Mechanism Study On Reduction Assisted Adsorption Removal Of Hexavalent Chromium By Iron-Doped Biochar

In this study,a synthetic method of high-performance reducing adsorbent using cow dung biomass as a precursor was proposed,and a magnetic iron-doped porous biomass carbon?Fe0.31?0?Fe2.69?II?C?was prepared.And the reduction-adsorption coordinated removal mechanism of Cr?VI?in aqueous solution was studied.In the preparation strategy of the adsorbent,the precursor was soaked and dried in a mixed solution of FeSO4 and K₂CO₃,and then sintered at 800°C under anaerobic conditions to obtain iron-doped magnetic biomass carbon.The iron-doped biomass charcoal prepared by this method is simple and easy to use,and uses few chemical reagents to treat waste with waste,and the preparation process is more environmentally friendly.The prepared adsorbents were characterized by Fourier transform infrared spectroscopy?FTIR?,field emission scanning electron microscope?FE-SEM?,X-ray diffraction?XRD?,vibrating sample magnetometer?VSM?,and Zeta surface potential for analysis.Its physical and chemical properties.Aiming at the adsorption behavior of hexavalent chromium by the adsorbent,the effects of pH,initial concentration,reaction time,and coexisting ions on the adsorption characteristics were investigated through experimental studies.The results of the batch experiments showed that the reaction process basically reached equilibrium within 180 minutes under the conditions of pH=2.0±0.1 and 25°C.The maximum adsorption capacity of iron-doped biomass carbon for Cr?VI?was89.30 mg·g^-1.The adsorption reaction is an endothermic reaction that occurs spontaneously.The process is mainly a single-layer chemical adsorption.The mechanism includes the synergistic effect of reduction of iron and divalent iron ions on the surface of the adsorbent with the target pollutant and electrostatic adsorption.In addition,the kinetic model of Cr?VI?for iron-doped biomass carbon corresponds to a pseudo-second-order kinetic model,and the adsorption isotherm corresponds to the Langmuir model.The presence of anions(Cl^-?NO₃^-?SO₄^2-?PO₄^3-)in the system is not conducive to the adsorption of Cr?VI?by iron-doped biomass carbon,and the order of influence is:PO₄^3->SO₄^2->Cl->NO₃^-.Through X-ray photoelectron spectroscopy?XPS?analysis,it was found that Cr?VI?was successfully adsorbed on iron-doped biomass charcoal,and the chromium element had a valence state change.Synergistic adsorption adsorbs the reduced pollutants on the surface of the adsorbent.In addition,the structure of the adsorbent before and after adsorption is complete,and its unique ferromagnetic properties confirm its separability from aqueous solutions.This study proves that iron-doped biomass charcoal prepared with cow dung as a precursor has good physical and chemical properties,is an inexpensive and efficient environment-friendly adsorbent,and has significant application potential in the field of wastewater treatment.