosilicate gel,and is more conducive to the synthesis of ZSM-5 zeolite.In the process,the mother liquor was recovered,so that the organic template of silicon and aluminum and the remaining alkali liquor could be used for the synthesis of ZSM-5 zeolite.The specific surface area of ZSM-5 zeolite synthesized from coal gasification slag without NaOH is 415m2/g,and the average adsorption pore size is 2.39nm.ZSM-5 zeolite synthesized from coal gasification coarse slag was used to remove ammonia nitrogen wastewater.Based on the adsorption principle of ZSM-5 zeolite prepared in the optimal environment,the effects of the amount of zeolite needed for adsorption,the pH of ammonia nitrogen liquid,the adsorption time of zeolite for ammonia nitrogen and the adsorption temperature of zeolite for ammonia nitrogen were studied,and the optimal scheme was determined.(3)ZSM-5 zeolite was synthesized from coarse coal gasification slag,silica,Na2CO3·10H2O and TPABr by solvent-free method at 150℃ for 60 h,adjusting SiO2:Al2O3:Na2O:TPABr=25:1.0:7:4.The factors such as grinding time,amount of template,amount of Na2CO3·10H2O,crystallization temperature and crystallization time were studied.In the conventional hydrothermal synthesis of ZSM-5 zeolite,more or less raw materials will be left and wasted in water,resulting in the decline of yield and water pollution.From the economic and environmental point of view,the solvent-free method has many advantages over the conventional hydrothermal method.For example,the solvent-free method overcomes the large amount of water necessary in the hydrothermal synthesis process,and directly avoids the waste liquid water pollution;This method only needs simple grinding and heating to synthesize ZSM-5 zeolite,which has high utilization of raw materials and high zeolite yield.The key to the synthesis of ZSM-5 by solid-state method is the addition of Na2CO3·10 H2O.The hydrolysis and condensation of Si-O-Si or Si-O-Al bonds play an important role in the crystallization of zeolite.Compared with the hydrothermal method,the solid-phase method has the advantages of lower synthesis temperature,faster synthesis speed,extremely simple process and no special requirements for equipment conditions,basically realizing "zero emission",which has high economic value and good industrial prospects.This is the first study on the preparation of ZSM-5 zeolite from coal based solid waste in anhydrous system. |
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