Removal Of Chromium From Water And Soils With Magnetic Biochar

In this study,a new adsorbent with high adsorption performance and separability was developed.The preparation method of magnetic biochar,the removal rates of chromium by the magnetic biochar from water and soil,and the recycle method of magnetic biochar were studied.The major results were shown in the following:The cheap waste peanut shells were used as a raw material of biochar.Two modification methods were tested.Fe Cl₃ and nano-sized Fe₃O₄ were used to modify the biochar to prepare magnetic biochar.Based on the magnetism and adsorption efficiency of hexavalent chromium（Cr（VI））,the Fe Cl₃-modified biochar had a magnetism value of 5.65emu/g and a high removal rate of Cr（VI）.The removal rate of Cr（VI）by the magnetic biochar increased with the heat temperature,heat time and Fe Cl₃concentration.The optimized Fe Cl₃ concentration,heat temperature and heat time were obtained.The adsorption of Cr（VI）by the magnetic biochar in water solution was studied by oscillation experiment.The removal process of Cr（VI）was well described using pseudosecond-order kinetic and Langmuir isotherm model.Based on the pseudosecond-order kinetic,the equilibrium adsorption capacity was 3.38mg/g.Based on the Langmuir isotherm model,the maximum adsorption capacity was 7.52mg/g.Moreover,multiple surface analysis methods（SEM,FTIR,XRD and XPS results）indicated that the adsorption mechanisms of Cr（VI）onto the magnetic biochar included the electrostatic force,ion exchange,complex reaction,metal reduction and precipitates.The magnetic biochar was applied for remediation of chromium-polluted soil.The results showed the magnetic biochar had a high efficiency.Chromium was effectively removed from soil by the magnetic biochar.The removal rates of chromium from the soil by the magnetic biochar increased with the magnetic biochar dosage,liquid-solid ratio,and contact time,and decreased with the humic acid concentration.The highest removal rate reached 38.84%.The recovery rate of chromium-adsorbed magnetic biochar reached about 40%.