Preparation Of Modified Slag-based Geopolymer Microspheres And Study On Adsorption Behavior Of Fluoride Ions In Water

The dispersion-suspension-solidification method was used to prepare slag-based geopolymer microspheres in this paper,investigating the effects of water glass modulus and water amount on the properties of slag-based geopolymer microspheres.Iron oxide and cerium oxide with better adsorption effect of fluoride ion were selected to modify the slag-based geopolymer microspheres and the optimal load concentration was determined.The performance of modified microspheres and the adsorption effect of fluoride ion were compared.Using solid waste slag as raw material to prepare adsorbent and using iron and cerium as the supporting elements can improve adsorbent's adsorption capacity and selectivity to fluorine ion,greatly reduce the preparation cost of adsorbent,and the whole preparation process is green and environmental friendly.The adsorbent is spherical particle?micron level?,which solves problems of lumpy,powdery and irregular shape adsorbent about small adsorption capacity,difficult solid-liquid separation and high adsorption column pressure in industrial.And further improves the application of slag-based geopolymer microspheres adsorbent in the field of fluorine removal.The adsorbent were characterized by SEM-EDS,PSD,BET,XRD,FT-IR,TG/DSC and XPS,Zeta potential analysis.Using batch adsorption experiments study adsorbent on fluorine removal performance and preparation ways,preparation conditions,adsorption performance,adsorption mechanism.For slag-based geopolymer microspheres has provided a theoretical foundation to industrial application.The main research results of this paper are as follows:?1?Slag-based geopolymer microspheres were prepared by dispersion-suspension-solidification method.The influences of water glass modulus and water amount on the properties of slag-based geopolymer microspheres were compared,and the optimal preparation ratio was obtained:slag 30 g,1.7 M water glass 12.86 g and water 8 g.Particle size of slag-based geopolymer microspheres adsorbent was concentrated in 75³00 microns.Under the preparation conditions,the specific surface area of slag-based geopolymer microspheres was 63.76 m²/g.Adsorption experiments show that the adsorbent of slag-based geopolymer microspheres has a certain adsorption effect on fluorine ion.?2?Iron oxide modified slag-based geopolymer microspheres were prepared by dispersion-precipitation method.The optimal iron ion concentration was 0.2 mol/L,and its specific surface area was 125.15 m²/g.The optimal adsorption conditions for fluorine ions were as follows:pH value was 2,adsorbent dose was 0.15 g/100mL,and adsorption time was 90 min.The adsorption process was in accordance with the Pseudo-second-order kinetic model,the Intra-particle diffusion model and the Langmuir isothermal adsorption model.The maximum saturation adsorption capacity of the adsorbent was 57.50 mg/g.The fitting of adsorption thermodynamic data indicates that the adsorption reaction belongs to exothermic reaction.Coexisting ions experiments showed that the adsorption of fluoride ion ability in turn are:PO₄^3-?SO₄^2-?NO^3-?Cl^-.Real water experiments show that the impact on fluorine ion adsorption pecking order:surface water?tap water?seawater.The curing experiment showed that the modified slag-based geopolymer microspheres of iron oxide had better solidification effect on fluorine ion.?3?Cerium oxide modified slag-based geopolymer microspheres were prepared by dispersed-precipitation oxidation method.The optimum concentration of cerium ion was 0.02 mol/L,and its specific surface area was109.47 m²/g.The optimal adsorption conditions for fluorine ions were as follows:pH value was 2,adsorbent dose was 0.10 g/100mL,and adsorption time was90min.The adsorption process was in accordance with the Pseudo-second-order kinetic model,the Intra-particle diffusion model and the Langmuir isothermal adsorption model.The maximum saturation adsorption capacity of the adsorbent was 125.79 mg/g.The fitting of adsorption thermodynamic data indicates that the adsorption reaction belongs to exothermic reaction.Coexisting ions experiments showed that the adsorption of fluoride ion ability in turn are:PO₄^3-?SO₄^2-?NO^3-?Cl^-.Real experiments show that the water on the impact on fluorine ion adsorption pecking order:surface water?tap water?seawater.The curing experiment showed that the modified slag-based geopolymer microspheres of cerium oxide had a good solidification effect on fluorine ions.?4?Dynamic adsorption kinetics data showed that the dynamic curves of fluorine ions to the two modified slag-based geopolymer microspheres were S-shaped,which was in line with the dynamic adsorption behavior,and the adsorption law was consistent with the adsorption behavior.The adsorption mechanism of two kinds of modified slag-based geopolymer microspheres on fluorine ions were studied by Zeta,EDS,FT-IR and XPS.The results showed that the adsorption mechanism of two kinds of modified slag-based geopolymer microspheres on fluorine ions was completed by ion exchange and electrostatic action.