Preparation Of Porous Carbon From Fatong Leaf/Fatong Fruit Hair And Its Adsorption Properties

Porous carbon materials have been paid considerable attention and been widely used in water treatment,catalyst support,electrochemical energy storage,bio-medicine and other fields mainly due to their high specific surface area,abundant pore structure and good electrochemical activity.In particular,porous carbon materials derived from biomass have attracted much concern of researchers for their unique advantages such as sustainability of resources,low-cost accessibility of raw materials and ample functional groups.However,the process to prepare porous biomass based carbon with uniform morphology usually needs organic solvents or other templates,which leads to tedious process and low added value of the product.In this thesis,the biomass-based porous carbon microspheres with large specific surface area,abundant functional groups and affluent porous structure are obtained by using fallen leaves and fruit fibers of platanus orientalis as raw materials,via a facile hydrothermal synthesis followed by calcination route,which are generally employed in laboratory.Besides,the as-obtained carbon microspheres are evaluated as the adsorbents for the removal of organic dyes and phenolic compounds with satisfactory adsorption performance.In the first part of the thesis work,uniform carbon microspheres with narrow size distribution are prepared from fallen platanus orientalis leaves via a hydrothermal synthesis by altering the temperature,time and concentration of raw materials.The platanus orientalis leaves-based porous carbon microspheres are then obtained by further activation and calcination of the hydrothermally synthesized carbon microspheres via altering the alkali-carbon ratio,calcination temperature and time.The as-obtained porous carbon microspheres have a specific surface area of 1355 m² g^-1,an average pore size of 2.7 nm,and a variety of functional groups such as-C=O on the surfaces.When utilized as the adsorbents,the removal rate of Rhodamine B（RhB）and Methyl Orange（MO）can reach higher than 95%in 10 minutes.The adsorption capacity of RhB can reach 556.0 mg g^-11 and the morphology of the adsorbents remains unchanged after five cycles,indicating the porous carbon materials of good cyclic stability.Moreover,the isothermal adsorption model kinetic model and diffusion model are employed,by which the adsorption process is investigated.The results show that,the adsorption process conforms to Langmuir isothermal model and pseudo-second-order kinetics,and the pore diffusion is the rate-limiting step.Subsequently,the hollow platanus orientalis fruit fibers are used as raw material to obtain the pre-calcined intermediate product with almost intact profile by altering the pre-calcination temperature.After the next activation and calcination by tuning the parameters such as the temperature,time,heating rate and atmosphere,the platanus orientalis fruit fibers based porous carbon with hollow tube-like structure is obtained by one-step calcination in water vapor atmosphere,and the nitrogen-doped platanus orientalis fruit fibers based porous carbon is acquired by multistage calcination in NH₃ atmosphere.The as-prepared porous carbon materials are employed as the adsorbents for the removal of O-nitrophenol（2-NP）and Methylene Blue（MB）.Compared with all other adsorbents reported,to the best of our knowledge,the present nitrogen-doped platanus orientalis fruit fibers based porous carbon exhibit distinct excellent adsorption performance,and the maximum adsorption capacity of 2-NP is confirmed as 347.8mg g^-1.In addition,the adsorption isotherm model and kinetic model are also discussed in detail.The experimental data analysis show that,the adsorption process accords with Langmuir isotherm adsorption and pseudo-second-order kinetics models.The transfer of 2-NP molecules from the surfaces of the porous carbon to the inner pores is evidenced as the rate-determining step.In brief,porous carbon materials are prepared from fallen leaves and fruit fibers of platanus orientalis by hydrothermal synthesis followed by calcination technique,which provides some new ideas for the preparation of biomass based porous carbon.At the same time,the as-prepared porous carbon materials are applied to adsorb organic dyes and phenolic compounds.Compared with other adsorbents in literature,the present platanus orientalis leaves and fruit fibers based porous carbon exhibit superior adsorption performance,thus revealing the biomass-based porous carbon as competitive candidates for adsorbents in water treatment and other related fields.