Study On The Preparation Of Single-phase Zeolite From Ningdong Coal Gasification Fine Slag And Removal Effect On Heavy Metals In Wastewater

Ningdong coal gasification slag is a solid waste produced by a high-pressure gasifier at 1400-1500℃under reducing atmosphere(CO,H2),with an annual output of nearly 10 million tons.Obtained by gas washing,flocculation,and suction filtration,accounting for about 50%of the total coal gasification waste residue,its physical and chemical properties are different from traditional solid waste such as fly ash,and there are very few reports on the utilization of coal gasification fine residue,Therefore,it is necessary to study the simple and easy treatment method of coal gasification fine slag,as well as to explore in depth the ways of coal gasification fine slag resource utilization.This paper mainly takes the fine slag of Ningdong Coal Gasification as the research object.Through research on the composition,structure and physicochemical characteristics of coal gasification fine slag,a method of easy to synthesize single-phase high crystallinity zeolite was proposed.The effects of the amount of alkali used in the solid-phase alkaline fusion process,the solid phase alkaline fusion temperature,the ratio of silicon to aluminum(SiO2/Al2O3),hydrothermal synthesis time,hydrothennal synthesis temperature,liquid-solid ratio etc on the synthesis of the single phase zeolite were investigated.And the acidic aluminum salt is used to neutralize the alkaline waste liquid generated during the hydrothermal reaction.On this basis,the effect of synthetic zeolite on the treatment of heavy metals in simulated wastewater was also studied.The main research contents are as follows:1.By XRF,XRD and BET characterization of Ningdong coal gasification fine slag,it is determined that the total mass fraction content of the main material composition SiO2 and Al2O3 in coal gasification fine slag reaches more than 70%,corresponding to n(SiO2)/n(Al2O3)is about 5;residual carbon content is 20%to 30%(mass fraction).The main diffraction peak of XRD pattern of coal gasification fine slag is quartz,and most substances exist in the form of glass;there is no reference to the existing experience about the utilization of coal gasification fine slag.2.In view of the unique properties of coal gasification fine slag,a single-phase zeolite A is prepared at a low cost by using a synthesis method of solid phase alkali fusion combined with hydrothermal reaction.The experimental results show that when the mass ratio of sodium hydroxide to coal gasification fine slag is 1.2,solid phase alkali fusion temperature 823K,hydrothermal reaction temperature 353 K.hydrothermal reaction time 12h,and the solid-liquid ratio is 5,the synthesized zeolite A has the relatively high crystallinity,Reaching 93.1%,its cation exchange capacity(CEC)is 268.4(mmol/100g),and the BET specific surface area is 61.1m2/g.3.In order to realize the resource conversion of coal gasification fine slag and obtain high value-added products,we prepared zeolite X by solid phase alkaline fusion combined with hydrothermal synthesis.The study found that when The mass ratio of sodium hydroxide to coal gasification fine slag is 1.2,solid phase alkali fusion temperature 823K,the hydrothermal synthesis temperature is 373K.the aging time is 2h;the hydrothermal synthesis time is 12h,and the liquid-solid ratio is 4.5～5mL/g.And use the acidic aluminum salt to neutralize the alkaline waste liquid generated in the hydrothermal synthesis reaction zeolite process,get a good neutralization effect.4.Aiming at the pollution of heavy metals in waste water,in order to realize the recycling of solid waste and "treatment of waste with waste",the zeolite prepared by coal gasification fine slag was used to study the removal effect of heavy metals Pb2+and Cu2+in waste water.Through the study of the factors affecting the amount of single-phase zeolite A,the initial pH value of the solution,and the shaking time,the dosage of the zeolite material was 1.5g/100mL,pH=6,and the removal rate of heavy metals Pb2+and Cu2+ in wastewater after 250 min horizontal shaking,Both can reach more than 99%.For the mixed heavy metal ions of Pb2+ and Cu2+in wastewater,the removal effect of Pb2+ is significantly better than that of Cu2+.