The Preparation Of Magnetic Biochar And Its PRB Remediation Effect And Mechanism On Groundwater Chromium Pollution

Cr（Ⅵ）,as a high concern contaminant in groundwater,are widely derived from industrial activity.With natural or man-made processes,it easily enters the aquifer,causing serious harm to the groundwater environment and even human health.In this study,reed was used as a raw material to prepare biochar,and magnetic biochar was prepared by nano ferroferric oxide Fe₃O₄based on in-situ microwave method and magnetic modification of the biochar.Multiple fine characterization results were combined to explore the adsorption and removal efficiency and mechanism of Cr（Ⅵ）in groundwater by magnetic biochar on properties by combining static batch experiments and dynamic Permeable Reactive Barrier（PRB）sand column remediation experiments.1.Taken Fe₃O₄ adsorption characteristics of Cr（Ⅵ）in simulated groundwater as the research object,combined with X-ray diffraction（XRD）,Fourier infrared spectroscopy（FTIR）,scanning electron microscope（SEM-EDS）,X-ray photoelectron spectroscopy（XPS）,automatic specific surface and pore analysis（BET）,Zeta potential,systematic investigation and simulation of the adsorption mechanism of Cr（Ⅵ）in groundwater on Fe₃O₄.Fe₃O₄had a smaller particle size of nanometers.Increasing the concentration of Cr（Ⅵ）in groundwater,the adsorption capacity of Fe₃O₄on Cr（Ⅵ）increased;The adsorption of Cr（Ⅵ）on Fe₃O₄in groundwater was positively correlated with ambient temperature.As the ionic strength of groundwater increased,the adsorption of Cr（Ⅵ）on Fe₃O₄decreased.Low p H conditions were more conducive to the removal of Cr（Ⅵ）in groundwater;The mechanism of Cr（Ⅵ）adsorption by Fe₃O₄included direct rapid adsorption and indirect reduction processes,and rapid adsorption was mainly through the electrostatic interaction between them.2.The adsorption mechanism,adsorption kinetics and adsorption of Cr（Ⅵ）in simulated groundwater by Biochar and m-Biochar were investigated.The thermodynamic process and the response of the adsorption process under the different environmental factors conditions were investigated.The adsorption process of Cr（Ⅵ）by m-Biochar in groundwater conformed to the quasi-second-order kinetic model and intra-particle diffusion model,indicating that the total adsorption rate of Cr（Ⅵ）was composed of chemical adsorption,liquid film diffusion（bulk diffusion）and intra-particle diffusion The rate was controlled together;the adsorption amount of Cr（Ⅵ）by Biochar and m-Biochar was positively correlated with the ambient temperature,increasing the ionic strength,and promoting the adsorption of Cr（Ⅵ）by m-Biochar;p H of groundwater affected the adsorption of Cr（Ⅵ）by m-Biochar was an important factor.Under acidic conditions,zeta potential of m-Biochar was positive,and the electrostatic interaction with Cr（Ⅵ）anions was strong,and the oxidation-reduction reaction between Fe（II）and hexavalent chromium stronger;3.Used mini columns to construct a one-dimensional continuous PRB reaction system and carried out simulation experiments on the restoration of Cr（Ⅵ）in groundwater by magnetic biochar composite materials.When the filling material was0.1 g,the penetration curve could be described better.Increasing the groundwater flow rate,the initial penetration time of Cr（Ⅵ）decreased,the removal rate of Cr（Ⅵ）decreased,and the penetration increased.When the groundwater flow rate was 0.5m L/min,the retention rate of Cr（Ⅵ）for mixed packing was large;When the p H of the Cr（Ⅵ）solution was 3,the retention rate of Cr（Ⅵ）by magnetic biochar was 95.58%.At p H was 7 and 9,Cr（Ⅵ）basically penetrated without retention.Under acidic conditions,magnetic biochar was positively charged,while Cr（Ⅵ）exists as an anion,and the two interacted through electrostatic attraction.And there was a“tailing”phenomenon;The ionic strength had little effect on the restoration of Cr（Ⅵ）by PRB.When the groundwater type was Ca²⁺,the PRB restoration of Cr（Ⅵ）was inhibited,and the interception rate of Cr（Ⅵ）was reduced by about 7%.When the groundwater type was Na HCO₃,there was no interception of Cr（Ⅵ）.