Synthesis Of NaA Zeolite From Coal Gangue And Adsorption Of F^- And PO₄^3- In Simulated Wastewater

Coal is an important energy pillar in China,coal gangue,as a companion to coal,is currently one of the largest solid wastes in China.Reasonable and efficient use of coal gangue can alleviate the resource consumption and environmental pollution problems caused by coal resources.In this paper,coal gangue is used as the raw material,and the characterization methods such as ICP-OES are used to analyze the raw material to determine that it has the basic ingredients for preparing zeolite;NaA zeolite was prepared by low-temperature hydrothermal synthesis.With the assistance of a series of characterization methods,the optimal synthesis conditions of zeolite were selected and determined;The structure and morphology of NaA zeolite were analyzed by five characterization methods such as XRD,etc.;The adsorption conditions of NaA zeolite for F^-and PO₄^3-were determined,and their adsorption mechanism was analyzed and explored.The conclusions are as follows:?1?The optimal process conditions for preparing NaA zeolite using coal gangue as the raw material of this experiment are:Coal gangue was crushed and sieved,and calcined at 750? for 2 h.By adding silicon source,alkali and water to regulate nSiO₂/nAl₂O₃=2.3,nNa₂O/nSiO₂=1.9,nH₂0/nNa₂O=45,after aging at 50? for 1.5 h,crystallized for 7h at 80?.After filtration,washing and drying,NaA zeolite was obtained;?2?Characterize the product:The XRD pattern is compared with the standard card to know that the synthesized product is NaA zeolite,the SEM analysis shows that the products are NaA zeolites with angular and cuboid structure,and the BET analysis show that micro-mesoporous structures exist simultaneously in the NaA zeolite,the pore volume is0.029 cm³/g,the surface area of 4.067 m²/g;?3?The best conditions for NaA zeolite to adsorb F^-are:Add 0.15 g of NaA zeolite to a 15 mg/L fluorine-containing solution,the solution pH is adjusted to 6.00,and shaken at 230 r/min for 60 minutes at room temperature.At this time,the NaA zeolite's adsorption amount of F^-in the simulated wastewater was 4.91 mg/g,and the removal rate was 98.11%;?4?The best conditions for NaA zeolite to adsorb PO₄^3-are:Add0.20 g of NaA zeolite to a 25 mg/L phosphorous-containing solution,and shaken at 230 r/min at room temperature for 180 min at the original solution pH?4.40?.At this time,the adsorption capacity of PO₄^3-by NaA zeolite was 6.17 mg/g,and the removal rate was 98.78%;?5?The fitting results of the quasi-first-order and quasi-second-order kinetic models on the kinetic test data of zeolite adsorption simulated wastewater show that:The adsorption of NaA zeolite to F^-and PO₄^3-reached equilibrium at 60 min and 180 min,respectively.The kinetic adsorption process fits well with the quasi-second-order model?R²>0.9991?,the calculated q_e of saturated adsorption capacity(F^-:4.99mg/g,PO₄^3-:6.41 mg/g)obtained by this model is close to the experimental values Q_e,exp(F^-:4.91 mg/g,PO₄^3-:6.17 mg/g),it indicates that chemical adsorption may be the main factor affecting the adsorption reaction rate of F^-,PO₄^3-by NaA zeolite;The results of intraparticle diffusion model fitting showed that the adsorption of NaA zeolite on F^-,PO₄^3-was influenced by surface diffusion and intraparticle diffusion;?6?The fitting results of the isothermal adsorption model to the isothermal adsorption test data of NaA zeolite adsorption simulation wastewater show that:The Langmuir model?R²:0.9986 and 0.9988?is suitable to describe the adsorption behavior of NaA zeolite to F^-and PO₄^3-,which indicates that the adsorption of fluorine and phosphorus by zeolite is mainly monolayer adsorption.The range of the equilibrium parameter R_L is 0.0191?0.3279 and 0.0162?0.0897,both of which are in the range of 0?1,indicating that its adsorption is easier to carry out;?7?It can be seen from the comparison of the adsorption of F^-and PO₄^3-by coal gangue and NaA zeolite,the adsorption capacity of NaA zeolite for F^-and PO₄^3-has been increased by 3?5 times compared with the raw coal gangue,indicating that the synthetic zeolite has a better adsorption effect.