Nitrogen-doped porous biochar for selective adsorption of toluene under humid conditions

Through experiments and simulation calculations to investigate the nitrogen(N)-doped porous biochar adsorption performance for volatile organic compounds (VOCs, toluene, C o = 110 mg/m(3)) in humid conditions was the purpose of this work. The results showed that the specific surface area of biochar increased by about 1000 m(2) g(-1) after N-doping, the surface N content increased by more than 3 %, and hydrophilicity and polarity declined. The adsorption capacity of toluene could reach up to 223 mg/g at 0 % relative humidity and maintained about 80 % adsorption capacity under humid conditions. The isosteric heats and the binding energies simulated density functional theory (DFT) manifested that the biochar with higher nitrogen content on surface could achieve strong interaction with toluene and weak interaction with water vapor. Moreover, the adsorption kinetic showed that water vapor and the greater number of micropores would slow down the mass transfer rate of toluene during the adsorption. These conclusions can provide an important reference for the application of N-doped porous biochar and development of adsorbent for high humidity environment.