The Prepatationof Biochar Combinedby Metaloxideandits Mechanismfor Removalheavymetalionsfromaq Ueous Solution

Heavy metal pollution has seriously compromised ecological balance and human survival,the composite adsorbent of biochar modificed by Fe₃O₄?MnFe₂O₄ and MnO₂ were preparated in this study.The structure of the adsorbents were analyzed by SEM,XRD,BET and FITR,the adsorption performance of adsorbents for heavy metal from aqueous solution was verified by different batches of experiments,theadsorption mechanism of composite adsorbent on heavy metal copper was investigated by the Kinetic and thermodynamic methords:?1?The biochar was prepared by the pine branch,which was combined with both magnetic Fe₃O₄ and chitosan to form the composite adsorbent.It has been used for Cu???removal from aqueous solution.There were three steps in the endothermic adsorption process,including the surface diffusion,the intraparticle diffusion and the final equilibrium.The maximum adsorption capacity was 74.83 mg·g^-1 at the equilibrium time of 90 min.The investigations on adsorption kinetics and isotherms showed that the pseudo-second-order kinetic and Langmuir isotherm model could well fit the experimental data.Further investigations on the activation energy and thermodynamics of the adsorption process elucidated that the Cu???adsorption on the adsorbent was an endothermic and spontaneous physi-sorption process.?2?MnFe₂O₄/biochar adsorbent was prepared through hydrothermal method using hydrothermal biochar,FeCl₃?6H₂O,MnCl₂?4H₂O and NaOH,which has been used for Cu???removal from aqueous solution.The pseudo-second-order kinetic and Langmuir isotherm model could well fit the Cu???adsorption on the adsorbent.The adsorption rate of low concentration was only controlled by the surface diffusion,and the adsorption rate of high concentration wasdominated by both surface diffusion and intraparticle diffusion,the maximum adsorption capacity was 44.00mg?g^-1.The thermodynamic analysis showed that Ea=26.99 kJ?mol^-1,?G<0 and?H=3.08kJ?mol^-1,it is a spontaneous and endothermic chemical absorption process with regards to MnFe₂O₄/biochar adsorbents removal Cu???from aqueous solution.?3?Using biochar as the main component,MnCl₂?4H₂O solution as the aqueous phase and absolute ethanol as the organic phase,theMnO₂/biochar composite adsorbent was prepared by aqueous two-phase organic-phase method.Adsorption performance studies show that MnO₂/biochar composite adsorbent has good adsorption capacity for Cu???,and the final removal rate of 75mg?L^-1 solution reaches95.4%.The pseudo-second-order kinetic and Langmuir isotherm model could well fit the Cu???adsorption on the adsorbent,the maximum adsorption capacity was 83.9mg?g^-1.Ea=84.36 kJ?mol^-1,?G<0 and?H=39.06 kJ?mol^-1,it is a spontaneous physical endothermic adsorption process with regards to MnO₂/biochar adsorbentremoval Cu???from aqueous solution,specific chemical interactions were the main mechanism of Cu???adsorption.