Preparation Of Xylose Residue Derived Biochar And Its Electrochemical Adsorptive Performance

Biochar has attracted widespread attention in the field of energy storage,electrode materials and environmental remediation due to the characteristics of good conductivity,high surface area,and developed porosity.Xylose residue is a kind of industrial waste produced from corn cob as raw material with large output and porous structure.In this dissertation,biochar was prepared with different structures from xylose residue and the electrochemical performance and adsorption performance of the biochar were studied.On the one hand to obtain high-quality carbon materials for the preparation of raw materials and methods,on the one hand,hope to achieve the high-value utilization of xylose residue.This study used different methods to prepare biochar.The physical and chemical structures of different biochar were characterized,and the electrochemical performances and capacitance characteristics as energy storage materials?super-capacitors and lithium-sulfur batteries?were analyzed.The adsorption properties of organic dyes methylene blue as adsorption material were investigated.The selective adsorption performance of heavy metal lead was investigated through surface modification,and the possible adsorption mechanism was analyzed.The main results are as follows:?1?The method of pre-carbonization to remove silicon+temperature optimization+optimization of KOH activator addition was adopted to optimize the preparation of biochar by xylose residue.Pre-carbonized xylose residue obtained biochar AM400 at400?.After optimization of activation temperature and KOH addition quantity,when the mass ratio of AM400 to KOH was 1:3,the biochar 850 NBC was obtained at 850°C with a large specific surface area?2025 m²/g?and oxygen-rich functional groups on the surface.When the mass ratio of AM400 to KOH was 1:5,biochar 850 BC was obtained with SSA of 3030 m²/g and rich pore structure.?2?The capacitive properties of biochar 850 BC with the largest surface area was studied as the energy storage material for supercapacitors.The results shown that 850 BC exhibited better capacitance characteristics in alkaline systems.The specific capacitance value was 1.24 times of commercial activated carbon under the constant current charge-discharge of 0.5 A/g.As the cathode material of lithium-sulfur battery,the 850 BC was charged and discharged 40 times at 0.1C with 1013 mAh/g specific capacitance value.By analyzing the linearity of the biochar with different specific surface areas and its corresponding specific capacitance,it can be seen that the larger the specific surface area of the biochar prepared in this study,the higher the specific capacitance value.?3?As the adsorbent of methylene blue,the maximum Langmuir adsorption capacity of 850 NBC was 1563.9 mg/g,and the adsorption capacity was 2249 mg/g when the pH was optimized to 11.65.The adsorption kinetics belonged to pseudo-second order kinetics.According to the fitting analysis of the Temkin model,the adsorption mechanism of methylene blue by 850 NBC is mainly electrostatic attraction.?4?The functional biochar-based adsorption material MgO-NBC was obtained by nitrogen doping and surface modification of MgO,and the maximum Langmuir adsorption capacity for heavy metal Pb²⁺was 1000 mg/g.In NH₄⁺and Cd²⁺binary system,MgO-NBC exhibited excellent selective adsorption performance on Pb²⁺.Base on the analysis of the adsorption mechanism,it unfolds that Pb²⁺was mainly deposited on the surface of MgO-NBC through cation exchange and formed the sediment carbonate.