Preparation Of Nitrogen-doped Porous Carbon From Agricultural Waste And Its Adsorption Performance For Dye

High efficiency treatment of wastewater containing organic dyes has become increasingly imperative worldwide nowadays,seeking high performance adsorbents is one of the most effective measures for this problem.Among multitudes of adsorbents,activated carbon especially porous carbon has been widely used in the long term for its high specific surface area and tunable porous structure.Activated carbon can be originated from waste biomass plants and animals,coal,polymers,etc.Of which,from a more sustainable point of view,forestal and agricultural waste biomass derived porous carbon has attracted more and more consideration as adsorbents for removal of organic dyes.Generally,the biomass-derived porous carbon is prepared by carbonization of the biomass precursor followed by activation,and also,the specific surface area and the porous structure vary with the biomass precursor itself and the synthetic conditions.Herein,the agricultural waste corn roots,corn peels,corn straw and soybean roots are used as raw materials to prepare trace N-doped porous carbon nanospheres via a hydrothermal treatment followed by a mild calcination,which have high specific surface area and affluent porous structure.The N-doped porous carbon nanospheres are employed as the adsorbents for removal of typical organic dyes,which exihibit significantly superior adsorption performance and will be briefly given as below.First,with the agricultural waste corn roots as raw materials for the first time and H₂SO₄ as the catalyst,uniform hydrothermal carbon nanospheres are prepared via a hydrothermal synthesis by altering the dosage amount of H₂SO₄,time and temperature.Then,followed by a mild calcination with K₂CO₃ and melamine as the activator and nitrogen source,corn roots induced trace N-doped porous carbon nanospheres(specific surface area:2745 m² g^-1,pore volume:2.07cm³ g^-1)are obtained.Cationic dye Rhodamine B（Rh B）and anionic dye Congo red（CR）are employed as the main model organic dye to evaluate the adsorption performances of the as-obtained N-doped porous carbon nanospheres,and the maximum adsorption capacities（q_m）for Rh B and CR are determined as 1630.7 and 1766.2 mg g^-1,respectively.Also,analyses on the adsorption isotherms,kinetics and intraparticle diffusion model are carried out.By characterization,the results indicate that the melamine not only serves as the nitrogen source for N-doping but also acts as the synergistic activator with K₂CO₃to promote the generation of pores,with distinct increases in the specific surface area,pore volume and surface defects of the trace N-doped porous carbon nanospheres.Moreover,the corn roots induced trace N-doped porous carbon nanospheres also exhibit satisfactory reusability for the adsorption of Rh B as well as good adsorption performances for the mixed dyes simultaneously containing Rh B and CR.This profoundly reveals corn roots induced trace N-doped porous carbon nanospheres as great promising low cost whereas high performance biomass-derived adsorbents for treatment of practical industrial wastewaters containing organic dyes.In addition,the agricultural waste corn peels,corn straw and soybean roots are also utilized as raw materials in a stable hydrothermal treatment and followed by a mild activated N-doped calcination for the N-doped porous carbon nanospheres,which all have high specific surface area,pore volume and porous structure.The N-doped porous carbon nanospheres,when deployed as the adsorbents to remove organic dyes Rh B and CR,all demonstrate great removal efficiency and a high q_m.Besides,analyses on the adsorption isotherms,kinetics and intraparticle diffusion model are also made systematically.In brief,the present work improves the diversified utilization level of the porous carbon originated form corn-and soybean-based waste biomass,and undoubtedly enlarges the high value-added comprehensive and practical utilization of agricultural waste in the near future.