Preparation And Powder Forming Of Huaning Coal Based Porous Carbon And Its Adsorption Properties For Cr(Ⅵ)

Extracting high value-added chemicals such as fulvic acid and humic acid from oxidized lignite will produce a large amount of waste residue of oxidized residual coal.How to effectively realize the reuse of oxidized residual coal is the key to the efficient utilization of lignite resources.In this thesis,powdered porous carbon material（DC）was prepared by one-step carbonization activation of potassium hydroxide with oxidized residual coal（after extracting fulvic acid from Yunnan Huaning Lignite by hydrogen peroxide）as carbon precursor,and the optimal preparation conditions are explored by response surface design.Combined with modern analysis methods such as infrared,X-ray diffraction and electron microscopy to explore the structure and properties of DC.Using polyvinyl alcohol（PVA）and carboxymethyl cellulose（CMC）as binders and powdered porous carbons,the porous carbons PVA-ZDC and CMC-ZDC were prepared by compression molding.Porous carbons Na₂Si O₃-PVA-ZDC and SAS-CMC-ZDC were prepared by modifying PVA and CMC with sodium silicate and silica sol（SAS）,respectively.Combined with adsorption experiment,kinetic adsorption model and isotherm adsorption model,the influencing factors and removal mechanism of Cr（Ⅵ）removal from water by forming porous carbon were explored.The main conclusions are as follows:The optimal preparation conditions of DC are activation temperature of 647.3℃,KOH addition ratio of 3.2:1,and activation time of 35.3 min.The methylene blue adsorption value of DC prepared under the optimal conditions is 527.06 mg·g^-1,and the yield is 15.6%.The proportion of micropores in the pore structure of DC is higher than that of mesopores,its specific surface area is 2744.98 m²·g^-1,the average pore diameter is 1.99 nm,and the mesoporosity is 5.8%.The content of hydroxyl functional groups in DC increased significantly,the branched aliphatic hydrocarbons disappeared,the amorphous carbon in the structure increased,the degree of disorder was high,and the degree of graphitization was low.Through binder compression molding,Under the optimum conditions of PVA addition of 30%and heat treatment at 190℃for 70 min,the compressive strength of formed porous carbon pva-zdc is 284.72 N and the adsorption value of methylene blue is 167.2 mg·g^-1,with a specific surface area of 1050.28 m²·g^-1,pore volume 0.56cm³·g^-1,the average pore diameter is 2.12 nm,and the mesoporous rate is 12.5%.Under the optimal conditions of CMC addition of 20%and heat treatment at 170°C for 70 min,the compressive strength of CMC-ZDC is 267.61 N,the methylene blue adsorption value is 191.7 mg·g^-1,the specific surface area is 1170.13 m²·g^-1,and the pores The volume is 0.58 cm³·g^-1,the average pore size is 1.98 nm,and the mesoporosity is 10.3%.The maximum methylene blue value of porous carbon Na₂Si O₃-PVA-ZDC prepared by 4.5%Na₂Si O₃ modified PVA is 137.5 mg·g^-1,which is lower than that before modification,but the compressive strength increases to498.11 N under the same heat treatment conditions.While the compressive strength of SAS-CMC-ZDC reached a maximum of 415.69 N when the mass ratio of SAS:CMC was 3:1,and the adsorption value of methylene blue under the same heat treatment was 181.8 mg·g^-1.Compared with that before modification,the pore size distribution of Na₂Si O₃-PVA-ZDC and SAS-CMC-ZDC is almost unchanged,and the pore volume and specific surface area are slightly reduced.After modification,the water stability of Na₂Si O₃-PVA-ZDC in acidic,neutral and alkaline water was improved.The water stability of SAS-CMC-ZDC in acidic and neutral water was improved,but the water stability in alkaline water was poor.After the binder modification,the adsorption performance of the formed carbon was not greatly improved,but the strength and water resistance of the formed carbon could be significantly improved.The experimental results of adsorption of Cr（Ⅵ）in water show that the adsorption equilibrium time of Na₂Si O₃-PVA-ZDC and SAS-CMC-ZDC is 500 min,and the equilibrium adsorption capacity is 20.46 mg·g^-1 and 26.11 mg·g^-1,respectively.p H affects the adsorption capacity of Cr（Ⅵ）on formed carbon by affecting the existing form of Cr（VI）in water and the protonation on the surface of formed carbon.The higher the p H,the lower the adsorption capacity.The greater the initial concentration of Cr（VI）solution,the greater the adsorption capacity.According to the fitting of the kinetic adsorption model and the isotherm adsorption model,Na₂Si O₃-PVA-ZDC and SAS-CMC-ZDC are more in line with the pseudo-second-order Kinetic adsorption model and Freundlich model,the adsorption process includes two stages of reduction of Cr（VI）on the surface of the formed carbon and diffusion of Cr（III）inside the pores.The thesis has 51 figures,19 tables and 104 references.