Structural Modification Of Coal By Solvent Extraction And Evaluation Of Adsorption Properties Of The Coal Residue

The microwave direct heating solvent extraction modification,plus sodium carbonate solid phase grinding pretreatment methanol solvent extraction,sodium hydroxide ?methanol extraction,Fenton-hydrothermal oxidation pretreatment extraction and other technical methods were used to investigate the influences of the different pretreatment processes on the composition and structure for coal which is derived from Hongshiwan,Ningxia province of China.Moreover,the extracted residues of coal were used as a modified porous material to study the adsorption properties for the water pollutant.The main results are as follows:(1):The Hongshiwan coal was extracted by microwave method with methanol solvent.The optimized process conditions are:the solid-liquid ratio(g:mL)of coal(below 80 mesh)to methanol is 1:4,the power of microwave was 600 W,the time of extraction is 25 min,the extraction rate is 0.6%.The structure properties of the extracted coal were detected by FT-IR,XRD,BET,and TG.The results show that the skeleton structure of the coal is destroyed,abundant functional groups can be observed in the coal surface,the distance between the aromatic rings is reduced,pyrolysis property is decreased,and the pore size decreases together with the specific surface area increases.It shows that the solvent extraction process has a significant effect on the composition and structure of coal.The result indicates that the extracted coal could be good absorption material.In addition,the extracts were analyzed by GC-MS.It shows that the main components of the extracts are fats,aromatics and heteroatoms.(2):The coal was pretreated by sodium carbonate solid-phase milling,sodium hydroxide extraction and Fenton-hydrothermal oxidation.The optimized process conditions are:the mass ratio of coal and sodium carbonate is 50:3,the milling time is 4h,the solid-liquid ratio(g:mL)of coal to methanol is 1:4,the power of microwave is 600W,and the time of extraction is 25min,the extraction rate can reach 1.45%.With the same extraction conditions,5g coal is added to 0.3g sodium hydroxide for extraction experiments,the extraction rate could reach 3.21%.For Fenton-hydrothermal pretreatment(5 g coal,1 g ferrous sulphate,1 mL hydrogen peroxide),the temperature is 180?,and the hydrothermal oxidation time is 6 h,5 g coal is added to 0.3 g sodium hydroxide extracted,the extraction rate could reach 4.8%.The extracted residues were subjected to FT-IR,XRD,BET and TG analysis.The results show that the stretching vibration peaks of the C-O bond is obviously enhanced for the grinding coal with sodium carbonate extracted residues and the extracted residues of sodium hydroxide.It indicates that the structure of coal is deoxidized by oxidation.The stacking height of the aromatic ring layer is decreased for the extracted residues that produced by sodium carbonate added solid-phase milling and Fenton-hydrothermal oxidation decreased.The stacking height is increased for the extracted residues which derived from sodium hydroxide extraction.In addition,GC-MS result shows that the main components of the extracts are chain alkanes,aromatic hydrocarbons,and oxygen-containing as well as nitrogen-containing compounds.(3)The above extracted residues were used as adsorbent materials to investigated adsorption performance of water model pollutions.The extracted residues that drived from sodium hydroxide extraction was used to tested adsorption removal performance for methylene blue and alkaline magenta dye.The results showed that the removal rate of methylene blue by the extracted coal was 95.7%and the adsorption amount was 0.48 mg/g with the conditions of 3.0 g extracted residues 15 mg/L methylene blue.However,the removal rate of the same quality raw coal was 40%and the adsorption amount was 0.20 mg/g.3.0 g extracted residues were used as adsorbent to remove 20 mg/L basic fuchsin solution,the removal rate is 97.1%,and the adsorption amount is 0,65 mg/g.The removal rate of the same quality raw coal was 42%and the adsorption amount was 0.28 mg/g.At the same time,the characteristics of adsorption kinetics were also explored,and the results showed that the above adsorption process conforms to the pseudo-second order kinetics model,there are multiple control steps in the adsorption process,while the adsorption isotherm data could be described with the Langmuir adsorption model and occurred on the monolayer surface.The above results indicate that the extracted residues derived from solvent extraction coal could be a good adsorbent material.