Study On The Controllable Preparation Of Slag-based Geopolymer Microspheres And Adsorption Performance Of Pb(Ⅱ)

Slag is a kind of amorphous aluminosilicate precursor material,which is formed by the depolymerization polycondensation reaction under alkaline conditions to produce geopolymer gel material with three-dimensional network structure.Due to its special three-dimensional network structure,geopolymer has the advantages of high strength,acid resistance,high temperature resistance and environmental protection.It is expected to be widely used in building materials,3D printing,adsorption of toxic heavy metal ions and other fields.In this study,slag is used as the raw material,water glass as alkali activator,and simethicone as dispersion medium.Preparing slag-based geopolymer microspheres（SGMs）with a particle size of under 30μm by means of suspension dispersion solidification method.The paper uses scanning electron microscope（SEM）,ultra-high-speed intelligent particle size analyzer,X-ray powder diffraction（XRD）,fourier transform infrared spectroscopy（FTIR）,energy dispersive spectrometer（EDS）,specific surface area and pore size distribution teste（BET）and spherical aberration correction environmental transmission electron microscope（STEM）to characterize the SGMs and to study the adsorption effect of this SGMs on the heavy metal Pb（Ⅱ）ion.The main research contents are as follows:（1）Water glass stimulated slag to prepare geopolymer microspheres（SGMs）:Slag and water glass are used as the main raw materials,and SGMs are prepared by means of suspension dispersion solidification method.The sphericity and particle size distribution of the microspheres are controlled by single-factor conditions such as continuous phase,dimethyl silicone oil temperature and viscosity,height diameter ratio of reaction vessel,curing temperature and time,slag particle size,and disperser speed.By analyzing the microstructure and particle size distribution of SGMs prepared under different conditions to determine the best technological parameters for the preparation of the ball:the best spherical degree of SGMs with a particle size of below 30μm was obtained when silicone oil was selected as the continuous phase,and the temperature was 50℃,height and diameter ratio of reaction vessel as 2.5 reactor and geopolymer slurry cured at low temperature for 0.5 h;the highest rate of SGMs below with a particle size of 30μm was produced with dimethylsilicone oil temperature as 50℃,slag particle size as 0.2-10μm,dispersar speed as 5000r/min,silicone oil viscosity as 1000 mm²/s,and the yield reached 48.19%.（2）In the experiment of different contact time between SGMs and Pb（Ⅱ）ion solution,the adsorption of SGMs on Pb（Ⅱ）ion basically reached equilibrium after contact for 20 h,at this time,the adsorption capacity was 353.9mg/g,and the removal rate was 88.03%.The adsorption of Pb（Ⅱ）ions by SGMs conforms to the quasi-second-order kinetic model,indicating that the adsorption process was mainly chemical adsorption.（3）In the experiments of Pb（Ⅱ）adsorption by SGMs with different particle sizes,it was found that the adsorption amount of Pb（Ⅱ）ions by the microspheres does not have a linear relationship with the specific surface area,average pore size and pore size distribution of the microspheres,and the pore size distribution is wider after SGMs adsorb Pb（Ⅱ）ions.（4）The dynamic adsorption experiments of Pb（Ⅱ）ions by SGMs were carried out.The experimental results showed that the dynamic adsorption breakthrough curve were affected by different column heights（bed height）,different flow rates,different initial concentrations Pb（Ⅱ）,and different particle size SGMs.high column height,low flow rate,low initial concentration of Pb（Ⅱ）and small particle size of SGMs are beneficial to prolong breakthrough time and saturation time.When the fixed bed H=3 cm,the flow rate of the peristaltic pumpμ=1 m L/min,the initial concentration is 200 mg/L,the particle size range of the SGMs adsorbent is 10-30μm,the breakthrough time is 2803 min,and the saturation time at 5623 min,the removal rate was 70.22%.（5）The adsorption of Pb（Ⅱ）by SGMs was compared with that before and after adsorption.The FTIR test showed that the main functional groups of SGMs did not change before and after adsorption.SEM tests showed that SGMs adsorbed Pb（Ⅱ）before the SGMs had a dense gel structure and had no crystal on the surface.After the adsorption of Pb（Ⅱ）,SGMs surface growth of about3-5μm nanorod crystal structure.XRD,EDS and STEM showed that on the surface of SGMs rod-shaped crystals are Pb₃Si₂O₇and Pb₅Si₄O₈（OH）₁₀.