The Preparation And Modification Of Coal Gangue Based Porous Silica Materials And Its Application Of CO₂ Adsorption

As a major greenhouse gas,CO₂ and its treatment technology has been extensively studied.Although the research and application of liquid amine absorption method for CO₂ was earlier and the most mature,the method has corrosion for equipment,large renewable energy consumption,big equipment input and other shortcomings.Thus,based on the concept of CO₂ capture and utilization?CCU?technique,CO₂ storage material?CO₂SM?prepared by CO₂ absorption of triethylene glycol + ethylenediamine?TEG + EDA?mixture system was used as a raw material to prepare solid adsorbent and applied to capture CO₂.Coal gangue as a large solid waste has a wide range of sources with low cost and a rich silicon content,and can be used as a cheap raw material to prepare porous silicon material?PSM?which can be used for the study of CO₂ adsorption process after modified by EDA.The study on preparation of porous silicon material using coal gangue and CO₂ SM as raw materials and its application to capture CO₂ mainly includes the following five parts.The CO₂ SM was formed in CO₂ absorption process with TEG + EDA mixture as the adsorbent.The alkyl ammonium carbonate structure of CO₂ SM was characterized by techniques of X-ray diffraction measurement?XRD?,X-ray photoelectron spectroscopy?XPS?,fourier transform infrared spectroscopy?FTIR?,nuclear magnetic resonance spectroscopy?13C-NMR?,and thermogravimetric analysis?TG-DSC?.Sodium silicate-based PSM was prepared by Na₂SiO₃ solution and CO₂ SM as raw materials,and its optimization of preparation conditions,analysis of influenced factors and establishment of CO₂ absorption mathematical model was achieved by single factor experiment,orthogonal test and response surface analyses.The optimum preparation conditions were 50 m L of 0.5 M Na₂SiO₃ solution,10 g CO₂ SM,80 ? reaction 36 h and 40-160 mesh.Besides,the adsorption mathematical model of sodium silicate-based porous silicon material was as follows : CO₂ adsorption capacity = 16.69625-0.75105A-0.12953 B + 0.31221C-0.0059AB-0.011458AC-0.00127083 BC + 0.044460A2 + 0.001465B2-0.0017083,where the significant factors in the mathematical model were A,C,AC and A2?A was CO₂ SM dosage,g;B was reaction temperature,oC;C was reaction time,h?.Based on the optimized preparation conditions of sodium silicate-based PSM,gangue-based PSM was prepared by coal gnague and CO₂ SM and its optimal preparation conditions was confirmed by single factor experiment and response surface analyses as follows: 50 mL 0.5 M SiO32-extraction from coal gnague,40 g CO₂ SM,reaction at 80 oC for 36 h and 40-160 mesh.Besides,the adsorption mathematical model of sodium silicate-based PSM was established by response surface analyses as follows : CO₂ adsorption capacity =-213.73300 + 3.02605 A + 1.59078 B + 5.37987 C + 0.009 AB + 0.007375 AC + 0.0000625BC-0.050760A2-0.011840B2-0.078531C2,where the significant factors in the mathematical model were A2?B2?C2?A was CO₂ SM dosage,g;B was reaction temperature,oC;C was reaction time,h?.The means of FTIR,XPS,TG,TEM and SEM were used to analyze the PSM which consisted of SiO2,adsorbed water,combined water and a small amount of organic ingredients.Sodium silicate-based PSM was composed of a large amount of irregularly shaped particles with a diameter of 20-30 nm,and its average pore size of the PSM was 29.983 nm,with the total pore volume of 0.966 m3·g-1 and the specific surface area of 114.653 m2·g-1.Similarly,gangue-based PSM was constituted by nearly spherical particles bonded together forming a uniform surface morphology and accumulating the voids as the main inside “pore” structure,and its average pore size was 11.20 nm with the specific surface area of 12.3419 m2·g-1,and the total pore volume of 0.0497 m3·g-1.The adsorption properties of PSMs under the optimum preparation conditions were improved by EDA modification using impregnated method.The adsorption capacity of 8% CO₂ at 25 ? was increased from 9.74 mg/g to 23.63 mg/g for sodium silicate-based PSM,and increased from 9.02 mg/g to 17.73 mg/g for the gangue-based PSM.