Abstract: High porosity and big specific surface area of biochar derived from Solidago canadensis L.was prepared using the activation-calcining technology and was applied to adsorb Cr(Ⅵ) in water. The preparation parameters for the optimal adsorbent and the effects of adsorbent amount, initial pH, reaction time, and temperature on adsorption removal of Cr(Ⅵ) in aqueous solution were explored. The characterization results obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy(FTIR), brunauer-emmett-teller(BET) and X-ray photoelectron spectroscopy(XPS) confirmed that the modified biochar had more abundant functional groups, higher porosity, and bigger specific surface area, compared to the pristine biochar. The adsorption experiment results showed that the optimal adsorption performance of the modified biochar was obtained by the mass ratio of ZnCl2to pre-carbonized biochar with 3:1 and the calcination temperature at 700 ℃. The highest removal efficiency of Cr(Ⅵ) was obtained at pH 2. The pseudo-second-order adsorption kinetics model and the Langmuir adsorption isothermal model were more suitable to fit the adsorption kinetics and adsorption equilibrium process. The chemisorption process mainly controlled the reaction rate, and the maximum adsorption capacity reached 32.6 mg/g at 318 K. Thus, the biochar derived from Solidago canadensis L. can effectively remove Cr(Ⅵ) in water. It not only has potential application value in wastewater treatment, but also can realize the effective control and comprehensive utilization of the invasive plant.

Key words: Solidagoc canadensis L., biochar, ZnCl2activation, Cr(VI), adsorption