The adsorption properties of 2,4-DCP on biochar derived from chitosan in aqueous solution

Organic pollutants in aqueous solutions may potentially be adsorbed on biochar. In this study, biochar was derived from the pyrolysis of chitosan at 800°C. The removal rate of 2,4-dichlorophenol (DCP) exceeded 80%. Investigations by Fourier transform infrared spectroscopy and Brunauer– Emmett–Teller indicated that the adsorption of organic pollutants on biochar tends to be a physical process. The optimized pH was 5. All three isotherm models involved (Freundlich, Koble–Corrigan, and Henry) could describe the adsorption process of 2,4-DCP well on chitosan-biochar, which was non-uniform surface adsorption in a diluted solution. The adsorption was an endothermic process. It took 40 min to reach the adsorption equilibrium, and kinetics of the Elovich equation and intraparticle diffusion (IPD) model indicated that the adsorption rate at the rapid adsorption stage was simultaneously controlled by surface diffusion and IPD and that at slow adsorption stage was controlled by surface diffusion. The ionic strengths suggested that electrostatic interaction was not the dominant mechanism during this process.