Composition Regulation Of Geopolymer Based On Fly Ash& Slag And Its Adsorption Characteristics Of Nitrogen And Phosphorus

Ammonia nitrogen and phosphorus are the main substances for eutrophication of water bodies and are also the targets of polluted water treatment.Adsorption of nitrogen（N-NH₄⁺）and phosphorus（P-H₂PO₄^-）has the advantages of simple operation and low maintenance cost,but the synchronous removal effect is poor.Geopolymer has certain cation exchange adsorption characteristics due to its zeolite-like phase,and the selection of suitable excitation system to prepare geopolymer can generate layered bimetallic hydroxides（LDHs）,which in turn imparts anion exchange adsorption properties to the geopolymer.Therefore,the preparation of LDHs@geopolymer composite materials（LDHs@GC）by composition regulation,which are simultaneously endowed with nitrogen and phosphorus removal functions and applied to water eutrophication treatment,provide a simple operation and excellent performance adsorbent material for sewage treatment,which has high theoretical research significance and engineering application value.In this paper,two LDHs@GC were prepared using high aluminum fly ash and granulated blast furnace slag as precursors,sodium hydroxide-sodium carbonate,calcium hydroxide-calcium sulfate dihydrate as mixed initiators,and mixed hydrogen peroxide and sodium dodecyl sulfonate as chemical foaming agents.XRD,SEM-EDS and BET microscopic test methods were used to analyze the main mineral composition and pore structure of the prepared LDHs@GC.Using LDHs@GC as adsorbent,static adsorption test was used to investigate its phosphorus removal effect.Secondly,the adsorption effect of internal clinoptilolite zeolite or artificial zeolite and alkaline heat conversion zeolite on improving the adsorption effect of the two LDHs@GC ammonia nitrogen was comparatively studied.Finally,the effects and adsorption characteristics of different adsorption environments on synchronous nitrogen and phosphorus removal of the two LDHs@GC after optimal modification treatment were studied.The main conclusions of this study are as follows:（1）The main mineral phases of Mg Al-LDHs@GC are Mg Al-LDHs,hydrocalumite,nepheline and hydrocalumite,and the main mineral phases of Ca Al-LDHs@GC are AFt.Mg Al-LDHs@GC with the increase of active magnesium oxide content,the adsorption effect of phosphorus first increased and then decreased,when the active magnesium oxide content was 8%,the adsorption effect was the best,and the adsorption capacity and removal rate of phosphorus were 9.51 mg/g and 95.1%,respectively.Ca Al-LDHs@GC changes from large to small with the ratio of Ca（OH）₂ and Ca SO₄·2H₂O,and the adsorption effect on phosphorus increases first and then decreases,when the mass ratio of Ca（OH）₂ and Ca SO₄·2H₂O is 1:1,the adsorption effect is the best,and the adsorption capacity and removal rate of phosphorus are 9.99 mg/g and99.9%,respectively.Under the same conditions,Ca Al-LDHs@GC has a better phosphorus removal effect than Mg Al-LDHs@GC.（2）Compared with LDHs@GC,the adsorption capacity of alkaline thermal conversion LDHs@GC（A-LDHs@GC）was increased,but the lifting effect was not obvious.Compared with LDHs@GC,the adsorption effect of modified LDHs@GC（C-LDHs@GC）and modified LDHs@GC type A zeolite（AZ-LDHs@GC）was significantly improved,and the adsorption effect of ammonia nitrogen increased with the increase of clinoptilolite and type A zeolite.The adsorption effect of AZ-LDHs@GC on ammonia nitrogen was better than that of C-LDHs@GC,and the adsorption effect of AZ-Ca Al-LDHs@GC on ammonia nitrogen was higher than that of AZ-Mg Al-LDHs@GC.（3）AZ-LDHs@GC achieves efficient synchronous nitrogen and phosphorus removal under the combined action of monolayer chemical adsorption and multilayer physical adsorption.The maximum adsorption capacity of AZ-LDHs@GC Mg Al-LDHs@GC for ammonia nitrogen and phosphorus was 8.333 mg/L and 11.111mg/L,respectively,and the adsorption capacity of AZ-Ca Al-LDHs@GC for ammonia nitrogen and phosphorus was 9.524 mg/L and 10.417 mg/L,respectively.