| Lignin is the main byproduct of pulp and paper industry is the world’s most abundant reserves aromatic green biomass resources,it’s environmental friendliness,molecular structure of regulatory,biodegradable,etc.,in food,energy,medicine,chemical industry and other fields has showed great application prospect,this topic using lignin as raw material,Lignin/polyaniline composites and O-N-S co-doped porous activated carbon composites were prepared with aniline,and their electrochemical properties and dye adsorption properties were studied.The results can realize the high value of lignin and its utilization.The research contents and results are as follows:(1)Lignosulfonate/polyaniline(LS/PANI)nanocomposite electrode material was prepared by chemical polymerization with aniline monomer using lignin as dopant and structure guide agent.The structure of LS/PANI nanocomposite electrode material was characterized by FT-IR,XRD and elemental analysis.The surface morphology and pore structure of LS/PANI nanocomposite were analyzed by SEM and XPS.Compared with the fibrous polyaniline,LS/PANI composite exhibits spherical particle morphology with a diameter of 85 nm,and the sulfonic group is successfully grafted into the polymer matrix,which improves the surface wettability and ion/electron transport efficiency of the electrode material.The effects of polymerization conditions(mass ratio of lignin to aniline)on the preparation and electrochemical properties of conductive composites were investigated.The results show that when the mass ratio of LS to Aniline is 1∶9 and the charge-discharge current density is 1A/g,the corresponding specific capacitance of LS/PANI composites can reach 553.73 F/g.PANI was 454.65 F/g;Under the high current density of 20 A/g,LS/PANI can still reach 254.15 F/g,and the capacitance loss rate is small.After 1000 cycles of charge and discharge,LS/PANI capacitor retention rate can still reach 62.32%,which has a good capacitance retention rate.(2)The prepared LS/PANI composite was used as a dye adsorbent to study the adsorption properties of anionic dye Congo red and cationic dye malachite green.The effects of adsorbent dosage,solution pH value,initial concentration of dye,adsorption time and temperature on the adsorption properties of dye malachite green and Congo red were investigated.The results are as follows:when LS/PANI composite is used as adsorbent of Congo red dye,the change of pH has little influence on the removal of Congo red dye.The optimal adsorption conditions for the removal of Congo red dye are as follows:the amount of adsorbent is 20 mg,the initial concentration of dye is 300 mg/L,the adsorption time is 200 min,and the temperature is 85℃.The adsorption of Congo red dye by LS/PANI composite conforms to Freundlich adsorption model and quasi-second-order adsorption dynamic model,which belongs to multi-molecular layer adsorption dominated by chemical adsorption.The maximum equilibrium adsorption capacity can reach 417.60 mg/g through electrostatic adsorption.The adsorption mechanism of Congo red mainly includes electrostatic attraction,hydrogen bonding,and electron transfer during the adsorption process.The internal diffusion model shows that the internal diffusion of particles is not the only factor controlling the adsorption rate.The whole adsorption process is entropy-increasing and spontaneous.When LS/PANI composite material is used as malachite green dye adsorbent,the best adsorption conditions for removing malachite green dye are as follows:The adsorption time was 300 min,and the temperature was 85℃.The adsorption of malachite green dye by LS/PANI composite was in accordance with Langmuir adsorption model and quasi-second-order adsorption dynamic model,belonging to monomolecial adsorption dominated by chemical adsorption.The equilibrium adsorption capacity is 245.75mg/g,and the adsorption mechanism isπ-πconjugation,hydrogen bond adsorption and chemisorption.The whole adsorption process is entropy-increasing and spontaneous(3)Use of lignin as a dopant of polyaniline polymerize and soft template,after pre-activation and synthesis of carbide carbide with three dimensional network structure of O-N-S total mixed activated carbon material,through the optimization of lignin and aniline mass ratio and carbonization temperature two conditions,the obtained material for structural characterization and electrochemical performance testing.The results show that when the mass ratio of LS to aniline is 4∶1 and the carbonization temperature is 700℃,LS is successfully doped into the structure of carbon material,and the porous skeleton structure is maintained well,the specific surface area is 511.00 m~2/g,and the average pore size is 2.75 nm,forming a graphitized three-dimensional network structure connected to each other.The extra pseudocapacitance is enhanced by the abundance of heteroatoms on the surface or edge of the carbon matrix.Under the condition of 0.5 A/g,the specific capacitance of O-N-S co-doped activated carbon material can reach 333.54 F/g,while the specific capacitance of polyaniline carbonized at 700℃can only reach 101.50 F/g.After charging and discharging 5000 times at 5 A/g,SNC700 material still retains good cyclic stability and can reach 95.14%capacitance retention.(4)When the prepared O-N-S co-doped activated carbon material was used as adsorbent,the adsorption of the cationic dye methylene blue was studied.In the methylene blue solution with an initial concentration of 100 mg/L,the removal rate of SNC700 was up to 99.53%,much higher than that of the undoped lignin carbon material.The dynamic model was in line with the quasi-second-order kinetic model.At the initial concentration of 500 mg/L,the adsorption equilibria of NC and SNC reach 478.30 mg/g and 509.00 mg/g,respectively,which accords with the Langmuir adsorption isotherm model.Methylene blue adsorption on the surface of carbon material is a monomolecular layer.The adsorption of methylene blue dye on carbon-based adsorbent is a spontaneous and feasible endothermic process. |
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