Analysis Of The Influence Of PH On The Preparation Of Geological Polymers By Carbonation Of Refining Slag

Refining slag is a kind of waste residue from the iron and steel industry and its resource-oriented utilization has the added value is low,can not be make full use of effective components from the slag and other issues,at present most of the iron and steel enterprises will be metallurgical refining slag recycling processing,but the refining slag is still part of the need to discharge after processing,reduces the utilization value of refining slag.It is found that the solid waste of refining slag contains relatively high base material which can directly react with CO₂ to produce inorganic carbonate or double salt,so as to achieve the purpose of waste control,cheap and efficient treatment of carbon dioxide emission from coal flue gas.At the same time,the activity of Si O₂and Al₂O₃ in the slag can be improved,making it become an effective raw material for the preparation of geopolymer,realizing the comprehensive utilization of double waste,which is in line with the national concept of green and emission reduction.In the carbonation process of refining slag,pH plays a dominant role,which affects the migration and transformation of ions,especially alkali metal ions such as Ca²⁺.Meanwhile solution pH affect sample carbonate change rate of weight gain and experimental studies have found that when the solution pH value of 6.samples for real weight gain rate was 7.5%,with the increase of solution pH,carbonate sample weight gain rate decreased,when the pH value of 8 weight gain rate fell to 4%,when the solution pH value is greater than 10 samples showed a trend of increased weight gain rate,pH=12.46,carbonate maximum weight gain rate.It can be seen that pH is an important influencing factor for the carbonation of refined slag.This paper focuses on exploring the influence of pH on the preparation of geopolymer by the carbonation of refined slag,optimizing the experimental conditions and improving the utilization efficiency of refined slag.XRD(X-Ray Diffractometer),TG-DTG(Thermo Gravimetry-Derivative Thermo Gravimetry),FT-IR(Fourier Transform Infrared Spectroscopy),SEM(Scanning Electron Microscope)and other analysis methods were used to characterize the carbonated refining slag and the base polymer of the carbonated refining slag under different pH conditions.Firstly,the thermodynamic calculation of carbonation was carried out by using HSC Chemistry software,which laid a theoretical foundation for the carbonation of refined slag.Then,the phase diagrams of typical Ca O-Al₂O₃ binary system and Ca O-Al₂O₃-Si O₂ ternary system of refined slag were analyzed and discussed.According to thermodynamic analysis,the Gibbs free energies of Ca O,Ca(OH)₂,Ca₂Si O₄,Ca₃Si O₅and Fe O in the refining slag are all negative below 673K,indicating the possibility of carbonation of the refining slag.At the same time,combining with the E-pH diagram of Ca-H₂O,Mg-H₂O,Al-H₂O and Fe-H₂O series,it is clearly pointed out that the carbonation reaction of pH>7 refining slag is easy under the alkaline condition.The single factor test of refining slag carbonation was carried out to investigate the variation of pH and conductivity of refining slag in the carbonation process with different particle size,liquid-solid ratio,ventilation rate and stirring speed at room temperature.The optimal combination of parameters of carbonation was obtained,that is,the particle size of the refining slag was 400 mesh,the liquid-solid ratio was 5,the ventilation rate was 500 m L/min,and the stirring speed was 700rpm.In order to further study the mechanism of the influence of pH on the carbonation of refining slag,the buffer solution with pH of 6,7,8,9.18,10,11 and 12.46 was selected for experimental study to explore the influence of solution pH on the ion migration and transformation and the weight gain rate of carbonation.And XRD?SEM?TG-DTG?FT-IR analysis under different pH buffer solution refining slag after the carbonate mineral phase composition change,The carbonation degree,the mass of Ca CO₃ and the amount of CO₂ absorption were quantitatively analyzed.It is concluded that pH will promote the higher dissolution of Ca²⁺under the condition of weak acid and strong base,and the C-S-H gel will be decalcified under the action of carbonation and finally produce Ca CO₃.When pH=6,the total weight loss rate reaches the maximum of 30.10%,and when pH is 12.46,the carbonation degree reaches the maximum of 40.48%.Finally,the raw material ratio of the geopolymer prepared from the refining slag and the mechanical properties and mineral phase changes of the base polymer from the carbonated refining slag were studied.It was found that the optimal raw material ratio for preparing geopolymer was the dosage of 24g Na OH and 90ml Na₂O·n Si O₂ with water-cement ratio of 0.16.When the pH of the solution is weak acid and strong alkali,the carbonation eliminates the influence of f-Ca O,and the carbonated refined slag-based mineral phase is filled in the pores with a more stable structure,which has good compactness and high mechanical strength.The pH value can directly affect the carbonation effect and improve the compressive strength of the base polymer of the carbonated refining slag.This article explore the refining slag through the experiment of carbonic acid,the optimal process parameters combination,to determine the optimum pH,carbonate by ICP ion chromatography found solution pH is the main influence factors of ion migration transformation mainly affects Ca²⁺dissolution in the calcium base material,through the analysis of the microstructure and mineralogical composition show that when the solution pH is weak acid and alkali carbonate after solid phase Ca CO₃ content increased significantly,carbonate chemical refining slag base polymer mainly stable calcite ore phase form distribution,products with higher mechanical and compressive strength.