Self-supporting Fly Ash-based Porous Absorbent Material Preparation And Its Denitrification And Dephosphorization Effect

The large amount of ammonia nitrogen and phosphorus in the water body will lead to eutrophication of the water body,and the control of ammonia nitrogen and phosphorus discharge is a difficult problem in water environmental governance.The adsorption method for treating ammonia nitrogen and phosphorus polluted water has the advantage of Stable removal effect,but the adsorption material is the core element.Natural zeolite as water treatment adsorption material has a wide source of materials,low cost advantages,the disadvantage is the choice of poor adsorption effect,although the synthetic zeolite can partially overcome the defects of natural zeolite,but there are high production cost,post-processing difficulties and other technical problems.Geopolymer is a three-dimensional network amorphous structure with[Si O4]^4-and[Al O4]^5-as structural units through depolymerization and condensation of fly ash,slag or steel slag and other industrial solid wastes under alkali activation.Because its preparation process is similar to the formation process of zeolite,it is considered as the precursor of zeolite synthesis.The theory of in situ conversion of geopolymer to zeolite is feasible,and it has important environmental benefits when applied to the treatment of polluted water bodies such as ammonia nitrogen and phosphorus.This study alumina powder coal ash as the precursor,by the chemical,chemical foaming technique was used to prepare the porous geopolymer basic skeleton,and through further in situ hydrothermal principle into rich in Quito hole zeolite from the support of the fly ash adsorption materials（SSFPAM）,based on the orthogonal experiment,optimized the porous geological polymer process conditions of in situ conversion of zeolite.Under the optimal in-situ conversion conditions,the influence of the composition of the precursor and the content of the blowing agent on the basic properties of SSFPAM and the ammonia nitrogen adsorption capacity was studied.SSFPAM and lanthanum chloride loaded modified SSFPAM（LCMSSPAM）were used as adsorption materials to study the influence of adsorption environment on the denitrification and phosphorus removal efficiency of the two materials.The mineral composition,micromorphology and pore structure of SSFPAM and LCMSSPAM were characterized by XRD,SEM,BET and EDS analysis.The above research results show that:（1）The optimal hydrothermal conditions for the conversion of porous geopolymers to SSFPAM are:the temperature is 180℃,the concentration of alkali is 1.5 mol/L,and the time is 24 h.Under the optimum in situ conversion conditions,the zeolite phase in SSFPAM is NAP zeolite.When the foaming agent（H₂O₂）content is 2.5%,the compressive strength of SSFPAM is 0.6 MPa,the pore porosity is 67.58%,the specific surface area is 50.87 m²/g.（2）Under the adsorption conditions of p H=7,solid-liquid ratio of 1:15,and initial ammonia concentration of 25 mg/L,SSFPAM has an ammonia nitrogen adsorption capacity of 0.327 mg/g,and an ammonia nitrogen removal rate of 87.2%.The isothermal adsorption process of NH₄⁺-N is consistent with the Langmuir model and Freundlich model,and the kinetic model is consistent with the quasi-second-order adsorption kinetic equation.（3）lanthanum chloride load modification can significantly increase SSFPAM on phosphorus adsorption effect,when the concentration of lanthanum chloride was 0.5%,the modification of p H value of 9.3,the modification time was 8 h,load modified phosphorus removal effect is best,When the initial H₂PO₄^-concentration is 20mg/L,the solid-liquid ratio is 1:15,and the p H is 6,LCMSSPAM can completely remove phosphate in the solution.（4）In the synchronous nitrogen and phosphorus removal process of LCMSSPAM,there will be a competitive adsorption process between ammonia nitrogen and phosphorus,especially the presence of NH₄⁺will have a significant inhibitory effect on the removal of phosphate.