Biomass Derived Nitrogen Doped Porous Carbon Materials asAdsorbents for Removal of Methylene Blue in Water

A series of biomass???willow leaves???derived nitrogen doped porous carbon materials???WNC???were preparedby a sol-gel route???and were characterized by a variety of means.The results show that the WNC materials possessedhigh surface areas???528-618m2/g???as well as large number of oxygen-containing and nitrogen-containing groups???molar fraction of nitrogen8.9%-9.9%???.The WNC materials exhibit excellent adsorption capacity for Methyleneblue???MB???in wastewater.The pseudo-second-order kinetic model and Langmuir isothermal model fit the adsorptiondata well and the adsorption process of MB was spontaneous and endothermic???the maximum monolayer adsorptioncapacity calculated from Langmuir model was263.2mg/g???pH=5???T=298K???.WNC-2material can be easily recycledfor many times without obvious loss in adsorption capability.Furthermore???two other samples of WNC-2-R and WNC-2-MB???which were obtained through the high-temperature calcination of the fresh WNC-2and the used WNC-2???after adsorption of dye MB??????show much higher adsorption capacity for MB???1.3and1.6times of the fresh sample??????respectively???possibly related to the significant increase of the zeta-potential and surface alkalinity.Combined withvarious characterization results???it can be concluded that the high specific surface area and the hierarchical porous pore structure of WNC materials are beneficial to the transport of the MB ions???while the abundant carbonyl???quinoneand pyridine nitrogen groups existed on the surface of WNC materials could strongly interact with the adsorbate???thusresulting in a higher adsorption rate and adsorption capacity for MB